Heatwaves are periods of anomalous temperature increases lasting more than 3 days and producing significant human and environmental alterations. Coastal wetlands are vulnerable to these changes due to their low thermal inertia. In these areas, microphytobenthos (MPB) contributes significantly to primary production, being an important carbon source for the higher trophic levels. The aim of this study was to determine the effects of diurnal temperature fluctuations and heatwaves on the abundance and productivity of MPB. Sediment cores sampled in the Guadalquivir River salt marshes (SW Spain) were exposed for 7 days to different thermal regimes in the laboratory, i.e. constant (20 deg), low (20-28 deg) and high daily fluctuation (20-34 deg). O2 microprofiles and light reflectance were measured every 30 minutes and used to estimate the net community production (NCP) and the MPB migration patterns, respectively. Our results show that even at constant temperatures, NCP and reflectance vary during the day, with no relevant changes over the course of a week. Under temperature fluctuations, NCP increases with increasing temperature during the day, but decreases overall after three days exposed to a simulated heatwave. Similarly, the migration pattern of MPB remained constant at constant temperature, whereas higher temperatures decreased the surface reflectance, suggesting that the MPB community moved away from the surface. Heat waves could therefore have a major impact on the metabolism and functioning of intertidal areas, decreasing productivity, and altering MPB migration patterns

Primary Presenter: Marika Mecca, Universidad de Cadiz (marika.mecca@uca.es)

Authors:

Marika Mecca, University of Cadiz  (marika.mecca@uca.es)

Alfonso Corzo, University of Cadiz  (alfonso.corzo@uca.es)

Sokratis Papaspyrou, University of Cadiz  (sokratis.papaspyrou@uca.es)

Maria Borrallo,   (maria.borrallosolis@alum.uca.es)

Julio Bohorquez Ferrando, University of Cadiz  (julio.bohorquez@gm.uca.es)

Emilio Garcia Robledo, University of Cadiz  (emilio.garcia@uca.es)