| Summary: | Anthropogenic CO2 emissions, which are resulting in ocean acidification and a decrease in the saturation state for calcium carbonate (Ω), are a particular threat to calcifying marine biota. The aim of this thesis is to fill important knowledge gaps that limit our understanding of the implication of these anthropogenically driven changes for calcifying organism in intertidal, coastal and deep-sea environments. Papers I and II investigate the intertidal environment where the range and rate of environmental changes are often extreme. Paper I describes seasonal and daily fluxes in the inorganic carbon system in tidal pool environments in relation to biological processes in a red calcifying coralline algal species (Ellisolandia elongata) through irradiance response curves. Paper II describes an experimental study where alga from the same population as studied in paper I were grown for 3 weeks at varying pCO2 concentrations: 380 µatm (representing modern day atmospheric CO2 concentration) and 550, 750 and 1000 µatm (representing future atmospheric CO2 concentrations). Results suggest intertidal algae are less susceptible to future atmospheric CO2 concentrations compared to coralline alga from the subtidal marine environments. Data on spatial and temporal variability in the inorganic carbon system in coastal regions is limited, which is an issue for understanding biological responses of coastal species to ocean acidification and for the construction of numerical biogeochemical models. Paper III investigates the seasonal variability in the inorganic carbon system in a pristine coastal region of Iceland, Breiðafjörður Bay. The study region was identified as a net sink of atmospheric CO2 at a rate of 1.8 mol C m-2 y-1 with surface pCO2 ranging from 212 to 417 µatm from summer to winter. The deep-sea is a relatively stable environment. Regardless, numerical model predictions suggest the Nordic Seas will be largely undersaturated with respect to aragonite by the year 2100, posing a severe threat to calcifying mollusc in the ...
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