Coastal ecosystems are areas of high ecological value and play a vital role in global biogeochemical cycling. However, they are particularly vulnerable to an increase in intensity and frequency of heat waves. To investigate the impact of heatwaves on benthic metabolism of the intertidal zone of the Guadalquivir Estuary (SW Spain), sediment cores were subjected to a range of temperatures (10ºC to 42ºC) for 4 days followed by a 7-day recovery period. Oxygen microprofiles and whole core incubations were performed daily to measure benthic metabolism (O₂ and CO₂) and nutrients fluxes (NH₄⁺, NO₂^-, NO₃^-). At the end of each phase, solid phase and porewater variables were also recorded. Oxygen uptake increased exponentially with temperature with maximum values on Day 2. However, at the highest temperatures, O₂ consumption decreased 40% within two days, probably due to an exhaustion of the available labile organic matter, being lower than background rates after the recovery period. Nutrient fluxes also increased with the temperature, followed by a decrease back to minimal fluxes during the recovery period. In the sediment, porewater NH₄⁺ and Fe²⁺ accumulated between 2.5 and 3.5 cm depth, more so at the highest temperatures. This buildup of solutes remained until the end of the recovery period. These data show that heatwaves can have longer lasting effects on the biogeochemistry and community metabolism and composition of intertidal sediments.

Primary Presenter: SANDRA RIZZO CALDERON, University of Cadiz (sandra.rizzo@gm.uca.es)

Authors:

Sandra Rizzo, Microbial Ecology and Biogeochemistry laboratory, Department of Biology, University of Cadiz, Faculty of Marine and Environmental Sciences, Puerto Real, Spain  (sandra.rizzo@gm.uca.es)

Emilio Garcia-Robledo, Microbial Ecology and Biogeochemistry laboratory, Department of Biology, University of Cadiz, Faculty of Marine and Environmental Sciences, Puerto Real, Spain  (emilio.garcia@uca.es)

Dolores Jiménez-Lopez, Microbial Ecology and Biogeochemistry laboratory, Department of Biology, University of Cadiz, Faculty of Marine and Environmental Sciences, Puerto Real, Spain  (dolores.jimenez@uca.es)

Jose Calderón-Caro, Microbial Ecology and Biogeochemistry laboratory, Department of Biology, University of Cadiz, Faculty of Marine and Environmental Sciences, Puerto Real, Spain  (jose.calderon@gm.uca.es)

Alfonso Corzo, Microbial Ecology and Biogeochemistry laboratory, Department of Biology, University of Cadiz, Faculty of Marine and Environmental Sciences, Puerto Real, Spain  (alfonso.corzo@uca.es)

Sokratis Papaspyrou, Microbial Ecology and Biogeochemistry laboratory, Department of Biology, University of Cadiz, Faculty of Marine and Environmental Sciences, Puerto Real, Spain  (sokratis.papaspyrou@uca.es)