Trophic Relationships

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Keith A. Hobson - One of the best experts on this subject based on the ideXlab platform.

  • Trophic Relationships among Antarctic fulmarine petrels : insights into dietary overlap and chick provisioning strategies inferred from stable-isotope (δ15N and δ13C) analyses
    Marine Ecology Progress Series, 2000
    Co-Authors: P. J. Hodum, Keith A. Hobson
    Abstract:

    We used stable-isotope analysis (SIA) to evaluate Trophic Relationships in an Antarctic seabird community. We determined natural abundances of stable-nitrogen (δ 15 N) and stable-carbon (δ 13 C) isotopes from blood samples (n = 283) from adults and chicks of 4 Antarctic fulmarine petrel species (Fulmarus glacialoides, Thalassoica antarctica, Daption capense and Pagodroma nivea) during 2 consecutive breeding seasons, 1994/1995 and 1995/1996, and from representative prey items. Our objectives were to use the isotope approach to infer Trophic status and diet composition within and between species, addressing interspecific and temporal variability within this seabird community, and to investigate potential age-related differences in assumed Trophic position within species. Prey δ 13 C values ranged from -26.8‰ in amphipods to -23.9%o in adult Antarctic silverfish. Seabird δ 13 C values ranged from-25.3‰ in Antarctic petrel chicks to -23.8‰ in cape petrel adults. Prey δ 15 N values ranged from 4.0‰ in euphausiids to 10.7 ‰ in adult Antarctic silverfish. Seabird δ 15 N values ranged from 8.4 ‰ in Antarctic petrel adults to 12.0‰ in snow petrel chicks. There was considerable interspecific overlap in assumed Trophic positions amongst the 4 petrel species, and we conclude all species consumed fish and krill. Despite this apparent overlap, the range in δ 15 N values for petrels corresponded to the equivalent of 1 full Trophic level, and estimated Trophic level varied with both species and age. A simple Trophic level model, constructed based on the δ 15 N data, predicted Trophic levels ranging from 2.3 in krill to 4.7 in snow petrel chicks. Snow petrels and Antarctic fulmars tended to have higher δ 15 N values than Antarctic and cape petrels, suggesting a higher proportion of fish in their diets. Petrel chicks consistently had higher δ 15 N values than adults, which suggests Trophic segregation between adults and chicks. We discuss advantages of selectively provisioning chicks with higher Trophic level prey. Extensive overlap and a relatively narrow range of δ 15 N values are consistent with a food web comprised of few Trophic steps.

  • stable carbon and nitrogen isotope ratios of songbird feathers grown in two terrestrial biomes implications for evaluating Trophic Relationships and breeding origins
    The Condor, 1999
    Co-Authors: Keith A. Hobson
    Abstract:

    The measurement of stable-carbon ( 13 C/ 12 C) and nitrogen ( 15 N/ 14 N) isotope ratios in bird feathers has potential to reveal important information on Trophic position and source of feeding during feather formation. This study investigated how stable-nitrogen (δ 15 N) and carbon (δ 13 C) isotope ratios in feathers of insectivorous songbirds and in their supporting foodwebs differed between boreal forest sites (50 feathers representing 5 species) and upland sites associated with southern prairie agro-wetland complexes in Saskatchewan and Manitoba, Canada (108 feathers representing 12 species). No difference in feather δ 13 C values between these biomes was found, but feathers from boreal forest songbirds were depleted in 15 N compared to feathers from birds in southern agricultural areas. This suggests that general Trophic models cannot be constructed based on δ 15 N values of feathers of birds from these different biomes alone unless they are related first to local foodweb isotopic signatures. However, foodweb δ 15 N analysis in each biome indicated that the stable isotope approach could be applied successfully to delineate Trophic Relationships involving birds. In addition, this technique will be a useful tool for investigating the degree of frugivory or nectarivory in birds.

  • Trophic Relationships among seabirds in central california combined stable isotope and conventional dietary approach
    The Condor, 1997
    Co-Authors: William J Sydeman, Keith A. Hobson, Peter Pyle, Elizabeth B Mclaren
    Abstract:

    We used stable isotope analysis (SIA) and conventional techniques of diet assessment to determine marine Trophic Relationships in the Gulf of the Farallones, California, with an emphasis on marine birds. Stable-carbon (δ 13 C) and nitrogen (δ 15 N) isotopes were obtained from 98 tissue samples of 16 species representing primary and secondary consumers in 1993-1994. The values of δ 13 C ranged from -20.1‰ in whole euphausiids (krill) to -15.0‰ in muscle of northern sea lions. Values of δ 15 N showed step-wise Trophic enrichment and ranged from 11.2‰ in euphausiids to 19.8‰ in sea lions. SIA of egg albumen from birds indicated reliance on zooplankton by Cassin's Auklet, Common Murre, and Western Gull, and on fish by Brandt's and Pelagic Cormorants, Rhinoceros Auklets, and Pigeon Guillemots during egg formation (April-May). However, analysis of prey brought to chicks during summer indicated the prevalence of fish in the diet of most seabirds, except Cassin's Auklet which fed primarily on krill. Results suggest a shift in Trophic level and diet between spring and summer from krill to fish for Common Murres. δ 13 C analysis confirmed that Brandt's Cormorants and northern sea lions feed in neritic habitats, whereas Cassin's and Rhinoceros Auklets foraged in epipelagic offshore waters. Our approach demonstrates the utility of combining both SIA and conventional dietary assessments to understand Trophic Relationships in dynamic marine ecosystems.

  • using stable isotopes to determine seabird Trophic Relationships
    Journal of Animal Ecology, 1994
    Co-Authors: Keith A. Hobson, John F. Piatt, Jay Pitocchelli
    Abstract:

    1. The stable isotopes of nitrogen (δ 15 N) and carbon (δ 13 C) were analysed in 22 species of marine birds from coastal waters of the northeast Pacific Ocean. Analyses confirm that stable nitrogen isotopes can predict seabird Trophic positions. 2. Based on δ 15 N analyses, seabird Trophic-level inferences generally agree with those of conventional dietary studies, but suggest that lower Trophic-level organisms are more important to several seabirds than was recognized previously. 3. Stable-carbon isotope analysis may be a good indicator of inshore vs. offshore feeding preference

  • Using Stable Isotopes to Determine Seabird Trophic Relationships
    The Journal of Animal Ecology, 1994
    Co-Authors: Keith A. Hobson, John F. Piatt, Jay Pitocchelli
    Abstract:

    1. The stable isotopes of nitrogen (delta 15N) and carbon (delta 13C) were analysed in 22 species of marine birds from coastal waters of the northeast Pacific Ocean. Analyses confirm that stable nitrogen isotopes can predict seabird Trophic positions. 2. Based on delta 15N analyses, seabird Trophic-level inferences generally agree with those of conventional dietary studies, but suggest that lower Trophic-level organisms are more important to several seabirds than was recognized previously. 3. Stable-carbon isotope analysis may be a good indicator of inshore vs. offshore feeding preference. 4. In general, stable-isotope analysis to determine Trophic level offers many advantages over conventional dietary approaches since Trophic inferences are based on time-integrated estimates of assimilated and not just ingested foods, and isotopic abundance represents a continuous variable that is amenable to statistical analysis.

Jay Pitocchelli - One of the best experts on this subject based on the ideXlab platform.

  • using stable isotopes to determine seabird Trophic Relationships
    Journal of Animal Ecology, 1994
    Co-Authors: Keith A. Hobson, John F. Piatt, Jay Pitocchelli
    Abstract:

    1. The stable isotopes of nitrogen (δ 15 N) and carbon (δ 13 C) were analysed in 22 species of marine birds from coastal waters of the northeast Pacific Ocean. Analyses confirm that stable nitrogen isotopes can predict seabird Trophic positions. 2. Based on δ 15 N analyses, seabird Trophic-level inferences generally agree with those of conventional dietary studies, but suggest that lower Trophic-level organisms are more important to several seabirds than was recognized previously. 3. Stable-carbon isotope analysis may be a good indicator of inshore vs. offshore feeding preference

  • Using Stable Isotopes to Determine Seabird Trophic Relationships
    The Journal of Animal Ecology, 1994
    Co-Authors: Keith A. Hobson, John F. Piatt, Jay Pitocchelli
    Abstract:

    1. The stable isotopes of nitrogen (delta 15N) and carbon (delta 13C) were analysed in 22 species of marine birds from coastal waters of the northeast Pacific Ocean. Analyses confirm that stable nitrogen isotopes can predict seabird Trophic positions. 2. Based on delta 15N analyses, seabird Trophic-level inferences generally agree with those of conventional dietary studies, but suggest that lower Trophic-level organisms are more important to several seabirds than was recognized previously. 3. Stable-carbon isotope analysis may be a good indicator of inshore vs. offshore feeding preference. 4. In general, stable-isotope analysis to determine Trophic level offers many advantages over conventional dietary approaches since Trophic inferences are based on time-integrated estimates of assimilated and not just ingested foods, and isotopic abundance represents a continuous variable that is amenable to statistical analysis.

Kenneth H Dunton - One of the best experts on this subject based on the ideXlab platform.

  • δ15n and δ13c measurements of antarctic peninsula fauna Trophic Relationships and assimilation of benthic seaweeds
    Integrative and Comparative Biology, 2001
    Co-Authors: Kenneth H Dunton
    Abstract:

    SYNOPSIS. Measurements of d 13 C, d 15 N, and C/N for a variety of Antarctic peninsula fauna and flora were used to quantify the importance of benthic brown algae to resident organisms and determine food web Relationships among this diverse littoral fauna. d 13 C values ranged from216.8‰ for benthic algal herbivores (limpets) to 229.8‰ for the krill, Euphausia superba; the average pooled value for brown macroalgae, including their attached filamentous diatoms, was220.6‰. There was no correlation between biomass d 13 Co rd 15 N with C/N content, and consequently both d 13 C and d 15 N values were useful in evaluating Trophic Relationships. d 15 N values of the fauna ranged from 3.1 to 12.5‰, with lowest values recorded in suspension feeders (e.g., bryozoans) and highest values in Adelie penguins (12.5‰) collected in 1989. The comparatively lower d 15 N value for a Chinstrap penguin (6.9‰) collected in 1997 is attributed to the different dietary food sources consumed by these species as reflected in their respective d 13 C values. Significant amounts of benthic macroalgal carbon is incorporated into the tissues of invertebrates and fishes that occupy up to four Trophic levels. For many benthic and epibenthic species, including various crustaceans and molluscs, assimilation of benthic algal carbon through detrital pathways ranges from 30 to 100%. Consequently, the Trophic importance of benthic brown algae may well extend to many pelagic organisms that are key prey species for birds, fishes, and marine mammals. These data support the hypothesis that benthic seaweeeds, together with their associated epiphytic diatoms, provide an important carbon source that is readily incorporated into Antarctic peninsula food webs.

  • 15N and 13C measurments of Antarctic peninsula fauna: Trophic Relationships and assimilation of benthic seaweeds
    American Zoologist, 2001
    Co-Authors: Kenneth H Dunton
    Abstract:

    Measurements ef 613C, 61sN, and C/N for a variety of Antarctic peninsula fauna and flora were used to quantify the importance of benthic brown algae to resident organisms and determine food web Relationships among this diverse littoral fauna. 613C values ranged from-16.8%o for benthic algal herbivores (limpets) to -29.8%o for the krill, Euphausia superbal; the average pooled value for brown macroalgae, including their attached filamentous diatoms, was-20.6%o. There was no correlation between biomass 613C or 61sN with C/N content, and consequently both 613C and 6rsN values were useful in evaluating Trophic Relationships. 61sN values of the fauna ranged from 3.1 to 12.5%o, with lowest values recorded in suspension feeders (e.g., bryozoans) and highest values in Adelie penguins (12.5%o) collected in 1989. The comparatively lower 61sN value for a Chinstrap penguin (6.9%o) collected in 1997 is attributed to the different dietary food sources consumed by these species as reflected in their respective 613C values. Significant amounts of benthic macroalgal carbon is incorporated into the tissues of invertebrates and fishes that occupy up to four Trophic levels. For many benthic and epibenthic species, including various crustaceans and molluscs, assimilation of benthic algal carbon through detrital pathways ranges from 30 to 100%. Consequently, the Trophic importance of benthic brown algae may well extend to many pelagic organisms that are key prey species for birds, fishes, and marine mammals. These data support the hypothesis that benthic seaweeeds, together with their associated epiphytic diatoms, provide an important carbon source that is readily incorporated into Antarctic peninsula food webs.

Federico Paezosuna - One of the best experts on this subject based on the ideXlab platform.

  • Trophic Relationships and transference of cadmium copper lead and zinc in a subtropical coastal lagoon food web from se gulf of california
    Chemosphere, 2009
    Co-Authors: Martin E Jaramarini, Martin F Sotojimenez, Federico Paezosuna
    Abstract:

    Trophic Relationships and heavy metal transference in a coastal subtropical lagoon marine food web were investigated through the use of stable isotopes in food sources and biota. A selective extraction scheme was applied to the surface sediments as an indirect way to evaluate the potential of toxicity of metals. Results showed that cadmium, copper, lead and zinc concentrations were within sediment quality guidelines criteria. Concentrations of these metals in organisms varied widely among functional groups and within the same and closely related taxa. δ13C values varied significantly among organisms from different functional groups, while the δ15N values varied according with their feeding habits. Cd, Cu, Pb, and Zn were not positively transferred (biomagnification factor <1) through entire food web. However, a partial positive transference was observed for Cu and Zn involving three Trophic levels (from the phytoplankton to crab as secondary consumer).

Natalia V Zhukova - One of the best experts on this subject based on the ideXlab platform.

  • association of the scalloppatinopecten yessoensisand epibiotic barnaclebalanus rostratus inter specific interactions and Trophic Relationships determined by fatty acid analysis
    Marine Ecology, 2016
    Co-Authors: Alla V Silina, Natalia V Zhukova
    Abstract:

    Marine mollusks provide shelter to epibiotic organisms which settle on the outer surface of their hard shells. Epibionts can exert beneficial or detrimental effects on the host mollusk. In this study, the ecology of the association of the commercially valuable marine mobile scallop Patinopecten (=Mizuhopecten) yessoensis with its epibiotic barnacle Balanus rostratus was investigated. Fatty acid analysis was performed to determine the Trophic Relationships between these species. The distribution of fatty acid markers in this scallop species suggests an important contribution of diatoms, flagellates and animal material in its diet. The fatty acid analysis indicated a predominance of diatoms in the diet of the adult barnacles and some detrital input into the diets of young individuals. It was found that adult barnacles may compete with the scallops for food sources such as diatoms and zooplankton. It was revealed that with a negligible biomass of epibionts, the interactions between the barnacle and scallop may be regarded as commensalisms. An increase in the weight of epibiotic barnacles resulted in decreases in the weights and shell heights of the scallops, testifying to the adverse influence of a high biomass of epibionts on their host.

  • Topical and Trophic Relationships in a boring polychaete-scallop association: fatty acid biomarker approach
    Marine Ecology Progress Series, 2009
    Co-Authors: Alla V Silina, Natalia V Zhukova
    Abstract:

    The association between the Japanese scallop Patinopecten yessoensis and the scallop- shell-boring polychaete worm Polydora brevipalpa was investigated in the natural environment. Fatty acid analyses were performed on the scallop, polychaete, and potential food materials available in the environment, with the aim of determining the main food sources of these animals and the Trophic Relationships between species. The scallop and the polychaete showed a similarity in their fatty acid compositions. High concentrations of 20:5n-3 and 14:0, substantial concentrations of 16:2n-4, 16:3n-4, and 16:4n-1, and ratios of 16:1n-7 to 16:0 close to 1 indicated significant contribu- tions of diatoms in the diets of both mollusk and polychaete. Detectable levels of 18:4n-3 suggest that dinoflagellates also contributed to the diet of the animals. The fatty acid markers showed that the scallop and polychaete feed extensively on a mixed, but probably diatom-dominated phytoplankton diet. Additionally, the elevated level of bacterially derived fatty acids and saturated (mainly 18:0) acids in polychaete lipids point to an additional dietary source, detritus and bacteria. Elevated amounts of 22:6n-3 and 18:1n-9 in the scallop digestive gland are indicative of zooplankton consump- tion. The similarity of the diets is a major determinant of the feeding competition between these species in the community. The decrease in the scallop internal volume concurrent with an increase in the degree of shell occupation by polychaetes suggests a reduction in water-filtering potential by the scallop. Linear regressions of the degree of polychaete occupation against scallop weight and shell height revealed negative relations in both cases. With high levels of shell occupation by polychaetes, the commensal relationship between scallop and polychaete acquires some elements of parasitism.