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Abstract

Pteropods are a group of small marine gastropods that are highly sensitive to multiple stressors associated with climate change. Their trophic ecology is not well studied, with most research having focused primarily on the effects of ocean acidification on their fragile, aragonite shells. Stable isotopes analysis coupled with isotope‐based Bayesian niche metrics is useful for characterizing the trophic structure of biological assemblages. These approaches have not been implemented for pteropod assemblages. We used isotope‐based Bayesian niche metrics to investigate the trophic relationships of three co‐occurring pteropod species, with distinct feeding behaviors, sampled from the Southern Kerguelen Plateau area in the Indian Sector of the Southern Ocean—a biologically and economically important but poorly studied region. Two of these species were gymnosomes (shell‐less pteropods), which are traditionally regarded as specialist predators on other pteropods, and the third species was a thecosome (shelled pteropod), which are typically generalist omnivores. For each species, we aimed to understand (a) variability and overlap among isotopic niches; and (b) whether there was a relationship between body size and trophic position. Observed isotopic niche areas were broadest for gymnosomes, especially Clione limacina antarctica, whose observed isotopic niche area was wider than expected on both δ13C and δ15N value axes. We also found that trophic position significantly increased with increasing body length for Spongiobranchaea australis. We found no indication of a dietary shift toward increased trophic position with increasing body size for Clio pyramidata f. sulcata. Trophic positions ranged from 2.8 to 3.5, revealing an assemblage composed of both primary and secondary consumer behaviors. This study provides a comprehensive comparative analysis on trophodynamics in Southern Ocean pteropod species, and supports previous studies using gut content, fatty acid and stable isotope analyses. Combined, our results illustrate differences in intraspecific trophic behavior that may be attributed to differential feeding strategies at species level.

Item Type:	Article
Authors/Creators:	Weldrick, CK and Trebilco, R and Davies, DM and Swadling, KM
Keywords:	marine snails, food webs, stable isotopes, Clio pyramidata, Clione limacina, isotopic niche, size-based, Spongiobranchaea australis, trophic position
Journal or Publication Title:	Ecology and Evolution
Publisher:	John Wiley & Sons Ltd.
ISSN:	2045-7758
DOI / ID Number:	https://doi.org/10.1002/ece3.5380
Copyright Information:	© 2019 The Authors Ecology and Evolution Published by John Wiley & Sons Ltd. This is an open access article under the terms of the Creative Commons Attribution License, (https://creativecommons.org/licenses/by/4.0/) which permits use, distribution and reproduction in any medium, provided the original work is properly cited.
Related URLs:	Google Scholar: Trebilco, R UTAS Profile: Swadling, KM
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