Pelagic ecosystem investigations of McMurdo Sound: plankton species composition and density, ocean environmental factors, levels of seston, bacteria analysis and ice algae composition

Comparisons of water column productivity and processes was completed by comparing 4 sites including on the edge of the McMurdo Ice Shelf some 12km west of Cape Armitage, off Scott Base on the east side of McMurdo Sound, near the centre of the Sound and near the Dailey Islands on the west side of the Sound, over a depth of up to 500 m of water. A similar program to that carried out at White Island was conducted to allow comparisons of the structure of the pelagic ecosystem under the seasonal sea ice in McMurdo Sound with that at White Island which is under permanent ice cover. An estimate of the transport of phytoplankton, zooplankton and detritus under the Ross Ice Shelf was made. The water column was sampled through each ice hole at intervals, with water samples taken at seven depths of 0, 5, 20, 50, 100, 200 and 300m (six depths 0, 25, 75, 150, 275 and 500m from site 12km of Cape Armitage). Sampling and samples were analysed for temperature, salinity, dissolved oxygen, light, alkalinity, current velocities, nutrients (nitrogen and phosphorous), chlorophyll, ATP, zooplankton and phytoplankton species composition and density, seston dry weight, total organic nitrogen, total organic carbon and bacterial numbers. In addition, zooplankton was sampled with fine and coarse nets, primary productivity was estimated using the light and dark bottle oxygen technique and settling detritus sampled using detrital trap. Stratified zooplankton samples were taken on several occasions using a coarse net, to determine the depth distribution of the species present. Weekly samples at a depth of 200m were taken with a detrital trap and were processed for detrital dry weights, total nitrogen, total organic carbon and ATP. During the weekly sampling program, a 300ml water sample was collected at each depth for analysis of bacterial number. Benthic collections were made throughout the season using baited fish traps and grabs. Species identification and descriptions of the benthos was carried out. The ice algal community which develops in association with the sea ice was investigated by drilling ice cores, dividing them into 25cm sections, melting each section and analysing each sample for salinity, chlorophyll, ATP, algal dry weight, bacterial numbers, algal species identification and relative abundances. Determination of bacterial numbers from the water column was conducted.