Human Footprint on the Seafloor Brussel - RBINS 2/9/2011

Changes in macrobenthos: past versus present

Jean-Sébastien Houziaux

BMM - UGMM Human Footprint on the Seafloor Brussel - RBINS 2/9/2011

New European legislation: what is a “Good Ecosystem State”? GES • Since the 1990s, various european Directives aimed at nature protection have been issued. The most recent is the « Marine Strategy » Framework Directive – « MSFD »

• The MSFD targets reaching a GES in European seas. Targets are defined for 11 different descriptors of the marine ecosystem, including « seafloor integrity ».

– “Sea-floor integrity is at a level that ensures that the structure and functions of the ecosystems are safeguarded and benthic ecosystems, in particular, are not adversely affected.”

• This directive and others involves the definition of objective criteria towards measurement of the GES

• The measurement of the amplitude of change induced by human pressures is necessary to set meaningful targets => Baseline assessment

=> Benthos composition = sensitive indicator for change in the seafloor condition => Monitoring Human Footprint on the Seafloor Brussel - RBINS 2/9/2011

Belgium: a unique historical macrobenthic data set: The surveys and material of G. Gilson, 1899-1908

Gilson’s « ground-collector »

Gilson’s dredge (Tow : one nautical mile) Human Footprint on the Seafloor Brussel - RBINS 2/9/2011

Seafloor and benthos, 1900: highlights Western coast: Epibenthic community moderate diversity of open-sea gravels: and density (in- and large taxonomic epifauna) diversity and densities

Highest densities (infauna), low species diversity Human Footprint on the Seafloor Brussel - RBINS 2/9/2011

Coastal waters: case of dominant bivalves • Long-term analysis challenges for coastal macrobenthos:

Gilson’s dredge data Ù Recent Van Veen data, 1994-2008 (joint DB of U. Gent + ILVO- Fisheries)

2°30 3° 3°30 ⇒ Sampling gear incompatibility: Point sampling Ù towed dredge (1,9 km long) Walchere Different efficiencies n 51°30 ⇒ Different spatial distributions NL ⇒ Historic data on soft-bottom

macrobenthos: polychaetes not robust yet Westerschelde estuary 51°20 • Solutions: – Spatial analysis of numerically dominant bivalves through data gridding 51°10 – Standardize abundances to maximum values => distribution of relative F densities – P/A data => difference maps Human Footprint on the Seafloor Brussel - RBINS 2/9/2011

Coastal waters: case of dominant bivalves General figures

45 1899-1914 40 1994-2008 Station occupancy rates 35

30

25

20

15

Station occupancy rate (%) 10

5

0

m ta ta a a la ida ica tus a ic e ru l c ta alba a u osa o pt tta n n lth enuis m Ensis 100%n to s lli i e a t g gi tul la e v id bra a y u a x btru A a b n p rru s s l a a llina fab ra u n lla b m e fe t is su e o lin a c Spi Do la s c Telli l T y a a is senegalensis 90% Sp Te im M isu My M ll e Sp T Venerup 80%

Tellimya ferruginosa 70% Ensis directus tenuis 60% Tellina pygmaea Tellina fabula Venerupis senegalensis 50% Mactra stultorum Macoma balthica 40% Spisula elliptica Spisula solida Contribution to total Mysella bidentata 30% Donax vittatus abundance Spisula subtruncata

Proportion oftotal abundance 20%

10%

0% 1899-1914 1994-2008 Human Footprint on the Seafloor Brussel - RBINS 2/9/2011

Coastal waters: case of dominant bivalves Geographic spreading

⇒ Probable impact of change in fine sediment dynamics (increased turbidity?)

Muddy fine sand ⇒ Probable effect of eutrophication / pollution: increased benthic species: biomass/productivity? Expansion BUT: (+ shifts in relative - Hydro-climatic factors (unlikely) density distribution) - Ensis directus invasion (unlikely) Shallow clean fine sand, filter- - Other factors (fishery effects)?… feeding species: Change 1900 – 1970 > Change 1970-2000s Regression => More ‘sophisticated’ biodiversity analyses once polychaete data checked Macoma balthica (estuarine): => Incorporation of recent data from Expansion from Schelde Dutch waters mouth to the entire coastal waters Human Footprint on the Seafloor Brussel - RBINS 2/9/2011

Westerschelde mouth : 1900 versus 1980-82 (J. Craeymeersch, IMARES)

Contribution to total density (14 species) Station occupancy (% stations - spreading)

100% Venerupis Phaxas 45.00 90% Nucula nitidosa 1900_F% Mya arenaria 40.00 Ensis siliqua var_ minor 1980_F% 80% Ensis 35.00 Cerastoderma edule 30.00 70% Angulus tenuis 25.00 60% Fabulina fabula 20.00 Aequipecten opercularis Tellimya ferruginosa 15.00 50% Striarca lactea Barnea candida 10.00 Modiolus modiolus 40% Spisula elliptica 5.00 Spisula solida Petricola pholadiformis 0.00 30% Mactra stultorum a t a a t a c a a Mytilus edulis t lb s n ic n a u is u e h t l r a t m s Donax vittatus t d l ta u i b i r a t d u a 20% b b i r m d a u b e o r i s Macoma balthica A v t l ic s a s l o t u a ll a x f o l a a u tu i s p o id l e m a l d li i e a Abra alba n ti s l d t s s u s o a la d i s y o y l e n c o r la i c a u o a s a r o a l n la u i Mysella bidentata p M D M t s la m c i is 10% c h i g u b u e S M p p u a n u l a s s a c u c fa a S i u r r r e n u s Spisula subtruncata a l e r e t in i r M l p n a a e d l o o i e p t e l s o S i r r f n a ia c a t o i s a n n a i d l in a g i r r o S a u l u E a s s t B y n l l b m a m n o a is 0% e M e e u r x m t a T g e _ e id p P li c e l r r t a l F n d e a i u e a n h r e p A o v e T i t m a P 1900_RA% 1980_RA% u s a a y la n a h e q r u M u e C q c V e li u A C i s N is s n E Human Footprint on the Seafloor Brussel - RBINS 2/9/2011

Present-day observation

• Ecosystem engineering – Rabaut and coll.

– Lanice conchilega (tube building segmented worm) • Essential structuring component of the “Abra alba” macrobenthic community – Owenia fusiformis (tube building segmented worm) • Sand bank stabilisation. Recently thriving

• And in the 1900s and 1970s? => Gilson data and literature Human Footprint on the Seafloor Brussel - RBINS 2/9/2011

Coastal ‘ecosystem engineers’ in the past

L. conchilega O. fusiformis • 1900: occasional - widespread • 1900: occasional, offshore • 1970: occasional • 1970: occasional, offshore • 1980s: common, max densities • 1980s: occasional, low densities 2000/m² • Mid-2000s: strong expansion in • 1990s-2000s: essential muddy fine sands with locally component of A. alba very large densities (max community – very large 11,000/m² => “reefs”) densities (max 10,000/m² => “reefs”)

• (NB. Typical component of sandy gravel associated fauna too)

=> Recent thriving Human Footprint on the Seafloor Brussel - RBINS 2/9/2011

Conclusions

• Macrobenthic communities of coastal waters since the 1970s are altered compared to the early 1900s, with different species thriving from the local pool. • Increased influence of background turbidity (i.e. increased chronic deposition of mud)? • Relatively more species contribute substantially to bivalve biomass: suggestion of biomass increase?

• Findings are consistent with moderate levels of organic enrichment in highly mixed coastal waters (eutrophisation effect)

• “Ecosystem engineer” tube-building worms: fate in the long run, link with ecosystem disturbance? Human Footprint on the Seafloor Brussel - RBINS 2/9/2011

Thank you for your attention !