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(IF 3.02 [2018]; Q1); International audience; The Rade de Cherbourg (RdC), in the North Cotentin (Normandy, English Channel) is the only French coastal zone where an offshore salmon farm has been in operation over the past three decades. Our study leads to the identification of the Ecological Quality status of benthic habitats based on a one-year survey (2013–2014) underneath and near the cages as well as in non-impacted areas lying outside the influence of salmon farming. The semi-diurnal high tide regime of the Rade de Cherbourg (5 to 8 m tidal range from neap to spring tide) should prevent any significant accumulation of Organic Matter (OM) under the cages. Nevertheless, higher Total Organic Carbon (TOC) and the presence of opportunistic species at sampling stations under and near the cages indicate an impact of salmon farming on the benthic habitats. Three benthic assemblages are identified, corresponding to three sediment types with different levels of OM enrichment. The presence of several indicator species, such as the polychaete worm Capitella minima belonging to the Capitellidae, reflects the local impact of fish farming without long-term accumulation of OM in the shallow waters of the RdC. Moreover, one of the main characteristics of the macrofauna of the RdC and neighbouring zones is the current very high abundance and dominance of the tanaid Apseudopsis latreillii in diverse sediment types. Benthic indices (AMBI, M-AMBI, and BO2A) were also able to distinguish three main zones in relation to the distance to salmon cages.

The ability of the two synthetic marine biotic indices, AMBI and M-AMBI, to account for changes in the ecological quality of coastal soft bottoms of Reunion Island according to disturbances was assessed from macrobenthic samples collected in five sectors between 1994 and 2004. Samples were collected under non-perturbed conditions and at two sites subjected to heavy organic enrichment. Both indices are based on a classification of macrofauna into ecological groups (EG), and their transfer to tropical waters required some adaptations. These indices proved efficient in detecting a degradation of habitat quality. Their use resulted in the classification of all sites sampled between 1996 and 1998 as "good" or "high". M-AMBI nevertheless tended to result in the attribution of a slightly worse ecological quality status than AMBI. Together with an update of the EG species list for the Indian Ocean area, our results support the extension of both indices for the assessment of tropical soft bottoms.

The occurrence and distribution of macrozoobenthos in estuaries are strongly related to sediment grain-size characteristics. However, statistical prediction of the distribution of benthic populations as a response to a single environmental gradient has proven to be difficult, because the focal variable may set upper limits to the abundance, but other (partly uncorrelated) variables may cause considerable deviation from the maximum. A multi-quantile regression approach is better suited to characterize biota–environment relationships than a single (average or boundary) estimation, because it shows the variation in responses and quantifies the relative importance of other unmeasured factors. Here, a univariate application of non-linear quantile regression is proposed to account for heteroskedasticity and non-linearity in the biological response to sediment grain size. The analysis was applied to a large macrozoobenthic dataset from the SW Delta area (The Netherlands) to compare the relationships between sediment granulometry and macrozoobenthos in 2 neighboring but differing temperate coastal ecosystems (Oosterschelde and Westerschelde). Preference of individual species for grain size was consistent between both systems, although in general, a slightly higher median grain size (ca. +60% in grain diameter) was preferred in the Oosterschelde than in the Westerschelde. The major difference in the community was, however, that mud-preferring species dominated the assemblage in the Westerschelde, and sand-preferring species dominated the Oosterschelde. Although the prevalence of muddy and sandy sediments in both systems is similar, in the Westerschelde, strong hydrodynamic stress is correlated with sandy habitats, causing impoverishment of assemblages at sandy sites. In the Oosterschelde, sandy sediments are usually associated with much more benign conditions and have the richest species assemblage.

Santo Andre is an enclosed brackish water coastal lagoon with temporary connections to the sea by a man-made channel. The exchange and mixture of saltwater and freshwater is irregular and the lagoon may show daily and seasonal fluctuations, but also long-term variation. Different benthic communities may be present along the annual cycle according to the magnitude of episodic freshwater and sea water inputs. In the last 30 years the communication with the sea has followed different regimes from year to year and, as a consequence, macrobenthic communities, assessed several times during the period before the opening to the sea, shifted from freshwater to marine affinities. Major differences were found between 1979 and 2010, with a preponderance of species with marine affinity, and the 1980s in which the organisms with freshwater affinity prevailed. Benthic communities are frequently used to assess aquatic environmental condition. Metrics used in the indices currently under discussion to assess ecological status of aquatic ecosystems within the scope of European Water Framework Directive were applied to Santo Andre data and the applicability of these metrics to assess quality in this coastal land-locked lagoon was discussed. (C) 2012 Elsevier Ltd. All rights reserved. National Institute of Scientific Research; ICNB (Nature, Conservation and Biodiversity Institute); EEC (European Economic Community); Cohesion Fund under Priority 111 of the Operational Programme for Territorial Development (POVT); FCT (Science and Technology Foundation) [PTDC/AAC-AMB/104639/2008, PEst-OE/MAR/UI0199/2011]; FCT [SFRH/BPD/29579/2006]

Numerical structure and the organisation of food webs within macrozoobenthic communities has been assessed in the European waters (Svalbard, Barents Sea, Baltic Sea, North Sea, Atlantic Ocean and the Mediterranean Sea) to address the interactions between biodiversity and ecosystem functioning. Abundance and classical species diversity indices (S, H', J) of macrofaunal communities were related to principal attributes of food webs (relative trophic level and food chain length, FCL) that were determined from carbon and nitrogen stable isotope values. Structure of marine macrobenthos varies substantially at a geographical scale; total abundance ranges from 63 ind. m(-2) to 34,517 ind. m(-2), species richness varies from 3 to 166 and the Shannon-Weaver diversity index from 0.26 to 3.26 while Pielou's evenness index is below 0.73. The major source of energy for macrobenthic communities is suspended particulate organic matter, consisting of phytoplankton and detrital particles, sediment particulate organic matter, and microphytobenthos in varying proportions. These food sources support the presence of suspension- and deposit-feeding communities, which dominate numerically on the sea floor. Benthic food webs include usually four to five trophic levels (FCL varies from 3.08 to 4.86). Most species are assigned to the second trophic level (primary consumers), fewer species are grouped in the third trophic level (secondary consumers), and benthic top predators are the least numerous. Most species cluster primarily at the lowest trophic level that is consistent with the typical organization of pyramidal food webs. Food chain length increases with biodiversity, highlighting a positive effect of more complex community structure on food web organisation. In more diverse benthic communities, energy is transferred through more trophic levels while species-poor communities sustain a shorter food chain. (C) 2011 Elsevier Ltd. All rights reserved.

International audience; Few works have examined the relative contributions of habitat variables to the distribution of coral reef urchins. In the present study, the spatial distribution of two common urchin species (Diadema setosum and Echinometra mathaei) was studied in the fringing reefs of two urban bays in New Caledonia (South Pacific). Urchins were surveyed at 105 stations with contrasted habitat structure/anthropic disturbance levels; 32 environmental variables (water/sediment characteristics, reef structuring species) were considered. Moderate densities were generally observed at station scale (mean 0.5 individuals m(-2)). The combination of univariate and multivariate techniques highlighted patchy distributions for Diadema as well as Echinometra, with distinct species/habitat associations; environmental gradients occurring within the bays did not seem to influence the species patterns. For Diadema, the spatial variability was better explained by sediment type than by biotic cover; increasing densities occurred across habitats with larger sediment sizes and decreasing coral complexity/macrophytes cover. In contrast, the distribution of E. mathaei exhibited weak relationships with habitat variables. In coral reefs, small-scale heterogeneity may thus be responsible for most of urchins spatial variability.

There is a growing need to predict ecological responses to long-term habitat change. However, statistical models for marine soft-substratum ecosystems are limited, and consequently there is a need for the development of such models. In order to assess the utility of statistical modelling approaches for predicting likely changes in species distributions under varying environmental conditions, we tested the utility of logistic modelling and classification approaches. We successfully developed models relating the presence/absence of common intertidal macrofauna to changing environmental variables such as sediment characteristics, depth/elevation, tidal currents and wind-wave (i.e. wind-generated wave activity) disturbance. The final model for each species contained between 1 and 6 variables, where the percentage correctly predicted was moderate to high, ranging from 59 to 97%. We were also able to identify relationships between higher level variables such as estuary type, basin morphometry and catchment-draining processes in driving macrobenthic community composition; however, we were unable to fully test the utility of the classification approach due to differences in the scale at which the macrobenthic data was collected and the scale of the higher level physical variables. These models were developed and tested using data that covered a range of environmental conditions in 5 estuaries in New Zealand. Such broad-scale statistical models play a critical role in our understanding of the likely effects of large-scale habitat change. However, a greater understanding of the fine-scale mechanistic controls on species distributions such as life-history characteristics, density information and biotic interactions would potentially lead to the development of more sensitive models. [KEYWORDS: Logistic regression · Statistical modelling · Classification systems · Benthic macrofauna · Sedimentation · Estuary · Macroecology · New Zealand]

Structured sampling designs are important in the assessment of environmental impacts of variable ecological systems. Recent developments have provided a useful framework extending existing univariate techniques into a multivariate context. Measures of taxonomic relatedness have also been introduced, which complement existing measures of diversity of assemblages. In this study, the potential effects of sewage discharge on spatial patterns of highly diverse molluscan assemblages in a Mediterranean rocky subtidal habitat were investigated. Nine 20 cm·20 cm quadrats were taken from each of three sites (80 m–100 m apart) within a putatively impacted location near a sewage outfall (I) and at each of two control locations (Cs) by destructive sampling by SCUBA divers at a depth of 3 m–4 m. A total of 5507 specimens of 151 species were collected. The average and the variance in total abundance of molluscs were greater, on average, at I than at Cs. Higher abundances at the sewage outfall were largely driven by greater numbers of juvenile molluscs. The Shannon diversity of molluscs (H¢) was significantly lower at I, but no difference among locations was detected for the total number of species (S). In addition, the taxonomic distinctness (D*) of molluscs was greater at Cs, although it was more variable at I. Multivariate analyses showed that there was a significant difference in the structure of assemblages at I compared with Cs. The location near the outfall was characterized by greater abundances of several species, including especially the gastropods Pusillina philippi, Bittium latreilli, and Bittium reticulatum. There was also greater variability in the structure of assemblages among sites and among quadrats at control locations compared to those near the outfall. Using a suite of univariate and multivariate measures, including diversity indices, detailed information on taxonomic structure and analyses of variability at different spatial scales, provided useful insights into the effects of sewage impacts on these diverse assemblages. These results also highlighted the importance of analysing measures of variance, as well as mean in considering effects of stress in natural communities. Structured sampling designs are important in the assessment of environmental impacts of variable ecological systems. Recent developments have provided a useful framework extending existing univariate techniques into a multivariate context. Measures of taxonomic relatedness have also been introduced, which complement existing measures of diversity of assemblages. In this study, the potential effects of sewage discharge on spatial patterns of highly diverse molluscan assemblages in a Mediterranean rocky subtidal habitat were investigated. Nine 20 cmx20 cm quadrats were taken from each of three sites (80 m-100 m apart) within a putatively impacted location near a sewage outfall (I) and at each of two control locations (Cs) by destructive sampling by SCUBA divers at a depth of 3 m-4 m. A total of 5507 specimens of 151 species were collected. The average and the variance in total abundance of molluscs were greater, on average, at I than at Cs. Higher abundances at the sewage outfall were largely driven by greater numbers of juvenile molluscs. The Shannon diversity of molluscs (H') was significantly lower at I, but no difference among locations was detected for the total number of species (S). In addition, the taxonomic distinctness (Delta*) of molluscs was greater at Cs, although it was more variable at I. Multivariate analyses showed that there was a significant difference in the structure of assemblages at I compared with Cs. The location near the outfall was characterized by greater abundances of several species, including especially the gastropods Pusillina philippi, Bittium latreilli, and Bittium reticulatum. There was also greater variability in the structure of assemblages among sites and among quadrats at control locations compared to those near the outfall. Using a suite of univariate and multivariate measures, including diversity indices, detailed information on taxonomic structure and analyses of variability at different spatial scales, provided useful insights into the effects of sewage impacts on these diverse assemblages. These results also highlighted the importance of analysing measures of variance, as well as mean in considering effects of stress in natural communities.

Five Weld surveys were conducted in an estu- arine intertidal sandXat of the Seto Inland Sea (Japan) between April 1994 and April 1995. Chlorophyll a, pheopigments, total organic carbon and acid-volatile sulphides (AVS) of surface and subsurface sediments, and macrofaunal assemblages were investigated in par- allel at 15 stations. Monthly hydrological data of low- tide creek water adjacent to the Xat were used as a com- plementary environmental characterisation of the study area. Strong temporal changes were found among sampling dates, most remarkably in autumn with a major increase of algal detritus and AVS, a sharp reduction in macrofaunal abundances and species rich- ness, and a massive mortality of the clam Ruditapes philippinarum. This dystrophic event was preceded by a photoautotrophic and hypertrophic spring-summer characterized by abundant fresh (i.e., living) algal mate- rial, including microphytobenthos and macroalgae (Ulva sp.). In summer, abundant macrofaunal assem- blages reached the highest biomass values (455 g wet weight m i2 or 60.6 g ash free dry weight m i2 ), with a major contribution of Wlter-feeding bivalves Musculista senhousia and R. philippinarum. These are among the highest values reported in the literature for sedimentary shores. From autumn, there was a progressive recoloni- sation of macrofauna, initiated by few opportunistic polychaetes (e.g., Cirriformia tentaculata and Polydora sp.), apparently promoting a fast sediment recovery in winter, and followed by new bivalve recruits in the next spring. This study provides the Wrst evidence of signiWcant and interlinked within-year changes in chemical char- acteristics of sediments and macrofaunal assemblages in an estuarine intertidal Xat at a small spatial scale (i.e., tens of meters). This demonstrates the high temporal variability of species-environment relations in these systems and a close relationship in seasonally driven trophodynamic processes among primary producers and benthic consumers. We conclude that a thorough parallel evaluation of the temporal changes in chemical characteristics of sediments should be taken into account in assessing the year-round distribution and changes of intertidal macrofauna, particularly in eutro- phic, estuarine intertidal Xats.