Seasonality in coastal macrobenthic biomass and its implications for estimating secondary production using empirical models

Macrobenthic secondary production is widely used to assess the trophic capacity, health, and functioning of marine and freshwater ecosystems. Annual production estimates are often calculated using empirical models and based on data collected during a single period of the year. Yet, many ecosystems show seasonal variations. Although ignoring seasonality may lead to biased and inaccurate estimates of annual secondary production, it has never been tested at the community level. Using time series of macrobenthic data collected seasonally at three temperate marine coastal soft-bottom sites, we assessed seasonal variations in biomass of macrobenthic invertebrates at both population and community levels. We then investigated how these seasonal variations affect the accuracy of annual benthic production when assessed using an empirical model and data from a single sampling event. Significant and consistent seasonal variations in biomass at the three study sites were highlighted. Macrobenthic biomass was significantly lower in late winter and higher in summer/early fall for 18 of the 30 populations analyzed and for all three communities studied. Seasonality led to inaccurate and often biased estimates of annual secondary production at the community level when based on data from a single sampling event. Bias varied by site and sampling period, but reached similar to 50% if biomass was sampled at its annual minimum or maximum. Since monthly sampling is rarely possible, we suggest that ecologists account for uncertainty in annual production estimates caused by seasonality.Agência financiadora EDF French Ministry of Higher Education, Research and Innovation French Ministry for the Ecological and Inclusive Transition through the Marine Strategy Framework Directive Agreement French Biodiversity Agency (Agence francaise pour la biodiversite) as part of the CAPANOUR projectinfo:eu-repo/semantics/publishedVersio

A life of systemic thinking : a tribute to Serge Frontier.

International audienc

Are the eastern and western basins of the English Channel two separate ecosystems: get back in line with some cautionary comments

International audienceThe European Marine Strategy Framework Directive (MSFD 2008/56/EC-17/06/2008) will be implemented in regions/subregions determined by their hydrology, oceanographic and biogeographic features. In this framework, Dauvin (2012) claimed that the English Channel (EC) is characterized by hydrologic, oceanographic and biogeographic features that support its division in two main ecosystems: the Western Basin (WBEC) and the Eastern Basin (EBEC). We think that this statement is controversial and that the conclusions drawn by Dauvin (2012) were not supported by the data presented, especially regarding the use of the term 'ecosystem'. We therefore re-evaluated this viewpoint with regard to the data and terminology used...

A Multilevel Core Sampler Device to Directly Estimate Food Supply Accessible to Waders

International audienceTo understand food webs functioning in intertidal soft-sediments, it is critical to assess the macrobenthic prey fraction accessible to waders. Here we describe a simple core sampler device allowing to directly relating the vertical distribu- tion of macrozoobenthos to waders bill length. Bill length measurements were used as a proxy of probing depth to esti- mate the amount of food supply accessible. Several metal plates can be inserted in the core sampler at different heights according to the bill length data of the studied species. These data are provided in a literature survey. For each species, the bill length variability is then explicitly taken into account in the estimation of food accessibility. The core is trans- parent to check for the quality of the sample. It could also be used to estimate a Benthic Habitat Quality index (BHQ) based on characteristics of the vertical structure of the sediment. This multilevel core is easy to build and to adapt to any studied wader species of the intertidal zone, floodplains or other wetlands. The samples are obtained with the same ef-fort as with usual circular cores leading to the possibility to survey large area. With one core sample, the ecological in-formation that can be achieved at once is threefold: 1) benthic community structure (partitioned in several depths), 2) estimate of the accessible food fraction to waders (range of values) and 3) habitat quality index assessmen

Rapid biogeographical plankton shifts in the North Atlantic Ocean.

International audienc

Effects of a brief climatic event on zooplankton community structure and distribution in Arcachon Bay (France)

Short-term changes in zooplankton community structure and distribution in relation to changes in hydrological features were studied during summer in two distinct areas of Arcachon Bay (France) from July to September 1986. One sampling site was chosen in the northern part of the bay, influenced by oceanic inputs, and the other one in the south-eastern part of the bay, close to an estuarine zone, influenced by the river Leyre's inputs. Three different zooplankton assemblages were identified according to a temperature-salinity gradient: (i) an estuarine assemblage dominated by Acartia bifilosa and Acartia tonsa, (ii) an autochthonous assemblage composed of Acartia discaudata, and (iii) a coastal neritic one composed of Paracalanus parvus, Oncaea venusta and Penilia avirostris. All these latter assemblages remained stable during most part of the study period. However, a brief climatic event (storm event) occurred in mid-August and gave rise to a sharp decrease in temperatures along with significant changes in zooplankton structure and distributions in the bay. The estuarine community vanished and was replaced by the autochthonous community. In the northern part of the bay, the coastal neritic community succeeded the previously observed autochthonous community

Surveillance Écologique et Halieutique Site de Gravelines. Novembre 2013 - Octobre 2014

This is the 37th annual surveillance report concerning the nuclear power plant of Gravelines. Its very high power level results from six plant units located on the shore and is characterised by a cooling system with a coastal surface input and output. The production of electricity began in 1980 and reached maximum in 1986. Surveys concern monitoring of pelagic system (hydrology, microbiology, phytoplankton, and zooplankton), fish populations (larvae and eggs of Sole and Sprat) or crustaceans (shrimps), and benthic macrofauna (intertidal and subtidal). This survey deals with spatial and temporal approaches (i) study of the direct impact by comparison of the input and output seawater stations, (ii) study of medium and long term evolution of the area by comparison with a reference station.Ce travail constitue le 37e rapport de surveillance du site électronucléaire de Gravelines dont la grande puissance énergétique est assurée par le fonctionnement de 6 tranches. Ce site, implanté sur le littoral, présente une prise d’eau de mer assurant le refroidissement du système et un rejet côtier d’eau chaude en surface. Le fonctionnement de la centrale a débuté en 1980 et elle a atteint la puissance maximale en 1986. La surveillance concerne les domaines pélagique (hydrologie, microbiologie, phytoplancton, zooplancton), halieutique (larves et œufs de Sole, de Sprat et crevettes grises), et benthique (intertidal et subtidal). La stratégie de surveillance est basée sur une approche spatiale et temporelle (i) Etude de l’impact immédiat par comparaison de la station « Prise d’eau » et de la station « Canal de rejet » sur une surface limitée (ii) Etude de l’évolution à moyen ou à long terme du milieu marin par rapport à une situation de référence (échelle locale)

Structure spatio-temporelle des peuplements macrobenthiques de la baie de Seine à plusieurs échelles d'observation

Structure spatio-temporelle du macrobenthos de la baie de Seine a été cartographiée, puis mise en relation avec les paramètres de l'environnement et enfin analysée à différentes échelles spatiales d'observation. Cette étude permet de mieux comprendre l'effet de l'incorporation de la dimension spatiale dans l'analyse du macrobenthos. Les données proviennet de deux campagnes d'échantillonnage, en septembre 1998 et en mai 1999, sur l'ensemble de la baie, et d'études conduites à plus échelles. La méthode de cartographie employée a identifié quatre groupes au sein de la baie. Parmi eux, le peuplement côtier des sables fins à Abra alba-Pectinaria koreni domine en automne, alors que celui des bancs denses d'Ophiothrix fragilis situé au large est dominant au printemps. À méso-échelle et aux deux saisons, la granulométrie et la profondeur structurent le mieux le macrobenthos. En revanche, au sein de chaque groupe, les relations espèces-environnement montrent une grande variabilité spatio-temporelle. Le changement d'échelle spatiale d'observation a montré l'étroite liaison existant entre ce changement d'échelle et les images en résultant. De plus, selon l'espèce considérée, la prise en compte dans les analyses soit des réplicats individuels, soit des stations cumulées a également un effet sur la représentation de leur répartition. Dans le cas des bancs denses d'Ophiothrix fragilis, le cumul des réplicats a formé des structures totalement isolés. En revanche, en considérant les données, réplicat par réplicat, une forte hétérogénéité spatiale est observée. Au niveau du peuplement, l'échelle de 15 km semblerait être suffisante pour pouvoir définir les grandes structures benthiques existantes. Des théories alternatives expliquant les structures et leurs liens avec les paramètres de l'environnement sont discutées et des perspectives de recherche sont proposés.LILLE1-BU (590092102) / SudocSudocFranceF

Surveillance écologique du site de production électronucléaire de Gravelines Novembre 2011– Octobre 2012

This is the 35th annual surveillance report concerning the nuclear power plant of Gravelines. Its very high power level results from six plant units located on the shore and is characterised by a cooling system with a coastal surface input and output. The production of electricity began in 1980 and reached maximum in 1986. Surveys concern monitoring of pelagic system (hydrology, microbiology, phytoplankton, and zooplankton), fish populations (larvae and eggs of Sole and Sprat) or crustaceans (shrimps), and benthic macrofauna (intertidal and subtidal). This survey deals with spatial and temporal approaches (i) study of the direct impact by comparison of the input and output seawater stations, (ii) study of medium and long term evolution of the area by comparison with a reference station.Ce travail constitue le 35e rapport de surveillance du site électronucléaire de Gravelines dont la grande puissance énergétique est assurée par le fonctionnement de 6 tranches. Ce site, implanté sur le littoral, présente une prise d’eau de mer assurant le refroidissement du système et un rejet côtier d’eau chaude en surface. Le fonctionnement de la centrale a débuté en 1980 et elle a atteint la puissance maximale en 1986. La surveillance concerne les domaines pélagique (hydrologie, microbiologie, phytoplancton, zooplancton), halieutique (larves et œufs de Sole, de Sprat et crevettes grises), et benthique (intertidal et subtidal). La stratégie de surveillance est basée sur une approche spatiale et temporelle (i) Etude de l’impact immédiat par comparaison de la station « Prise d’eau » et de la station « Canal de rejet » sur une surface limitée (ii) Etude de l’évolution à moyen ou à long terme du milieu marin par rapport à une situation de référence (échelle locale)