Effects of heat wave events on the brown alga Fucus ceranoides and on the established exotic species Egeria densa and associated fauna in the Minho river estuary (NW Iberian Peninsula)
摘要
Aquatic vegetation provides unique habitats for a wide range of organisms, playing an important role in estuarine ecosystems. Between the summers of 2021 and 2022 an unusual dry period was observed for the North region of Portugal, with punctual heat waves occurring throughout the year. The aim of this study was to assess the impact of these heat wave events on the brown algae Fucus ceranoides (polyhaline zone) and on the exotic macrophyte Egeria densa (tidal freshwater zone) and their associated invertebrate diversity. Both Fucus ceranoides and Egeria densa were sampled monthly from September 2021 to September 2022. It was noted that following those heat wave events both Egeria densa biomass and diversity of its associated fauna declined considerably, pointing the increases of water temperature and salinity as factors that limit the maintenance of these populations at the upper estuary. On the other hand the effect of those heat waves was less noticeable on populations of Fucus ceranoides, even if associated invertebrate diversity, abundance and biomass dipped during those events. Species such as Echinogammarus marinus and the exotic gastropods Physella acuta and Menetus dilatatus thrived under extreme climate change conditions which limited other invertebrate species. Therefore, increased frequencies of heat wave scenarios could lead to alterations on the biomass of submerged aquatic vegetation and on the abundance, diversity and biomass of its associated invertebrate assemblages.