Trophic interaction of invertebrate zooplankton on either side of the Charlie Gibbs Fracture Zone/Subpolar Front of the Mid-Atlantic Ridge

Trophic relationships and vertical distribution patterns of dominant mesozooplankton (2-20mm) and macrozooplankton (>20mm) invertebrates (Euphausiacea, Copepoda, Decapoda, Amphipoda, Thecosomata and Lophogastrida) were investigated within the epi- and meso-pelagic zone (0-200 and 200-800m depth), north (54° N) and south (49° N) of the Subpolar Front (SPF) on the Mid-Atlantic Ridge (MAR). Dietary relationships were explored using stable isotope ratios of nitrogen and carbon, and fatty acid trophic markers (FATM). Individuals from the southern stations (~49° N) had higher concentrations of the dinoflagellate FATM (22:6(n-3)), and individuals from northern stations had higher concentration in Calanus sp. and storage FATMs (20:1(n-9) and 22:1(n-9)). Energy pathways on either side of the SPF showed retention of δ ¹³C differences (as measured in POM) in bathypelagic species. Observations of FATM levels and abundance patterns are consistent with present theories pertaining to primary production patterns at the base of the food chain, which states that the peak of the production is higher in the northern sector than in the south.