Data from: Characterizing niche differentiation among marine consumers with amino acid δ13C fingerprinting

Marine food webs are highly compartmentalized and characterizing the
trophic niches among consumers is important for predicting how impact from
human activities affect the structuring and functioning of marine food
webs. Biomarkers such as bulk stable isotopes have proven to be powerful
tools to elucidate trophic niches, but they may lack in resolution,
particularly when spatio-temporal variability in a system is high. To
close this gap, we investigated whether carbon isotope (δ13C )
patterns of essential amino acids (EAAs), also termed d13CAA fingerprints,
can characterize niche differentiation in a highly dynamic marine system.
Specifically, we tested the ability of d13CAA fingerprints to
differentiate trophic niches among six functional groups and ten
individual species in the Baltic Sea. We also tested whether fingerprints
of the common zooplanktivorous fishes, herring and sprat, differ among
four Baltic Sea regions with different biochemical conditions and
phytoplankton assemblages. Additionally, we investigated how these results
compared to bulk C and N isotope data for the same sample set. We found
significantly different d13CAA fingerprints among all six functional
groups. Species differentiation was in comparison less distinct, due to
partial convergence of the species’ fingerprints within functional groups.
Herring and sprat displayed region specific d13CAA fingerprints indicating
that this approach could be used as a migratory marker. Niche metrics
analyses showed that bulk isotope data had a lower power to differentiate
between trophic niches than 13CAA fingerprinting. We conclude that d13CAA
fingerprinting has a strong potential to advance our understanding of
ecological niches, and trophic linkages from producers to higher trophic
levels in dynamic marine systems. Given how management practices of marine
resources and habitats are reshaping the structure and function of marine
food webs, implementing new and powerful tracer methods are urgently
needed to improve the knowledge base for policy makers.