Characterising intertidal sediment temperature gradients in estuarine systems

Coastal marine ecosystems are under increasing threat from environmental shifts associated with climate change, particularly increasing temperatures, as temperature influences the physiology, distribution, and abundance of marine organisms. Sediment temperatures on soft sediment intertidal flats are highly variable in space and time due to intermittent exposure to air and seawater. Surface sediment layers may have greater temperature variation relative to deeper layers, and local physical and biological characteristics as well as oceanic and atmospheric temperature conditions are expected to influence the temperatures experienced by sediment dwelling fauna. However, there is little reporting of the dynamics of sediment temperatures in these ecosystems and the local conditions that drive them. We focused on measuring estuarine intertidal sediment temperatures to describe the conditions that resident intertidal macroinvertebrates, including infauna, are being exposed to. Monitoring of sediment temperatures in intertidal ecosystems during summer revealed that sandy intertidal flats had greater temperature fluctuations than muddy intertidal flats. Local weather conditions were important drivers of both low and high tide sediment temperatures, and satellite derived sea surface temperature (SST) data for the study area were sparse and poorly matched sediment temperatures, revealing limitations of satellite SST for predicting site-specific intertidal sediment temperatures in nearshore areas. This study demonstrates the need for long term monitoring of intertidal sediment temperatures across large spatial scales and environmental gradients to understand and predict the potential impacts of climate change.