Coastal ph variability in the Balearic sea

Abstract

The Mediterranean Sea is one of the most fragile ecosystems in the world to increases in carbon dioxide (CO2) emissions due to its distinct physical and biogeochemical characteristics. However, until recently, only two permanent stations were monitoring trends in pH in this basin; the Mediterranean Ocean Observing System for the Environment station (DYFAMED) in the Ligurian Sea and the Gibraltar Fixed Timeseries (GIFT) mooring line in the Strait of Gibraltar. Evaluating trends in pH in coastal systems can be complex, as the measured signal is influenced by a multitude of drivers, including watershed processes, nutrient inputs, and changes in ecosystem structure and metabolism. Interaction between ocean acidification due to anthropogenic CO2 emissions and dynamic local drivers of coastal ecosystems cause high variability of pH in coastal waters. Therefore, it is crucial to disentangle local drivers and elucidate pH trends in coastal stations. Here we evaluate data from high-resolution autonomous sensors in surface waters in the Balearic Sea, in two stations with different anthropogenic pressures. These sites belong to the Balearic Ocean Acidification Time Series (BOATS), with sites at the Balearic Islands Coastal Ocean Observing and Forecasting System (SOCIB) fixed station (Palma Bay, Spain) and Cabrera National Park. We compare the seasonal variability of coastal surface waters with over two years of data from a SAMI (Sunburst LLC.) pH sensor. Reconstruction of pH data with other available biogeochemical parameters is applied to evaluate the robustness of found patterns