About sediments and marine life: A clear cut and tight ...

Steven Degraer

About sediments and marine life:A clear cut and tight relationship?Some snapshots to set the scene for the NCK theme day

My background

PhD in Biology (Ghent University, 1999)

Scientific career

1994 – 2008 Ghent University: scientific collaborator

2008 – ctd.: Royal Belgian Institute of Natural Sciences: senior scientist Ghent University: guest professor

Scientific focus: benthic ecology of intertidal and shallow subtidal marine ecosystems

1994 – 2008: soft sediment environments 2008 – ctd.: hard substrate environments (among other topics)

Key messages

1. Benthos is abundant and can be found (nearly) everywhere.

2. Specific sediment types host specific benthic communities.

3. The sediment-benthos relationship can be used to predict what benthic fauna (and other fauna) to occur where.

4. Not only sediments drive benthos distribution patterns.

5. Sediment-benthos correlations do not equal cause-effect relationships.

6. On its turn, benthos activities impacts sediments.

Photographs: Hans Hillewaert, ILVO

Poster: Hans Hillewaert, ILVO

Benthos is numerous and can be found (nearly) everywhere

• Macro-infauna Belgian part of the North Sea

• 400+ species• Polychaetes, bivalves, amphipods,

decapods,…

• Habitat type• Soft sediment and hard substrate

benthos• Position

• Infauna, epibenthos and hyperbenthos

• Size• Microbenthos, meiobenthos,

macrobenthos,…

Grain size distribution

Benthos compositionSpecies richness, density, community composition

Sediment types and benthic communities

Hydrodynamic regime Sediment availabilityConceptual model

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Detrended Correspondence Analysis

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group 1 group 2group 3 group 4group 5 group 6group 7 group 8group 9 group 10

depthmud content

mediaan grain size Ophelia limacina – Glycera lapidumcommunity

Nephtys cirrosacommunity

INTERTIDALScolelepis squamata – Eurydice pulchra

community

Abra alba – Mysella bidentatacommunity

Van Hoey et al., 2004, ECSS

Median grain size

Increasing sediment mud content

Increasing (median) grain size

Degraer et al., 2003, reportVan Hoey et al., 2004, ECSS

Macoma balthicagemeenschap

Abra albagemeenschap

Nephtys cirrosagemeenschap

Ophelia limacinagemeenschap


Degraer et al., 2002, report


466000 467000 468000 469000 470000 471000 472000 473000 474000 475000

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UTM31-ED50 coordinates

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Median (µm)grain-size

Fine sands(125-250 µm)

Medium sands(250-500 µm)

Coarse sands(500-1000 µm)

Community GroupsM. mirabilis spec. ass.A. alba - M. bidentata comm.N. cirrosa comm.O. limacina - G. lapidum comm.

Nephtys cirrosacommunity

Abra alba – Mysella bidentatacommunity

Ophelia limacina – Glycera lapidumcommunity


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Sediment types and benthic communitiesHabitat suitability modeling

Sediment types and benthic communitiesHabitat suitability modeling

Degraer et al., 2008, CSR

Verfaillie et al., 2006, JCRVan Lancker et al., 2007, GIS@SEA

• Belgian part of the North Sea• Muds, muddy sands, fine

sands, medium sands, coarse sands to gravels

• High resolution maps of median grain size and mud content available

Sediment types and benthic communitiesSpatial interpolation of sediment distribution

Sediment types and benthic communitiesHabitat suitability modelling


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Macoma balthica community Abra alba community

Nephtys cirrosa community Ophelia limacina community


• Likelihood of occurrence

• Wider ecological relevance?

• Reliable within domain, less reliable outside domain

• Applicable to other ecosystem components?

Sediment types and benthic communitiesHabitat suitability mapping

Rees et al., 2007, ICES CRR

NSBP2000

Verfaillie et al., 2006, PhD thesis

• Similar macrobenthic communities in Southern Bight

• High resolution maps• Median grain size• Mud content

Sediment types and benthic communitiesHabitat suitability mapping outside model domain

Macoma balthica community Abra alba community

Nephtys cirrosa community Ophelia limacina community

Verfaillie et al., 2006, PhD thesis

Sediment types and benthic communitiesHabitat suitability mapping outside model domain

• Promising, yet with cross-border inconsistencies

Courtens & Stienen, 2012, Vogelnieuws


Sediment-based habitat suitabilityAlso relevant for higher trophic level organisms?


Great crested grebe

Abra alba community

Common scoter

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Habitat suitabilityNot only sediments matter



1 Macoma balthica community2 Abra alba community3 Nephtys cirrosa community4 Ophelia limacina community

400 - 450 m

SPM distribution types

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Median grain size categories

Rodriguez Palma, 2011, MSc thesis


Water column suspended particulate matter concentration

Hydrodynamic regime Sediment availability


Benthos compositionFeeding mode, living mode, …

Foodavailability

Oxygenconcentration

…

Conceptual model

Sediment-benthos correlations ≠ cause-effect relationships

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Example environmental drivers

• Grain size distribution• Sediment oxygenation• Organic matter concentration

Habitat needs determined by

• Substrate needs• Oxygen needs• Food needs

Example traits

• Burrowing mode• Breathing mode• Feeding mode

Correlation is not causation


Bulldozing does not work in muds.

Correlation is not causation

Example: burrowing modeEchinocardium cordatum

Lanice conchilega

Example: breathing mode

Pumping down oxygen-rich surface water supplies the organism with oxygen in an oxygen-poor environment.

Example: feeding mode

Deposit feeding only possible in areas where organic matter and hence fines are being deposited.

Arenicola marina

Hydrodynamic regime Sediment availability


Benthos compositionActivities linked to feeding and living mode

Foodavailability

Oxygenconcentration

…

Conceptual model

Sediment-benthos relation feedback loopsBenthos impacts sediments

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Braeckman et al., 2011, MEPSPhotographs: Hans Hillewaert, ILVO

• Surface deposit feeding• Abra alba

• Bio-irrigation(~ sediment “flushing”)

• Lanice conchilega

• Bioturbation(~ sediment reworking)

• Nephtys hombergii

Sediment-benthos relation feedback loopsBenthos activities impact sediments

Water content in sediment

Chlorophyll a in sediment

Phaeophtytin a

Degraer et al., 2008, RSEPhotograph: Hans Hillewaert, ILVO

• Locally elevated sediments• Higher sediment compaction• More fines inside aggregations

Sediment-benthos relation feedback loopsBenthos activities impact sediments and its morphology

Lanice conchilega

Side-scan sonar image

1. Benthos is abundant and can be found (nearly) everywhere.

2. Specific sediment types host specific benthic communities.

3. The sediment-benthos relationship can be used to predict what benthic fauna (and other fauna) to occur where.

4. Not only sediments drive benthos distribution patterns.

5. Sediment-benthos correlations do not equal cause-effect relationships.

6. On its turn, benthos activities impacts sediments.

Take home messages


QUESTIONS?

About sediments and marine life: A clear cut and tight ...

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