Marine Ecology Jetty Es Chapter 10
-
Upload
tonni-kurniawan -
Category
Documents
-
view
219 -
download
0
Transcript of Marine Ecology Jetty Es Chapter 10
-
7/29/2019 Marine Ecology Jetty Es Chapter 10
1/100
Hinkley Point C Preliminary Works 10 - 1 Environmental Statement
Temporary Jetty Development November 2010
10 MARINE ECOLOGY
10.1 Introduction
10.1.1 This Chapter of the ES provides an assessment of the potential impacts to marine
ecology in respect of the proposed temporary jetty during the construction, operation
and subsequent dismantling and restoration phases. In addition it considers the impacts
associated with removal of the jetty and site reinstatement should the IPC not grant a
DCO. Where appropriate, mitigation measures are proposed to reduce potential adverse
impacts.
a) Scoping of Assessment
Scoping
10.1.2 An Environmental Scoping Report for the jetty development was produced in March
2010 (Ref 10.1), which provided a summary of baseline environmental conditions for the
study area and information on likely environmental effects relating to marine ecology.
10.1.3 A Scoping Opinion (Ref 10.2) was received from the Marine Management Organisation
(MMO) in June 2010 (see Appendix 5-1, Volume 4). This Scoping Opinion included
responses from a range of organisations, including the Environment Agency, Natural
England, the Countryside Council for Wales (CCW), Somerset County Council and West
Somerset and Sedgemoor District Councils. In relation to marine ecology the Scoping
Opinion raised a number of points, notably a requirement to consider if the works could
impact on Sabellariareef orCorallinaturfs on the foreshore (see Section 10.5), as well
as a requirement for a thorough assessment to be carried out of potential cumulative
impacts (see Chapter 25). The Scoping Opinion has been taken into account during the
preparation of this Chapter (see Annex 10.1 at the end of the Chapter).
Consultation
10.1.4 The assessment of impacts on marine ecology as reported in this Chapter has been
informed by detailed consultations with relevant bodies dating back to 2008.
10.1.5 On 3 November 2008 an initial meeting was held with Natural England and Somerset
County Council) to discuss and agree the proposed scope and range of near shore and
offshore marine ecological surveys to be undertaken. A Method Statement was issued
prior to the meeting and Natural England confirmed that it was content with the
proposed surveys but requested a full 12 months baseline survey period for certain key
species.
10.1.6 A subsequent meeting was held with Natural England and CCW on 16 January 2009. It
was agreed that the Revised Method Statement for Marine Ecology (revised following
the initial meeting) would be sent to Natural England and CCW for any further comment.
CCW raised the issue of potential impacts to Welsh Special Areas of Conservation
(SACs), including the River Wye, River Usk and River Tywi, partly designated for the
following fish species: sea lamprey Petromyzon marinus, brook lamprey Lampetra
planeri, twaite shad Alosa fallax, Atlantic salmon Salmo salar and bullhead Cottus
gobio. However, due to the limited nature of the potential impacts associated with the
jetty development and the distance of the works from these features, separate
assessments have not been undertaken for these sites (see Section 10.5).
-
7/29/2019 Marine Ecology Jetty Es Chapter 10
2/100
Hinkley Point C Preliminary Works 10 - 2 Environmental Statement
Temporary Jetty Development November 2010
10.1.7 Comments were received on the proposed marine ecology methodology (CCW 09/02/09
and Natural England 12/02/09) but no further changes to survey design were requested
other than the previously agreed extension of the survey period. Natural England agreed
that marine mammals could reasonably be addressed through desk-based assessment.
10.1.8 A series of meetings were held with the Marine Authorities Liaison Group (MALG) to
discuss all stages of the assessment and the jetty development engineering and
construction design. MALG members include the Centre for Environment, Fisheries and
Aquaculture Science (Cefas), CCW, Natural England, Environment Agency, MMO,
Somerset County Council, Sedgemoor District Council, Royal Society for the Protection
of Birds (RSPB), Crown Estates, English Heritage and West Somerset Council. A
summary of marine ecology issues discussed at these meetings is presented in Annex
10.2 (located at the end of this Chapter).
10.1.9 Following a meeting between EDF Energy and the Environment Agency and Natural
England on 23 July 2010, the Environment Agency provided a written response dated 6
August 2010. The marine ecology elements of this response are also reviewed in
Annex 10.2.
Assessment Content
10.1.10 The assessment of impacts on marine ecology receptors arising from the jetty
development has been undertaken for the study area and uses the best practices and
standard methodologies as described in Section 10.3.
10.1.11 The baseline conditions described in Section 10.4 are based on a number of surveys
undertaken by EDF Energy of the wider scale environmental and ecological
characteristics up to 15km from the application site as well as others that focussed on
the proposed working areas both offshore and in the inter-tidal zone at Hinkley Point.
10.1.12 Impacts on marine ecology are assessed in Section 10.5. This includes potential
impacts on marine ecology receptors. Appropriate mitigation measures that are aimed
at reducing the impact of the proposed jetty on marine ecology receptors are identified in
Section 10.6. The residual impacts following implementation of the mitigation measures
are presented in Section 10.7. A summary of the impact assessment in tabulated form
is provided in Section 10.8.
10.1.13 The cumulative effects on marine ecology are assessed and set out in Chapter 25. For
this assessment, the effects of the proposed jetty works are assessed cumulatively with:
the site preparation works; the Hinkley Point C Project; and
other relevant plans and projects.
b) Objectives of Assessment
10.1.14 The assessment had the following objectives:
identify marine ecology receptors within the study area that may potentially be
affected by the jetty development;
characterise the baseline environmental and ecological conditions against which
any potential impacts can be measured;
-
7/29/2019 Marine Ecology Jetty Es Chapter 10
3/100
Hinkley Point C Preliminary Works 10 - 3 Environmental Statement
Temporary Jetty Development November 2010
assess the impacts on marine ecology receptors of the jetty developments
construction, operation, dismantling / restoration and, if no DCO consent is granted,
removal and site reinstatement phases;
provide information to inform any Habitat Regulations Assessment (HRA) (this
assessment will be submitted after the application for a HEO);
recommend mitigation measures, if determined necessary, to reduce the jettydevelopments impacts on marine ecology; and
assess the residual impacts of the jetty development on marine ecology.
10.2 Legislation, Policy and Guidance
a) International Legislation and Policy
The Ramsar Convention of Wetlands of International Importance 1971 (Ref 10.3)
10.2.1 The Ramsar Convention on Wetlands of International Importance 1971 provides the
framework for national action and international co-operation for the conservation and
considerate use of wetlands and their resources. Suitable wetlands are designated forinclusion in the List of Wetlands of International Importance. Many Ramsar sites are
also Special Protection Areas (SPAs) classified under the Birds Directive (see below) as
a result of selection of sites of importance to waterbirds within the UK. Of relevance to
the proposed development is the Severn Estuary Ramsar status. The Severn Estuary
Ramsar site is designated due to a number of attributes, including: the high tidal range,
the presence of Annex I habitats protected under the Habitats Directive (see below), the
presence of unusual estuarine communities (reduced diversity and high productivity),
the run of migratory fish between the sea and river via the estuary, the fish of the whole
estuarine and river system which is one of the most diverse in Britain, and wildfowl and
wader assemblages and species/populations of international importance. The
Bridgwater Bay National Nature Reserve (NNR) was designated a wetland ofinternational importance under the Ramsar Convention. Although this designation
applies to ornithological interest, this interest is in part dependent on the marine food
resources that are described and assessed in this Chapter and the Convention is
therefore of relevance in that respect.
The Convention on Biological Diversity 1992 (Ref 10.4)
10.2.2 This Convention focuses on the conservation of all species and ecosystems and
therefore provides protection to all biodiversity. The Convention requires the
development of national strategies, plans or programmes for the conservation and
sustainable use of biodiversity. In accordance with this the UK developed Biodiversity
Action Plans (BAPs) (see below for further information). For inter-tidal and sub-tidalzones, Species, Habitat, and Biodiversity Action Plans have been developed and are
considered in the evaluation of features potentially affected by the development. The
action plans provide guidance for the conservation and management of biodiversity
within the natural environment and are taken account of in this impact assessment.
The Oslo Paris (OSPAR) Convention for the Protection of the Marine Environment of the
North-East Atlantic (Ref. 10.5)
10.2.3 Annex V of the Convention provides a framework for contracting parties to develop their
own conservation measures. Article 2 requires parties to take necessary measures to
protect and conserve the ecosystems and the biological diversity of the maritime area,and to restore, where practicable, marine areas which have already been adversely
-
7/29/2019 Marine Ecology Jetty Es Chapter 10
4/100
Hinkley Point C Preliminary Works 10 - 4 Environmental Statement
Temporary Jetty Development November 2010
affected. Guidelines have been developed for the selection and management of Marine
Protected Areas and a series of Ecological Quality Objectives are being developed.
b) European Legislation
EC Directive on the Conservation of Wild Birds (2009/147 EC) (Ref 10.6)
10.2.4 The Birds Directive aims to protect all wild birds, their eggs, nests and habitats within
the EC. It also provides for the protection, management and control of all species of
naturally occurring wild birds that are considered rare or vulnerable within the EC as
listed in Annex I of the Directive. Under the Directive the most suitable areas for the
conservation of these species (land and sea) are classified at EU level as SPAs. In
England and Wales the Directive is implemented under the Wildlife and Countryside Act
1981 (as amended) and the Conservation of Habitats and Species Regulations 2010.
Of specific relevance to the proposed development is the Severn Estuary SPA.
10.2.5 The Severn Estuary qualifies as an SPA under Article 4.1 of the Birds Directive because
it is classified as a wetland of international importance regularly supporting at least20,000 waterfowl. In addition, it supports internationally important populations of over
wintering birds and birds on passage (see Chapter 11). Although this designation
applies to ornithological interest, this interest is in part dependent on marine food
resources that are described and assessed in this Chapter and the Directive is therefore
of relevance in this respect.
EC Directive on the Conservation of Natural Habitats and of Wild Fauna and Flora
(92/43/EEC) (EC Habitats Directive) (Ref 10.7)
10.2.6 Under the Habitats Directive, Special Areas of Conservation (SACs) can be designated
to maintain or restore the habitats listed in Annex I and the species listed in Annex II of
the Directive to favourable conservation status. Favourable Conservation Status is
defined in the context of habitats as the establishment of conditions which will ensure
that the extent and range of the habitat and the populations of the species within that
habitat will be maintained or increased over time. In relation to species; the viability,
population size and range of the species should be maintained in the long term. In
England and Wales the Directive is implemented under the Conservation of Habitats
and Species Regulations 2010. Of specific relevance to the proposed development is
the Severn Estuary SAC.
10.2.7 The designation of the SAC is due primarily to the presence of the Annex I habitats:
'Atlantic salt meadows', 'estuaries' and 'mudflats and sandflats not covered by seawater
at low tide'. The Annex I habitats: 'sandbanks which are slightly covered by seawater allthe time' and 'reefs' are also present as qualifying features, but are not the primary
reasons for the designation. The site is also designated due to the presence of the
Annex II species: twaite shad Alosa fallax, sea lamprey Petromyzon marinusand river
lamprey Lampetra fluviatilis.
The Water Framework Directive (2000/60EC) (Ref 10.8)
10.2.8 The Water Framework Directive (WFD) is the framework European legislation relating to
the protection of water quality and ecological status of freshwaters and coastal waters
and is, therefore, of relevance to the assessment of impacts on marine ecological
receptors.
-
7/29/2019 Marine Ecology Jetty Es Chapter 10
5/100
Hinkley Point C Preliminary Works 10 - 5 Environmental Statement
Temporary Jetty Development November 2010
10.2.9 The WFD provides a mechanism by which disparate regulatory controls on human
activities that have the potential to impact on water quality may be managed effectively
and consistently. In addition to a range of inland surface and groundwaters, the WFD
covers transitional waters (estuaries and lagoons) and coastal waters up to one nautical
mile from mean low water (the baseline from which territorial waters are measured).
10.2.10 Under the WFD all UK surface waters have been identified as waterbodies with
meaningful typologies that relate to physical and ecological characteristics. Based upon
ecology and water quality, these water bodies have been classified as falling into one of
five status classes. The WFD requires that all inland and coastal waters must reach at
least good status by 2015 and defines how this should be achieved through the
establishment of environmental objectives and ecological targets for surface waters.
EU Marine Strategy Framework Directive (Ref 10.9)
10.2.11 The objective of the EUs Marine Strategy Framework Directive is for EU marine waters
to achieve good environmental status by 2021 and to protect the resource base upon
which marine-related economic and social activities depend. This Directive constitutesthe environmental component of the EUs future maritime policy which has been
designed to achieve the full economic potential of the oceans and seas while conserving
the marine environment and is therefore of relevance to the assessment of impacts on
marine ecological receptors.
10.2.12 Under the Directive, each Member State within a marine region is required to develop
strategies for their marine waters. These strategies must contain a detailed assessment
of the state of the environment, a definition of good environmental status at a regional
level and the environmental targets and the establishment of monitoring programmes.
Cost-effective measures must be drawn up which include an impact assessment which
details a cost-benefit analysis of the proposed measures.
European Eel Regulation (Ref. 10. 10)
10.2.13 This Regulation established measures for the recovery of the stock of European eel.
The UK submitted 15 Eel Management Plans for approval by the European Commission
in December 2008. These plans are set at the River Basin District level, as defined
under the Water Framework Directive 2000/60/EC, covering England and Wales,
Scotland and Northern Ireland.
10.2.14 Eel Management Plans have been implemented from 2010 for the Severn Catchment
(Ref 10.11) and for South West England river basins, including the River Parrett (Ref
10.12), which aim to provide an escapement of silver eel biomass that is at least equalto 40% of the potential escapement to be expected in the absence of anthropogenic
influence. In addition, the European Eel Regulation requires that a system is in place to
ensure that by 2013, 60% of eel less than 12cm long which are caught commercially
each year are used for restocking in suitable habitat.
c) UK Legislation
10.2.15 The following environmental legislation is applicable to the proposed development:
-
7/29/2019 Marine Ecology Jetty Es Chapter 10
6/100
Hinkley Point C Preliminary Works 10 - 6 Environmental Statement
Temporary Jetty Development November 2010
The Water Environment (Water Framework Directive) (England and Wales) Regulations
2003 SI 3242 (Ref 10.13)
10.2.16 The Regulations provide the mechanism to implement river basin districts within
England and Wales in accordance with the WFD Directive. The Regulations require a
new strategic planning process to be established for the purpose of managing,protecting and improving the quality of water resources. Since the jetty development
could affect water quality, which could in turn indirectly affect marine ecology, the
Regulations are therefore of relevance herein.
The Conservation of Habitats and Species Regulations (2010) (Ref 10.14)
10.2.17 The Conservation of Habitats and Species Regulations 2010 (the Habitats Regulations)
consolidate and update the Conservation (Natural Habitats, &c.) Regulations 1994. The
1994 Regulations transposed Council Directive 92/43/EEC on the Conservation of
Natural Habitats and of Wild Fauna and Flora (EC Habitats Directive) into national law.
The Regulations implement the Habitats and Birds Directives (described earlier) and
make provision for the protection and management of sites, including the control ofpotentially damaging operations that may affect designated sites.
10.2.18 The Severn Estuary European Marine Site (EMS) is not a statutory site designation but
comprises the Severn Estuary SAC, SPA and Ramsar site. It represents a management
unit for those parts of Natura 2000 sites which extend beyond the Site of Special
Scientific Interest (SSSI). Advice on management and protection of the constituent
designated sites is provided by Natural England and CCW under Regulation 33 of the
Conservation (Natural Habitats, &c.) Regulations 1994 (now part of the Conservation of
Habitats and Species Regulations 2010).
The Wildlife and Countryside Act 1981 (as amended) (Ref 10.15)
10.2.19 The Wildlife and Countryside Act 1981 Act (as amended by the Countryside and Rights
of Way Act 2000 (CRoW)) (the Act) consolidates and amends existing legislation to
implement the Bern Convention and the Birds Directive. The Act strengthens provisions
under the National Parks and Access to the Countryside Act 1949 to establish National
Nature Reserves (NNRs) in England and Wales. The legislation provides for the
designation, protection and management of NNRs which can be established on land and
land covered by water so can therefore extend into the inter-tidal zone but not below low
water (e.g. the Bridgwater Bay NNR). These areas can be designated for their flora,
fauna or geological interests. The Act provides for the designation of SSSIs and Marine
Nature Reserves. The Bridgwater Bay SSSI is designated for a number of reasons
including the inter-tidal mudflats and saltmarshes and associated communities, theinternationally and nationally important numbers of over-wintering and passage migrant
wildfowl and waders and a number of other features.
Countryside and Rights of Way Act 2000 (Ref 10.16)
10.2.20 The Countryside and Rights of Way Act increases protection for SSSIs and strengthens
wildlife enforcement legislation (and is therefore of relevance to the assessment of
impacts on marine ecological receptors).
The Marine and Coastal Access Act 2009 (Ref 10.17)
10.2.21 The Marine and Coastal Access Act 2009 (the Act) aims to enable better protection of
marine ecosystems and prevent a decline in marine biodiversity. The Act sets out
-
7/29/2019 Marine Ecology Jetty Es Chapter 10
7/100
Hinkley Point C Preliminary Works 10 - 7 Environmental Statement
Temporary Jetty Development November 2010
provisions for more coherent planning in the marine environment in terms of issuing
consents and permits for activities in the marine and coastal environment. It provides
for enhanced protection of the marine environment and biodiversity, improved
management of freshwater and migratory fisheries in England and Wales and improved
access to the English coast. The Act contains provisions to allow for the designation of
Marine Conservation Zones (MCZs) and the creation of a network or Marine ProtectedAreas (MPAs). As one of the Acts aims is to protect marine ecosystems it is of
relevance to the consideration of the impacts of the jetty development on marine
ecology.
Salmon and Freshwater Fisheries Act (Ref 10.18)
10.2.22 The Salmon and Freshwater Fisheries Act 1975 (SAFFA) applies to salmon, trout
(including sea trout) and freshwater fish and, following implementation of the Marine and
Coastal Access Act (2009) (Ref 10.17), smelt and lampreys, This legislation is therefore
of relevance to the assessment of impacts on marine ecological receptors.
d) National Policy
Planning Policy Statement (PPS9): Biodiversity and Geological Conservation (Ref
10.19)
10.2.23 PPS9 sets out the Governments national planning policies on the protection of
biodiversity and geological conservation. Government objectives in relation to
biodiversity and geological conservation aim to conserve, enhance and restore
biodiversity, and promote sustainability. The aims and objectives of PPS9 are intended
to be delivered via Local Development Frameworks implemented by local planning
bodies.
10.2.24 PPS9 establishes a series of key principles that local planning authorities should adhere
to ensure that the potential impacts of planning decisions on biodiversity and geological
conservation are fully considered. This is accompanied by Office of the Deputy Prime
Minister (ODPM) Circular 06/2005 which provides administrative guidance on the
application of the law relating to planning and nature conservation.
10.2.25 The guidance advises that a strategic approach to the conservation, enhancement and
restoration of biodiversity and geology should be taken, recognising the contribution that
sites, areas and features (both individually and in combination) make to conserve these
resources.
10.2.26 The UK Biodiversity Action Plan (UK BAP) provides a detailed plan for the protection ofbiological resources and involves the implementation of Species Action Plans, Habitat
Action Plans and Local BAPs.
10.2.27 PPS9 advises that a key aim of planning decisions should be to prevent harm to
biodiversity and geological conservation interests. Adequate mitigation measures
should be put in place where necessary. Where a planning decision would result in
significant harm to biodiversity and geological interests which cannot be prevented or
adequately mitigated, then appropriate compensation measures should be sought.
10.2.28 With regard to SSSI designation the guidance states that where a proposed
development on land within or outside a SSSI is likely to have an adverse effect,
planning permission should not normally be granted. Where an adverse effect on thesites notified special interest features is likely, PPS9 advises that an exception should:
-
7/29/2019 Marine Ecology Jetty Es Chapter 10
8/100
Hinkley Point C Preliminary Works 10 - 8 Environmental Statement
Temporary Jetty Development November 2010
only be made where the benefits of the development clearly outweigh both the impacts
that it is likely to have on the features of the site that make it of special scientific interest
and any broader impacts on the national network of SSSIs.
10.2.29 Networks of natural habitats are considered within PPS9 to represent a valuable
resource. To reflect their importance, emphasis is placed upon Local Planning
Authorities to maintain networks by avoiding or repairing the fragmentation and isolation
of natural habitats through policies in plans.
UK Biodiversity Action Plan (Ref 10.20)
10.2.30 The UK BAP is the UK response to the Convention on Biological Diversity 1992. The
UK BAP describes the UKs biological resources and commits to a detailed plan for the
protection of these resources. Within the plan a list of priority species and habitats is
developed, for which specific action should be taken to conserve these species and
habitats. The implementation of the BAP is the responsibility of various statutory and
non-statutory organisations. This is a requirement of the Countryside and Rights of Way
Act 2000.
Eel Management Plans
10.2.31 Eel Management Plans have been implemented for the Severn Catchment and the
River Parrett (Refs 10.11 and 10.12).
e) Regional Policy
10.2.32 On 6 July 2010 the Secretary of State for Communities and Local Government revoked
all Regional Strategies with immediate effect under section 79(6) of the Local
Democracy, Economic Development and Construction Act 2009. This includes the
Regional Planning Guidance for the South West (RPG10).
10.2.33 Therefore, Regional Strategies no longer form part of the development plan for the
purposes of section 38(6) of the Planning and Compulsory Purchase Act 2004.
However, EDF Energy will continue to have regard to development plan documents,
saved policies and any old style plans that have not lapsed, as well as national policy
where relevant.
Somerset and Exmoor Joint Structure Plan 1996 2016 (Ref 10.21)
10.2.34 The Joint Structure Plan (JSP) provides the strategic base for all land use planning in
the combined area covered by Somerset and the Exmoor National Park for the periodup to 2016. The JSP policies relevant to marine ecology in the vicinity of the proposed
development include Policy 1: Nature Conservation and Policy 15: Coastal
Development.
10.2.35 Policy 1 on Nature Conservation states that the biodiversity of Somerset (and the
Exmoor National Park) would be protected, conserved, restored, enhanced, and
managed in accordance with the UK and relevant regional and local BAPs. Spatial
target habitats are provided for coastal sand dune, coastal vegetated shingle, and
Sabellaria alveolatareef. Maintenance target areas are set for coastal sand dune and
coastal vegetated sand dune, however, the full extent ofS. alveolatareef is not known.
A target has been set to mitigate the natural loss of coastal sand dune, although
establishment and restoration targets are ongoing for coastal vegetated shingle and S.alveolatareef.
-
7/29/2019 Marine Ecology Jetty Es Chapter 10
9/100
Hinkley Point C Preliminary Works 10 - 9 Environmental Statement
Temporary Jetty Development November 2010
10.2.36 Policy 15 on Coastal Development principally considers development on the coast and
emphasises the importance of protecting and enhancing natural marine resources
including those afforded international protection.
f) Local Policy
The West Somerset District Local Plan 2006 (Ref 10.22)
10.2.37 The Planning and Compulsory Purchase Act 2004 made a number of changes to the
planning system at the local level and, as a consequence, the West Somerset Local
Development Framework (LDF) (Ref 10.23) will replace the West Somerset District
Local Plan. However, until that time, policies in the West Somerset District Local Plan
have been saved for use in the planning process.
10.2.38 The objective that is defined in the Local Plan relating to nature conservation is: to
protect and where possible enhance the diversity of wildlife and habitats including
important landscape features in West Somerset. The policies in the Local Plan relating
to biodiversity are: NC/1 relating to effects on SSSIs; NC/2 relating to the protection ofsites of international importance; NC/3 relating to sites of local nature conservation
interest; NC/4 relating to species protection; and NC/5 relating to important wildlife
habitats.
Local Biodiversity Action Plan (LBAP) (West Somerset) (Ref 10.24)
10.2.39 Under the West Somerset biodiversity action plan, coastal vegetated shingle and S.
alveolatareefs are identified as priority habitats.
10.3 Methodology
a) Introduction
10.3.1 The baseline environmental studies and surveys and the impact assessment for marine
ecology have been conducted in accordance with all relevant best practices and
standard methodologies.
10.3.2 The identification of marine ecological impacts throughout the EIA process has been
based on guidelines provided by the Institute of Ecology and Environmental
Management (IEEM) (Ref 10.25). In this case the EIA methodology has been modified
to ensure generic consistency with the other Chapters in this ES and follows best
practice guidance.
10.3.3 The main elements of the EIA methodology include:
evaluation of marine ecological baseline information;
characterisation of potential impacts;
assessment of magnitude and significance of impacts;
proposal of mitigation measures appropriate to impacts; and
identification of residual impacts.
10.3.4 The elements of the jetty development which may have implications for marine ecology
were identified and assessed.
-
7/29/2019 Marine Ecology Jetty Es Chapter 10
10/100
Hinkley Point C Preliminary Works 10 - 10 Environmental Statement
Temporary Jetty Development November 2010
10.3.5 Impacts were assessed after taking into consideration aspects of project design, good
practices and protective measures which would be implemented as part of the
development (e.g. compliance with discharge consents).
b) Study Area
10.3.6 The study area for the inter-tidal marine ecology surveys for the Hinkley Point C Project
is outlined in Ref 10.26 (Volume 4, Section 10, Part B) (local scale studies stretching
from the western boundary of the development site to 100m east of the existing Hinkley
Point B water intake) and in Ref 10.27 (widescale studies from up to 8km north of the
River Parrett Estuary to 15km west of Hinkley Point). The sub-tidal study area is set out
in Ref 10.26 (Volume 4, Section 10, Part B) (local scale studies around proposed
intake and outfall locations), BEEMS (2009b) (Ref 10.28) and BEEMS (2009c) (Ref
10.29) (widescale studies within a radius of approximately 15km from the proposed
Hinkley Point C nuclear Power Station).
10.3.7 The main surveys of relevance to the impact assessment for this Chapter are the local
scale inter-tidal surveys, as identified above. These data have been supplemented withspecific surveys to record the presence of Corallina within the same study area, and
sub-tidal Sabellaria studies within a short distance offshore along the Hinkley Point
foreshore (see Figures 10-4 and 10-5, Volume 3). These studies identified and mapped
the location and extent of receptors of conservation importance, such as Sabellariaand
Corallina, which could be potentially impacted by the jetty development. The surveys
also provided information regarding receptors which could be present further afield, such
as diadromous fish and marine mammals; however, the main area of concern is the
Hinkley Point foreshore and the nearshore sub-tidal zone.
c) Baseline Environment Assessment
Marine Receptors
10.3.8 Marine ecological receptors were identified through:
a review of historical and recent data gathered specifically for the development;
desk-based assessment and modelling; and
consultation with Natural England, CCW and the Environment Agency, as detailed
in Section 10.1.
10.3.9 The baseline environmental assessment for marine ecology included the following
receptors:
microscopic plants, animals and fish larvae (phytoplankton, zooplankton, and
ichthyoplankton);
plants and animals on and in the sediment in offshore locations (sub-tidal benthic
flora, epifauna and infauna);
fish that live on or near to the sea bed and within the water column (benthic,
demersal and pelagic fish); and
inter-tidal fish, invertebrates and algae on the foreshore in front of and to the west of
Hinkley Point B.
10.3.10 A comprehensive review of the survey and sampling programmes undertaken for the
assessment is provided in the APEM Final Baseline Report (Ref 10.26) (Volume 4,
Section 10, Part B).
-
7/29/2019 Marine Ecology Jetty Es Chapter 10
11/100
Hinkley Point C Preliminary Works 10 - 11 Environmental Statement
Temporary Jetty Development November 2010
10.3.11 A two-year sampling programme was implemented to collect marine environmental
information for Hinkley Point and Bridgwater Bay. Field data were obtained from a
number of surveys and sources to collate a representative baseline marine ecology data
set for the area of potential impact around Hinkley Point.
10.3.12 The sampling commenced in February 2008 and included:
animals in the sediment in offshore locations (sub-tidal benthic infauna);
animals on the sediment in offshore locations (sub-tidal benthic epifauna);
fish that live on or near the sea bed (benthic/demersal);
fish larvae and eggs;
inter-tidal surveys from approximately 8km north of the River Parrett to
approximately 15km west of Hinkley Point; and
inter-tidal fish and epifauna.
10.3.13 These investigations were combined with mapping of the sea bed substrate and
physical studies (e.g. investigations of current speed, sediment load etc.). The results
were used to characterise the area and produce biotope maps for the area of potentialimpact.
d) Impact Assessment Methodology
10.3.14 The generic approach adopted for this impact assessment is presented in Chapter 5.
The specific methodology adopted for assessing the potential and actual environmental
impacts to marine ecology are outlined below.
Impact Magnitude
10.3.15 In addition to the generic guidance in Chapter 5, the following guidelines for the
assessment of magnitude in relation to impacts on marine ecology have been adopted
(Table 10.1).
Table 10.1 Guidelines for the Assessment of Magnitude
Magnitude Guideline
High The change permanently affects the ecological function of the habitat/speciesby reducing the ability to sustain the habitat or population levels of species ofinterest across its whole area. The integrity of the habitats/species and theconservation status of any of the designations are compromised. Habitats andspecies are degraded to the extent that locally rare populations and habitats
are lost and protected species and habitats experience widespread change.
Impacts not limited to areas within and adjacent to the development.
Medium Habitats/species are degraded to the extent that they experience a reductionin extent or number of individuals. The change substantially affects theecological structure and function of the habitat/species on a local scale but isnot likely to have an effect at a regional scale. Although it is not likely topermanently affect the integrity of the receptor it may change the evaluation ofthe habitat/species in terms of conservation status.
Impacts limited to the areas within and adjacent to the development.
-
7/29/2019 Marine Ecology Jetty Es Chapter 10
12/100
Hinkley Point C Preliminary Works 10 - 12 Environmental Statement
Temporary Jetty Development November 2010
Magnitude Guideline
Low The quality and availability of habitats and species experience some limiteddegradation. Disturbance to population size and occupied area is within therange of natural variability and there is not expected to be any permanenteffect on the integrity and/or key attributes of the receptor. The change isunlikely to change the evaluation of the habitat/species in terms ofconservation status.
Impacts limited to the area within the development.
Very Low Although there may be some impacts on individuals it is considered that thequality and availability of habitats and species would experience little or nodegradation. Any disturbance would be in the range of natural variability andthere would be no short-term or long-term effects on the integrity or keyattributes of the receptor.
Activities predicted to occur occasionally and for a short period. Impacts likely
to be reversible and not likely to coincide with sensitive life stages.
Impacts limited to the area within the development.
Receptor Value
10.3.16 In addition to the generic guidance in Chapter 5, an additional guideline definition of
value specific to marine ecology has also been proposed (Table 10.2). The overall
value rating is a combination of the generic and specific guidance.
Table 10.2 Guidelines for the Assessment of Value
Definition Value
High Feature / receptor possess key characteristics which contribute considerablyto the distinctiveness, rarity and character of the site / receptor, e.g.designated features of International/National designation / importance (SAC,SPA, Ramsar, SSSI, UK BAP etc.).
Feature / receptor possess important biodiversity, social/community value and/ or economic value.
Feature / receptor is rarely sighted.
Medium Feature / receptor possess key characteristics which contribute considerablyto the distinctiveness, rarity and character of the site / receptor, e.g.designated features of Regional / County designation / importance (RegionalBAP, SSSI, Local Nature Reserves).
Feature / receptor possess moderate biodiversity, social / community valueand / or economic value.
Feature / receptor is occasionally sighted.
-
7/29/2019 Marine Ecology Jetty Es Chapter 10
13/100
Hinkley Point C Preliminary Works 10 - 13 Environmental Statement
Temporary Jetty Development November 2010
Definition Value
Low Feature / receptor only possess characteristics which are of District or Localimportance. Feature / receptor not designated or only designated at thedistrict or local level, e.g. Local Nature Reserve.
Feature / receptor possess some biodiversity, social/community value and / oreconomic value.
Feature / receptor is relatively common.
Very Low Feature / receptor characteristics do not make a contribution to the characteror distinctiveness locally. Feature / receptor not designated.
Feature / receptor possess low biodiversity, social / community value and / oreconomic value.
Feature / receptor is abundant.
e) Uncertainties, Limitations and Assumptions
10.3.17 The assessment herein is based on available ecological information which has been
largely derived from baseline surveys conducted for the Hinkley Point C Project.
Methods used for the surveys adopted best practice including those outlined in the
Marine Monitoring Handbook (Davies et al. 2001; Ref 10.30) which incorporates the
recommendations of the Handbook for Marine Inter-tidal Phase 1 Survey and Mapping
(Wyn et al. 2000; Ref 10.31). Aspects of the UK National Marine Monitoring Programme
Green Book (NMMP 2003; Ref 10.32) were also taken into account. These documents
provide detailed standard methodologies for inter-tidal and sub-tidal sampling.
10.3.18 It should be noted that the surveys constitute a sample of a large and complex estuarine
system which, although undertaken throughout the year to allow for seasonal variations
(frequency depending upon survey subject), does not equate to continuous monitoring.
Variability in habitats and species may not therefore be fully recorded. However, it is
considered that the surveys were sufficiently well scoped and frequent to adequately
characterise the habitats and species main species and habitats present for this impact
assessment.
10.4 Baseline Environmental Characteristics
a) Introduction
10.4.1 This section presents the baseline environmental characteristics for the areas
designated for jetty development and surrounding area with specific reference to marine
ecology. The location of the area proposed for the jetty development is shown on Figure
10-1, Volume 3.
10.4.2 The Severn Estuary has one of the largest tidal ranges in the world, reaching in excess
of 13m at Avonmouth, a regime classified as hypertidal. The extreme tidal and turbidity
regimes of the Severn Estuary make it unique amongst British estuaries, with the
physical environment strongly influencing the distribution and productivity of the
biological assemblages present.
10.4.3 A consideration of these physical key features is provided in Chapter 9 and summarised
in Table 10.3 below.
-
7/29/2019 Marine Ecology Jetty Es Chapter 10
14/100
Hinkley Point C Preliminary Works 10 - 14 Environmental Statement
Temporary Jetty Development November 2010
Table 10.3 Key Physical Features of the Severn Estuary
Key Features:Physical
Comment
Large funnel shaped
estuary facing theAtlantic
Influences fish species (particularly migratory) and other physical
features, particularly tidal regime.
Large branchingestuary
Sub-estuaries absorb energy at tidal frequencies, but input energy atlonger frequencies because of river flow variation. The Parrett, Uskand others are not insignificant regarding freshwater influx into thesystem.
High salinityvariation
Seasonal and tidal variation Parrett significantly adds to this in theHinkley Point area.
Hypertidal Rare at global scale others include the Bay of Fundy (Canada),the Seine and the Somme (France).
Periodic energyinputs
Spring to Neap changes are major in magnitude, resulting in asystem with a major component of fortnightly change (as well asother tidal periods). Long periods of low winds reduce thesuspended solids concentrations, at least in surface waters. Thesedimentary system is therefore periodic, which directly effects thelight regime (hence production), the benthic habitats and thus thebenthos.
Waves dominant inshallow water
In shallow areas, waves are dominant over the effects of tidalcurrents. Most important in the Hinkley Point area are the inter-tidaland shallow flats where it is waves that are mostly responsible interms of mobilising and/or changing the physical environment andthus affecting the biota.
Areas of exposedrock
Large portions of the Bristol Channel and lower Severn Estuaryarecharacterised by exposed rock (see the figure provided in Appendix9-9, Volume 4).
Physics makeschange in sub-tidalhabitats the normnot the exception
Changes to the sediment transport system have the potential toinduce major changes in habitat. Changes in sediment distribution(natural and manmade) are likely and these would affect habitats by definition.
Highly turbid unique in UK
High concentrations of sediment are present within the water column(in both permanent and temporary suspension and is intermittently
deposited) but there is relatively little contribution from rivers or fromthe outer Bristol Channel.
Entrance to Parrett mobile banks
The mouth of the Parrett has a variety of inter-tidal and sub-tidalbanks, which consist of layered sediments and are extremelymobile. They thus tend to have low density biota.
Existing Parrettplume impact oninter-tidal area
Freshwater run-off peaks are significant in that they affect the extentof the existing Hinkley Point B power station thermal plume acrossBridgwater Bay.
Periodic majorchanges in bedelevation
Erosion/deposition cycles occur naturally and periodically, especiallyin the outer Bridgwater Bay.
-
7/29/2019 Marine Ecology Jetty Es Chapter 10
15/100
Hinkley Point C Preliminary Works 10 - 15 Environmental Statement
Temporary Jetty Development November 2010
Key Features:Physical
Comment
Residual circulation Tidal averaging of flows shows strong outward residual flow fromFlat Holm to the south side of channel off Kilve. Recirculation cellsoccur to north and south. This could trap persistent contaminants or
effluent, and provides routes for fish migration. Crudely summarisedas: fish in north, out south. This feature persists to Holm Island.Given the small magnitude of any residual circulation compared tothe regular tidal flows the significance of this feature is uncertain.
Benthic productiondominated by inter-tidal compared tosub-tidal
Due to a combination of the distribution of tidally driven bed shearforces and the extreme levels of turbidity present in the watercolumn, there is an apparent discontinuity in ecological productionwith little sub-tidally and that, over the soft inter-tidal areas, drivenlargely by microphytobenthos. The balance of primary production isthus skewed towards the inter-tidal zone.
Contains sub-
systems which arerelatively simple
The Bridgwater Bay ecosystem is relatively simple with few species
dominant. Mysids, crabs and brown shrimp (Crangon) are importantlinks in the food chain.
Migratory fishcorridor
Important for a number of species of conservation interest (shad,salmonids, eel, lampreys).
Impoverished sub-tidal benthos
Extremely poor compared to other estuaries, because of periodichighly mobile sea bed.
Highly productiveinter-tidal soft shorebenthos
Stable highly productive mud flats. The mudflats are of two generaltypes: (1) eroding Holocene muds and clays, which are relativelyresistant to erosion and able to form a habitat for infauna, and (2)periodically layered mobile sands and muds.
10.4.4 The Severn Estuary is recognised as an important conservation area and supports a
number of international, national and local designations for wetland habitats, bird
populations and the presence of other habitats and species of conservation interest.
Hinkley Point is fronted by a rocky foreshore with large areas of inter-tidal mudflats to
the east, and saltmarsh areas bordering the River Parrett. These inter-tidal areas are of
importance due to their role in supporting large numbers of over-wintering wildfowl.
10.4.5 The assemblages of organisms found in both inter-tidal and sub-tidal habitats are
characteristic of other UK estuaries in terms of the number and types of species present,
but are generally impoverished in terms of abundance. This is the direct result of high
tidal shear forces resulting in chronic sediment surface instability and extremely highturbidity levels.
10.4.6 The inter-tidal zone in front of, and on either side of, Hinkley Point B is dominated by a
shelving rocky shore with low abundances of organisms and low macroalgae biomass,
although patchy areas of high macroalgal cover are present. Sub-tidal habitats in the
vicinity of Hinkley Point consist of extensive areas of muddy sediments. The main
habitats of ecological importance on the foreshore are turfs of the red alga Corallina sp.
and those formed by tubes of the honeycomb worm Sabellaria sp.; aggregations of
these particular species can provide habitat for many other organisms and thus increase
local biodiversity. In its reef form, Sabellaria is listed as an Annex I species, protected
under the Habitats Directive. Although sub-tidal habitats exist within the study area that
are likely to be suitable forSabellariareef, no such formations have been identified.
-
7/29/2019 Marine Ecology Jetty Es Chapter 10
16/100
Hinkley Point C Preliminary Works 10 - 16 Environmental Statement
Temporary Jetty Development November 2010
10.4.7 Sub-tidal habitats are dominated by just a few species including bivalve molluscs,
polychaete worms and crustaceans. The dominant sub-tidal epifaunal species observed
is the brown shrimp Crangon crangon, and this species also has high abundance
relative to others within the inter-tidal zone. This species provides an important food
source for a number of fish species (e.g. cod, flatfishes, sea bass) and birds.
10.4.8 The high turbidity of the water column limits the primary production of phytoplankton
within the Severn Estuary. As such, densities of phytoplankton and zooplankton, and
the number of different species which can tolerate these conditions, have been found to
be relatively low when compared with other coastal waters. The sub-tidal benthic flora is
relatively homogenous in the vicinity of Hinkley Point and is dominated by inter-tidal
microalgae (microphytobenthos) which had been washed into sub-tidal areas. Remote
sensing studies provided evidence for the potential presence ofSabellaria reef in some
sub-tidal areas with some sections confirmed by means of ground-truthing.
10.4.9 Seven diadromous fish species are known to migrate through the Severn Estuary;
Atlantic salmon, twaite shad, allis shad, river lamprey, sea lamprey, sea trout and eel, all
of which are afforded protection under European Directives and/or national legislation.These species were either absent or recorded in low numbers at the Hinkley Point B
intake location and were not recorded during the local or widescale trawl surveys.
10.4.10 Some of the commercial fish species were caught in relatively large numbers; and the
most abundant species recorded at the cooling water intake screens at Hinkley Point B
to date have been sprat, whiting, sand goby, poor cod, Dover sole, pout, common sea
snail, bass, flounder and dab. The following ten UK BAP marine species (commercial
fish BAP) are found within the estuary: cod, herring, plaice, sole, whiting, blue whiting,
hake, horse mackerel, ling and saithe (coalfish). Fish populations were found to be
dominated by marine migrant species which spend most of their time at sea and a
number of months within the estuary. In addition, the majority of fish caught during
surveys were juveniles supporting the view that Bridgwater Bay is an importance
nursery area for juvenile fish. Few fish larvae or eggs were collected within the water
column during ichthyoplankton surveys although inter-tidal fish surveys found a number
of fish species utilised inter-tidal areas including species of potential commercial
importance such as sea bass. There is, however, little commercial fishing activity within
the Severn Estuary.
10.4.11 There are no resident populations of marine mammals within the estuary although a
number of species are thought to use the estuary as a feeding area during different
times of the year. The harbour porpoise is the most commonly recorded marine
mammal species in the Bristol Channel.
b) Statutory Designations
Severn Estuary SAC
10.4.12 The proposed development is situated at Hinkley Point adjacent to Bridgwater Bay
within the Bristol Channel (see Figure 1-2, Volume 3). The Severn Estuary is a SAC
(designated under the EC Habitats Directive (Ref 10.7)). The SAC has a western extent
which is slightly east of Hinkley Point (Figure 11-2, Volume 3). Its designation is due to
the presence of the following habitats and species:
10.4.13 Annex I Habitats (primary features)
-
7/29/2019 Marine Ecology Jetty Es Chapter 10
17/100
Hinkley Point C Preliminary Works 10 - 17 Environmental Statement
Temporary Jetty Development November 2010
Atlantic saltmeadows - Glauco-Puccinellietalia maritimae;
estuaries; and
mudflats and sandflats not covered by seawater at low tide.
10.4.14 Annex I Habitats (present)
sandbanks which are slightly covered by seawater all the time; and
Sabellariareefs.
10.4.15 Annex II Species (primary features)
twaite shad - Alosa fallax;
river lamprey - Lampetra fluviatilis; and
sea lamprey - Petromyzon marinus.
Severn Estuary SPA
10.4.16 The Severn Estuary occupies 24,663ha and was designated as a SPA in 1995. Itcomprises a range of different habitat types including: extensive inter-tidal mudflat and
sandflat, sub-tidal sandflat, saltmarsh, rocky platforms and islands. The estuary
qualifies as a SPA, under Article 4.1 of the Birds Directive, because it is classified as a
wetland of international importance regularly supporting at least 20,000 waterfowl.
10.4.17 In addition, it supports internationally important Annex I populations of overwintering
Bewicks swan (C. columbianus bewickii), curlew (N. arquata), dunlin (C. alpina alpina),
pintail (A. acuta), redshank (T. totanus) and shelduck (T. tadorna), and passage species
including ringed plover (C. hiaticula).
c) Marine Ecological Receptors
10.4.18 This section outlines baseline conditions based, in large, on Refs 10.26, 10.29, 10.30
10.33 and 10.34. In addition, the description draws on the findings of the long term
Severn Estuary Data Set (SEDS) data (Ref 10.35), which is the culmination of routine
sampling of fish and invertebrate catches over many years at Hinkley Point B.
Phytoplankton
10.4.19 Due to the very high suspended sediment concentrations, the photic depth in the
estuary is confined to the immediate surface waters, which greatly limits the primary
production of phytoplankton (Cloern, 1987 (Ref 10.36), Joint & Pomroy, 1981 (Ref
10.37), Joint, 1984 (Ref 10.38), STPG, 1989 (Ref 10.39)). Although somephytoplankton are present in the highly turbid sections of the Bristol Channel, primary
production rates are far greater in the less turbid areas. Inter-tidal sediments in the
Severn Estuary are known to support microphytobenthic populations, which are
frequently dominated by diatoms (Underwood, 1994; Ref 10.40). The re-suspension of
these algae (and the substrates they inhabit) has been demonstrated in the Eems
estuary, a large, physically dynamic estuary similar to the Severn (e.g. De Jonge & van
Beusekom, 1995 (Ref 10.41)). This suggests that it is largely re-suspended
microphytobenthos that contributes to the phytoplankton recorded in the Severn
Estuary.
10.4.20 There is limited published information available regarding phytoplankton populations in
the Bristol Channel and Severn Estuary. Rees (1939; Ref 10.42) and Underwood (1994;
Ref 10.40) provide some data on phytoplankton species recorded in the inner Bristol
-
7/29/2019 Marine Ecology Jetty Es Chapter 10
18/100
Hinkley Point C Preliminary Works 10 - 18 Environmental Statement
Temporary Jetty Development November 2010
Channel. Of the diatom species indicated in these records some species are primarily
benthic (e.g. Actinoptychusspp., Bacillaria paxillifer, Gyrosigma spp., Melosira arctica
and all the Nitzschia species), while planktonic species include Asterionella spp.,
Chaetocerosspp, Ditylum brightwellii, Odontella spp. and Helicotheca tamesis. This
suggests that at least some of phytoplankton component has a microphytobenthic origin.
10.4.21 In total 21 species were recorded off Hinkley Point from the phytoplankton surveys
carried out between November 2008 and October 2009. The most frequently recorded
species between November 2008 and July 2009 was the diatom Odontella regiawhich
was present at all, or nearly all, of the sites on each occasion. This species also had the
greatest density with the highest values recorded in July 2009 (reaching up to 1006
individuals per m3). However, this species was not recorded in the August and October
2009 samples, with Paralina sulcatabeing present at all sites in August and Odontella
sinensis present at nearly all sites during October. The densities of phytoplankton
varied among sampling periods with the highest phytoplankton densities recorded in
July 2009, at a mean density of 278 individuals per m3
(which was mainly due to high
numbers of O. regia). However, when compared with other British coastal waters,
phytoplankton densities were relatively low, which is likely due in part to the highturbidity of the Bristol Channel (water transparency of 10cm) (Ref 10.39).
10.4.22 The most frequently recorded species, Odontella regia, is regarded as a planktonic form.
This species was found to occur in a low light group of algae at Helgoland in the North
Sea (Ref 10.40) suggesting it may be capable of growth within the extreme conditions of
the Severn Estuary. In contrast, G. delicatulaand S. unipunctataare more typical of
coastal waters, suggesting they may have been transported into the estuary.
Zooplankton
10.4.23 The limitation of primary production due to elevated turbidity levels within the Severn
Estuary has the potential to reduce production of any zooplankton which feed on these
microscopic plants (Ref 10.36, Ref 10.37 and Ref 10.38). Estuarine zooplankton,
however, are primarily detritivores and it is considered that the main factor limiting
zooplankton growth within this system is the need to process high levels of solids for
relatively little gain.
10.4.24 Surveys of zooplankton were carried out by the Institute for Marine Environmental
Research (IMER) between 1971 and 1981 (Williams 1984; Ref 10.43). Williams
reviewed these data to describe the species assemblages, biomass and seasonal
cycles of zooplankton in the Bristol Channel and Severn Estuary. The assemblages
found were typical of estuaries in northern latitudes, both in terms of their abundance
and species composition. However, species diversity of the zooplankton in the BristolChannel, and in the Severn Estuary in particular, has been found to be relatively low
when compared to other coastal shelf areas around the UK (Collins & Williams 1981;
Ref 10.44).
10.4.25 The permanent planktonic animals (holoplankton) in the Bristol Channel are
predominantly copepods, as is the case for many other estuaries in the UK (Ref 10.43).
The temporary plankton (meroplankton) are represented by phyla such as decapods,
molluscs, echinoderms, annelids and fish (Ref 10.43). The dominant species are the
calanoid copepods which have been recorded in maximum densities in July following
increases in abundance in March, April and May (Refs 10.41 and 10.42). Mysids
(particularly Schistomysis spiritus) also constitute a large part of the total zooplankton
biomass in summer (approximately 80%) (Refs 10.45 and 10.43).
-
7/29/2019 Marine Ecology Jetty Es Chapter 10
19/100
Hinkley Point C Preliminary Works 10 - 19 Environmental Statement
Temporary Jetty Development November 2010
10.4.26 Salinity is an important environmental variable affecting zooplankton distribution, along
with temperature variation. The powerful tidal movements also have a considerable
influence (Refs 10.44 and 10.42). When considering the biomass of zooplankton in the
Bristol Channel and Severn Estuary, Rees (1939; Ref 10.42) identified a gradient from
high biomass at the seaward extent to low values further upstream. This gradient was
more pronounced in spring for the omnivores and in summer for the carnivores(reflecting the pattern of food availability). Peaks in omnivorous zooplankton biomass
occurred throughout the year. The carnivores, e.g. Sagitta spp. tended to be more
abundant in the latter half of the year when biomass was similar to that recorded for the
omnivores.
10.4.27 Entrainment sampling for zooplankton from the Hinkley Point B station has recorded a
total of 43 taxa between April 2007 and June 2009. Few species were recorded in
samples from the intake screens at Hinkley Point B during January and February 2009
which is likely to be due to reduced salinities within this area during the winter months
(Bamber & Henderson, 1994; Ref 10.45). The most abundant group over this sampling
period was the mysids which show a strong seasonal pattern in abundance. In addition
a notable feature of the long-term data collected at Hinkley Point has been the dramaticincrease in mysid abundance over the last 30 years. Peak mysid abundance is now
almost six times the level observed in the 1980s and 1990s (peak of ~3000 individuals
in 2008 samples in comparison with maximum of 500 individuals per sample in the
1980s and 1990s). Since the commencement of sampling, the mysid assemblage has
been dominated by three species, Schistomysis spiritus, Mesopodopsis slabberiand to
a lesser extent Gastrosaccus spinifer.
Ichthyoplankton
10.4.28 Zooplankton surveys conducted as part of the BEEMS programme were dedicated
towards gaining an understanding of ichthyoplankton (fish larvae and egg) abundance
and distribution. Overall, fish eggs from nine taxa were recorded: anchovy (Engraulis
encrasicolus), rocklings (Lotidae), gurnard (Triglidae), European sea bass
(Dicentrarchus labrax), Dover sole (Solea solea), solonette (Buglossidium luteum),
mackerel (Scomber scombrus) pilchard (Sardina pilchardus) scaldfish (Arnoglossus
laterna) and some unidentified eggs were also collected in June 2008 and May 2009.
Larvae of herring (Clupeidae), sprat (Sprattus sprattus), sandeel (Ammodytidae),
dragonet (Callionymidae), gobies (Gobiidae), Dover sole, European seabass and
solenette were also recorded (Ref 10.46). The majority of ichthyoplankton were caught
during the May 2009 surveys.
10.4.29 The most frequently recorded component of the ichthyoplankton was anchovy eggs
which were collected at over 30% of the sampling stations, with a maximum abundanceof 6.51 eggs per m
2(where abundance is standardised to the number of units under 1m
2
of sea surface). Historically, anchovy have been rarely reported in the area and its
presence here (in particular, the presence of eggs, indicating local spawning) might
indicate an increased northward distribution of the species from southern waters. The
second most abundant ichthyoplankton group was goby larvae (eggs were collected at
35% of the stations, with a maximum abundance of 2.46 eggs per m2) (Ref 10.46). High
densities of seabass larvae were recorded during the May 2009 surveys whereas
previously these had not been recorded. With the possible exception of anchovy, the
ichthyoplankton species identified during these surveys are not uncommon in coastal or
inshore waters and did not have distributions which could be construed as unusual.
-
7/29/2019 Marine Ecology Jetty Es Chapter 10
20/100
Hinkley Point C Preliminary Works 10 - 20 Environmental Statement
Temporary Jetty Development November 2010
Sub-tidal Benthic Fauna
10.4.30 The benthic faunal assemblage of the Severn Estuary is generally regarded as being an
impoverished and predominantly opportunistic assemblage of species due to the mobile
muddy sediments, high tidal shears and the highly turbid conditions of the estuary
(Mettam et al. 1994 (Ref 10.47) and Langston et al. 2007 (Ref 10.48)). For example, asurvey of the fauna of the deep water channel and marginal areas of the Severn Estuary
between Flatholm Island and King Pool, upstream of Hinkley Point reported that the
fauna of the Severn Estuary Sabellaria reefs is impoverished compared to similar
habitats in the Bristol Channel and elsewhere in the British Isles (Warwick et al. 2001;
Ref 10.49). Furthermore, Warwick & Davies (1977; Ref 10.50) collected samples of the
bottom fauna at 155 stations in the Bristol Channel from Lundy Island to just above
Holme Islands, and described the area around Hinkley Point as having a reduced hard
bottom community due to strong tidal scour.
10.4.31 As a result of the high tidal shears in the estuary a component of the infauna sampled in
the surveys detailed below may include hyperbenthic species (i.e. species which live
above, but close to the substratum) which would not normally be considered as acomponent of the infauna. Tidal shear may draw these species into the sediment
temporarily. Discussion of those species caught during each survey which could be
classed as hyperbenthic is provided in the relevant sections below.
10.4.32 Across the five survey periods a total of 56 distinct macrofauna taxa and 6 meiofauna
phyla were recorded. Of these the cumaceans Diastylis bradyiand D. rathkei, mysid
species and the amphipod Photis longicaudata could be classed as hyperbenthic
species. The highest numbers of taxa were recorded in February, June and August of
2008 (26, 30 and 26 taxa respectively (Ref 10.29)). During each of the surveys, several
stations had no macrofauna in any of the Day Grab samples and overall species
richness and macrofauna abundance was considered to be low.
10.4.33 Molluscs contributed the most to the macrofaunal biomass during each quarterly survey
period (typically contributing to >90% of the total biomass), although biomass varied
considerably across surveys. Distribution of biomass across the survey sites was
uneven, however, the dominance of molluscs (e.g. the bivalves Macoma balthicaand
Nucula nucleus) suggests that these taxa have an important role in the ecosystem as a
food source for fish.
10.4.34 Across all surveys, four species were consistently the most frequently sampled (i.e.
found at the most sites) and were also sampled at the greatest densities (i.e. mean
abundance per 0.1m2) within the macrofaunal samples. These species were N. nucleus
(bivalve), (mean of 3.2 individuals per m2
); M. balthica(bivalve), (mean of 2.2 individualsper m
2); Nephtys hombergii(polychaete), (mean of 0.7 individuals per m2); and Diastylis
rathkei(crustacean), (mean of 0.6 individuals per m2) (Ref 10.29).
10.4.35 In general, both macrofaunal species number and densities were found to be highest in
nearshore locations and were lower at the sampling sites further offshore. The
macrofaunal grab sample data showed no clear link between substratum type and the
assemblage present. Few colonial species were collected from the area.
10.4.36 The number of meiofauna phyla found at most stations was relatively low. Nematoda
was the dominant phylum across surveys and sites accounting for 94% of the meiofauna
present. There was some evidence that nematode densities were highest in November
2008 (77 130 individuals per 10cm2 SD.), and lowest in June (38 65 individuals per
10cm2
SD) (Ref 10.29) although the trend was weak. The composition of meiofaunal
-
7/29/2019 Marine Ecology Jetty Es Chapter 10
21/100
Hinkley Point C Preliminary Works 10 - 21 Environmental Statement
Temporary Jetty Development November 2010
assemblages with a dominance of nematodes was comparable with those encountered
in similar benthic environments worldwide (Coull, 1985 (Ref 10.51) and Probert, 1984
(Ref 10.52)). Meiofauna and nematode abundance was greatest at sites with mixed
sediments (e.g. sandy mud) as opposed to homogenous substrates of sand and mud, a
pattern which appeared unrelated to sediment depth.
10.4.37 A combination of widescale remote sensing studies and the results of the grab surveys
were used to generate a map of biotopes for the region (Figure 10-1, Volume 3 and
Table 4.2, for further details see Ref 10.26 (Volume 4, Section 10, Part B)). Biotopes
form basic mapping units and are defined according to a combination of both the
biological assemblages present and consideration of the physical characteristics of the
habitat. Biotopes were defined using the marine biotope classification of Connor et al.
(2004) (Ref 10.53). It should be noted that hyperbenthos and infauna within fluid muds
may be tidally redistributed over spring/neap cycles. Therefore, biotope descriptions
based on the assemblages of organisms present could vary considerably over relatively
short temporal scales and higher level descriptions based predominantly on sediment
type would be expected to remain more consistent across temporal scales. In other
words, habitat maps are generally a more reliable guide to the likely assemblageinvolved at any given sub-tidal locality.
Sabellaria
10.4.38 There are two species ofSabellaria in the UK, S. alveolataand S. spinulosa. The two
species have similar biology and ecology. Although individuals are not protected, they
tend to form large biogenic reefs by cementing together tubes constructed from sand. It
is the reefs themselves that are protected owing to the important ecological function they
perform. They often stabilise the sedimentary environment; provide hard substratum for
other sessile organisms to attach; can provide diverse habitat types (e.g. crevices); and
can alter local hydrodynamics, leading to accumulations of food particles for other
organisms (Holt et al. 1998; Ref 10.54). Their reefs are therefore protected under the
EC Habitats Directive (under which they are classed as Annex I biogenic habitats under
the 'Reefs' feature). The reefs are also referenced in the UK BAP which aims to:
maintain the extent ofS. alveolatareef habitats;
maintain the quality ofS. alveolatareef habitats; and
within 15 years, attempt to re-establish S. alveolatareefs in five areas where they
were formerly present.
10.4.39 A review of MarLIN habitat preferences and the sea bed surface map Figure 10-2,
Volume 3 suggest that areas dominated by mud and sand are unlikely to support the
development ofSabellariareefs in Bridgwater Bay. The recent extensive surveys havenot revealed any Sabellaria alveolata reef structures within these sandy and muddy
areas and their presence in these areas of substrate is unlikely.
10.4.40 Coarser sea bed habitats are most likely to support the development ofSabellariareefs.
Sabellaria presence has been recorded from some of the survey sites where such
substrates are present, but not in a form that would constitute reef habitat.
10.4.41 Sabellaria is, however, present in a form that would constitute reef on the lower shore
directly in front of Hinkley Point A. The distributions of the reef forms on the Hinkley
Point foreshore are directly coincident with the midfield dispersion pattern of the Hinkley
Point B power station thermal plume. Surveys carried out locally on the foreshore at
Hinkley Point report that the reefs growing within the flow of the cooling water discharge
from the power station are substantially larger, commonly greater than 15cm in height
-
7/29/2019 Marine Ecology Jetty Es Chapter 10
22/100
Hinkley Point C Preliminary Works 10 - 22 Environmental Statement
Temporary Jetty Development November 2010
and over 1m across, than those recorded elsewhere in the area. In addition, the greater
size and complexity of the reefs in the outfall area have been found to support a denser
and more diverse range of associated fauna (Bamber 1995; Ref 10.55). In 1990 a
detailed survey programme was initiated to investigate these differential growth rates.
10.4.42 The results of studies undertaken between September 1991 and March 1993 indicated
that individual worms were neither larger nor more abundant at the outfall; they were not
of a different species and displayed no differential recruitment. These factors could
therefore not account for the difference in reef size. Tube building has been found to be
greatest at 15 to 20C, lower at 10C and absent at 5C. Therefore the authors
suggested that the differential growth rates could be attributed to maintenance of a
higher metabolism and tube-building activity at the outfall site as a result of constant
temperatures during the winter months. In addition, any frost-effects are limited at the
outfall. In effect, there exists a functional relationship between the warmed plume and
the distribution of the Sabellaria reefs, with the most likely explanation being that the
plume, or the overlying warmed air at low tide, has protected these reefs from extremes
of air temperature in the past (Ref 10.55). Therefore, it is likely that upon cessation of
Hinkley Point B cooling water effluent discharges this particular reef could be lost, if notimmediately then possibly following a low temperature event. Such cyclic patterns of
growth and retreat ofSabellaria, even within undisturbed habitats, are expected within
the estuarine habitat.
10.4.43 Surveys of Sabellaria reef fronting the Hinkley Point site (for the distribution of
Sabellaria, see Figure 10-4, Volume 3) show that coverage on the lower shore fronting
the Hinkley Point A power station is relatively extensive covering lower shore bedrock.
The reef in this area was generally low lying with high percentage coverage throughout
its distribution, large areas were covered with a thin layer of sediment and some of the
areas of the reef higher up the shore were overgrown with ephemeral algae. Overall,
based on the classifications summarised in Connor et al. 2004 (Ref 10.53) it was
considered that the reef in this area was generally of reduced quality, with some areas
of moderate quality in which colonies were 10cm in height.
10.4.44 Recent characterisation surveys of Sabellaria aggregations off Hinkley Point (BEEMS
2010a; Ref 10.56) indicate that Sabellaria alveolata is more widespread and abundant
than S. spinulosain this area.
Sub-tidal Epifauna
10.4.45 Impingement and entrainment studies carried out at Hinkley Point B have provided
information on the epifauna captured each month at the cooling water intake for over
two decades. Of the epifauna caught, the common brown shrimp Crangon crangonwasthe most commonly caught species and had the greatest abundances (Henderson et al.
2007; Ref 10.57). The abundance of this species varied temporally with spawning
occurring in spring and high numbers of juveniles causing abundances to peak in the
autumn (Ref 10.45 and Henderson et al. 2006 (Ref 10.58)). Winter increases in
abundance ofC. crangonwere also evident at Hinkley Point as some individuals move
seawards to avoid low winter salinities and females move inshore to brood (Ref 10.45).
The population size of C. crangon has been found to be positively correlated with
average water temperature from January to August, and negatively correlated with the
Winter North Atlantic Oscillation Index (Ref 10.58). In general, the population of this
species has remained relatively stable since the 1980s, although there was a year of
exceptional recruitment in 2002 (Ref 10.58).
-
7/29/2019 Marine Ecology Jetty Es Chapter 10
23/100
Hinkley Point C Preliminary Works 10 - 23 Environmental Statement
Temporary Jetty Development November 2010
10.4.46 The preferred habitat forC. crangonis sandy and muddy ground with a grain size range
of 125 to 710m (MarLIN 2009; Ref 10.59). It is considered to be highly intolerant of
substratum loss, due to a decreased ability to forage and increased predation from
gadoids (e.g. cod). However, this species exhibits rapid growth, early maturation and
high fecundity, which would allow rapid population recovery (Ref 10.59). C. crangonwas
also found to be one of the most abundant epifaunal species during both the widescaleand local scale studies.
10.4.47 The second most abundant species caught at the intake screens was the pelagic ghost
shrimp Pasiphaea sivado (Ref 10.57). Whilst this species is considered pelagic as
opposed to strictly epifaunal it undergoes diurnal vertical migrations, moving throughout
the water column during the day and resting on the bottom at night. Other common
species caught at the intake screens included the demersal common prawn Palaemon
serratus, and pink shrimp Pandalus montagui, which have both shown a clear gradual
trend of increasing abundance in the estuary (Ref 10.57). Data from 2006 to 2007 and
previous decades, suggests that the abundance of shrimp and prawns near Hinkley
Point has increased since the 1980s. Due to a warm summer in 2006, the abundance of
species favouring warmer conditions was particularly high in 2007 with a record numberof these organisms being captured since the commencement of sampling (Ref 10.57).
Abundance of each of these species is known to vary seasonally in relation to
migrations and the timing of reproduction and the subsequent occurrence of juveniles
(Ref 10.45).
Inter-tidal Flora and Fauna
10.4.48 Hinkley Point is fronted by an area of inter-tidal rocky ledges and is flanked by further
inter-tidal rock, with occasional pockets of sediment to the west. To the east lie the
inter-tidal mudflats of Bridgwater Bay and the saltmarsh areas lining the River Parrett
Estuary.
10.4.49 In turbid estuarine environments with a restricted light regime, it is considered that
phytoplankton grow poorly in the water column, and that the microflora and macroflora
of inter-tidal areas and saltmarshes provide the greatest contribution to primary
production within the system (Radford 1994 (Ref 10.60)). In addition, sub-tidal
assemblages in the Severn Estuary and inner Bristol Channel generally have low
numbers of benthic fauna and low biodiversity (Warwick and Uncles 1980 (Ref 10.61),
Warwick 1984 (Ref 10.62), Ref 10.26 and Ref 10.29). This is due to the severe tidal
scouring, with frequent re-suspension of sediment, low primary production and variable
salinity regime. Hence, it can be expected that ecological activity in the Severn Estuary
is disproportionately concentrated in the inter-tidal zone and that any changes in the
function of the inter-tidal system could have direct impacts on the important migratorybird (and inter-tidal fish) populations, as well as other ecosystem services such as
nutrient cycling and sediment stabilisation.
10.4.50 The Severn Estuary supports an impoverished algal flora especially in terms of red
algae (Bamber & Irving 1992 (Ref 10.63), Ref 10.55, Seaby & Somes 2001 (Ref 10.64)
and Langston et al. 2003 (Ref 10.65). There are, however, small locally important red
algae communities such as the Corallina sp. run-offs in Bridgwater Bay (Ref 10.63,
Bamber & Irving 1993b Ref 10.66)). Corallinaturf habitats involving this species can be
found at Hinkley Point where they have developed on the littoral rock platforms. The
green algae Ulva lactuca can also be found associated with the Corallina turfs while
Fucus serratusis often present around the mat edges (Refs. 10.64, 10.65 and BEEMS
2008 (Ref 10.67)).
-
7/29/2019 Marine Ecology Jetty Es Chapter 10
24/100
Hinkley Point C Preliminary Works 10 - 24 Environmental Statement
Temporary Jetty Development November 2010
10.4.51 A number of surveys of the foreshore at Hinkley Point have been undertaken between
1982 and 2001 (Ref 10.67 and Martin 1993a (Ref 10.68)). Some of these studies have
recorded the presence of the mussel Mytilus edulis. The results of these surveys
indicate a stable community with low faunal and floral diversity.
10.4.52 Bamber (1984; Ref 10.69) undertook core sampling of the littoral fine mud substrate to
the east of Hinkley Point. The dominant macrofaunal species was the bivalve M.
balthicaand the polychaete worm Nepthys hombergii. Juvenile gastropods and small
spionid polychaetes were also frequently found within samples.
10.4.53 Underwood (1994; Ref 10.40) described the inter-tidal epipelic (sediment surface) floral
assemblages in the Severn Estuary from samples collected between 1990 and 1991.
Diatoms comprised over 95% of the living cells in most of these samples and
occasionally the non-flagellated euglenoid Euglena deseswas also abundant. Over 60
diatom taxa were identified with 15 to 20 of these recorded regularly throughout the
survey period. Nitzschia epithymoides dominated samples from the upper and mid-
shore sites in the early summer months and Navicula pargeminaduring the spring and
autumn. Rhaphoneis minutissimawas present in relatively high numbers throughout theyear on lower shores, although in winter, this species was more abundant on upper and
mid shores. Seasonal changes in diatom assemblages were more pronounced on the
upper shores of the inter-tidal mudflats. In general these areas were dominated by
single taxa (e.g. N. epithymoidesorN. pargemina) and diversity was greatest on the
lower shore.
10.4.54 Smith (1978; Ref 10.70) surveyed eleven inter-tidal sites between Kilve (downstream of
Hinkley Point) and Sharpness (in the upper estuary) on the English side of the estuary.
All of these sites lacked macroalgae below the limit of Mean Low Water Springs (MLWS)
which is thought to be due to the effects of high turbidity and sediment scour (Langston
et al. 2003 (Ref 10.65)). Zonation of algae within the inter-tidal areas was characteristic
of that normally observed on rocky shores with species such as Pelvetia canaliculata
and Fucus spiralis inhabiting areas higher on the shore and Fucus serratus and
Ascophyllum nodosumpresent from the mid to lower shore.
10.4.55 Two communities of algae were found to be present at most of the sites surveyed. One
of these was formed by the green algae Ulva intestinalis, Ulva prolifera, Blidingia
minima, and Blidingia marginataand the fucoids Fucus vesiculosusand P. canaliculata
which dominated between the limits of mean high water neap and spring tides. Between
mean high and low water neap tides, however, a different community was formed by the
dominant species A. nodosum, F. vesiculosusand F. serratus. On occasion, F. serratus
was found to extend beyond the mean low water neap mark, however, it was never
found below the mean low water spring mark (Ref 10.70).
10.4.56 There are large fringes of saltmarsh in the estuary. Spartinaspp. is particularly common
and is abundant in Bridgwater Bay NNR (especially around the mouth of the River
Parrett) in which Spartina anglicawas planted in 1929 as a flood defence measure. In
Bridgwater Bay, this species now covers an area 3km long and 0.3 to 0.45km wide with
an area of approximately 120ha (Hubbard & Ranwell 2006 (Ref 10.71)). The total area
of saltmarsh habitat in the Severn Estuary as a whole is reported as 1,521ha, the
majority of which (75%) occurs on the English side (Ref 10.48). The saltmarshes are
regarded as significant nature conservation features and contribute to the SPA, Ramsar
and SAC designations.
10.4.57 During recent inter-tidal surveys (see Figure 10-3, Volume 3) a total of 40 macrofaunal
taxa were sampled across the 40 soft-sediment inter-tidal stations. There was a mean
-
7/29/2019 Marine Ecology Jetty Es Chapter 10
25/100
Hinkley Point C Preliminary Works 10 - 25 Environmental Statement
Temporary Jetty Development November 2010
of 6.6 taxa per station and a trend of increasing species richness with increasing
elevation was noticeable in places, such as Berrow Flats. Data suggest that the areas
with the highest total macrofaunal densities were generally found along the higher-shore
regions of Berrow Flats and near the mouth of the River Parrett Estuary. Similarly,
areas with the greatest macrofaunal biomass were found to be along the upper shore
region of Brean Down and Berrow Flats and at a number of stations towards the west ofStert Flats. Initial univariate analysis indicated that neither elevation nor median
sediment grain size were useful predictors of macrofaunal biomass or numbers of
individuals. Total biomass was disproportionately dominated by relatively few taxa (i.e.
M. balthica 63%, Hediste diversicolor 15%, Hydrobia ulvae 8%). The most widely
distributed taxa were Hydrobia ulvaeand M. balthica(each observed at 36 stations) (Ref
10.72).
10.4.58 Comparison of these data with historical records suggests that current conditions may
not be universally consistent with the biotope map previously produced (e.g. EMU 2006
(Ref 10.73)). This may indicate the local sedimentary and biological environment is
heterogeneous on a smaller scale than shown on earlier biotope maps. Inconsistencies,
however, could also be due to slight differences in methodology, rather than changes inthe sedimentary environment or biological assemblages themselves.
10.4.59 Cluster analysis of the data was used to characterise six macrofauna assemblages, see
Figure 10-3, Volume 3. Of particular note are Assemblage D, Assemblage F and the
species S. alveolatathat form part of Assemblage E.
10.4.60 Assemblage D is comprised of two stations on the south bank of the River Parrett.
Assemblage D features Bathyporeia pelagica, which forms an important component of
the diet of shore birds. The majority of stations (31 of 40 stations), ranging in location
from the mid and upper shore regions of the Berrow and Stert Flats to the mouth of the
River Parrett form part of 'Assemblage F'. This mid to high shore mudflat assemblage is
critical to the overwintering bird populations and hence international legislative
protection of the Bridgwater Bay area. Although the assembl