Coastal cities are among the most highly disturbed of all environments due to urbanization and industrial activities that increasingly impact below the waterline. Apart from physical stressors (e.g. addition of artificial structures and loss of important habitat), urban estuaries are exposed to multiple chemical stressors from legacy contaminants in sediments and ongoing inputs of nutrients and metals via storm water discharges. In some Australian estuaries, contaminants released by bushfires are an emerging threat to biodiversity and functioning. These represent cumulative threats that could pose serious problems for ecosystem integrity.
Here I focus on a dominant estuarine habitat – soft sediments - which are among the most threatened by urban change processes. I will present the results from two studies that link ecological change to human impacts along the coast. Firstly, a large-scale study of ten Australian estuaries, which compared the sensitivity of novel biomonitoring tools and the potential for microbes to act as proxies of ecosystem health. Secondly, a study of storm water impacts, which used environmental genomics to link changes in ecosystem structure to function. The results have implications for future biomonitoring and management of estuaries and increase our understanding of how to conserve coastal systems.