Effects of thermal stress on bioturbation-mediated sediment stability: a study on the burrowing behavior of Cerastoderma edule

Cristian Martin

Sediment dynamics on tidal flats represent an important process in shaping the contiguous intertidal ecosystems, as well as tidal flats themselves. Bioturbation activities loosen the sediment and contribute to its erodibility. By modifying individuals’ burrowing behavior, changes in temperature alter the magnitude of bioturbation. In the Scheldt estuary, where a climate change-induced increase in temperature is expected on the following decades, the common cockle Cerastoderma edule represents the main bioturbator in many tidal flat areas. Cockles live at shallow depths in the sediment and show vertical migrations in response to changes in temperature during exposure time. On this study, the relation between sediment temperature and sediment resuspension induced by cockles’ vertical migrations was studied. The results showed that an increase of 2.7 °C in mean summer temperature, as expected by the end of the century, might imply up to 1.18 times greater sediment resuspension in tidal flats dominated by cockles. This increase of bioturbation suggests a decrease on the elevation of tidal flats, which could in turn promote the erosion of the lower limit of salt marshes. However, results suggest that presence of water pools on sediment surface during exposure time can contribute to reduce this effect.