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The trophic ecology of piscivorous Arctic charr (Salvelinus alpinus (L.); charr) in the food webs of large subarctic lakes is not well understood. We assessed charr diets, parasites, growth, maturity, and stable isotope ratios in Fennoscandian subarctic lakes dominated by monomorphic or polymorphic whitefish (Coregonus lavaretus (L.)) populations. Charr density was low in all lakes, except in profundal habitats. Charr shifted to piscivory at small size (16-25 cm total length) and consumed a range of prey-fish sizes (2-25 cm). Cannibalism was observed in a few individuals from one monomorphic whitefish lake. Charr matured at 37-51 cm (5-8 years old), grew to 52-74 cm maximum observed length and 47-83 cm asymptotic length. Charr increased total area of convex hull and core stable isotopic diversity area of the fish community by 51-98% and 44-51% in monomorphic whitefish lakes, but only 8-11% and 7-10% in polymorphic whitefish lakes. The difference was due to increasing food-chain length in monomorphic whitefish lakes, whereas reliance on littoral carbon did not change. Charr were the top piscivores in monomorphic whitefish lakes, but played a less important role in polymorphic whitefish lakes, which contained a more diverse predator fauna.

Offshore wind farms (OWFs) in the North Sea are proliferating, causing alterations in local ecosystems by adding artificial hard substrates into naturally soft-bottom areas. These substrates are densely colonized by fouling organisms, which may compete for the available resources. While the distribution of some species is restricted to specific parts of the turbine, others occur across depth zones and may therefore face different competitive environments. Here we investigate the trophic niches of seven invertebrate species: three sessile (Diadumene cincta, Metridium senile, and Mytilus edulis), one hemi-sessile (Jassa herdmani) and three mobile species (Ophiothrix fragilis, Necora puber, and Pisidia longicomis) that occur in multiple depth zones. We hypothesized that these species would be trophic generalists, exhibiting trophic plasticity by selecting different resources in different depth zones, to cope with the different competitive environments in which they occur. We analyzed delta C-13 and delta N-15 of these species and their potential resources across depth zones. Our results show that most of these invertebrates are indeed trophic generalists which display substantial trophic plasticity, selecting different resources in different zones. Degree of trophic plasticity was not related to mobility of the species. There are two possible explanations for these dietary changes with depth: either consumers switch diet to avoid competition with other (dominant) species, or they benefit from the consumption of a non-limiting resource. Only Diadumene cincta was a trophic specialist that consumed suspended particulate organic matter (SPOM) independent of its zone of occurrence. Altogether, trophic plasticity appears an important mechanism for the co-existence of invertebrate species along the depth gradient of an offshore wind turbine.

Soil communities are considered to be remarkably species-rich and to have many generalist species with seemingly similar niche requirements. The composition of soil fauna communities is often highly variable even at the plot scale, and both the environment and the spatial configuration of microhabitats are regarded as important forces shaping the structure of local communities. However, to what extent these forces are important in different ecosystems is not clear. We examined the relative roles of environmental (abiotic), vegetation (biotic) and spatial variables (using Moran's eigenvector maps, MEM) for the small-scale variation in springtail (Collembola) communities in a 100 m(2) area of the forest floor of a mature Scots pine forest in central Sweden, with small variation in important environmental variables.We found that most of the small-scale variation in community composition could be explained by spatial variables, either alone or jointly with the environmental variables. Spatial variability in community composition, in turn, could be related to shifts in functional traits of the component species. Within local communities (samples), species showed a higher diversity than expected by chance in almost all examined traits, indicating that differences in resource and micro-habitat utilisation enable Collembola species to coexist. Competition between species is therefore likely to be important for structuring Collembola communities at this spatial scale. The results indicate that the spatial scale of study and heterogeneity of environmental factors influence soil fauna community assembly processes through effects on the relative importance of environmental filtering compared to filtering by limiting similarity or competitive exclusion. (C) 2016 The Authors. Published by Elsevier Ltd.

Soil communities are considered to be remarkably species-rich and to have many generalist species with seemingly similar niche requirements. The composition of soil fauna communities is often highly variable even at the plot scale, and both the environment and the spatial configuration of microhabitats are regarded as important forces shaping the structure of local communities. However, to what extent these forces are important in different ecosystems is not clear. We examined the relative roles of environmental (abiotic), vegetation (biotic) and spatial variables (using Moran's eigenvector maps, MEM) for the small-scale variation in springtail (Collembola) communities in a 100 m2 area of the forest floor of a mature Scots pine forest in central Sweden, with small variation in important environmental variables. We found that most of the small-scale variation in community composition could be explained by spatial variables, either alone or jointly with the environmental variables. Spatial variability in community composition, in turn, could be related to shifts in functional traits of the component species. Within local communities (samples), species showed a higher diversity than expected by chance in almost all examined traits, indicating that differences in resource and micro-habitat utilisation enable Collembola species to coexist. Competition between species is therefore likely to be important for structuring Collembola communities at this spatial scale. The results indicate that the spatial scale of study and heterogeneity of environmental factors influence soil fauna community assembly processes through effects on the relative importance of environmental filtering compared to filtering by limiting similarity or competitive exclusion.

International audience; Trace metal contamination in the European sardine and anchovy food web was investigated in the Gulf of Lions, NW Mediterranean Sea, including seawater and size fractions of plankton. The results highlighted: i) higher and more variable concentrations in the smaller plankton size classes for all metals except cadmium; ii) higher concentrations in anchovy versus sardine for all elements except lead; iii) different patterns of metal bioaccumulation through the food web: cobalt, nickel, copper, silver, lead and zinc displayed continuously decreasing concentrations (with the exception of increased zinc in fish only), while mercury concentrations dropped considerably in larger plankton size classes and rose significantly in fish. Lastly, cadmium concentrations were found to be highest in intermediate plankton size classes, with very low levels in fish. The need to efficiently characterize the biological composition of plankton in order to fully identify its role in the mobilization and transfer of metals was highlighted.

WOS:000463281500015; International audience; Understanding the nature and origins of food sources supporting coastal lagoon-inhabiting organisms is necessary to evaluate the ecological status of such ecosystems. The trophic ecology of a bivalve species Spondylus crassisquama was studied in the Ojo de Liebre lagoon (Baja California, Mexico), combining stable isotope (SI), fatty acid (FA) and sterol analyses along a transect under oceanic influences. The second objective of the study was to investigate if sterol compositions give complementary information to those obtained from FA and SI. Temporal and spatial patterns of the three biomarkers in bivalve tissues suggest oceanic inputs at the mouth of the lagoon, while the inner station was characterized by a contribution of local sources including an important role of micro heterotrophs. This study revealed that the association of lipid biomarkers provide higher taxonomic resolution of the spatiotemporal heterogeneity in nutrient sources influencing the trophic functioning of a large coastal lagoon.

Climate warming and consequent greening of subarctic landscapes increase the availability of organic carbon to the detrital food webs in aquatic ecosystems. This may cause important shifts in ecosystem functioning through the functional feeding patterns of benthic organisms that rely differently on climatically altered carbon resources. Twenty-five subarctic lakes in Finnish Lapland across a tree line ecotone were analysed for limnological and optical variables, carbon (delta C-13) and nitrogen (delta N-15) stable isotope (SI) composition of surface sediment organic matter (OM) and fossil Chironomidae (Diptera) remains to examine environmental controls behind chironomid functional feeding group (FFG) structure and their isotopic associations for assessing ecosystem functioning and carbon utilisation. We hypothesise that the chironomid SI signatures reflect increased allochthony with increasing allochthonous input, but the resource use may be altered by the functional characteristics of the assemblage. Multivariate analyses indicated that carbon geochemistry in the sediments (delta C-13, delta N-15, C/N), nutrients, indices of productivity (chlorophyll-a) and lake water optical properties, related to increasing presence of OM, played a key role in defining the chironomid FFG composition and isotopic signatures. Response modelling was used to examine how individual FFGs respond to environmental gradients. They showed divergent responses for OM quantity, dissolved organic carbon and nutrients between feeding strategies, suggesting that detritivores and filter feeders prefer contrasting carbon and nutrient conditions, and may thus hold paleoecological indicator potential to identify changes between different carbon fluxes. Benthic production was the primary carbon source for the chironomid assemblages according to a three-source SI mixing model, whereas pelagic and terrestrial components contributed less. Between-lake variability in source utilisation was high and controlled primarily by allochthonous OM inputs. Combination of biogeochemical modelling and functional classification is useful to widen our understanding of subarctic lake ecosystem functions and responses to climate-driven changes in limnology and catchment characteristics for long-term environmental change assessments and functional paleoecology.

Although seagrasses cover only a minor fraction of the ocean seafloor, their carbon sink capacity accounts for nearly one-fifth of the total oceanic carbon burial and thus play a critical structural and functional role in many coastal ecosystems. We sampled 10 eelgrass (Zostera marina) meadows in Finland and 10 in Denmark to explore seagrass carbon stocks (Corg stock) and carbon accumulation rates (Corg accumulation) in the Baltic Sea area. The study sites represent a gradient from sheltered to exposed locations in both regions to reflect expected minimum and maximum stocks and accumulation. The Corg stock integrated over the top 25 cm of the sediment averaged 627 g C m−2 in Finland, while in Denmark the average Corg stock was over 6 times higher (4324 g C m−2). A conservative estimate of the total organic carbon pool in the regions ranged between 6.98 and 44.9 t C ha−1. Our results suggest that the Finnish eelgrass meadows are minor carbon sinks compared to the Danish meadows, and that majority of the Corg produced in the Finnish meadows is exported. Our analysis further showed that > 40 % of the variation in the Corg stocks was explained by sediment characteristics, i.e. dry density, porosity and silt content. In addition, our analysis show that the root : shoot ratio of Z. marina explained > 12 % and the contribution of Z. marina detritus to the sediment surface Corg pool explained > 10 % of the variation in the Corg stocks. The mean monetary value for the present carbon storage and carbon sink capacity of eelgrass meadows in Finland and Denmark, were 281 and 1809 EUR ha−1, respectively. For a more comprehensive picture of seagrass carbon storage capacity, we conclude that future blue carbon studies should, in a more integrative way, investigate the interactions between sediment biogeochemistry, seascape structure, plant species architecture and the hydrodynamic regime.

WOS:000426027100014; Seasonal shell growth patterns were analyzed using the stable oxygen and carbon isotope values of live-collected specimens of the bivalve Callista chione from two sites in the Adriatic Sea (Pag and Cetina, Croatia). Micromilling was performed on the shell surface of three shells per site and shell oxygen isotopes of the powder samples were measured. The timing and rate of seasonal shell growth was determined by aligning the delta O-18(shell)-derived temperatures so that the best fit was achieved with the instrumental temperature curve. According to the data, shells grew only at very low rates or not at all during the winter months, i.e., between January and March. Shell growth slowdown/shutdown temperatures varied among sites, i.e., 13.6 degrees C at Pag and 16.6 degrees C at Cetina, indicating that temperature was not the only driver of shell growth. Likely, seasonal differences in seawater temperature and food supply were the major component explaining contrasting growth rates of C. chione at two study sites. Decreasing shell growth rates were also associated with the onset of gametogenesis suggesting a major energy reallocation toward reproduction rather than growth. These results highlight the need to combine scier-ochronological analyses with ecological studies to understand life history traits of bivalves as archives of environmental variables.

The limpet Patella vulgata is a key species of northern Atlantic rocky shore-associated communities, and is commonly considered to be important in regulating populations of canopy-forming Ascophyllum nodosum, through consumption of propagules and young recruits. Although P. vulgata is usually regarded as a non-selective epilithic biofilm grazer, a role in the collapse of established A. nodosum through grazing of adult plants has been repeatedly suggested. Factors controlling the preference of P. vulgata for epilithic biofilm or adult algae are still not clearly established. Here, we test the hypothesis that the diet of P. vulgata is mainly driven by the local availability of food sources. Limpets were sampled along the first 6 metres of an A. nodosum bed–bare rock gradient. Stable isotope ratios of their muscle tissue and digestive glands were measured. The contribution of A. nodosum to the diet of limpets was the highest in the immediate vicinity of macroalgae beds, which confirmed our initial hypothesis. However, the contribution of epilithic biofilm did not match our hypothesis, being the lowest for limpets colonizing bare rock. Instead, these limpets relied on a wide array of sources, including ephemeral green algae, biofilm and drifting A. nodosum fragments. Overall, our results indicate that A. nodosum can be readily grazed by limpets, which challenges the hypothesis that these macroalgae dominate rocky shores due to the absence of strong top-down control exerted by herbivores. Our results also highlight the need to consider the small spatial scale to understand the dynamic of herbivore–algae interactions in natural environments.

When a diet switch results in a change in dietary isotopic values, isotope ratios of the consumer's tissues will change until a new equilibrium is reached. This change is generally best described by an exponential decay curve. Indeed, after a diet switch in captive red knot shorebirds (Calidris canutus islandica), the depletion of C-13 in both blood cells and plasma followed an exponential decay curve. Surprisingly, the diet switch with a dietary N-15/N-14 ratio (N-15) change from 11.4 to 8.8 parts per thousand had little effect on N-15 in the same tissues. The diet-plasma and diet-cellular discrimination factors of N-15 with the initial diet were very low (0.5 and 0.2 parts per thousand, respectively). N-15 in blood cells and plasma decreased linearly with increasing body mass, explaining about 40 % of the variation in N-15. N-15 in plasma also decreased with increasing body-mass change (r(2)=.07). This suggests that the unusual variation in N-15 with time after the diet switch was due to interferences with simultaneous changes in body-protein turnover.

International audience; The influence of the crab Parasesarma erythrodactyla on the entry of the organic matter derived from Avicennia marina mangrove leaves in a sub-tropical mangrove ecosystem of southeast Queensland, Australia, was simulated using tidal mesocosms. Degradation of mangrove leaf organic matter was followed by analysing the fatty acid composition, carbon, and nitrogen isotopic signatures of the surface sediment and suspended particulate organic matter (SPOM) with and without the presence of crabs. Assimilation of mangrove organic matter by P. erythrodactyla was also assessed by stable isotope and fatty acid analyses in tissues and faeces. Results of the chemical tracer analyses question the adaptability of P. erythrodactyla to a diet comprised exclusively of mangrove leaves, and suggest that these organisms were dependent on additional food sources in their natural environment. Crab processing of senescent leaves significantly accelerated the transfer of mangrove organic matter to the surface sediments, as shown by a higher C/N ratio, a higher contribution of long-chain fatty acids and a more depleted C isotopic signature of sediment samples in the mesocosms with crabs compared to those without crabs

The potential of ecosystem engineers to modify the structure and dynamics of food webs has recently been hypothesised from a conceptual point of view. Empirical data on the integration of ecosystem engineers and food webs is however largely lacking. This paper investigates the hypothesised link based on a field sampling approach of intertidal biogenic aggregations created by the ecosystem engineer Lanice conchilega (Polychaeta, Terebellidae). The aggregations are known to have a considerable impact on the physical and biogeochemical characteristics of their environment and subsequently on the abundance and biomass of primary food sources and the macrofaunal (i.e. the macro-, hyper- and epibenthos) community. Therefore, we hypothesise that L. conchilega aggregations affect the structure, stability and isotopic niche of the consumer assemblage of a soft-bottom intertidal food web. Primary food sources and the bentho-pelagic consumer assemblage of a L. conchilega aggregation and a control area were sampled on two soft-bottom intertidal areas along the French coast and analysed for their stable isotopes. Despite the structural impacts of the ecosystem engineer on the associated macrofaunal community, the presence of L. conchilega aggregations only has a minor effect on the food web structure of soft-bottom intertidal areas. The isotopic niche width of the consumer communities of the L. conchilega aggregations and control areas are highly similar, implying that consumer taxa do not shift their diet when feeding in a L. conchilega aggregation. Besides, species packing and hence trophic redundancy were not affected, pointing to an unaltered stability of the food web in the presence of L. conchilega.

Xavier, José C. ... et. al.-- 17 pages, 2 figures, 1 table, Cephalopods (Mollusca: Cephalopoda) play an important role as keystone invertebrates in various marine ecosystems, as well as being a valuable fisheries resource. At the World Malacological Congress, held 21–28 July 2013 in Ponta Delgada, Azores, Portugal, a number of cephalopod experts convened to honour the contribution of the late Malcolm R. Clarke, FRS (1930–2013) to cephalopod research. Endorsed by the Cephalopod International Advisory Council (CIAC), the meeting discussed some of the major challenges that cephalopod research will face in the future. These challenges were identified as follows: (1) to find new ways to ascertain the trophic role and food web links of cephalopods using hard tissues, stable isotopes and novel concepts in theoretical ecology; (2) to explore new approaches to the study of cephalopod morphology; (3) to further develop cephalopod aquaculture research; (4) to find new ways to ascertain cephalopod adaptation and response to environmental change; (5) to strengthen cephalopod genetics research; and (6) to develop new approaches for cephalopod fisheries and conservation. The present paper presents brief reviews on these topics, followed by a discussion of the general challenges that cephalopod research is bound to face in the near future. By contributing to initiatives both within CIAC and independent of CIAC, the principle aim of the paper is to stimulate future cephalopod research

The western Antarctic Peninsula is experiencing strong environmental changes as a consequence of ongoing regional warming. Glaciers in the area are retreating rapidly and increased sediment-laden meltwater runoff threatens the benthic biodiversity at shallow depths. We identified three sites with a distinct glacier-retreat related history and different levels of glacial influence in the inner part of Potter Cove (King George Island, South Shetland Islands), a fjord-like embayment impacted since the 1950s by a tidewater glacier retreat. We compared the soft sediment meio- and macrofauna isotopic niche widths (d13C and d15N stable isotope analysis) at the three sites to investigate possible glacier retreat-related influences on benthic trophic interactions. The isotopic niches were locally shaped by the different degrees of glacier retreat-related disturbance within the Cove. Wider isotopic niche widths were found at the site that has become ice-free most recently, and narrower niches at the older ice-free sites. At an intermediate state of glacier retreat-related disturbance (e.g. via ice-growler scouring) species with different strategies could settle. The site at the earliest stage of post-retreat development was characterized by an assemblage with lower trophic redundancy. Generally, the isotopic niche widths increased with increasing size spectra of organisms within the community, excepting the youngest assemblage, where the pioneer colonizer meiofauna size class displayed the highest isotopic niche width. Meiofauna at all sites generally occupied positions in the isotopic space that suggested a detrital-pool food source and/or the presence of predatory taxa. In general ice scour and glacial impact appeared to play a two-fold role within the Cove: i) either stimulating trophic diversity by allowing continuous re-colonization of meiofaunal species or, ii) over time driving the benthic assemblages into a more compact trophic structure with increased connectedness and resource recycling.

Ecologically similar species may coexist when resource partitioning over time and space reduces interspecific competition. Understanding resource use within these species assem- blages may help predict how species relative abundance might influence ecosystem functioning. In the Gulf of St. Lawrence, Canada, 4 species of rorqual whales (blue Balaenoptera musculus, fin B. physalus, minke B. acutorostrata and humpback Megaptera novaeangliae) coexist during the summer feeding period. They can be observed within hundreds of meters of one another, suggest- ing an overlap in ecological niches; yet fine-scale habitat use analyses suggest some resource par- titioning. While major ecological changes have been observed in marine ecosystems, including the Gulf of St. Lawrence, we have little understanding of how the removal of predatory fish might cascade through ecosystems. Here, we take advantage of a 19 yr tissue collection subsequent to a fishery collapse (which occurred in 1992) to investigate trophic niche partitioning within a guild of rorqual whales following the loss of a key ecosystem component, groundfish. We analyzed stable isotope ratios for 626 rorqual individuals sampled between 1992 and 2010. Using Bayesian iso- topic mixing models, we demonstrated that the 4 rorqual species segregated trophically by consuming different proportions of shared prey. An overall increase in δ 15 N values over the study period (post groundfish collapse), particularly for fin and humpback whales, suggested a progres- sive use of higher-trophic level prey, such as small pelagic fish, whereas the stability of blue whale diet over time confirmed their specialized feeding behaviour. This study provides the first long- term assessment of trophic ecology among rorqual populations on this Northwest Atlantic feeding ground, and evidence for differential resource use among large marine predators following ecosystem change.

Global climate models suggest that Antarctic snowfall should increase in a warming climate and mitigate rises in the sea level. Several processes affect surface mass balance (SMB), introducing large uncertainties in past, present and future ice sheet mass balance. To provide an extended perspective on the past SMB of Antarctica, we used 67 firn/ice core records to reconstruct the temporal variability in the SMB over the past 800 yr and, in greater detail, over the last 200 yr. Our SMB reconstructions indicate that the SMB changes over most of Antarctica are statistically negligible and that the current SMB is not exceptionally high compared to the last 800 yr. High-accumulation periods have occurred in the past, specifically during the 1370s and 1610s. However, a clear increase in accumulation of more than 10% has occurred in high SMB coastal regions and over the highest part of the East Antarctic ice divide since the 1960s. To explain the differences in behaviour between the coastal/ice divide sites and the rest of Antarctica, we suggest that a higher frequency of blocking anticyclones increases the precipitation at coastal sites, leading to the advection of moist air in the highest areas, whereas blowing snow and/or erosion have significant negative impacts on the SMB at windy sites. Eight hundred years of stacked records of the SMB mimic the total solar irradiance during the 13th and 18th centuries. The link between those two variables is probably indirect and linked to a teleconnection in atmospheric circulation that forces complex feedback between the tropical Pacific and Antarctica via the generation and propagation of a large-scale atmospheric wave train.

Summary 1. New patterns and trends in land use are becoming increasingly evident in Europe's heavily modified landscape and else whereas sustainable agriculture and nature restoration are developed as viable long-term alternatives to intensively farmed arable land. The success of these changes depends on how soil biodiversity and processes respond to changes in management. To improve our understanding of the community structure and ecosystem functioning of the soil biota, we analyzed abiotic variables across 200 sites, and biological variables across 170 sites in The Netherlands, one of the most intensively farmed countries. The data were derived from the Dutch Soil Quality Network (DSQN), a long-term monitoring framework designed to obtain ecological insight into soil types ( STs ) and ecosystem types ( ETs ). 2. At the outset we describe ST s and biota, and we estimate the contribution of various groups to the provision of ecosystem services. We focused on interactive effects of soil properties on community patterns and ecosystem functioning using food web models. Ecologists analyze soil food webs by means of mechanistic and statistical modelling, linking network structure to energy flow and elemental dynamics commonly based on allometric scaling. 3. We also explored how predatory and metabolic processes are constrained by body size, diet and metabolic type, and how these constraints govern the interactions within and between trophic groups. In particular, we focused on how elemental fluxes determine the strengths of ecological interactions, and the resulting ecosystem services, in terms of sustenance of soil fertility. 4. We discuss data mining, food web visualizations, and an appropriate categorical way to capture subtle interrelationships within the DSQN dataset. Sampled metazoans were used to provide an overview of belowground processes and influences of land use. Unlike most studies to date we used data from the entire size spectrum, across 15 orders of magnitude, using body size as a continuous trait crucial for understanding ecological services. 5. Multimodality in the frequency distributions of body size represents a performance filter that acts as a buffer to environmental change. Large differences in the body-size distributions across ET s and ST s were evident. Most observed trends support the hypothesis that the direct influence of ecological stoichiometry on the soil biota as an independent predictor (e.g. in the form of nutrient to carbon ratios), and consequently on the allometric scaling, is more dominant than either ET or ST . This provides opportunities to develop a mechanistic and physiologically oriented model for the distribution of species’ body sizes, where responses of invertebrates can be predicted. 6. Our results highlight the different roles that organisms play in a number of key ecosystem services. Such a trait-based research has unique strengths in its rigorous formulation of fundamental scaling rules, as well as in its verifiability by empirical data. Nonetheless, it still has weaknesses that remain to be addressed, like the consequences of intraspecific size variation, the high degree of omnivory, and a possibly inaccurate assignment to trophic groups. 7. Studying the extent to which nutrient levels influence multitrophic interactions and how different land-use regimes affect soil biodiversity is clearly a fruitful area for future research to develop predictive models for soil ecosystem services under different management regimes. No similar efforts have been attempted previously for soil food webs, and our dataset has the potential to test and further verify its usefulness at an unprecedented space scale.

We analyzed stomach contents and muscle isotopic composition (delta C-13, delta N-15) of yellowstripe goatfish Mulloidichthys flavolineatus from a coral reef to investigate size-related dietary changes and resource or habitat partitioning. Juveniles (\textless 12 cm total length [TL]), young adults (12 \textless= TL \textless 17 cm) and adults (\textgreater= 17 cm TL) showed a high diet overlap, especially between juveniles and young adults. According to stomach contents analysis, M. flavolineatus widens its prey spectrum with increasing size from a common prey pool that includes polychaetes, tanaids and harpacticoid copepods. We observed a significant increase in delta C-13 values (from -17.1 +/- 0.5 parts per thousand for juveniles to -10.7 +/- 0.8 parts per thousand for adults), which were correlated to fish size. Adults (delta N-15 mean of 11.1 +/- 1.8 parts per thousand) were one trophic level above juveniles and young adults (7.7 +/- 0.5 and 7.4 +/- 0.5 parts per thousand, respectively). These patterns of isotopic changes confirmed ontogenetic dietary shifts. However, trophodynamics can be influenced by physiological factors such as growth and sexual maturity. M flavolineatus shift from a pelagic to a macrobenthic diet, which is equilibrated at the adult stage. Results from combined stomach contents (prey volume) and stable isotope analyses suggested a dominant contribution of polychaetes (macrofauna), possibly through selective feeding. Conversely, on the basis of prey volume and stable isotope data, meiofauna did not feature significantly in the diet despite their high abundance in stomachs. Two adult groups were distinguished based on their delta N-15 values (11.9 +/- 0.8 and 7.8 +/- 0.6 parts per thousand), indicating possible stage-specific partitioning in habitat use inside the reef.

International audience; Agricultural pests are not restricted to crops, but often simultaneously or successively use different cultivated and uncultivated hosts. Nevertheless, the source-sink role of cultivated and uncultivated habitats in the life cycle of crop pests remains poorly understood. This is largely due to the difficulty of tracking displacements of small organisms in agricultural landscapes. We used stable-isotope ratios in order to infer the natal host plant of individuals of the English grain aphid Sitobion avenae colonizing wheat fields in autumn. We showed that among the numerous plant sources of S. avenae, maize, which has been intensively grown in western France since the 1960s, provided most aphids that attack wheat fields early in autumn. This study illustrates how insect pests respond to land-use changes within a relatively short period of time, rapidly acquiring a new host that in turn affected their population biology considerably by playing a pivotal role on their annual life cycle