Spatial and temporal shifts in stable isotope values of the bottom-dwelling shrimp Nauticaris marionis at the sub-Antarctic archipelago

Pakhomov, EA McClelland, JW Bernard, K Kaehler, S Montoya, JP

MARINE BIOLOGY 144:2 317-325

Spatial and temporal dynamics of carbon and nitrogen stable isotope signatures of the bottom-dwelling caridean shrimp Nauticaris marionis were measured during April and May between 1984 and 2000 in the vicinity of Marion Island (the Prince Edward Islands, Southern Ocean). There was one trophic-level enrichment in bulk delta(15)N and delta(13)C signatures between small (<20 mm long) and large (>20 mm) specimens of N. marionis, suggesting distinct trophic differentiation among major shrimp size groups. Both delta(15)N and delta(13)C values of N. marionis increased with the depth, reflecting changes in their diet. There were no clear temporal trends in bulk delta(15)N signatures of N. marionis. However, compound-specific delta(15)N measurements of amino acids indicated that N. marionis from the inter-island realm occupied the trophic level of second order carnivores, while similarly sized shrimps in the near-shore realm were at the trophic level of first order carnivores. Compound-specific measurements also identified a change in the source of inorganic nitrogen at the base of the food web between the inter-island and near-shore realms. In contrast to the bulk delta(15)N values, a significant shift in bulk delta(13)C values of N. marionis was observed between 1984 and more recent years. This temporal change appears to be linked to changes in the overall productivity of the Prince Edward Island inter-island system, which could be linked to global climate change.

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