3.2 Differentiating functional groups and species with δ13CEAA fingerprinting
To further investigate the ability of δ13CEAA fingerprints to differentiate among functional groups and species, we used data from this study only. In terms of functional groups for the compiled Kiel Bay and Arkona Basin datasets, all six groups cluster separately (Fig. 3). Suspension feeders belong to the most distinct and isolated group; scavengers and benthic predators cluster adjacent to one another; pelagic piscivores, planktivores, and benthic flatfish also cluster adjacently. The median values of the five largest groups are significantly different (Pillai’s Trace = 1.55, F6,112 = 63.6; P < 0.001). Our comparison between species for each site show that most sprat and herring specimens have similar principal component scores for Kiel Bay (Fig. 4A) and Arkona Basin (Fig. 4B). Sprat and herring cluster adjacent to the three species of benthic flatfish. Starfish and the two suspension feeding species each group in distinct and isolated clusters. We did not test for differences in median values at a species level because we had five or less specimens of each species. For both sites, the most effective set of variables for predicting species membership are Thr, Val and Met (Figs. 4A and 4B).