Stepped water warming effects on coastal ecosystem dynamics as monitored from fixed mooring stations in NW Mediterranean Sea

Abstract

Average global land and ocean surface temperature has stepped up since 2014 above the average. The Mediterranean Sea temperature follows this global trend. The effects of the warming on coastal areas in the Mediterranean are worrying, as they are biodiversity hotspots. Atypical warmer summer periods in the Mediterranean have been pointed out as potential drivers of massive mortalities of deep-sea organisms. Multi-sensor mooring arrays are fundamental to assess the magnitude and effects of water warming. Analysis of long-term oceanographic and biogeochemical data collected in two fixed coastal observation stations in northwestern Mediterranean Sea reveals that marine oligotrophy has intensified since 2014, with increasing water temperature by 0.25°C, greater transparency and an earlier starting of the summer conditions. Phytoplankton biomass and nutrients show no apparent change of trends. Further studies are required to assess an eventual mismatch between the life cycles of the organisms and the expected environmental conditions. These fixed stations may be considered as reference monitoring locations to assess the effects of water warming on marine ecosystem functioning