Acidification and its effect on the ecosystems of the ICES Area

Abstract

This focuses on the impacts of ocean acidification (OA) on ecosystems and higher trophic levels in the ICES Area. One of ICES distinguishing features is its access to scientists across the entire marine field. This report is based on the Report of the Workshop on the Significance of Changes in Surface CO2 and Ocean pH in ICES Shelf Sea Ecosystems (WKCpH; ICES, 2007c), updated to include recent research, using inputs from the chairs of ICES working groups. Oceanic uptake of atmospheric CO2 has led to a perturbation of the chemical environment, primarily in ocean surface waters, which is associated with an increase in dissolved inorganic carbon (DIC). The increase in atmospheric CO2 from ca. 280 ppmv (parts per million by volume) 200 years ago to 390 ppmv today (2011) has most probably been caused by an average reduction across the surface of the oceans of ca. 0.08 pH units (Caldeira and Wickett, 2003) and a decrease in the carbonate ion (CO32−) of ca. 20 μmol kg −1 (Keshgi, 1995; Figure 5.1). It has been estimated that the level could drop by a further 0.3 – 0.4 pH units by the year 2100 if CO2 emissions are not regulated (Caldeira and Wickett, 2003; Raven et al., 2005). A study of potential changes in most of the North Sea (Blackford and Gilbert, 2007) suggests that pH change this century may exceed its natural annual variability. Impacts of acidity induced change are likely, but their exact nature remains largely unknown, and they may occur across the whole range of ecosystem processes. Most work has concentrated on open‐ocean systems, and little research has been applied to the complex systems found in shelf‐sea environments.