Nutrient Sources, Water Quality and Biogeochemical Processes in the Coorong, South Australia

The Coorong, a shallow coastal lagoon at the mouth of the Murray River, has had a significant decline in water quality over the last 15 years because of reduced freshwater inflows. Salinity has increased throughout the lagoon and currently ranges between 60 and 190 psu depending on the proximity to the Murray Mouth and the season. Although nutrient inflow has been negligible in recent years, the lagoon is considered euthrophic. This study aimed to identify the source of nutrients and the biogeochemical processes that transform them. The key findings were:
1. Groundwater discharge is likely to be an important nutrient source
2. Nitrogen appears to be the nutrient limiting primary production
3. Decomposition of organic matter in the sediments is highly seasonal with much higher rates in the summer.