Inundation of saline supratidal mudflats provides an important source of carbon and nutrients in an aquatic system

Supratidal mudflats are a poorly understood habitat adjacent to coastal areas and are under pressure from human development and climate change. These habitats are only inundated infrequently but may be important contributors to coastal productivity. This study determined nutrient release and primary productivity (PP) on a large, pristine supratidal mudflat in the wet–dry tropics of Australia. Results of experimental studies on nutrient release and PP upon freshwater inundation were incorporated into a simple model of supratidal mudflat inundation based on remote sensing data and long-term river height data. The model was used to hind-cast potential annual primary production and nutrient release for a period capturing high and low inundation years. Our experimental studies measured a rapid release of nitrate, ammonium and phosphate in the first 2 d after inundation. Some days later there was measurable algal growth. Incorporating this data into the model showed that the main driver for the whole-system PP rates was the areal extent of inundation, rather than the duration of inundation, provided that inundation lasted longer than the minimum period for primary production to occur. The same was true for nutrient release although a shorter period of inundation was needed for release to occur. Future changes in flow and associated flooding, as a result of climate change and/or water resource development, could therefore have significant effects on productivity in these coastal systems.