Spatial patterns and diversity of foraminifera from an intermittently closed and open lagoon, Smiths Lake, Australia

Foraminifera represent an important tool for assessing and monitoring the past, present and future relative health of marine systems, but this is only possible where baseline assemblage characteristics have been previously established. This type of baseline data is currently lacking for intermittently closed and open lakes or lagoons (ICOLL). ICOLLs are estuarine environments that are isolated from the open ocean for much of the time, but are subject to distinct periods of tidal exchange and large fluctuations in hydrodynamic factors when the barrier that isolates the ICOLL is opened to the sea. This study provides new data on diversity and distribution of foraminifera from Smiths Lake, an ICOLL on the Australian eastern coastline. Environmental parameters were measured to identify potential abiotic controls on the distribution and relative abundance of assemblages and individual taxa. Results indicate that, whilst the Smiths Lake assemblage is largely similar to foraminifera assemblages found in estuaries consistently open to the sea, it can be differentiated based upon lower species richness and a lack of calcareous taxa, even in the seaward parts of the lagoon. Parameters associated with depth, including sediment grain size and nutrient supply, are identified as significant controls on both assemblage distribution and the relative abundance of common taxa in Smiths Lake. ICOLLs are considered extremely sensitive to anthropogenic activities and these results represent an important potential tool in ICOLL management.