Carbon and nitrogen stable isotope ratios of subtidal benthic invertebrates in an estuarine mangrove ecosystem (Andhra Pradesh, India)

in Estuarine Coastal and Shelf Science (2002), 54(5), 901-913

In order to assess the relative trophic importance of mangrove litterfall and aquatic primary production in the mangrove creeks of the Coringa Wildlife Sanctuary (Andhra Pradesh, India) and the adjacent ... [more ▼]

In order to assess the relative trophic importance of mangrove litterfall and aquatic primary production in the mangrove creeks of the Coringa Wildlife Sanctuary (Andhra Pradesh, India) and the adjacent semi-enclosed Kakinada Bay, carbon and nitrogen stable isotope ratios were determined in a variety of benthic invertebrate species collected at 22 sites during the pre-monsoon period (May-June) of 1997 and 1999. delta(13)C values showed little interspecific variation at any given location, but there was a distinct spatial gradient in consumer delta(13)C values of about 7parts per thousand, with more depleted values in the mangrove creeks ( - 23.6 +/- 0.6parts per thousand), and gradually increasing in the mangrove outlets ( - 21.5 +/- 0.9parts per thousand), a relatively restricted zone in the south-eastern part of Kakinada Bay adjacent to the mangroves ( - 18.8 +/- 0.8parts per thousand), and the central and northern part of the Bay ( - 16.7 +/- 1.4parts per thousand) which opens into the Bay of Bengal. This gradient is much larger than that observed during a previous study in suspended organic matter (maximum about 2.7parts per thousand) and during this study in sediment organic matter (about 1.5-2.5parts per thousand). The observed carbon stable isotope ratios thus suggest a marked selectivity of the benthic invertebrate community for pelagic and benthic microalgal food sources and indicate that mangrove-derived and other terrestrial carbon is not a significant food source for benthic invertebrate communities in this ecosystem during the pre-monsoon period. Furthermore, delta(13)C values of sediment organic matter (SOM) suggest that terrestrial carbon is not a major contributor to the SOM-pool in this ecosystem. Evidence for seaward migration of Penaeid prawns was provided by some individuals caught in the North Bay which displayed low delta(13)C values of characteristic of fauna found in the mangrove creeks or outlets. Nitrogen stable isotope ratios were found to be a useful indicator of trophic level, even though there remained some overlap between delta(15)N values of presumed low and higher trophic levels. Benthic invertebrates showed a delta(15)N gradient of about 3.2parts per thousand between the mangrove creeks and the Central and North Bay whereas sediment delta(15)N values showed a smaller spatial gradient of about 1.6parts per thousand. This gradient which is hypothesized to reflect differences in inorganic nitrogen sources and availability. (C) 2001 Elsevier Science Ltd. All rights reserved. [less ▲]

The role of benthic amphipods in the eastern Weddell Sea trophic web as determined from stable isotope and fatty acid analyses

Conference (2001, August)

Within the Southern Ocean, amphipods have achieved a conspicuous adaptative radiation which gave rise to the development of numerous feeding strategies (Jazdzewski et al. 1996; Dauby et al. in press; De ... [more ▼]

Within the Southern Ocean, amphipods have achieved a conspicuous adaptative radiation which gave rise to the development of numerous feeding strategies (Jazdzewski et al. 1996; Dauby et al. in press; De Broyer et al. in press). The discrepancy between the ecological significance of amphipods in the Antarctic and our poor knowledge of their ecofunctional role calls for a more detailed investigation of their importance in this ecosystem trophodynamics. This study focused on the eight amphipods species which were collected and from which isotopic and lipidic (when available) (Graeve et al. in press) compositions were compared to their respective gut contents previously described (Dauby et al. in press). The interest of both first techniques rely upon the direct relationship between the isotopic signatures and the lipid composition of organisms and those of their diet (De Niro and Epstein 1978, 1981; Peterson and Fry 1987; Graeve et al. 1994; Cripps et al 1999). Amphipod stable isotope ratios and fatty acids composition correspond rather accurately to the trophic classification based on gut contents and attest to their high spectrum of feeding types. Since the fundamental difference between the approaches to diet studies is the time scale each method addresses, this coincidence indicates that there would be no significant changes in feeding strategies over time. Three levels of the food web are covered by the eight species and, instead of belonging strictly to one trophic category, amphipods display a continuum of values from the suspension-feeder to scavengers. [less ▲]

Amphipod as food sources for higher trophic levels in the Southern Ocean

Poster (2001, July)

A stable isotope approach to the eastern Weddell Sea trophic web: focus on benthic amphipods

in Polar Biology (2001), 25(4),

isotope (C-13/C-12 and N-15/N-14) analyses were performed on 90 species belonging to different benthic communities sampled in the eastern Weddell Sea. The study focused on eight amphipod species whose ... [more ▼]

isotope (C-13/C-12 and N-15/N-14) analyses were performed on 90 species belonging to different benthic communities sampled in the eastern Weddell Sea. The study focused on eight amphipod species whose isotopic composition was compared to their previously described respective gut contents. Amphipod stable isotope ratios correspond fairly accurately to the trophic classification based on gut contents and attest to their wide spectrum of feeding types. Since the fundamental difference between the isotope and the gut content approaches to diet studies is the time scale each method addresses. this coincidence indicates that there would be no significant changes in feeding strategies over time. Three levels of the food web are covered by the eight species and, instead of belonging strictly to one trophic category, amphipods display a continuum of values from the suspension-feeder to scavengers. [less ▲]

Trophic diversiy within the eastern Weddell Sea amphipod community

in Hydrobiologia (2001), 443

Variations saisonnières des isotopes stables du carbone (13C) et de l'azote (15N) dans un réservoir mésotrophe

Conference (2000, July 17)

Tuna and dolphin associations in the Northeast Atlantic: Evidence of different ecological niches from stable isotope and heavy metal measurements

in Marine Pollution Bulletin (2000), 40

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 ... [more ▼]

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 isotopes (13C/12C and 15N/14N) analyses were performed in three predator species from the Northeast 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. Tunas muscles display higher delta15N than in common and striped dolphins (mean: 11.4 0/00 vs. 10.3 0/00 and 10.4 0/00, respectively) which reflects its higher trophic level nutrition. Higher delta13C are found in common (-18.4 0/00) and striped dolphin (-18.10/00) muscles than in albacore tuna (-19.3 0/00) likely 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-1 dry weight vs. 5 mg kg-1 dry weight). These two groups also differ by their iron concentrations and their delta15N and delta 13C liver values. These results suggest that in the Biscay Bay, tunas occupy two different ecological niches likely based on different squid input in their diet. [less ▲]

Use of stable isotope to delineate amphipod trophic status in Antarctic food webs

in Polish Archives for Hydrobiology (2000), 47

Relative impact of a seagrass bed and its adjacent epilithic algal community in consumer diets

in Marine Biology (2000), 136

The aim of this work was to identify and compare, using nitrogen and carbon stable isotope data, the food sources supporting consumer communities in a Mediterranean seagrass bed (Gulf of Calvi, Corsica ... [more ▼]

The aim of this work was to identify and compare, using nitrogen and carbon stable isotope data, the food sources supporting consumer communities in a Mediterranean seagrass bed (Gulf of Calvi, Corsica) with those in an adjacent epilithic algal dominated community. Isotopic data for consumers are not significantly different in the two communities. Particulate matter and algal material (seagrass epiflora and dominant epilithic macroalgae) appear to be the main food sources in both communities. Generally, the 13C of animals suggests that the seagrass Posidonia oceanica (L.) Delile represents only a minor component of their diet or of the diet of their prey, but the occurrence of a mixed diet is not excluded. P.oceanica dominates the diet of only of few species, among which holothurians appear as key components in the cycling of seagrass material. [less ▲]

Amphipods of a stony beach in the maritime Antarctic

in Polish Polar Studies (1999)