Primary production and nutrients in Darwin Harbour, Northern Territory

On three trips (in February and October 2004 and February 2006) samples were collected in Darwin Harbour.Primary production, respiration, nutrient fluxes and N fixation were measured.Surface-to-near bottom profiles of temperature and salinity were obtained at each site by CTD. Additional samples were analysed for Chlorophyll a, particulate nitrogen, phosphorus and suspended solids.Dissolved inorganic nutrients (ammonium, nitrate, nitrite and phosphate) concentrations were determined. DON and DOP concentrations were calclulated.Experiments were conducted to determine differences in phytoplankton production and pelagic respiration at different stages of the tide. Phytoplankton growth rates were measured on the basis of changes in concentrations of chlorophyll a using the dilution method.Dissolved oxygen concetration and 15N-nitrogen uptake were determined.Net community production (NCP) and community respiration (CR)were estimated. Gross primary production was calculated as the sum of NCP and CR. To determine the main sources of primary production and the sources of nutrients supporting growth in a macrotidal estuary, Darwin Harbour.