Abundance and distribution of coastal, inshore zooplankton in the Huon Estuary and D'Entrecasteaux Channel, Tasmania: Grazing study in North West Bay (1-2 October, 2006)

Mesozooplankton community composition and structure were examined throughout the D’Entrecasteaux Channel, Huon Estuary and North West Bay, Tasmania. The data represented by this record was collected as part of a grazing study conducted in North West Bay (1-2 October, 2006).

The grazing impacts of microzooplankton and mesoplankton on the phytoplankton communities were examined during several process studies. Experiments with mesozooplankton grazers were restricted to dominant omnivorous copepods (e.g. Acartia tranteri, Paracalanus indicus, Centropages australiensis) cladocerans and appendicularians. Grazing rates of microzooplankton reached as high as 96% of daily primary production, while that of mesozooplankton herbivours was never greater than 20%. Trophic interactions between the species are complicated by the recent arrival of the heterotrophic dinoflagellate Noctiluca scintillans to the region. This species grazes heavily on phytoplankton, smaller zooplankton and faecal pellets. Noctiluca scintillans accounted for up to 20% of mesozooplankton abundance in autumn and it is capable of both suppressing zooplankton abundance and reducing the sedimentation of faecal pellets to the seafloor.