LAUSR

Climate change is impacting ecosystems worldwide. Estuaries are diverse and important aquatic ecosystems; and yet until now we have lacked information on the response of estuaries to climate change. Here we present data from a twelve-year monitoring program, involving 6200 observations of 166 estuaries along >1100 kilometres of the Australian coastline encompassing all estuary morphologies. Estuary temperatures increased by 2.16 °C on average over 12 years, at a rate of 0.2 °C year −1 , with waters acidifying at a rate of 0.09 pH units and freshening at 0.086 PSU year −1 . The response of estuaries to climate change is dependent on their morphology. Lagoons and rivers are warming and acidifying at the fastest rate because of shallow average depths and limited oceanic exchange. The changes measured are an order of magnitude faster than predicted by global ocean and atmospheric models, indicating that existing global models may not be useful to predict change in estuaries. Estuaries are diverse and important aquatic ecosystems, yet we lack information on their response to climate change. Here, the authors show that east Australian estuaries are warming and acidifying faster than predicted by ocean or atmospheric models; a trend that is magnified in shallow estuaries.