Trends in biomass, density and diversity of North Sea macrofauna

Total biomass and biomass of large taxonomic groups (polychaetes, molluscs, crustaceans, echinoderms) and species diversity of the macrofauna were determined for almost 200 North Sea stations sampled synoptically by seven vessels during Spring 1986 and for 120 additional stations sampled in earlier years by the Marine Laboratory in Aberdeen. There exists a clear and significant decreasing trend in biomass with latitude, both in total biomass and for the different taxonomic groups. Apart from latitude, sediment composition and chlorophyll a content of the sediment also infuence total biomass and biomass of most groups significantly. Biomass increases consistently in finer sediments and sediments with a higher chlorophyll a content. The same trends are found for the results within laboratories. Some interaction exists, indicating weak laboratory and zonal effects. Diversity, as measured by Hill's diversity index N1 = (exp H′) shows a clear and significant trend with latitude. Towards the north of the North Sea diversity increases considerably. The trend is also found for laboratories separately and is everywhere equally strong. Also longitude and depth show an effect on diversity. Sediment variables have no clear influence on diversity. Other diversity measures show the same trend but are more variable than N1,. Total density tends to increase towards the north, but sediment related variables have a larger influence. Mean individual weight becomes considerably smaller towards the northern part of the North Sea

The North Sea Benthos Project: planning, management and objectives

The ICES Benthos Ecology Working Group is integrating recent macrobenthic infaunal data (1999-2001) available from various sources, including national monitoring surveys, in North Sea soft bottom sediments. lt is expected to cover most of the North Sea. The main goal is an overall comparison with the North Sea Benthos Survey data of 1986, in order to determine whether there have been any significant changes and, if so, what may be the causal influences (e.g., climate change, fishing impacts). The work will contribute valuable information on several other topics such as habitat classification and the distribution of endangered species. Therefore, in addition to physico-chemical measurements of sediments samples alongside the benthic fauna, information on water depths, temperature, water quality and salinity will be incorporated in the analysis of species and community distributions. Also, we will use existing ecological and hydrographical models for currents, bottom shear stress and carbon input, along with information on the distribution of habitat types, to explain the observed distribution patterns. At the ASC, an overview of the data available will be presented as well as the anticipated outcomes, and the first steps taken to deal with taxonomic differences and other issues affecting the capability to integrate submitted information

Changes in North Sea macrofauna communities between 1986 and 2000

This paper is chapter 5.2 of the ICES CRR “Structure and dynamics of the North Sea benthos” (ICES 2007) compiled by the ICES Study Group on the North Sea Benthos Project 2000. The North Sea Benthos Project 2000 (NSBP) was initiated as a follow-up to the earlier 1986 ICES North Sea Benthos Survey (NSBS). One major aim of the NSBP 2000 was to compare the outcome with that of the 1986 NSBS, in order to identify any significant changes in the community structure and their likely causes. In general, the spatial distribution of the macrofaunal communities in 2000 was rather similar to that in 1986. But changes were found within communities which were addressed to changes in the hydroclimate caused by changes in the North Atlantic Oscillation influencing changes in currents and sediment structure as well as food availability

Alfred Giard et ses élèves Jules Bonnier et Philippe François. In "Du naturalisme à l'écologie", edité par F.G. Schmitt

L'année 2008 a marqué le centenaire de la mort de d'Alfred Giard, qui a été l'initiateur des recherches et observations sur la côte d'opale, et de l'établissement d'institutions de recherche à Wimereux. Auteur de plusieurs centaines d'articles, il a fait connaître Wimereux à l'étrangerà travers ses travaux. Par ses observations réalisés sur la côte d'opale, il a été le premier à faire connaître cet environnement au sein de la littérature scientifique internationale. Lorsqu'il a fondé la station zoololique de Wimereux en 1874 il s'agissait du quatrième laboratoire maritime ouvert sur les littoraux français, après Concarneau,Marseille et Roscoff. Nous avons organisé en juillet 2008 un coloque international et interdisciplinaire pour marquer le centenaire de la disparition d'Alfred Giard. Une première journée a été consacrée à des aspects historiques liés à l'activite scientifique de Giard : histoire des stations marines, histoire des activités de recherches marines dans le Boulonnais, histoire des théories sur l'évolution. Laseconde journée a été consacrée à l'écologie et observation de l'écosystème de la côte d'opale. Cet article d'introduction rappelle certains faits sur Giard,sur les stations de Wimereux et de la côte d'opale, et sur leur héritage et introduit les autres contribution

Long-term changes (1979-1994) in two coastal benthic communities (English Channel): analysis of structural developments

The long-term variations of two coastal benthic communities (Eastern English Channel, France) were studied between 1979 and 1994 by means of factor correspondence analysis (FCA), trophic structure and rank-frequency diagrams (RFD). FCA identified periods of relative homogeneity and periods of strong variation in the structure of the two communities. The first community, established on heterogeneous sand, showed a multi-annual cycle Linked to grain-size variations in the sediment. As passive supplies of organic matter were not important and suspension feeders could hardly live in these conditions, the community remained poor and stable and was dominated by deposit-feeders and carnivores. The other one, a rich and diverse mussel (Mytilus edulis) bed, showed great variations in the abundance of the main species which generated the enrichment of the community by its suspension-feeding behaviour (biodeposition). Beyond these variations, the community remained stable until 1990 as no continuous trend or permanent change could be seen. Since 1990, no recruitment of M. edulis occurred and the relative dominance of suspension feeders, as well as the number of species, strongly decreased. During the following years, several species of tunicates (sessile suspension feeders with gregarious recruitment) recruited and partly took the ecological niche of M. edulis but they did not induce an increase of biodeposition and the previous richness was not restored. After a strong and rapid shift in the structure, a new equilibrium has been established within the community.Les variations à long terme de deux peuplements benthiques côtiers ont été étudiées entre 1979 et 1994 au moyen d'analyses factorielles des correspondances (AFC), de l'étude de la structure trophique et des diagrammes rang-fréquence. Les AFC ont mis en évidence des périodes relativement homogènes et des périodes de variations importantes pour les deux peuplements. Le premier peuplement, établi sur des sables hétérogènes, montre une variation pluri-annuelle de sa structure fortement liée à celle de la granulométrie du sédiment. Les apports de matière organique étant assez faibles et les suspensivores étant peu abondants dans ce type de peuplement, celui-ci reste pauvre, relativement stable et dominé par les déposivores et les carnivores. Le deuxième peuplement, une moulière àMytilus edulis, présente de grandes variations de l'abondance relative de l'espèce principale M. edulis, à l'origine de l'enrichissement du peuplement et de la modification du sédiment par biodéposition. Au-delà de ces variations, la structure globale du peuplement paraissait stable jusqu'en 1990, quand aucun recrutement de M. edulis n'a été constaté. Après cette année-là, il semble qu'il n'y ait plus de recrutement de moules, ce qui s'est d'abord traduit par une baisse sensible du nombre d'espèces et de la dominance relative des suspensivores. Depuis, plusieurs espèces de Tuniciers (espèces sessiles suspensivores à recrutement grégaire) occupent la niche de M. edulis, mais leur activité suspensivore n'induit pas de bio-déposition susceptible d'enrichir le peuplement ou de modifier le sédiment et la richesse spécifique n'a pas été entièrement restaurée. Le peuplement a ainsi brusquement changé de structure pour constituer un nouvel équilibre stable à l'échelle de quelques années