The ecology (tidal and weather records, distribution and abundance of microbes and quantification of nitrogen transformation) of an Antarctic tidal lagoon and mudflats at Bratina Island, McMurdo Ice Shelf

A tidal lagoon at Bratina Island experiences a daily inundation with tidal height varying. Low tide reveals a network of ponds, streams and tidal flats that appear to be highly productive with all but the highest intertidal flats colonised by flora of diatoms and cyanobacteria. The tidal lagoon environment and microbial communities was described. The rate of primary production within the communities, the effects of tidal cycles on this process and quantification of nitrogen transformations within the lagoon system was investigated. A sketch map was drawn of the lagoon and photos were taken to characterise the area. A tide gauge was installed to provide a near continuous tidal record. An automatic weather station (air temperature, relative humidity, total and net radiation, wind speed and direction and UV-A and UV-B radiation) was installed close to the lagoon inflow/outflow region. In addition, this station logged temperatures of five thermistors in selected locations within the lagoon system. The effects of prolonged aerial exposure on salinity and water content in intertidal sediments was monitored with sediment cores being analysed for water content, salt content, dry weight and conductivity. Spatial and temporal variability in pond and stream water including diel changes were monitored at different depths by measuring temperature, pH, conductivity, dissolved oxygen, nutrient analysis, NO3, NH4, dissolved organic nitrogen, dissolved reactive phosphorus and dissolved organic phosphorus. The algae distribution and abundance was measured by collecting samples from several habitat types for determination of algal species composition, microscopic identification, analysis of dry and ash-free dry weight, and particulate carbon, nitrogen and phosphorus. Chlorophyll a was measured for biomass determination and for pigment analysis. To relate algal distribution and abundance to tidal height, a number of transects were established across the lagoon. Photosynthetic rates of submerged and benthic algal communities were carried out along with experiments in situ for effects of radiation flux, desiccation, salinity and de-nitrification.