Elevated atmospheric CO₂ is a major driver of global change in the ocean, causing sea surface temperatures to rise and acidification of marine environments. Together these stressors may have additive, synergistic or unforeseen consequences for many marine organisms, particularly during early life stages. The economically important King Scallop (Pecten maximus) is found along a large latitudinal gradient in the Eastern Atlantic, but it is unclear how this species will respond to changing environmental conditions. Studies of genetic structure suggest that Atlantic populations (from Spain to the UK) are genetically distinct from Norwegian populations, a result that is borne out by phenotypic differences. Yet whether genetic differences arise as a result of adaptive or neutral processes is not clear, and the extent to which plasticity accounts for phenotypic differences is unknown. 

In order to address these questions and test how climate stressors influence early life traits in P. maximus, we carried out a common garden experiment on hatchery-reared juvenile scallops (age 3-6 months, shell height 2-14 mm) from two populations (progenies originated from Tinduff hatchery, Brittany, France, and Scalpro hatchery, Hordaland, Norway). Scallops were reared for 5 weeks under controlled conditions in 6 different pH/temperature combinations: control pH (8.0) and reduced pH (7.7) at each of three temperatures (13, 16 and 19 °C).

A number of physiological, morphological and molecular analyses are currently being analysed. Individual basal metabolic rate and filtration were measured, as were shell dry weights, and body dry and ash-free dry weights. Shells of additional individuals were photographed for growth estimations and morphological measurements. Finally a proteomic approach using two-dimensional electrophoresis (2-DE) is being used to quantify and relate protein abundance to physiological and phenotypic traits. Integrating these approaches is vital to gauging how these populations will adapt to climate change.