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Microplastic particles (MP) contaminate oceans and affect marine organisms in several ways. Ingestion combined with food intake is generally reported. However, data interpretation often is circumvented by the difficulty to separate MP from bulk samples. Visual examination often is used as one or the only step to sort these particles. However, color, size, and shape are insufficient and often unreliable criteria. We present an extraction method based on hypochlorite digestion and isolation of MP from the membrane by sonication. The protocol is especially well adapted to a subsequent analysis by Raman spectroscopy. The method avoids fluorescence problems, allowing better identification of anthropogenic particles (AP) from stomach contents of fish by Raman spectroscopy. It was developed with commercial samples of microplastics and cotton along with stomach contents from three different Clupeiformes fishes: Clupea harengus, Sardina pilchardus, and Engraulis encrasicolus. The optimized digestion and isolation protocol showed no visible impact on microplastics and cotton particles while the Raman spectroscopic spectrum allowed the precise identification of microplastics and textile fibers. Thirty-five particles were isolated from nine fish stomach contents. Raman analysis has confirmed 11 microplastics and 13 fibers mainly made of cellulose or lignin. Some particles were not completely identified but contained artificial dyes. The novel approach developed in this manuscript should help to assess the presence, quantity, and composition of AP in planktivorous fish stomachs.

SUMMARYThere is currently a great deal of interest in using stable isotope methods to investigate diet, trophic level and migration in wild cetaceans. In order to correctly interpret the results stemming from these methods, it is crucial to understand how diet isotopic values are reflected in consumer tissues. In this study, we investigated patterns of isotopic discrimination between diet and blood constituents of two species of cetaceans (killer whale, Orcinus orca, and bottlenose dolphin, Tursiops truncatus) fed controlled diets over 308 and 312days, respectively. Diet discrimination factors (⌬; mean ± s.d.) for plasma were estimated to ⌬ Supplementary material available online at

Effects of physiological processes such as gestation, lactation and nutritional stress on stable isotope ratios remain poorly understood. To determine their impact, we investigated these processes in simultaneously fasting and lactating northern elephant seals (Mirounga angustirostris). Stable carbon and nitrogen isotope values were measured in blood and milk of 10 mother-pup pairs on days 5 and 22 of lactation. As long-and short-term integrators of diet, blood cells and serum may reflect foraging data or energy reserves from late gestation and lactation, respectively. Limited changes in isotopic signatures of maternal blood over the lactating period were highlighted. Nitrogen isotope fractionation associated with mother-to-offspring 1 2 MARINE MAMMAL SCIENCE, VOL. **, NO. **, 2010 transfer of nutrients was generated between mother and offspring during gestation and lactation. This fractionation was tissue and time-specific, it varied between early and late lactation from +0.6 to +1.3 in blood cells and from +1.1 to nonsignificant value in serum. Therefore, if pups appear to be good proxies to investigate the female trophic ecology especially for C sources, much more caution is required in using ␦ 15 N values. Further studies are also needed to better define the relative impact of fasting and lactation on the enrichment or depletion of isotopes in different tissues.Key words: northern elephant seal, Mirounga angustirostris, stable isotopes, lactation, fasting, gestation.Stable carbon and nitrogen isotope ratios ( 13 C/ 12 C reported as ␦ 13 C and 15 N/ 14 N reported as ␦ 15 N, respectively) in animal tissues have been widely used to study trophic relationships and foraging locations in terrestrial and marine food webs (Hobson and Stirling 1997, Burns et al. 1998, Burton and Koch 1999, Kelly 2000, Kurle and Worthy 2001, Das et al. 2003, Dehn et al. 2007. Isotopic ratios in the various foods consumed are reflected in the animal's tissues, proportionate to the amount assimilated for each food source, after accounting for fractionation against heavier isotopes in the digestion and assimilation process Epstein 1978, 1981). Stable nitrogen isotopes undergo fractionation between predator and prey, leading to an enrichment in 15 N with increasing trophic level Epstein 1981, Minagawa andWada 1984), thereby denoting an animal's trophic position. The ␦ 13 C value is close to that of the diet and is used to indicate relative contributions to the diet of two different potential primary sources in a trophic network, indicating for example the aquatic vs. terrestrial, inshore vs. offshore, or pelagic vs. benthic contribution to food intake (Hobson et al. 1995, Dauby et al. 1998. Geographic differences in ␦ 13 C values can be used to indicate foraging locations of animals in marine environments (Kelly 2000, Kurle andWorthy 2002). Stable isotope methodology, however, is dependent on physiological and biochemical assumptions that are not sufficiently taken into consideration (Cherel et al. 2005). Indeed, nutritional st...

Associations of tunas and dolphins in the wild are quite frequent events and the question arises how predators requiring similar diet in the same habitat share their environmental resources. As isotopic composition of an animal is related to that of its preys, stable isotope ( 13 C/ 12 C and 15 N/ 14 N) analyses were performed in three predator species from the North-east Atlantic: the striped dolphin, Stenella coeruleoalba, the common dolphin Delphinus delphis and the albacore tuna, Thunnus alalunga, and compared to their previously described stomach content. Heavy metals (Cd, Zn, Cu and Fe) are mainly transferred through the diet and so, have been determined in the tissues of the animals. Tuna muscles display higher d 15 N than in common and striped dolphins (mean: 11.4 vs. 10.3½ and 10.4½, respectively) which re¯ects their higher trophic level nutrition. Higher d 13 C are found in common ()18.4½) and striped dolphin ()18.1½) muscles than in albacore tuna ()19.3½) probably in relation with its migratory pattern. The most striking feature is the presence of two levels of cadmium concentrations in the livers of the tunas (32 mg kg À1 dry weight (DW) vs. 5 mg kg À1 DW). These two groups also di er by their iron concentrations and their d 15 N and d 13 C liver values. These results suggest that in the Biscay Bay, tunas occupy two di erent ecological niches probably based on di erent squid inputs in their diet. Ó