The bloom dynamics and trophic ecology of salps and doliolids in storm bay, Tasmania

Abstract

Zooplankton are important grazers of primary production and play a central role in the transfer of energy from primary producers to higher order consumers. Zooplankton are sensitive to environmental variability, making them useful indicators of climate change; importantly, their physiology is strongly coupled to temperature, they exhibit generally short life cycles and they are excluded from most pressures associated with commercial fishing. However, given the diversity of organisms found in the pelagic environment the responses of different groups of zooplankton to environmental variability are most likely different. In this study I have investigated the bloom dynamics and trophic ecology of dominant thaliaceans in Storm Bay: two species of salp (Thalia democratica and Salpa fusiformis) and two species of doliolid (Dolioletta sp. and Doliolum sp .). Storm Bay is a region of dynamic oceanography that is influenced by (i} warm, low nutrient waters from the East Australian Current in the summer, (ii) cooler, nutrient-rich subantarctic waters in the winter, (iii) the Leeuwin (Zeehan) Current flowing along the west coast and (iv) flows from the Derwent Estuary. Key challenges in this study included the fragility of the gelatinous zooplankton, their unpredictable presence in Storm Bay and the absence of doliolids during certain years.