Sediment data was collected for analyses of potential environmental impacts from a sea cage barramundi (Lates calcarifer) aquaculture farm.Analyses were conducted on solid wastes for N, P, OC, trace elements (e.g. Zn) and other components included in feeds. Sediment oxygen consumption rates (respiration) were used an indicator of OC input, and ammonium, phosphate, and nitrite + nitrate flux rates (umol/m2/day) as indicators of organic N and P input and breakdown (mineralisation). The N:P molar ratio of fluxes and the Redfield ratio (C:N:Si:P) were calculated.Sediments were also analysed for grain size, OC, TC, TN, TP, Zn, Li, redox and pH. Sediment Grain size (um) categories: fine silt, clay, quartz sand and coarse material (leaves, wood, rocks and shell). Sediment C, N and Total Organic C (TOC) percentages were measured. C:N ratios were calculated for the different sites (cage, north, reference and south). The ratios of Zn:Li and P:Li in sediments were also calculatedThe reference location, a transect through the cages and sites at adjacent mudbanks were sampled for sediment Redox potential (Eh), pH, temperature, and surface dissolved oxygen, temperature and salinity. Leaves from Rhizophora stylosa (the dominant mangrove species) were analysed for 15N along the entire length of Conn Creek and at the reference location.Water column sampling: Transects comprised single water samples taken subsurface at each station throughout Conn Creek. Variables measured were: dissolved nitrogen (ammonium, nitrate and TDN), dissolved phosphorus, particulate nutrients, suspended solids and dissolved silica.Other variables were: tides (spring and neap); seasons (wet/summer and dry/winter); and place in the water column (near surface and near bottom).Chlorophyll a and bacterial abundances were measured and a chl:bacteria ratio calculated (as an indicator of organic pollution).Water column photosynthetic and community respiration rates were estimated at sites near cages and remote from cages.
To estimate the area of influence of the farm, the carrying capacity of the environment in the area, and the fate of uneaten feed and other aquaculture wastes.
