Effect of weather conditions, atmospheric CO2 and marine macroalgae on the seawater chemical conditions in Galway Bay (Ireland) during winter and summer

Abstract

The effect of weather conditions, atmospheric carbon dioxide and marine macroalgae on the seawater chemical conditions in Galway Bay, in the west coast of Ireland, has been studied during winter and summer 2018. Data collected from a survey in the RV Celtic Explorer at both outside and inside Galway Bay on February 2018 were used as a wintertime representative sample. In addition, a mooring was set at Carraroe, north coast of Galway Bay, which was recording data during June and July 2018. The results of the present study shown a marked seasonal influence between winter and summer periods. Firstly, meteorological parameters, such as wind force, precipitation and the consequent river runoff, have governed the observed changes in the chemical conditions, mainly due to both vertical mixing drove by the wind force and the minimal influence of the biological activity during the winter period. On the other hand, changes in the surface ocean chemistry in summer were mostly driven by the marine macroalgae biological activity rather than the physical forcing. Daily seawater pH fluctuations were observed due to the uptake of dissolved inorganic carbon during the day via photosynthesis, driving an increase in pH in the surrounding seawater, and decreasing pH at night as a result of CO2 release owing to respiration. Although overall the Atlantic Ocean has an extraordinary capacity to uptake CO2 from the atmosphere, its coastal marine areas can either uptake or release CO2 to the atmosphere. In this regard, the studied kelp bed was actively uptaking carbon during the summer sampling (maximum daily uptake rate of 3.307 gC·h-1), having become an effective carbon sink during this time period. Moreover, metabolic processes may were boosted by both the high seawater temperatures and solar radiation levels during this warm period.