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 45 40 35 Coastal waters: case of dominant bivalves 30 25 20 Station 15occupancy rate (%) 10 5 0 Mactra stultorum Spisula solida General figures Spisula elliptica Donax vittatus Human Footprint on the Seafloor Spisula subtruncata Mysella bidentata 1899-1914 Abra alba 1994-2008 Brussel - RBINS 2/9/2011 Macoma balthica Contribution to total abundance Tellina tenuis Tellina pygmaea Venerupis senegalensis Station occupancy rates Tellina fabula Ensis Tellimya ferruginosa 100% 90% 80% 70% 60% 50% 40% Proportion30% of total abundance 20% 10% 0% 1899-1914 1994-2008 Tellimya ferruginosa Ensis directus Tellina tenuis Tellina pygmaea Tellina fabula Venerupis senegalensis Mactra stultorum Macoma balthica Spisula elliptica Spisula solida Mysella bidentata Donax vittatus Spisula subtruncata Abra alba 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 Contribution to total density (14 species) 100% 90% 80% 70% Westerschelde mouth : 1900 versus 1980-82 (J. 60% 50% 40% 30% 20% 10% 0% Craeymeersch, IMARES) 1900_RA% 1980_RA% Venerupis Phaxas Nucula nitidosa Mya arenaria Ensis siliqua var_ minor Ensis Chamelea gallina Cerastoderma edule Angulus tenuis Tellina tenuis Fabulina fabula Aequipecten opercularis Tellimya ferruginosa Striarca lactea Barnea candida Modiolus modiolus Human Footprint on the Seafloor Spisula elliptica 45.00 Spisula solida Station occupancy (% stations - spreading) Petricola pholadiformis 40.00 Mactra stultorum Mytilus edulis 35.00 Donax vittatus Macoma balthica 30.00 Abra alba Mysella bidentata Spisula subtruncata 25.00 Brussel - RBINS 2/9/2011 20.00 15.00 10.00 5.00 0.00 Spisula subtruncata Mysella bidentata Abra alba Macoma balthica Donax vittatus Mytilus edulis Mactra stultorum Petricola pholadiformis Spisula solida Spisula elliptica Modiolus modiolus Barnea candida Striarca lactea Tellimya ferruginosa Aequipecten opercularis Fabulina fabula Tellina tenuis Angulus tenuis Cerastoderma edule 1900_F% 1980_F% Chamelea gallina Ensis Ensis siliqua var_ minor Mya arenaria Nucula nitidosa Phaxas Venerupis 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 !.