Impacts on seabed - Approaches for assessment and successful measures

Contents1. Introduction....................................................................................................................................................2

2. Pressures on benthic habitats.........................................................................................................................2

2.1 Physical pressures...................................................................................................................................2

2.2 Impacts of human activities on seabed..................................................................................................8

2.3 Input of substances.................................................................................................................................9

2.4 Marine litter..........................................................................................................................................10

2.5 Biological pressures..............................................................................................................................12

3 The sensitivity of habitats.............................................................................................................................13

3.1 Components affecting sensitivity..........................................................................................................13

3.2 Sensitivity assessments.........................................................................................................................14

4 Approaches to assess adversely affected habitats........................................................................................16

4.1 Definition of adversely affected habitats..............................................................................................16

4.2 Thresholds for the assessment of habitats...........................................................................................17

4.3 HELCOM indicators for assessing benthic habitats...............................................................................20

4.4 Cross-comparison of environmental assessments and pressures...............................................................21

5 Habitat integration across different hierarchical levels ...............................................................................23

5.1 Benthic broad habitat types present in the Baltic Sea................................................................................23

5.2 Combining different hierarchical levels of habitats in the same assessment........................................24

6 Method for assessment of impacts on benthic habitats...............................................................................26

6.1 A stepwise method guideline for a technical assessment of the lost, disturbed and adversely affected area (km2).........................................................................................................................................................26

7 Measures to reach GES of benthic habitats and seafloor integrity...............................................................27

8 Conclusions...................................................................................................................................................29

References............................................................................................................................................................30

Annex 1.................................................................................................................................................................36

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1. Introduction

The state of benthic habitats and species is threatened by various human activities occurring at sea and coastal areas as well as by several land-based activities. Understanding the impacts of human activities on the seabed is highly important for preserving the habitats and their diversity. The objective of the report is to consolidate existing information on pressures and major impacts on seabed. Pressures and their adverse effects on benthic habitats and assessment as well as restoration of benthic habitats will be included.

Based on their primary way of impact on the environment, pressures from human activities can be broadly categorised into four groups; inputs of substances (including for example nutrients and hazardous substances), inputs of energy (underwater sound, heat), biological pressures (non-indigenous species, disturbance of species and extraction of species, for example), and physical pressures (disturbance to the seabed, loss of seabed, and changes to hydrological conditions) (HELCOM 2018b). In this report, the focus is in physical pressures. Biological pressures (non-indigenous species) and inputs of substances (nutrients and hazardous substances) will also be addressed. Input of energy is not included in this report.

At current, there is no regionally agreed method to assess how physical loss and physical disturbance are adversely affecting the seabed. For these needs, a couple of indicators are under development: an indicator on cumulative impacts on benthic biotopes as well as an indicator for condition of benthic habitats.

2. Pressures on benthic habitats

Several human activities at sea cause various pressures in the marine environment. Pressures affecting seabed and habitats have been studied in several Baltic wide projects and at EU scale. In this chapter, pressures affecting seabed are defined and described. Also, the contribution of activities to pressures is included.

2.1 Physical pressures

2.1.1 Physical loss

Physical loss has been defined in the revised Marine Strategy Framework Directive (MSFD) Annex III as ‘physical loss due to permanent change of seabed substrate or morphology and to extraction of seabed substrate’. Moreover, the revised Commission Decision XX (COM DEC) defines this as ‘a permanent change to the seabed which has lasted or is expected to last for a period of two reporting cycles (12 years) or more’ (HELCOM 2018b). The MSFD criteria for physical loss require an assessment of the spatial extent of seabed area being lost.

In the HELCOM BalticBOOST project, the following activities were considered to cause physical loss:

- all dredging and sand and gravel extraction activities where seabed substrate is removed- disposal of dredged matter and other dumps on seabed which change the seabed substrate; if the

deposited material is similar to the buried seabed, the recovery may take place, but in other cases, the original seabed will not recover

- all built structures, such as wind turbines and electricity cables, as they cover seabed area- marinas and harbors as they have built structures and also continuous propeller currents which change

the seabed characteristics- land claim where marine area is filled with land material and turned as dry land

(HELCOM 2018b.)

The same activities that cause physical loss also cause physical disturbance (siltation) to the seabed. Therefore, the BalticBOOST project defined loss from these activities according to the following:

- the core zone of the activity (extraction/ dredging/ disposal/ construction site) is considered ‘lost’ because the seabed morphology (topography, bathymetry) or substrate type (grain size, substrate type) has been changed for at least 12 years;

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- the core zone may be lost forever, if the site is emptied of the particular substrate (e.g. extracting specific grain size) or covered by a new substrate (e.g. depositing dredged matter over a different substrate type). (HELCOM 2018b.)

In a series of workshops (WKBEDPRES1, WKBEDLOSS, WKBEDPRES2) delivering an advice on the seafloor integrity for the MSFD, organized by International Council for the Exploration of the Sea (ICES), group of experts has defined the physical loss slightly differently:: physical loss has been defined as “any human-induced permanent alteration of the physical habitat from which recovery is impossible without further intervention” (ICES 2019a). Within this definition, physical loss from a human activity would be denoted by a shift in habitat type from one category to another (e.g. littoral mud to littoral coarse sediment habitat type). Physical loss can be given as percentage loss per EUNIS level 2 habitat (for definition, see chapter 5) or as square kilometres. Human interventions facilitating recovery (e.g. removal of man-made structures from the seabed) refer to actions allowing the physical habitat to return to its original EUNIS level 2 habitat type. (ICES 2019a.)

The ICES experts distinguished three different types of physical loss: - Sealed loss is largely informed by the distribution of structures placed in the marine environment (e.g.

wind turbines, port infrastructure) and substrates introduced to the marine environment (e.g. dredge disposal sites).

- Unsealed loss is largely informed by the distribution of seabed habitat change (e.g. at aggregate extraction sites).

- The loss of biogenic habitat necessitates an assessment of the historical distribution of the habitat as these habitats often have limited spatial extents and may be challenging to assess within broad-scale regional assessments. (ICES 2019a.)

ICES has identified pressure subtypes that cause physical loss and physical disturbance:

• Abrasion: the scraping of the substrate (e.g. by a trawl door or an anchor). Whilst abrasion could result in the mixing of sedimentary substrates, any sediment removal is considered a “Removal” pressure subtype. The abrasion pressure subtype can result in physical loss and/or physical disturbance.

• Removal: the net transference of substrate away from the seabed resulting from human activities (e.g. either directly by human activities or indirectly through the modification of hydrodynamics). This pressure subtype can result in physical loss and/or physical disturbance.

• Sealing: the capping of the original substrate with structures (e.g. metal pilings, concrete footings, or blankets) or substrates (e.g. rock or stone fills, dredge disposal) which in and of themselves change the physical habitat. This pressure subtype can result in physical loss. (ICES 2019d.)

Both HELCOM and ICES have noted that the borderline between physical disturbance and physical loss is hard to evaluate. In cases where better data are available (e.g. in situ observation of habitat change) and where a smaller spatial scale is relevant, a finer distinction of disturbance and loss can be appropriate. (HELCOM 2018b, ICES 2019a.)

Human activities causing physical loss have been recognized in several international projects, yet the extent of the loss is case specific and depending on the individual structure. Estimates on the spatial extent of the loss from human activities and man-made structures have been listed in table XXX.

The physical loss of seabed from 15 human activities were assessed in the 2nd holistic assessment of the Baltic sea (State of the Baltic Sea assessment). On the regional scale, less than 1% of the seabed in the Baltic sea was lost up to year 2016 (HELCOM xxx). The human activities resulting in physical loss are listed in the legend of figure 1. In the Baltic Sea, the human activities causing physical loss are not similar between sub-basins. The relative contributions per total lost area of each sub-basin is shown below (figure 1). Extraction of sand and gravel is

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causing physical loss in the southern parts of the Baltic Sea but in the northern parts the activity is almost non-existent. On the contrary, marinas are contributing to the loss relatively more in the northern parts of the Baltic Sea. On the whole Baltic Sea scale, extraction of sand and gravel is contributing most (~40%) to the physical loss of the sea bed while harbors (~30%), marinas (11%) and coastal defense (10%) are the next vastest activities leading to loss.

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Contributions of activities causing physical lossWatercourse modification

Extraction of sand and gravel

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Shellfish mariculture

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Harbours

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Figure 1. Proportions of human activities causing physical loss per sub-basins of the Baltic Sea. The figures were derived from HELCOM human activity data prepared for the aggregated physical loss datalayer in the BSPI development during the HOLAS2 process. The total lost area due to each activity per sub-basin was calculated and divided by the total lost area per sub-basin.

A table including human activities causing physical loss on seabed as well as the spatial extent of the activities will be included HERE.

2.1.2 Physical disturbance

Physical disturbance to seabed is listed in the revised MSFD Annex III and is further defined in the revised COM DEC as ‘a change to the seabed which can be restored if the activity causing the disturbance pressure ceases’. The criterion requires an assessment of the spatial extent of seabed area being disturbed. The HELCOM BalticBOOST project suggests that because recovery time leading to the physical loss was defined >12 years, disturbance can be refined on the basis of the recovery of <12 years (HELCOM 2018b).

According to the BalticBOOST, physical disturbance includes the following more specific pressure types:

- Siltation/sedimentation: this pressure is caused by sediment particles resuspended to the water column and re-settlement to new areas as a result of seabed disturbance. This can take place either as a result of physical modification of the seabed, propeller currents causing resuspension, lifting sediments to a barge, sieving the sand/gravel on the barge, depositing material to a seabed or spreading abiotic or biotic

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matter. It is caused outside the core area of all the activities causing ‘physical loss’. If the sedimentation is heavier, it is often called smothering.

- Turbidity: this pressure is caused by sediment particles resuspended to the water column where it affects the light penetration to seabed; it is caused by the same activities as in siltation/sedimentation;

- Abrasion: this pressure is caused by activities which cause seabed surface to erode; such activities are different types of demersal fishing, anchoring and mooring by ships as well as erosion effects by shipping and boating in shallow or narrow routes.(HECOM 2018b.)

The ICES experts have defined physical disturbance as activities that disturb benthic biota, but do not change the benthic substrate permanently, even when full recovery would take longer than 12 years, as long as recovery to the original state can be expected given enough time. (ICES 2019a).

ICES has identified the pressure subtypes that cause physical disturbance:

• Abrasion and removal can result in physical disturbance and/or physical loss as described in the previous chapter ‘Physical loss’.

• Deposition: the movement of sediment and/or particulates to a new position on top of or in existing substrates (e.g. directly by human activities such as dredge disposal or indirectly through the modification of hydrodynamics). This pressure subtype can result in physical disturbance. (ICES 2019d.)

Human activities causing physical disturbance and estimations of the spatial extent are listed in the table XX. The human activities resulting in physical disturbance in the Baltic Sea are listed in the legend of figure 2. The proportion and distribution of human activities causing physical disturbance to seabed is not uniform throughout the Baltic Sea sub-basins, but some area specific phenomena can be recognize. The relative contributions of activities per total disturbed area of each Baltic sub-basin are shown in figure 2. The human activities contributing most to physical disturbance differ between the Eastern Gotland basin and the Western Gotland basin. Fishing with mobile bottom-contacting gear is causing most of the pressure in the southern Baltic Sea while recreational boating is dominating in the northern areas (figure 2).

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Dredging

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Maerl and furcellaria harvesting

Pipelines

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Shellfish mariculture

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Figure 2. Proportions of human activities causing physical disturbance per sub-basins in the Baltic Sea. The proportions (%) were derived from HELCOM human activity data prepared for the aggregated physical disturbance data layer in the BSPI development during the HOLAS2 process. The sum intensity of each human activity per sub-basin was divided by the sum of all activities per sub-basin.

Estimations of the proportions (%) of broad habitat types affected by physical disturbance per sub-basin shows that most of the broad habitats in the southern Baltic Sea are potentially widely affected (figure 3).

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Figure 3 Estimate of the proportion (%, given in ranges) of the different broad habitat types potentially affected by physical disturbance per sub-basin. The estimate is calculated based on the HELCOM HOLAS II BSII datasets and does not reflect the actual level of impact. ‘NA’ denotes that the habitat type is not represented (HELCOM 2018a).

A table including human activities causing physical disturbance on seabed as well as the spatial extent of the activities will be included HERE.

2.1.3 Changes to hydrological conditions

Changes to hydrological conditions affect the seabed indirectly near built structures such as wind turbines, platforms, piers, breakwaters and groynes. Permanent hydrographical alterations due to built structures take place in the vicinity of the object. If these cause changes in water flows, they may exert abrasion, erosion, resuspension and sedimentation to the seabed. The indirect effects are, however, difficult to assess and approximations are needed (HELCOM 2018b).

In the BalticBOOST project, the following activities were considered to cause changes to hydrological conditions:

- Wind energy production: operational wind farms- Wave energy production- Oil and gas industry infrastructure (Oil platforms)- Built structures such as marinas and leisure harbors, piers, artificial reefs and islands, groynes,

breakwaters and coastal dams and weirs(HELCOM 2018b.)

A table including human activities causing changes in hydrological conditions on seabed as well as the spatial extent of the activities will be included HERE.

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2.2 Impacts of human activities on seabed

In the HELCOM’s BalticBOOST project, the impacts of human activities causing physical pressures on seabed were estimated based on the findings from a literature survey (HELCOM 2018b).

Capital and maintenance dredging cause - removal of substrate (physical loss of a habitat)- changes in the seabed topography (altered physical conditions)- resuspension of silt (turbidity)- sedimentation of the dredged matter on nearby areas (smothering if sedimentation is high or siltation if

sedimentation is low).

Disposal of dredged matter causes- smothering of benthic organisms and changing sediment characteristics (physical loss). However, the

effect is strongly affected by the environmental characteristics of the disposal site.- increased siltation; the impacts of disposal of sediment depend on the seafloor habitat type, type and

amount of disposed material and distance to the disposal site.- increased sedimentation in the areas surrounding the disposal sites which causes for example mortality

and changes in the population structure of benthic organisms.- increased water turbidity (short-term effect)

Sand and gravel extraction causes- removal of substrate (more or less complete mortality of benthic organisms)- changes in the seabed topography- resuspension and sedimentation in nearby areas- most often a permanent change in the grainsize composition (due to the sieving of wanted grain size and

discharging unwanted matter overboard), water depth and hydrological features

Shipping and ferry traffic causes- abrasion because of propeller induced currents- resuspension and siltation of sediments - stress in littoral habitats because of waves - physical disturbance because of anchor dragging - negative effects on the coverage and species richness of benthic vegetation - negative effects on fish dependent on the benthic habitat for spawning or as nursery grounds

Wind turbine construction causes- drilling and relocation of land masses (abrasion, smothering, sealing) - siltation and turbidity in the surrounding area- physical loss (area determined by the scour protection)

Wind turbine operation causes- hydrographical secondary effects caused by averted currents- abrasion effects around the turbines

Placement of cables and pipelines causes- changes in sediment composition as cables are covered with sediment extracted elsewhere- siltation - loss of habitats by smothering and sealing; generally a 2 m wide band- in case of the big gas pipelines the seabed is disturbed through ploughing, explosions, burial and

relocations of sediment masses

Motor boating

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- same physical impact to benthic habitats as shipping but in a smaller scale- maintenance of boating channels by smallscale dredging in shallow inlets has large impacts on benthic

vegetation

Marinas- decreases in vegetation cover and species richness

Demersal fishing- decrease of biodiversity, density and mean weight of benthic macrofauna- the main impact is the abrasion which causes direct mortality, bycatch of larger features and abrasion of

the seafloor

Land claim- physical loss of the seabed as a marine area is turned into dry land

2.3 Input of substances

2.3.1 Eutrophication

Eutrophication is the main environmental problem of the Baltic Sea (Vahtera et al., 2007; HELCOM,2009). It is the consequence of very intensive industrialisation, population growth, agriculture and animal farming. During the last century, nutrient loads have increased by c. 2.5 times for nitrogen and 3.7 times for phosphorus (Savchuk et al., 2008). In 2008, the total inputs of P and N to the Baltic Sea were 29 000 metric tonnes and 859 600 metric tonnes, respectively, but the sediment-released nutrients are considered as a much higher annual source of nutrients (HELCOM, 2012).

Perhaps the single strongest factor influencing the biodiversity of benthic communities is the increased prevalence of oxygen-depleted (hypoxic) bottom water due to eutrophication (Di´az and Rosenberg, 2008). Typically, hypoxia is defined as the oxygen concentration range between 0 and 2.8 mg L -1 (Diaz & Rosenberg 1995, Vaquer-Sunyer and Duarte 2008). Hypoxia develops as the increased biomass on the seabed degrades in chemical and biological consumption processes and due to the increased metabolisation of the increased abundance of benthic consumers (reviewed by Korpinen & Bonsdorff 2015). The hypoxic sediments also continuously release sediment bound phosphates to the water column (HELCOM, 2009). In modern times, most of the deep sub-basins of the Baltic Sea are continuously hypoxic. (Karlson et al., 2002; Conley et al., 2009a). Seasonal hypoxia is found in some of the shallower gulfs, while the northernmost sub-basins are well oxygenated due to lower nutrient inputs (HELCOM, 2009). A more severe condition of hypoxia is anoxia, which means lack of oxygen (0 mg L-1). Anoxic conditions result in the formation of hydrogen sulfide (H2S), which is lethal to higher organisms (reviewed by Korpinen & Bonsdorff 2015).

Eutrophication in shallow, coastal bays causes a shift in dominance from seagrasses and perennial macroalgae to ephemeral macroalgae and epiphytes, and ultimately to phytoplankton dominance in the most heavily eutrophied systems (Dahlgren and Kautsky 2004; McGlathery et al. 2007). The shift from large phytobenthos to filamentous algae and/or phytoplankton means a loss of a benthic biogenic habitat, loss of nutrient transfer from water column to seabed and loss of retention of nutrients in sediment (Cloern 2001). The filamentous algae may detach and cover large areas of seabed. The algal mats consume oxygen from the underlying seabed and can decrease light levels by similar magnitudes or higher as epiphytes (Norkko and Bonsdorff 1996; Sundbäck and McGlathery 2005).

High mortality of benthic fauna has been found from areas affected by the loose-lying algae (Norkko and Bonsdorff 1996), although the algae can also provide an alternative habitat to a variety of invertebrate species (Salovius et al. 2005). A reduction of bioturbation by benthic fauna may decrease the natural purification capacity and increase the internal nutrient loading of sediments (Karlson et al. 2007). Benthic ecosystem functionality has been shown to change in threshold-like shifts which take place when species tolerance levels are exceeded

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(Villnäs et al. 2012). In the Baltic Sea, where anoxia and hypoxia are more or less permanent features at present, macrobenthic communities in deeper water are never fully developed due to low oxygen concentrations and are characterised by small shallow-dwelling species (Rumohr et al. 1996; Bonsdorff 2006; Villnäs and Norkko 2011). Macrobenthic communities in deeper waters are severely degraded and below a 40-year average for the entire area. Changes in the macrozoobenthos alter food availability for demersal fish (HELCOM 2010).

Mobile species, such as fish and invertebrates, tend to move away from areas of low dissolved oxygen (reviewed by Craig et al. 2001). Lower trophic-level organisms may, however, decrease activity or change behavior when exposed to low dissolved oxygen, possibly to conserve energy until levels increase again (Sandberg 1994). Some species are able to use alternative breathing modes when subjected to low dissolved oxygen that may be ecologically costly or physiologically less efficient. Increased energy requirements for the maintenance of metabolism may impact growth, reproduction and ecological performance. (reviewed by Korpinen & Bonsdorff 2015.)

Climate change is predicted to increase the occurrence of hypoxia in the Baltic Sea as a response to higher water temperatures (increased metabolisation, lower oxygen saturation), increased stratification due to higher freshwater runoff and increased runoff of organic matter and nutrients from catchment areas (Meier et al., 2011). Repeated hypoxic events enhance eutrophication with positive feedback mechanisms and make the system susceptible to further hypoxia (Conley et al., 2009b). Hypoxia is related to nutrient inputs in a nonlinear way with a threshold and hysteresis can arise, reducing the chance of a return to the original status (Conley et al., 2009b)

2.2.2. Hazardous substances

Thousands of environmentally hazardous substances have been identified as potentially occurring in the Baltic Sea (HELCOM 2018d). Hazardous substances are introduced to aquatic ecosystems via many routes, e.g. effluent discharge, disposal, nonpoint sources, contaminant spills or airborne deposition (Burton (ed.) 1992). The most harmful substances are persistent, toxic and accumulate in biota (HELCOM 2018d). Sediments can serve as both sinks and sources of these contaminants (Burton (ed.) 1992).

There are three potential sources/paths for contaminants to reach benthic organisms: the sediments themselves (e.g., ingestion), overlying water, and pore water (e.g., across respiratory surfaces and across body walls). In general, sediment-sorbed contaminants are more persistent, less mobile, and occur at higher concentrations than those in the overlying waters. However, not all benthic organisms ingest sediments, and the major source of organic chemicals for many is primarily interstitial water or water at the sediment-water interface. (Burton (ed.) 1992.)

The role of bioavailability of the contaminants is highly important: even relatively high levels of contamination may be of little biological significance if bioavailability is limited (Payne et al. 1988). On the other hand, sediment contaminant mixtures can produce toxic effects that are different from those of the individual contaminants (Burton (ed.) 1992).

Hazardous substances in the sediments can have both immediately lethal and long-term deleterious effects (Burton (ed. 1992). Many of the hazardous substances can cause metabolic disorders (Vuori 1994), increase in disease prevalence (McDowell et al. 1999), and, potentially, effects on populations through changes in growth (Suedel et al. 1996), reproduction (Sundelin & Eriksson 1998, Matthiessen & Gibbs 1998), or survival (Suedel et al. 1996). Many contaminants degrade slowly, and their impacts can magnify as they bioaccumulate in body tissues and enter the aquatic food web (Helcom 2018d).

HELCOM monitors hazardous substances in the Baltic Sea in three types of matrices: biota, water and sediment. Each of these has specific threshold values defined for each substance (or substance group) (HELCOM 2018d). Some hundreds of substances are regularly monitored. A subset of these is represented in the core indicators that can be found in the ‘Thematic assessment of hazardous substances 2011–2016’ –report (HELCOM 2018d).

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2.4 Marine litter

Marine litter comprises a wide range of materials such as glass, metal, wood, rubber and plastics. Litter can be transported over long distances in the sea by winds and water currents (Eriksen et al. 2014), and it often accumulates on the seafloor, far away from its original source (Derraik 2002). Hence, multiple sources can contribute to seafloor litter. However, items associated with maritime activities are a major component. So called ‘ghost nets’, which are defined as abandoned, lost, or otherwise discarded fishing gear, pose an especially large risk to marine life since they continue trapping marine life over long timeframes (WWF Poland 2015).

Seafloor litter has been surveyed in the Baltic Sea under the BITS (Baltic international trawl surveys) monitoring program during the years 2012-2016. The monitoring was carried out in connection to fish trawling surveys, by counting litter caught in the fish trawl. The survey provides an indication of litter on the seafloor but does not cover shallow water areas or complex substrates, and not all parts of the Baltic Sea (Nilsson 2017). The average total number of seafloor litter items was 58.9 ± 20.9 items per km2 (average ± 95 confidence interval). The average total weight of items was 85.3 ± 65.2 kg per km2 (average ± 95% confidence interval). Items made of natural materials were most common both in terms of number of items (44.6%) and in terms of weight (56.6%). Plastic was the second most common material (30.6 % of number of items, 15.7 % of the weight) (Nilsson 2017).

In a study by Urban-Malinga et al. (2018), marine litter occurrence and composition on the seafloor were investigated in the Polish Maritime Areas (the southern Baltic Sea). Litter densities between 0 – 2.23 items per ha with a mean of 0.20 items/ha (SD = 0.30) were found. Overall, plastic was the most common litter type (67% of all items) found. The results were considered to be low compared to litter densities reported from other shelf habitats worldwide at similar water depths (Urban-Malinga et al. 2018). Another study by Galgani et al. (2000) found 1.26 litter items per ha (st. dev. 0.82) on the seafloor. Plastic litter densities were 0.45 items/ha (st. dev. 0.29) (Galgani et al. 2000).

Anthropogenic debris, in particular plastic, affects marine organisms in many ways. The most visible effect of plastic pollution on marine organisms is the entanglement of organisms in plastic litter. Entangled biota are hindered in their ability to move, feed and breathe. (Schrey & Vauk 1987, Carr 1987). In addition, many marine organisms ingest litter. The ingestion of larger plastic items represents a serious threat and affects the condition of animals negatively by e.g. leading to internal blockage of the digestive tract (Foekema et al., 2013).

The discovery of microplastics in marine ecosystems has added concern, as microplastics have been found in the GITs of marine organisms in several studies (e.g. Lusher et al. 2013, Rummel et al. 2016, Foekema et al. 2013). The measurement of plastic-related mortality is difficult in the natural environments because disabled or dead animals are likely to be consumed by predators or decompose rapidly (Laist 1987). Laboratory results suggest, however, that the impact of microplastics on animals could be significant given that microplastics may contain contaminants (e.g. phthalates) (Mato et al. 2001, Thompson et al. 2007, Talsness et al. 2009) and they also have the ability to adsorb contaminants (e.g. lead, aluminum, cadmium) from the seawater (Rochman et al. 2014). Microplastics have also been found to enter the food chain at lower trophic levels (Setälä et al. 2014).

In addition to the issues of entanglement and ingestion, synthetic materials represent a long-lived substrate that may present the possibility of transporting non-indigenous species horizontally to ecosystems elsewhere or vertically from the sea surface through the water column to the seafloor. Plastics may also smother sea bottoms where effects may range from suffocating organisms to offering new habitats for species that are otherwise unable to settle (reviewed by Kühn et al. 2015).

Currently, there is only a limited amount of data available concerning litter on the Baltic Sea bottom. The most obvious problem of representativeness are the areas where fish survey trawling does not occur at all presently, i.e. mainly north and east of the current geographical scope of the BITS program, and in coastal shallow areas. There are several alternative solutions to trawl surveys for monitoring litter on the seafloor, including scuba surveys, ROVs, or video surveys. Several countries (e.g. Finland) have done pilot surveys for this particular purpose or included monitoring for seafloor litter in surveys conducted for the purpose of habitat mapping. The results from such alternative methods are difficult to include in a common statistical analysis with trawl survey

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data, as the methods differ so much in terms of temporal/spatial scope. However, it may be important to start a discussion on the possibility of using similar (compatible) protocols for shallow-water surveys in different HELCOM countries (Nilsson 2017).

2.5 Biological pressures

Non-indigenous species

Non-indigenous species (NIS) are species that have spread or been transferred as a result of human activities, reaching environments in which they previously did not naturally occur. Not all NIS are invasive, i.e. not all NIS spread to a degree to cause damage to the environment, human economy or human health (HELCOM 2018c). However, some of the most successful NIS tend to markedly alter the habitats they invaded or were intentionally introduced to (Olenin & Leppäkoski 1999).

The most probable vectors for NIS into the Baltic Sea are aquaculture and shipping (Galil et al. 2014). Furthermore, the openings of connections to different river systems created by canals are important vectors for dispersal, and many Ponto-Caspian species have found new routes to the Baltic Sea in this way (HELCOM 2018c).

Established NIS may influence the biodiversity and ecosystem in different ways, and their effects are often difficult to foresee (HELCOM 2018c). A species does not ‘carry’ its niche with it but may develop a different realised niche in its novel environment, as a response to new ecological conditions (Herbold & Moyle 1986; Leppäkoski, 1994). The invasion of some successful NIS has resulted in major changes in community structure and functional biodiversity of the receiving ecosystems of the most intensively inoculated recipient regions, such as the coastal lagoons (at least in the south-eastern Baltic), in which entire food chains can be based on alien organisms (Leppäkoski, 1984).

Depending on their feeding/mobility status, the benthic non-indigenous animals can alter physical and chemical characteristics of bottom sediments in different ways. Surface deposit feeders collect food particles deposited on the bottom sediment, and thus change the sediment surface by feeding and crawling on it. Filter feeders add new material to the sediment (biodeposition). Mechanical and chemical properties of a habitat may be extensively modified by animals burrowing within the sediment; by production of pellets; by construction of sandy and muddy tubes within, and/or on, the sediment; by fluid transport when burrowing or irrigating/ventilating holes and burrows of benthic invertebrates. (Lee & Swartz 1980). Furthermore, non-indigenous benthic animals may alter the physical and chemical structure of the sediment by producing calcareous shells and trapping particles (Olenin & Leppäkoski 1999).

Besides active biodeposition, a mechanical trapping and accumulation of seston particles is also an important source of new material introduced by benthic species into their environment. Trapping and biodeposition result in increasing eutrophication of the semienclosed systems but decrease the outflow of organic loading from them into the Baltic. These novel functions modify the assimilative capacity of coastal waters and affect their important role as metabolic converters, or huge ‘treatment plants’, processing both material and energy at interfaces between land/sea and water/bottom (Olenin & Leppäkoski 1999).

Around 140 NIS or species with unknown means of arrival have so far been recorded in the Baltic Sea (HELCOM 2018c). HELCOM has assessed the number of new introductions to the Baltic Sea region during the assessment period of 2011-2016. During this period, twelve species arrived as new NIS in the Baltic Sea. The agreed threshold value for good status is zero new introductions of NIS due to human activities. Hence, the core indicator fails the threshold value for good status during 2011-2016. (HELCOM 2018c.)

Once a NIS has become established and spread to a wide area, eradication is not a viable management option. Full recovery in the sense of returning to the previous state is not possible. Hence, management should primarily aim to prevent further introductions, along with minimizing the negative effects of the already introduced NIS (HELCOM 2018c).

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3 The sensitivity of habitats

To assess the condition of seabed habitats, the understanding of the impacts affecting to the state is in vital role. Here, components affecting sensitivity as well as different sensitivity assessments will be presented and discussed.

3.1 Components affecting sensitivity

The sensitivity of a species or a habitat to a pressure is a product of- resistance: the ability of a receptor to tolerate a pressure without changing its characteristics and- resilience: the rate of or time taken for recovery once the pressure has abated or been removed (Tyler-

Walters et al. 2018, ICES 2019b).

Resistance (also referred to as fragility) depends on the organism’s physiology and/or structure including strength or flexibility as well as the intensity of the impact (MacDonald et al. 1996).

Resilience (recovery) incorporates several concepts: - the ability of damaged organisms to repair or regenerate lost or damaged parts;- the ability of the organisms to continue occupying the disturbed habitat;- the supply of larvae to the disturbed habitat and their settlement success; - recruitment to the adult population from settled larvae; slow recruiting animals are considered to be

more susceptible to disturbance than species with high recruitment rates (MacDonald et al. 1996.)

The terms resistance and resilience are both related to the longevity of the community (Rijnsdorp et al. 2018). Longevity refers to the lifespan of species and communities. A habitat will be more sensitive to pressures, e.g. trawling, if a large fraction of the biomass of the community is made up of long-lived organisms compared to a community which is made up of short-lived organisms. (ICES 2019b.) Resistance will be negatively related to longevity, because longer lived taxa are likely to be larger and are more likely to build biogenic structures, ‐enhancing their mortality rate to physical disturbance. Resilience is expected to be negatively related to longevity, as long lived species start reproducing later in life and have a lower population growth rate. (reviewed by ‐Rijnsdorp et al. 2018.)

Differences in the longevity distribution of benthic communities are likely to be related to the environment they live in. Habitats with high levels of other disturbance, for example by waves or hypoxia, are likely to have a low fraction of long-lived species as these disturbances will have already led to the loss of such species and are instead dominated by short-lived fauna. As a result, communities in high natural-disturbance environments with shorter-lived fauna will be less sensitive to anthropogenic disturbance (reviewed by ICES 2019b.)

As benthic functional groups differ in their longevity composition, a comparative analysis of the longevity compositions can be used to determine which ecological functions are most sensitive to disturbance. The results by Rijnsdorp et al. (2018) show that bioturbators have a higher median longevity than suspension feeders suggesting a higher sensitivity for disturbance.

Although resistance and resilience as well as longevity affect sensitivity, other factors may also have an influence and in some cases the different components of overall sensitivity may not be well known (Korpinen et al. 2016?). The sensitivity of a habitat is dependent on the sensitivity of the species that make up the community, together with the hydrographic, physical or chemical nature of the habitat. (Tyler-Walters et al. 2018.) In addition, seasonality can affect the sensitivity of species and habitats. For example, during the breeding time a species may be highly affected by pressures occurring near the breeding area, whereas the impact may be smaller during other times of the year (Korpinen et al. year?). Also, the mobility of the species affects sensitivity. For example, in areas affected by short-term disturbance the abundances of mobile species such as Hediste diversicolor and

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Hydrobia ulvae have been found to be within the range of natural variability, while the distribution of bivalves in the same areas were altered (Rossi et al. 2007).

3.2 Sensitivity assessments

To combine the resistance and resilience as single sensitivity value, a meaningful index of sensitivity must be based upon consistent assessment of each of the factors discussed above and in relation to the human activity that might impact upon it. For example, a species may be very sensitive to damage from physical disturbance but be tolerant of some form of localized pollution, such as nearby fish farm effluent (MacDonald et al. 1996).

Sensitivity of benthic biota and habitats for different pressures have been assessed in several Baltic wide projects. In the HELCOM TAPAS project, an expert survey and a literature review were utilized and combined in order to develop sensitivity scores for habitats and species and to arrive at reliable and evidence-based sensitivities. The scores range from 0 (low sensitivity) to 1.0 (intermediate sensitivity) and 2.0 (high sensitivity). The sensitivity scores of the benthic habitats and species in the Baltic Sea, modified from the TAPAS results, are presented in table 1.

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Sensitivity scores: average

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1. Infralittoral hard bottom 2,0 1,6 1,2 0,2 0,2 0,6 1,3 1,5 1,3 0,4 1,7 0,4 1,7 0,3 0,6 0,7 1,1 1,4 1,12. Infralittoral sand 2,0 1,5 0,9 0,3 0,3 0,5 1,0 1,5 1,3 0,2 1,4 0,3 1,7 0,3 0,3 0,7 0,9 0,7 0,93. Infralittoral mud 2,0 1,4 1,1 0,3 0,3 0,6 1,0 1,5 1,3 0,4 1,4 0,4 1,9 0,4 0,3 0,7 0,9 0,8 0,94. Circalittoral hard bottom 2,0 1,6 1,4 0,3 0,3 0,6 1,2 1,5 1,3 0,5 1,3 0,4 1,9 0,4 0,8 1,0 1,2 1,5 1,45. Circalittoral sand 2,0 1,4 1,1 0,2 0,3 0,5 0,7 1,5 1,2 0,2 0,9 0,3 1,8 0,3 0,3 0,7 1,0 0,7 0,96. Circalittoral mud 2,0 1,3 1,3 0,3 0,3 0,8 0,9 1,5 1,2 0,5 1,1 0,5 1,7 0,4 0,6 0,5 0,9 0,7 1,07. Furcellaria lumbricalis 2,0 1,7 1,7 0,2 0,3 0,6 1,5 1,5 1,5 0,5 1,5 0,3 1,6 0,6 0,7 0,7 0,8 1,1 0,78. Zostera marina 2,0 1,9 1,7 0,2 0,1 0,5 1,6 1,5 1,9 0,6 1,6 0,4 2,0 1,2 0,9 0,8 0,7 1,0 0,69. Charophytes 2,0 1,9 1,4 0,0 0,0 0,6 0,9 1,5 1,7 0,4 1,5 0,3 1,8 0,7 0,8 0,7 0,9 0,7 0,610. Mytilus edulis 2,0 1,6 1,6 0,2 0,1 0,5 1,0 1,5 0,9 0,5 1,6 0,5 1,5 0,4 0,4 0,2 0,9 1,1 0,911. Fucus sp. 2,0 1,7 1,3 0,3 0,3 0,5 1,5 1,5 1,3 0,5 1,4 0,4 1,7 0,6 0,5 0,3 0,8 1,1 0,512. Sandbanks which are slightly covered by sea water at all time (1110) 1,9 1,6 1,3 0,2 0,2 0,5 0,9 1,5 1,5 0,4 1,5 0,6 1,9 1,1 0,9 1,0 0,9 0,8 0,613. Coastal lagoons (1150) 1,9 1,7 1,6 0,7 0,8 0,6 1,3 1,5 1,5 0,2 1,7 0,6 1,7 1,0 1,1 0,6 1,4 1,3 1,014. Large shallow inlets and bays (1160) 1,8 1,6 1,3 0,8 0,9 0,8 1,2 1,5 1,3 0,2 1,6 0,6 1,5 0,9 1,1 0,7 1,3 0,9 1,015. Reefs (1170) 2,0 1,6 1,4 0,3 0,3 0,6 1,0 1,5 1,3 0,6 1,9 0,7 1,7 0,8 0,9 1,1 1,2 1,2 0,916. Submarine structures made by leaking gas (1180) 1,7 1,2 1,3 1,0 1,0 1,0 1,0 1,5 1,6 0,5 1,8 0,7 1,6 1,0 0,8 1,5 1,4 1,0 2,017. Cod abundance 1,0 0,7 0,4 0,2 0,9 0,5 0,7 1,6 1,5 0,6 0,5 0,2 1,1 0,9 1,6 0,7 0,6 1,1 0,318. Herring abundance 0,9 0,7 0,7 0,6 1,1 0,5 0,6 1,6 0,7 0,3 0,9 0,1 0,2 0,4 1,2 0,2 0,6 1,0 0,619. Distribution of demersal spawning flounder 1,7 1,3 0,8 0,2 0,7 0,6 0,7 1,6 1,6 0,5 1,3 0,4 0,8 1,0 1,8 0,3 0,9 1,4 1,020. Abundance of pelagic spawning flounder 1,0 0,8 0,9 0,3 0,7 0,6 0,8 1,6 1,3 0,4 1,1 0,3 0,7 0,9 1,8 0,0 0,8 0,8 1,021. Recruitment areas of perch 1,8 1,6 1,2 0,4 0,9 0,7 0,4 1,6 1,4 0,4 1,6 0,4 1,0 1,3 1,6 0,0 1,0 0,5 1,322. Recruitment areas of pikeperch 1,8 1,4 1,2 0,6 1,1 0,7 0,3 1,6 0,7 0,5 1,7 0,3 0,9 1,0 2,0 0,5 0,9 0,3 1,0

23. Recruitment areas of roach 1,8 1,5 1,2 0,6 1,0 0,4 0,3 1,6 0,5 0,5 1,7 0,4 0,9 0,8 1,6 0,5 0,9 0,3 1,0

15

Table 1. Sensitivity scores of the benthic habitats and species in the Baltic Sea based on literature review and expert survey (modified from Korpinen et al. year?).

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Sensitivities of the Baltic Sea biota and habitats have also been evaluated using the Symphony method which is a model-based assessment method developed to support ecosystem-based marine spatial planning in Sweden. The information in Symphony is based on mainly Swedish data.

The Symphony’s sensitivity categories for ‘species, population or group’ as well as for ‘habitat’ are presented in table 2.

Table 2. The Symphony’s sensitivity categories of ‘species, population or group’ as well as ‘habitat’ (adopted from Hammar et al. 2018)

Value Criteria for a species, population or group Criteria for a habitat

-0,2 Positive effect0 No impact or negligible impact No impact or negligible impact0,2 Stress only from the cumulative perspective Minor disturbance, only from the

cumulative perspective0,4 Stress regarding survival or reproduction Disturbance regarding survival or

reproduction0,6 Severe stress or certain direct mortality Severe disturbance or certain direct

destruction of the habitat0,8 Substantial direct mortality Substantial direct destruction of habitat1,0 High mortality Permanent destruction of habitat

The sensitivity scores of different species, populations or groups and habitats in the Baltic Sea according to the Symphony will be included HERE (modified from Hammar et al. 2018).

The fragility of benthic biota has been included also in the Biological Traits Information Catalogue (BIOTIC) which is a tool for data analyses within the field of benthic community ecology. The BIOTIC database has been developed by the Marine Life Information Network (MarLIN) in collaboration with MBA scientists and Plymouth Marine Laboratory. The database contains information on over 40 biological trait categories on selected benthic species. The emphasis is on benthic invertebrates and plants. Users can browse the species list or search for information by specific categories of biological trait. The BIOTIC allows benthic data to be analysed not only on a taxonomic level but also on a functional level. (MarLIN 2006.)

Another tool developed by MarLIN is the Marine Evidence based Sensitivity Assessment (MarESA). The MarESA methodology provides a systematic process to compile and assess the best available scientific evidence to determine each sensitivity assessment. The evidence used is documented throughout the process to provide an audit trail to explain each sensitivity assessment. This means that the MarESA assessments can be repeated and updated. (Tyler-Walters et al. 2018.) The MarESA methodology is described in more detail in the guide by Tyler-Walters et al. (2018). The sensitivity descriptions of different habitats and species are available on the MarESA webpage under ‘Sensitivity’.

The tools provided by MarLIN have been applied to benthic species and habitats in the UK and Ireland. Thus, the BIOTIC database and the MarESA methodology should be used with deliberation in the Baltic Sea area, taking the local differences into account.

4 Approaches to assess adversely affected habitats

4.1 Definition of adversely affected habitats

The adverse effects on habitat condition is described in the MSFD as “alterations in its biotic and abiotic structure and its functions”. The term ‘adversely affected habitat’ has been further defined in the HELCOM SPICE project.

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The SPICE project noted that adversely affected habitats can be defined from at least the following three perspectives: (Virtanen et al. 2017)

a) GES status of predominant fauna or flora of the habitat : this approach builds on the available state indicators such as benthic invertebrate indices and macrophyte indicators, which have GES thresholds. These thresholds are already established under other regimes, such as the EU Water Framework Directive (WFD), the EU Habitats Directive or HELCOM core indicators. A habitat status can be assessed by the state indicator alone, but also from the pressure point of view. The intensity of pressure causing the adverse effect can, in principle, be found from the pressure – status correlation (reviewed by Virtanen et al. 2017).

b) State of fauna or flora (not established indicators): biological state parameters can show significant reductions in extent, abundance or condition which are caused by increased pressures. As no GES threshold has been established, the link to the pressure must be shown and the adverse effect is defined from that correlation. The state of the habitat can, however, be assessed either from the pressure or state point of view.

c) Physical or chemical indicators (with GES threshold) or parameters (without a threshold) reflect the living conditions of the predominant fauna or flora of a habitat. A threshold can be found in values where the conditions start deteriorating. These conditions need to be shown to affect the state indicators and they need to be caused by anthropogenic pressures.

4.2 Thresholds for the assessment of habitatsThere should be a story about why we need tresholds and where can we find them? The respective spatial distance thresholds or temporal exposure thresholds to benthic habitats still require more work in order to obtain encompassing thresholds for the entire Baltic Sea area.

Species- and habitat-specific thresholds for different pressures causing 'adverse effects' have been proposed in the HELCOM SPICE project. Table 3 presents the oxygen concentrations (mg O2 L-1) for the Baltic Sea species which were considered as thresholds for the HUB biotopes based on a literature review. For some species no threshold was available, but LT50 values which indicate the survival time for 50% of the population (Virtanen et al. 2017).

Table 3. Sensitivity of benthic species to oxygen concentration. Adopted from Virtanen et al. (2017).

Table 4. Sensitivity of benthic species to oxygen concentration. The affected species is linked to a habitat type, if it is considered as a predominant or significant element of the habitat. The threshold (or its range) is justified by literature reference and explanation how the species is affected. For each species a single threshold (or range) is identified.

Threshold (mg O2 L-1)

Affected species

Literature reference and arguments Affected broad habitat type HUB habitat code

2.8 mg L-1 Macoma balthica

Constant hypoxia (0.5-0.8mg L-1) reduced the number of individuals significantly, but weekly pulses of hypoxic (0.5-0.8 mg L-1) water did not increase mortality (Modig & Olafsson 1998)

Infralittoral muddy habitats, Infralittoral sandy habitats, Circalittoral muddy habitats, Offshore circalittoral muddy habitats, Circalittoral sandy habitats, Offshore circalittoral sandy habitats

AA.H3L1, AA.J3L1, AA.J3L9, AB.H3L1, AB.J3L1

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2.96 mg L-1

(sublethal effects)

Zostera marina

Pedersen et al. 2004 Infralittoral muddy habitats, Infralittoral coarse sediment habitats, Infralittoral sandy habitats, Infralittoral mixed sediment habitats

AA.H1B7, AA.I1B7, AA.J1B7, AA.M1B7

0.57 mg L-1

(sublethal effects)

Cyanea capillata

Rutherford and Thuesen 2005 Photic habitat above halocline AD.N5

0.57 mg L-1

(sublethal effects)

Mya arenaria

Jorgensen 1980; Mya arenaria LT50 (under 2 mg O2 L-1) is 504 hours (Theede 1969).

Infralittoral sandy habitats, Circralittoral sandy habitats

AA.J3L4, AA.J3L9, AB.J3L4, AB.J3L9

0.57 mg L-1

(sublethal effects)

Abra alba Jorgensen 1980; Infralittoral muddy habitats AA.H3L8

0.57 mg L-1

(sublethal effects)

Cerastoderma edule

Jorgensen 1980; C. edule LT50 (under 2 mg O2 L -

1)102 hours (Theede 1969).Infralittoral sand, Circalittoral sand

AA.J3L2, AA.J3L9, AB.J3L9

0.57 mg L-1

(sublethal effects)

Hydrobia ulvae

Jorgensen 1980 Infralittoral rocky habitats, Infralittoral hard clay habitats, Infralittoral coarse sediment habitats, Infralittoral sandy habitats, Infralittoral mixed sediment habitats, Circalittoral rocky habitats

AA.A1V, AA.I2W, AA.B1V, AA.K, AA.M2W, AB.A1V, AB.A2T

1.43 mg L-1

(sublethal effects)

Carcinus maenas

Renaud 1986 All types of infralittoral habitats All AA-HUB biotopes

2.9 mg L -1

(for survival)

Harmothoe sarsi

Field sampling (Witek 1993) Circalittoral muddy habitats, Offshore circalittoral muddy habitats,

AB.H3L1

3.90 mg L-1

(sublethal effects)

Monoporeia affinis (Pontoporeia femorata was more sensitive but no threshold was found)

Experiment, >80% survival >2 mg L-1, after 24 d (Johansson 1997, Goedkoop & Johnson 2001). Weekly pulses of hypoxic (0.5-0.8 mg L-1) water killed (Modig & Olafsson 1998)

Infralittoral muddy habitats, Circalittoral muddy habitats, Offshore circalittoral muddy habitats, Circalittoral sandy habitats, Offshore circalittoral sandy habitats. Salinity up to 18 (Cedervall 1977)

AA.H3N1, AB.H3N1, AB.J3N1

<1 – 2 mg L-1

Gmelinoides fasciatus

Berezina et al. 2013 Gulf of Finland sediments in up to 2 (but likely 5) salinity (Berezina 2007)

?? Halicryptus spinulosus

Survived 2 months in hypoxia (0.5-0.8 mg L-1), but with high mortality; older individuals are more tolerant (Modig & Olafson 1998).

Infralittoral muddy habitats, Infralittoral sandy habitats, Circalittoral muddy habitats, Offshore circalittoral muddy habitats, Circalittoral sandy habitats, Offshore circalittoral sandy habitats.

AA.H3, AA.J1, AB.H3, AB.J1

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?? Ostracoda, Nematoda, Oligochaeta and Turbellaria

Survived 2 months in hypoxia (0.5-0.8 mg L-1), but with high mortality (Modig & Olafson 1998).

1.25 mg L-1

(sublethal effects)

Saduria entomon

Johansson 1997 Circalittoral sandy habitats AB.J3N1

2.58 mg L-1

(sublethal effects)

Crangon crangon

Sandberg et al. 1996 Infralittoral sandy habitats AA.J

4.5 mg L-1

(sublethal effects)

Salmo salar

Kutty and Saunders 1973

3.22 mg L-1

(sublethal effects)

Esox lucius

Siefert et al. 1973

0.52-2.78 mg L-1

(LT50)

Gadus morhua

Schurmann and Steffensen 1992, Plante et al.1998,

2.65 mg L-1

(LT50)Rhithropanopeus harrisii

Stickle et al. 1989

Hediste diversicolor

LT50 (under 2 mg O2 L-1) of 14 hours, 105 hours and 120/192 hours for postlarval, juvenile and adult stages respectively (Henriksson 1969, Theede 1969, Gamenick et al. 1996)

Infralittoral sand, Circalittoral sand, Offshore circalittoral sand

AA.J3M4, AB.J3M4

Capitella capitata

LT50 (under 2 mg O2 L-1)of 312 hours (Rosenberg 1972)

Infralittoral muddy habitats AA.H3M, AA.H3M5

Arenicola marina

LT50 (under 2 mg O2 L-1)of 398 hours (Groenendaal et al. 1980)

Infralittoral sandy habitats AA.J3M2

Scolops armiger

LT50 (under 2 mg O2 L-1)of 46 or 120 hours (Henriksson 1969, Schöttler and Grieshaber 1988)

Infralittoral muddy habitats, Circalittoral muddy habitats, Offshore circalittoral muddy habitats

AA.H3M, AA.H3M5, AB.H3M1,

Corophium volutator

LT50 (under 2 mg O2 L-1)of 4-42 hours (Gamble 1970, Gamenick et al. 1996)

Infralittoral muddy habitats AA.H3N2

Idotea baltica

LT50 (under 2 mg O2 L-1)of 2-6 hours (Vetter et al. 1999)

Infralittoral rocky habitats AA.A1C1, AA.A1C4

Gammarus oceanicus

LT50 (under 2 mg O2 L-1)of 15 hours (Theede et al. 1969)

Infralittoral rocky habitats AA.A1C1, AA.A1C2, AA.A1C3, AA.A1C4, AA.A1C5

Chironomus plumosus

LT50 (O2 deficiency) of 200 days (Nagell 1978) Infralittoral muddy habitats AA.H3C1

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-t.

Marenzelleria viridis

LT50 (O2 deficiency) 4-11 hours for larvae, 23 hours for juveniles and 100-300 hours for adults (depending on salinity) (Fritzsche and Von Oertzen 1995). High tolerance to low oxygen and anoxia (Schiedek 1997).

Infralittoral muddy habitats, Circalittoral muddy habitats, Offshore circalittoral muddy habitats

AA.H3M, AA.H3M3, AB.H3M, AB.H3M3

HELCOM SPICE project’s proposals for pressure thresholds (or ranges) are available also for:

- sensitivity of benthic species to hydrogen sulphide concentrations (µmol L-1 in sediment) in the Baltic Sea- different pressures (e.g. turbidity, nutrients, hypoxia) correlating with the benthic indices and- sensitive and tolerant macrophyte species in the Northern Baltic Sea.

4.3 HELCOM indicators for assessing benthic habitats The state of benthic habitats has been assessed by HELCOM (2018e) based on the biodiversity core indicator ‘State of the soft- bottom macrofauna community’. This indicator evaluates the status of the environment using an index developed to show changes in the relative abundance of sensitive and tolerant species, as well as the diversity of the community in soft sediments.

The evaluation is done using a method based on the Benthic Quality Index (BQI), where the abundance weighted proportion of sensitive to tolerant taxa and the diversity of the community are the determining parameters. In general terms, the higher the proportion of sensitive taxa and the higher the number of different species, the better the environmental status is evaluated to be. (HELCOM 2018e.)

The indicator only represents the areas above the permanent halocline (< 60m depth). The indicator is not used in coastal areas which are assessed by national methods or in areas below the halocline where the eutrophication core indicator ‘Oxygen debt’ was used in order to give information on living conditions for macrofauna in deeper areas.

Currently, the indicator ‘State of the soft- bottom macrofauna community’ is operational only in a part of the Baltic Sea due to the lack of agreed threshold values in some assessment units. The current results should thus be considered as intermediate. No threshold value has been agreed for the following open sea assessment units: Kattegat, Great Belt, the Sound, Arkona Basin, Bornholm Basin and Gdansk Basin. The indicator is in principle applicable in these areas, and further work for these assessment units is underway. (HELCOM 2018e.)

The current evaluation spans the years 2011 – 2016 and is based on monitoring data reported by HELCOM Contracting Parties. The status of the indicator ‘State of the soft- bottom macrofauna community’ is good in all assessed sub-basins, except the Bay of Mecklenburg (HELCOM 2018e). The indicator ‘Oxygen debt’ does not achieve the threshold value in any of the assessment units where it is included (HELCOM 2018f). Coastal areas have good integrated status in around half of the area that was assessed, measured by area covered, or in 39 out of 128 assessed units (HELCOM 2018g).

A more detailed description of the in indicator ‘State of the soft- bottom macrofauna community’, including the thresholds and the assessment protocol, is available from the Core indicator report: HELCOM 2018e and a more detailed description of the indicator ‘Oxygen debt’ is available from the Core indicator report: HELCOM 2018f.

The applied indicators are biased towards addressing impacts from eutrophication, and the assessment may overlook the influence of other pressures on benthic habitats, e.g. physical loss and disturbance. HELCOM is currently developing a core indicator on ‘Condition of benthic habitats’ aiming to evaluate the area, extent and

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quality of specific benthic habitats in relation to a quantitative threshold value and on ‘Cumulative impact on benthic biotopes’ to assess adverse effects from physical disturbance. (HELCOM 2018g.)

4.4 Cross-comparison of environmental assessments and pressures

Adversely affected habitats can sometimes be assessed through cross-comparison with xxxx. In the HELCOM SPICE project, a cross-comparison of different environmental pressure and impact datasets was made against the EU Water Framework Directive (WFD) and the HELCOM HOLAS II status assessments. Furthermore, the correlation between different marine environmental status assessments was assessed. (Herkül & Martin 2017.) The data used for cross-comparisons are from HELCOM HOLAS II project and WFD assessments. HELCOM HOLAS II assessment results and pressure datasets were available as georeferenced layers in geographical information system (GIS) and the WFD assessment results were available in a table format with identification column that enabled to join the assessment results with national GIS layers of coastal water bodies. The spatial extent of the data included only the marine waters of Sweden, Finland, and Estonia. All input data of the assessment results and pressures were compiled using the 1 km European Environmental Agency grid (EEA grid). The values of all assessment results and pressures were extracted for each EEA grid cell (n = 282604) and this data set served as the main input for the further analyses. More details about the procedure is available in (Herkül & Martin 2017).

With only a few exceptions, all status assessments were statistically significantly correlated to pressures (figure 4). Negative correlations showed higher (better) status related to lower pressures. Positive correlations showed higher (better) status related to higher pressures. (Herkül & Martin 2017.) This means that the assessment of pressures can already indicate the relative status of the environmental component.

WFD assessment results (pooled data from Sweden, Finland, Estonia) were negatively correlated with pressures except the chemical status that was positively correlated with pressures. The correlations were low or non-significant in WFD zoobenthos. Among HOLAS assessments, the benthic habitat status negatively correlated with pressures while the other HOLAS statuses had mostly no or positive correlations with pressures (Figure 4).

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Herkül & Martin (2017) presented also more detailed information on the relationships between status classes and pressure inputs. The more detailed results from WFD status assessments versus different pressures and from the HOLAS benthic habitat status assessments versus different pressures are included in Annex 1.

Herkül & Martin (2017) noted that the status assessment results were statistically significantly correlated with each other with only a single exception of WFD chemical status and WFD zoobenthos status that were not

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Figure 4. Correlations between assessments (vertical axis) and pressures (horizontal axis). Colors and circle diameters signify the Spearman rank correlation coefficients. Numbers show the p-values in cases where p > 0.05. Dots represent cases where data was not available or there was no variation in the data. Negative correlations show that higher (better) status is related to lower pressures. Positive correlations show that higher (better) status is related to higher pressures (Herkül & Martin 2017).

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correlated in the EEA grid based pooled data (se, fi, ee). The correlations were mainly positive, i.e. higher (better) status of one assessment corresponded to higher (better) status of the other assessment. However, there were some negative correlations that were mainly related to the WFD chemical status (Figure 5).

5 Habitat integration across different hierarchical levels

For assessing impacts on seabed, different hierarchical levels of seabed habitats can be tackled in together. Practical guidance for the integration of the levels is discussed in this chapter.

5.1 Benthic broad habitat types present in the Baltic Sea

In the European habitat classification system (EUNIS), habitat types are arranged in a hierarchy. Table 4 summarises the benthic broad habitat types present in the Baltic Sea which equate to one or more habitat types of the European nature information system (EUNIS) habitat classification, as listed in the MSFD Commission’s Decision 2017/847/EU.

Table 4. The MSFD broad habitat types present in the Baltic Sea, and the relevant EUNIS habitat codes (version 2016).

Broad habitat types present in the Baltic Sea

Relevant EUNIS habitat codes (version 2016)

Littoral rock and biogenic reef MA1, MA2Littoral sediment MA3, MA4, MA5, MA6Infralittoral rock and biogenic reef MB1, MB2

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Figure 5. Correlations between assessments based on EEA grid. Colors and circle diameters signify the Spearman rank correlation coefficients. Numbers show the p-values in cases where p > 0.05. Dots represent cases where data was not available or there was no variation in the data. Positive correlations show that higher (better) status of one assessment corresponds to higher (better) status in the other assessment. Negative correlations show that higher (better) status in one assessment corresponds to lower (worse) status in the other assessment (Herkül & Martin 2017).

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Infralittoral coarse sediment MB3Infralittoral mixed sediment MB4Infralittoral sand MB5Infralittoral mud MB6Circalittoral rock and biogenic reef MC1, MC2Circalittoral coarse sediment MC3Circalittoral mixed sediment MC4Circalittoral sand MC5Circalittoral mud MC6Offshore circalittoral rock and biogenic reef

MD1, MD2

Offshore circalittoral coarse sediment MD3Offshore circalittoral mixed sediment MD4Offshore circalittoral sand MD5Offshore circalittoral mud MD6

5.2 Combining different hierarchical levels of habitats in the same assessment

Currently, the Habitat Directive (HD), the Marine Strategy Framework Directive (MSFD) and the HELCOM Underwater Biotope and Habitat classification system (HUB) are utilised in the assessments of seabed in the Baltic Sea area. The HD and the MSFD are lists of terms for policy implementation. The habitat classification system for the HD is a list of marine habitat types. It is based on a mixture of broadscale hydro-morphological, landscape level properties and some selected physical or biological features of marine benthic habitats. The list is not all inclusive but reflects the natural features in most need of protection on European scale. The MSFD consists of an all-inclusive list of very broad scale habitat features. It covers a full range of possible habitats on the tidal shelf and open sea. The HUB system is a hierarchical, all-inclusive classification system covering all possible habitats occurring in the Baltic Sea. The MSFD and the HUB are comparable with the EUNIS system. (Martin et al. 2017.)

For assessing impacts on seabed, the hierarchical levels of technically different systems can be tackled within the same assessment. In the HELCOM SPICE project, a translation matrix between the MSFD and the HD, and between the MSFD and the HUB classification system were developed.

The resulting translation matrix between the MSFD and the HD classification systems of marine habitat types in the Baltic Sea (Table 5) demonstrates that there is no 1:1 compatibility between these two systems and this goes in both directions; one classification unit of one system can include several classification units of another system. This means that for practical translation of the e.g. status classification results between those two systems more detailed, quantitative information is needed (e.g. area of different substrate types within the assessment unit) and each case should be dealt separately. Automated status translation can be done only when quantitative information is available. (Martin et al. 2017.)

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Table 5 Translation matrix between MSFD and HD classification systems of marine habitat types in the Baltic Sea (Martin et al. 2017). Shaded units are not occurring in the Baltic Sea.

1110 Sandbanks wgich are slightly covered by sea water all the time

1130 Estuaries

1140 Mudflats and sandflats not covered by seawater at low tide

1150 Coastal lagoons

1160 Large shallow inlets and bays

1170 Reefs

1180 Submarine structures made by leaking gases

1650 Boreal Baltic narrow inlets

8330 submerged or partially submerged sea caves

Littoral rock and biogenic reefLittoral sedimentInfralittoral rock and biogenic reefInfralittoral coarse sedimentInfralittoral mixed sedimentInfralittoral sand *Infralittoral mud *Circalittoral rock and biogenic reefCircalittoral coarse sedimentCircalittoral mixed sedimentCircalittoral sandCircalittoral mudOffshore circalittoral rock and biogenic reefOffshore circalittoral coarse sedimentOffshore circalittoral mixed sedimentOffshore circalittoral sandOffshore circalittoral mudUpper bathyal rock and biogenic reefUpper bathyal sedimentLower bathyal rock and biogenic reefLower bathyal sedimentAbyssal

In order to develope a proposal for a translation matrix between the MSFD and the HELCOM HUB system, Martin et al. (2017) used available guidance documents and modified them according to the Baltic Sea conditions. As the HUB is a hierarchical system and the MSFD system covers only the very broad scale features of marine environment only one HUB level (level 3) was included in the translation matrix. (Martin et al. 2017.)

The aim was to transfer the status classification result from lowest hierarchical habitat classification system (level at which the classification of single stations is usually performed) to higher levels (HUB level 3) with translation to status of MSFD broad habitat types. The proposal for a stepwise procedure for hierarchical aggregation of the habitat status classification includes the following steps:

Step 1. Status assessment of the HUB level 5/6 habitat. This is performed using a metric expressing the final result in numeric value/ratio.

Step 2. Option A. Assessment is done for a single HUB level 5/6 “important” habitat. Aggregation for HUB levels 4 and 3 is carried out by applying averaging of assessment ratio (EQR) of previous level.

Option B. Assessment is done for each HUB level 5/6 habitat available in the assessment unit (Figure 6). Aggregation for the HUB level 4 is carried out using weighted averaging using the HUB level 5/6 habitat area as weighting factor. Aggregation to level 3 is done through averaging the assessment ratio of level 4.

Step 3. Transferring the assessment result from the HUB level 3 to the MSFD broad habitat type using the translation matrix.(Martin et al. 2017.)

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Figure 6. Aggregation principle according to option B (using all HUB level 5/6 habitats in the assessment unit) (Martin et al. 2017).

An important prerequisite for using this procedure is that all the following conditions should be met: - availability of data- availability of assessment method and - agreement on the list of “important“ or “valuable“ habitats (Martin et al. 2017).

A more detailed description of the procedure for hierarchical aggregation as well as a practical example from Estonia are available from the SPICE Deliverable 4.1.2 by Martin et al. (2017).

6 Method for assessment of impacts on benthic habitats

6.1 A stepwise method guideline for a technical assessment of the lost, disturbed and adversely affected area (km2)

A stepwise assessment guideline for the assessment of lost, disturbed and adversely affected benthic and pelagic habitats was developed in the SPICE project. The protocol has also utilized the HELCOM’s protocol for preparing pressure layers and assessing cumulative impacts (Weigel et al. 2017). The guideline is presented as a shorter version in Figure 7. A more detailed description of the protocol is available from the SPICE Deliverable 4.1.1 (Weigel et al. 2017).

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Figure 7. A stepwise assessment guideline for the assessment of lost, disturbed and adversely affected benthic and pelagic habitats.

A process to assess the physical disturbance and loss per broad habitat type has also been presented in the ICES WKBEDPRES2 report (ICES 2019c, under review). The assessment process describes the methodologies to be applied to assess different physical pressure types and their impacts on broad habitat types on a scale of an ecoregion.

7 Measures to reach GES of benthic habitats and seafloor integrity

Maintenance and capital dredging as well as sediment disposal cause high impacts on hard, sandy and muddy bottoms and fish production areas of the Baltic Sea. On hard bottoms, extraction of minerals (e.g. sand and gravel) causes high impacts. Placement of gas pipelines causes high impacts on vegetated habitats. Furthermore, shipping and ferry traffic, marinas and wind turbine construction cause moderate to high physical disturbance on the seabed in many areas (HELCOM 2018b).

In the HELCOM ACTION project, information will be gathered on existing measures that can contribute to improving the state of the Baltic Sea and their implementation status. The addressed pressure categories include inter alia seabed loss and disturbance, input of different hazardous substances, input and spread of non-indigenous species and input of litter. The measures include i. a. global and regional conventions, EU directives and regulations, regional HELCOM actions and national measures.

Currently, there is not much evidence-based information on the effectiveness of measures to mitigate the adverse effects of different activities in the Baltic Sea.

Examples of potential measures:

Michel et al. (2013) have reviewed the biological and biophysical impacts from dredging and sand extraction in the offshore areas of the U.S. They have suggested measures to mitigate the adverse effects of dredging and sand

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extraction, and to facilitate recovery. The measures have been applied for the offshore areas in the U.S. Thus, caution in the application of these guidelines to other areas is emphasized.

The following measures were suggested by Michel et al. (2013):

- Buffer zones: Adequate buffer zones protect sensitive areas.

- Siltation risk models: With characterisation of the hydrodynamic environment around the disturbed area, probability of siltation on nearby bottoms could be modeled so as to make more rigorous siltation risk computations and establish effective buffer distance requirements.

- Timing: The timing of disturbance relative to the reproductive seasons of the benthic organisms plays a role in the recovery. Thus, the recovery after dredging can be facilitated, and the nature of recovery directed, by appropriate seasonal timing of dredging. However, not all benthic taxa reproduce most intensively during the same season, so timing of dredging can select for dominance of different taxa during the recovery process.

- Depth restrictions: Dredging might be constrained to relatively shallow depths to avoid creating deep pits, some of which require long recovery times. The trade-off that accompanies shallow excavation of sand is the need for disturbing more surface area of the seafloor, where the benthos lives and functions, implying greater initial benthic mortality. Nevertheless, the slow pace of recovery in deeper dredge pits suggests that avoiding their creation may be advisable as a mitigation measure. Further compelling studies or necessary field tests are still needed to confirm this. (Michel et al. 2013).

A protective curtain was used in the Vuosaari harbor, Finland during dredging in order to reduce turbidity in nearby areas. The curtain was built between two embankments and it had a gate through which vessels could enter the harbour area. (Vatanen et al. 2012.) The effects of the curtain were studied by Vatanen (2006). Increased turbidity was found in nearby areas outside the curtain, but the amount of turbidity was substantially lower than inside the protective structure. A part of the curtain was removed for autumn 2005 which substantially increased turbidity in nearby areas. (Vatanen 2006.) Thus, it was deduced that the curtain reduced turbidity in nearby areas during dredging (Vatanen et al. 2012).

Callaway et al. (2018) have studied the effectiveness of bubble curtains in restricting sediment movement in seawater under laboratory conditions. Generally, the finer the sediment the more bubble curtains were necessary to retain the material. Three parallel bubble curtains retained 80-90% of sediment of all grain sizes (63 – 500 μm). The transferability of the laboratory results to the field should be viewed with caution as the natural environment differs in many ways from laboratory conditions. However, the laboratory results indicated that bubble curtains could potentially be a tool to limit sediment dispersion in coastal environments (Callaway et al. 2018).

One of the most effective steps towards minimising the effects of mobile fishing gears, such as trawls and dredges, on benthic ecosystems is the overall reduction of fishing effort, by means of implementing permanent or temporary closures (reviewed by Demestre et al. 2008). In a study by Demestre et al. (2008), a positive response in community structure and composition in a short time (2 months in the Catalan Sea and 40 days in the Adriatic Sea) indicated that closures can limit degradation of benthic communities and habitats. However, a decrease of faunal abundance was observed with the resumption of fishing activity after the closure at both fishing grounds (Demestre et al. 2008). Demestre et al. (2008) point out that longer closure periods would be beneficial and allow the maintenance of more structured systems.

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8 Conclusions

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References

Bonsdorff, E. (2006). Zoobenthic diversity gradients in the Baltic Sea: continuous post-glacial succession in a stressed ecosystem. Journal of Experimental Marine Biology and Ecology, 330, 383–391.

Burton G. Allen Jr. (ed.) (1992). Sediment Toxicity Assessment. Lewis Publishers, Inc.

Callaway R., Davies R., Mendzil A. (2018). Micro bubble curtains: impact on sediment dispersal. Technical Report of the SEACAMS2 project (SC2-R&D-SU03) with Frog Environmental Ltd. Swansea University. 21 pp.

Carr A. (1987) Impact of nondegradable marine debris on the ecology and survival outlook of sea turtles. Marine Pollution Bulletin, 18 (6), pp. 352–356.

Cloern, J. E. (2001). Our evolving conceptual model of the coastal eutrophication problem. Marine Ecology Progress Series, 210, 223–253.

Conley, D. J., Björk, S., Bonsdorff, E. et al. (2009a). Hypoxia-related processes in the Baltic Sea. Environmental Science and Technology, 43, 3412–3420.

Conley, D. J., Carstensen, J., Vaquer-Sunyer, R. and Duarte, C. M. (2009b). Ecosystem thresholds with hypoxia. Hydrobiologia, 629, 21–29.

Craig, J. K., Crowder, L. B., Gray, C. D. et al. (2001). Ecological effects of hypoxia on fish, sea turtles, and marine mammals in the northwestern Gulf of Mexico. In Coastal Hypoxia: Consequences for Living Resources and Ecosystems, ed. N. N. Rabalais and R. E. Turner. Washington DC: American Geophysical Union,pp. 269–292.

Dahlgren, S. and Kautsky, L. (2004). Can different vegetative states in shallow coastal bays of the Baltic Sea be linked to internal nutrient levels and external nutrient load? Hydrobiologia, 514, 249–258.

Demestre M., de Juan S., Sartor P., Ligas A. (2008). Seasonal closures as a measure of trawling effort control in two Mediterranean trawling grounds: Effects on epibenthic communities. Marine Pollution Bulletin Volume 56, Issue 10, October 2008, Pages 1765-1773

Derraik J. (2002). The pollution of the marine environment by plastic debris: a review. Marine Pollution Bulletin, 44(9), pp.842–852.

Diaz R.L., Rosenberg R. (1995). Marine benthic hypoxia: a review of its ecological effects and the behavioural responses of benthic macrofauna. Oceanogr. Mar. Biol. Ann. Rev. 33, 245–303.

Di´az R.J. & Rosenberg R. (2008). Spreading dead zone and consequences for marine ecosystems. Science, 321, 926–929.

Eriksen M., Lebreton L.C.M., Carson H.S., Thiel M., Moore C.J., Borerro J.C., Galgani F., Ryan P.G., Reisser J. (2014). Plastic pollution in the World's oceans: more than 5 trillion plastic pieces weighing over 250,000 tons afloat at sea. PLoS ONE, 9(12), p.e111913.

Foekema E., De Gruijter C., Mergia M., van Franeker J., Murk A., Koelmans A. (2013). Plastic in North Sea fish. Environmental Science and Technology, 47(15), pp.8818–8824.

30

------------ DRAFT ------------

Galgani F., Leaute J.P., Moguedet P., Souplet A., Verin Y., Carpentier A., Goraguer H., Latrouite D., Andral B., Cadiou Y., Mahe J.C., Poulard J.C., Nerisson P. (2000). Litter on the Sea Floor Along European Coasts. Marine Pollution Bulletin, 40(6), pp.516–527.

Galil B.S., Marchini A., Occhipinti-Ambrogi A., Minchin D., Naršcius A., Ojaveer H., Olenin S. (2014). International arrivals: widespread bioinvasions in European Seas. Ethology Ecology and Evolution 26: 152– 171.

Hammar L., Schmidtbauer Crona J., Kågesten G., Hume D., Pålsson J., Aarsrud M., Mattsson D., Åberg F., Hallberg M., Johansson T. (2018). Symphony. Integrerat planeringsstöd för statlig havsplanering utifrån en ekosystemansats. Havs- och vattenmyndighetens rapport 2018:1. Available from https://www.havochvatten.se/download/18.52d593d41624ea1d549cfe1d/1523361761104/rapport-symphony-integrerat-planeringsstod-for-statlig-havsplanering-utifran-en-ekosystemansats.pdf

HELCOM (2009). Eutrophication of the Baltic Sea: an integrated thematic assessment of the effects of nutrient enrichment in the Baltic Sea region. Baltic Sea Environment Proceedings, 115.

HELCOM (2010). Ecosystem Health of the Baltic Sea 2003–2007: HELCOM initial holistic assessment. Baltic Sea Environment Proceedings, 122.

HELCOM (2012). Fifth Pollution Load Compilation (PLC-5). Baltic Sea Environment Proceedings, 128.

HELCOM (2017). The assessment of cumulative impacts using the Baltic Sea Pressure Index and the Baltic Sea Impact Index - supplementary report to the first version of the HELCOM ‘State of the Baltic Sea’ report 2017. Available at: http://stateofthebalticsea.helcom.fi/about-helcom-and-the-assessment/downloads-and-data/

HELCOM (2018a). Thematic assessment of cumulative impacts on the Baltic Sea 2011-2016. Supplementary report to the HELCOM ‘State of the Baltic Sea’ report. Available from: http://stateofthebalticsea.helcom.fi/wp-content/uploads/2019/09/BSEP159-Cumulative-impacts.pdf

HELCOM (2018b). Estimating physical disturbance on seabed – Baltic Sea Environment Proceedings No. 164. Available at: http://www.helcom.fi/Lists/Publications/BSEP164.pdf

HELCOM (2018c). State of the Baltic Sea – Second HELCOM holistic assessment 2011-2016. Baltic Sea Environment Proceedings 155.

HELCOM (2018d). HELCOM Thematic assessment of hazardous substances 2011-2016. Available at: http://www.helcom.fi/baltic-sea-trends/holistic-assessments/state-of-the-baltic-sea2018/reports-and-materials/

HELCOM (2018e). State of the soft-bottom macrofauna community. HELCOM core indicator report. Available from https://helcom.fi/wp-content/uploads/2019/08/State-of-the-soft-bottom-macrofauna-community-HELCOM-core-indicator-2018.pdf

HELCOM (2018f). Oxygen debt HELCOM core indicator 2018. HELCOM core indicator report. Available from: http://www.helcom.fi/baltic-sea-trends/holistic-assessments/state-of-the-baltic-sea-2018/reports-and-materials

HELCOM (2018g). Benthic habitats. Available from http://stateofthebalticsea.helcom.fi/biodiversity-and-its-status/benthic-habitats/

Herbold B. & Moyle P. B. (1986). Introduced species and vacant niches. Am. Nat. 128: 751–761.

Herkül K. & Martin G. (2017). Task 4.2.3 Cross-comparison of environmental assessments and pressures. HELCOM SPICE. Available from http://www.helcom.fi/Documents/HELCOM%20at%20work/Projects/Completed%20projects/SPICE/Theme%204_Deliverable%204.2.3.pdf

31

------------ DRAFT ------------

ICES (2016). Report of the Workshop on guidance on how pressure maps of fishing intensity contribute to an assessment of the state of seabed habitats (WKFBI), 31 May – 1 June 2016, ICES HQ, Copenhagen, Denmark. ICES CM 2016/ACOM:46. 109 pp.

ICES (2019a). Workshop on scoping of physical pressure layers causing loss of benthic habitats D6C1– methods to operational data products (WKBEDLOSS). ICES Scientific Reports. 1:15. 37 pp. http://doi.org/10.17895/ices.pub.5138

ICES (2019b). Interim Report of the Working Group on Fisheries Benthic Impact and Trade-offs (WGFBIT), 12–16 November 2018, ICES Headquarters, Copenhagen, Denmark. ICES CM 2018/HAPISG:21. 74 pp.Karlson, K.,Rosenberg, R. and Bonsdorf, E. (2002). Temporal and spatial large-scale effects of eutrophication and oxygen deficiency on benthic fauna in Scandinavian and Baltic waters: a review. Oceanography and Marine Biology, 40, 427–489.

ICES (2019c, under review) ICES WKBEDPRES2 report.

ICES (2019d). EU request to advise on a seafloor assessment process for physical loss (D6C1, D6C4) and physical disturbance (D6C2) on benthic habitats. ICES Special Request Advice EU ecoregions. Available from http://www.ices.dk/sites/pub/Publication%20Reports/Advice/2019/Special_Requests/eu.2019.25.pdf

Karlson K., Rosenberg R., Bonsdorf E. (2002). Temporal and spatial large-scale effects of eutrophication and oxygen deficiency on benthic fauna in Scandinavian and Baltic waters: a review. Oceanography and Marine Biology, 40, 427–489.

Karlson K., Bonsdorff E., Rosenberg, R. (2007). The impact of benthic macrofauna for nutrient fluxes from Baltic Sea sediments. Ambio, 36, 161–167.

Korpinen S. & Bonsdorff E. (2015). Eutrophication and hypoxia: impacts of nutrient and organic enrichment. In book: Marine ecosystems: human impacts on biodiversity, functioning and services. Publisher: Cambridge University Press, Editors: Tasman Crowe; Christopher LJ Frid

Korpinen S., Nurmi M., Laamanen L., Andersen J.H., Rinne H., Nygård H., Murray C., Kallenbach E., Li Zweifel U. (2016?) A protocol for the calculation of the Baltic Sea Impact Index and the Baltic Sea Pressure Index. HELCOM TAPAS. Available from http://www.helcom.fi/Documents/HELCOM%20at%20work/Projects/Completed%20projects/TAPAS/TAPAS%20Theme%201%20Deliverable.pdf

Kühn S., Bravo Rebolledo E.L., van Franeker J.A. (2015). Deleterious Effects of Litter on Marine Life. In Marine Anthropogenic Litter (edited by Bergmann Melanie, Gutow Lars, Klages Michael). Available from file:///D:/Users/e1003700/Downloads/1001966.pdf

Laist D.W. (1987). Overview of the biological effects of lost and discarded plastic debris in the marine environment. Marine Pollution Bulletin, Volume 18, Issue 6, pp. 319-326.

Lee H. & Swartz R. C. (1980). Biological processes affecting the distribution of pollutants in marine sediments. Part II. Biodeposition and Bioturbation. In: Baker, R.A. (ed.), Contaminants and Sediments. Vol. 2. Ann Arbor Science Publ., Ann Arbor, MI: 555–606.

Leppäkoski E. (1984). Introduced species in the Baltic Sea and its coastal ecosystems. Ophelia Suppl. 3: 123–135.

Leppäkoski E. (1994). Non-indigenous species in the Baltic Sea. In Boudouresque, C. F., F. Briand & C. Nolan (eds), Introduced species in European coastal waters. European Commission, Ecosyst. Res. Rep 8: 67–75.

Lusher A.L., McHugh M., Thompson R. (2013). Occurrence of microplastics in the gastrointestinal tract of pelagic and demersal fish from the English Channel. Marine Pollution Bulletin, 67(1-2), pp.94–99.

32

------------ DRAFT ------------

MacDonald D.S., Little M., Eno N. C., Hiscock K. (1996). Disturbance of benthic species by fishing activities: a sensitivity index. Aquatic conservation: marine and freshwater ecosystems, vol. 6. pp. 257 – 268.

MarLIN (2006). BIOTIC - Biological Traits Information Catalogue. Marine Life Information Network. Plymouth: Marine Biological Association of the United Kingdom. [Cited 12.9.2019] Available from www.marlin.ac.uk/biotic

Martin G., Torn K., Nystrom Sandman A., Nygård H. (2017). Task 4.1.2 A practical guidance how different hierarchical levels of habitats (e.g. broader and more-detailed HELCOM underwater biotopes) can be tackled within the same assessment. HELCOM SPICE. Available from http://www.helcom.fi/Documents/HELCOM%20at%20work/Projects/Completed%20projects/SPICE/Theme%204_Deliverable%204.1.2.pdf

Mato Y., Isobe T., Takada H., Kanehiro H., Ohtake C., Kaminuma T. (2001). Plastic Resin Pellets as a Transport Medium for Toxic Chemicals in the Marine Environment. Environmental Science & Technology, 35(2), pp.318–324.

Matthiessen P. & Gibbs Peter E. (1998) Critical appraisal of the evidence for tributyltin mediated endocrine ‐disruption in mollusks. Environmental Toxicology and Chemistry, Vol. 17, No. 1, pp. 37–43.

McDowell J.E., Lancaster B.A., Leavitt D.F., Rantamaki P., Ripley B. (1999). The effects of lipophilic organic contaminants on reproductive physiology and disease processes in marine bivalve molluscs. Limnol. Oceanogr., 44 (3, part 2), 1999, 903–909.

McGlathery K. J., Sundbäck K., Anderson I.C. (2007). Eutrophication in shallow coastal bays and lagoons: the role of plants in the coastal filter. Marine Ecology Progress Series, 348, 1–18.

Meier H.E.M., Anderson H.C., Eilola K. et al. (2011). Hypoxia in future climates: a model ensemble study for the Baltic Sea. Geophysical Research Letters, 38, L24608.

Michel J., Bejarano A.C., Peterson C.H., Voss C. (2013). Review of Biological and Biophysical Impacts from Dredging and Handling of Offshore Sand. U.S. Department of the Interior, Bureau of Ocean Energy Management, Herndon, VA. OCS Study BOEM 2013-0119. 258 pp.

Nilsson (2017). WP 2.1 Development of baselines of marine litter. Litter on the seafloor in the HELCOM area- analyses of data from BITS trawling hauls 2012-2016. HELCOM SPICE. Available from https://portal.helcom.fi/meetings/HELCOM%20SPICE%20ML%20WS%201-2017-459/MeetingDocuments/Document%203_Litter%20on%20the%20seafloor%20in%20the%20HELCOM%20area-%20analyses%20of%20data%20from%20BITS%20trawling%20hauls%202012-2016.pdf

Norkko A. & Bonsdorff E. (1996). Rapid zoobenthic community responses to accumulations of drifting algae. Marine Ecology Progress Series, 131, 143– 157.

Olenin S. & Leppäkoski E. (1999). Non-native animals in the Baltic Sea: alteration of benthic habitats in coastal inlets and lagoons. Hydrobiologia. February 1999, Volume 393, Issue 0, pp. 233–243

Payne J.F., Kiceniuk J., Fancey L.L., Williams V., Fletcher G.L., Rahimtula A., Fowler B. (1988). What is a Safe Level of Polycyclic Aromatic Hydrocarbons for Fish: Subchronic Toxicity Study on Winter Flounder (Pseudopleuronectes americanus)," Can. J. Fish. Aquat. Sci. 45:1983-1993.

Rochman C.M., Hentschel B.T., Teh S.J. (2014). Long-Term Sorption of Metals Is Similar among Plastic Types: Implications for Plastic Debris in Aquatic Environments. PLoS ONE, 9(1), p.e85433.

33

------------ DRAFT ------------

Rossi F., Forster R.M., Montserrat F., Ponti M., Terlizzi A., Ysebaert T., Middelburg J.J. (2007). Human trampling as short-term disturbance on intertidal mudflats: effects on macrofauna biodiversity and population dynamics of bivalves. Marine Biology, 151, pp. 2077 – 2090.

Rummel C.D., Löder M.G.J., Fricke N.F., Lang T., Griebeler E.M., Janke M., Gerdts G. (2016). Plastic ingestion by pelagic and demersal fish from the North Sea and Baltic Sea. Marine Pollution Bulletin, 102(1), pp. 134–141.

Rumohr H., Bonsdorff E., Pearson T.H. (1996). Zoobenthic succession in Baltic sedimentary habitats. Archive of Fishery And Marine Research, 44, 179–214.

Salovius S., Nyqvist M., Bonsdorff E. (2005). Life in the fast lane: macrobenthos use temporary drifting algal habitats. Journal of Sea Research, 53, 169–180.

Sandberg E. (1994). Does short-term oxygen depletion affect predator–prey relationships in zoobenthos? Experiments with the isopod Saduria entomon. Marine Ecology Progress Series, 103, 73–80.

Savchuk O.P., Wulff F., Hille S., Humborg C., Pollehne F. (2008). The Baltic Sea a century ago: a reconstruction from model simulations, verified by observations. Journal of Marine Systems, 74, 485–494.

Schrey E., Vauk G.J.M. (1987). Records of entangled gannets (Sula bassana) at Helgoland, German Bight. Marine Pollution Bulletin, 18(6), pp. 350–352.

Setälä O., Fleming-Lehtinen V., Lehtiniemi M. (2014). Ingestion and transfer of microplastics in the planktonic food web. Environmental Pollution, 185, pp.77–83.

Suedel B.C., Deaver E., Rodgers J.H.Jr. (1996). Experimental factors that may affect toxicity of aqueous and sediment-bound copper to freshwater organisms. Archives of Environmental Contamination and ToxicologyJanuary 1996, Volume 30, Issue 1, pp 40–46

Sundelin B., Eriksson A.-K. (1998). Malformations in embryos of the deposit-feedingamphipod Monoporeia affinis in the Baltic Sea. Marine ecology progress series, vol. 171: 165-180.

Talsness C. E., Andrade A. J. M., Kuriyama S. N., Taylor J. A., vom Saal F. S. (2009). Components of plastic: experimental studies in animals and relevance for human health. Philosophical Transactions of the Royal Society B, 364(1526), pp.2079–2096.

Thompson R., Browne M., Galloway T. (2007). Microplastic – an emerging contaminant of potential concern? Integrated environmental assessment and management, 3(4), pp.559–561.

Tyler-Walters H., Tillin H.M., d’Avack E.A.S., Perry F., Stamp T. (2018). Marine Evidence-basedSensitivity Assessment (MarESA) – A Guide. Marine Life Information Network (MarLIN).Marine Biological Association of the UK, Plymouth, pp. 91. Available fromhttps://www.marlin.ac.uk/publications

Urban-Malinga B., Wodzinowski T., Witalis B., Zalewski M., Radtke K., Grygiel W. (2018). Marine litter on the seafloor of the southern Baltic. Marine Pollution Bulletin, 127: pp. 612-617.

Vahtera E., Conley D.J., Gustafsson B.G. et al. (2007). Internal ecosystem feedbacks enhance nitrogen-fixing cyanobacteria blooms and complicate management in the Baltic Sea. Ambio, 36, 1–10.

Vaquer-Sunyer R. & Duarte C. M. (2008). Thresholds of hypoxia for marine biodiversity. Proceedings of the National Academy of Sciences, 105, 15452–15457.

34

------------ DRAFT ------------

Vatanen S. (2006). Vuosaaren sataman ja väylän rakentamisen vesistö- ja kalataloustarkkailuohjelma. Kala- ja vesitutkimus Oy.

Vatanen S., Haikonen A., Piispanen A. (ed.) (2012). Vuosaaren sataman rakentamisen aikaisen (2003-2008) vesistö- ja kalataloustarkkailun yhteenvetoraportti. Kala- ja vesitutkimus Oy. Kala- ja vesimonisteita nro 57.

Villnäs A. & Norkko A. (2011). Benthic diversity gradients and shifting baselines: implications for assessing environmental status. Ecological Applications, 21, 2172– 2186.

Villnäs A., Norkko J., Lukkari K., Hewitt J., Norkko A. (2012). Consequences of increasing hypoxic disturbance on benthic communities and ecosystem functioning. PLOS One, 7, e44920.

Virtanen E., Korpinen S., Nyström Sandman A., Nygård H. (2017). Task 4.2.1 Definition of adversely affected habitats. HELCOM SPICE. Available from http://www.helcom.fi/Documents/HELCOM%20at%20work/Projects/Completed%20projects/SPICE/Theme%204_Deliverable%204.2.1.pdf

Vuori K.-M. (1994). Rapid behavioural and morphological responses of hydropsychid larvae (trichoptera, hydropsychidae) to sublethal cadmium exposure. Environmental Pollution Volume 84, Issue 3, 1994, Pages 291-299

Weigel B., Haldin J., Korpinen S., Martin G., Nystrom Sandman A., Torn K., Nygård H. (2017). Task 4.1.1: A step-wise method guideline for carrying out a technical assessment of the lost, disturbed and adversely affected area (km2) of benthic and pelagic habitat types from different activities. HELCOM SPICE. Available from http://www.helcom.fi/Documents/HELCOM%20at%20work/Projects/Completed%20projects/SPICE/Theme%204_Deliverable%204.1.1.pdf

WWF Poland (2015). Removal of derelict fishing gear, lost or discarded by fishermen in the Baltic Sea. Final project report. Available from http://d2ouvy59p0dg6k.cloudfront.net/downloads/wwf_poland_removal_of_derelict_fising_gear_oct_2015_1.pdf

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Annex 1. Figure x presents examples of the more detailed results from WFD status assessments versus different pressures. Figure y presents the more detailed results from the HOLAS benthic habitat status assessments versus different pressures. Both figures x and y have been adopted from SPICE Deliverable 4.2.3., and more figures are available there.

Figure x. Examples of the WFD status assessments versus pressures. Letters after status class names indicate the results of pairwise post-hoc tests: levels are significantly different if they do not have any letters in common.

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Figure y. HOLAS benthic habitat status assessments versus different pressure inputs. Letters after status class names indicate the results of pairwise post-hoc tests: levels are significantly different if they do not have any letters in common.

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