Abstract
Boundary currents generate cyclonic and anticyclonic eddies, which strongly influence the composition of plankton communities and their spatial dynamics. We explored the gelatinous zooplankton communities where the East Australian Current (EAC) intensifies between 25-31°S, forming a dynamic eddy field at a tropical/temperate boundary. Five types of mesoscale features including the EAC were sampled: the adjacent continental shelf, a transient upwelling feature at the shelf break, a cyclonic frontal eddy which had entrained shelf water and a larger cyclonic eddy that had originated in the Tasman Sea. Forty-two gelatinous taxa were sampled from 62 plankton tows, including 24 cnidarians (9 hydromedusae, 14 siphonophores, 1 scyphozoan), 5 ctenophores and 12 thaliaceans. Assemblages of gelatinous zooplankton differed significantly among oceanographic features but were dominated by the salp, Salpa fusiformis, which comprised 66% of the overall catch. Abundances of gelatinous zooplankton were lowest in the EAC, the shelf break upwelling feature and over the continental shelf, which at the time sampled was flooded by a coastal incursion of the EAC. Abundances were greatest in the two cyclonic eddies and increased four-fold in the Tasman Sea cyclonic eddy over the three times it was sampled, highlighting the importance of cyclonic eddies in driving production of gelatinous zooplankton.