Characteristics of the Microplankton and Nanoplankton Communities of an Australian Coastal Plain Estuary

Abstract

The relative importance of micro- and nanoplankton was evaluated in the Parramatta Estuary and Sydney Harbour, a culturally eutrophicated southern hemisphere estuarial complex, during a non- upwelling period following an extended drought. Nanoplankton : microplankton production ratios increased to 4.2 in the inner estuary, where the nanoplankton were dominant under conditions of increased nutrient supply. Primary production rates and chlorophyll a standing crops increased about 40-fold into the estuary, reaching 175 mg C m^-3 h^-1 and 19 mg chl a m^-3 respectively. Outer, middle, and inner estuarial regions were distinct, and clearly defined by phytoplankton community characteristics and species distribution. All dominants and co-dominants were neritic temperate species ubiquitous in the estuary, but less abundant microplankton species of tropical origin were the most useful as indicator species of the extent of oceanic influence.