Effect of Carbonate Chemistry Alteration on the Early Embryonic Development of the Pacific Oyster (Crassostrea gigas)

Ocean acidification, due to anthropogenic CO2 absorption by the ocean, may have profound impacts on marine biota. Calcareous organisms are expected to be particularly sensitive due to the decreasing availability of carbonate ions driven by decreasing pH levels. Recently, some studies focused on the early life stages of mollusks that are supposedly more sensitive to environmental disturbances than adult stages. Although these studies have shown decreased growth rates and increased proportions of abnormal development under low pH conditions, they did not allow attribution to pH induced changes in physiology or changes due to a decrease in aragonite saturation state. This study aims to assess the impact of several carbonate-system perturbations on the growth of Pacific oyster (Crassostrea gigas) larvae during the first 3 days of development (until shelled D-veliger larvae). Seawater with five different chemistries was obtained by separately manipulating pH, total alkalinity and aragonite saturation state (calcium addition). Results showed that the developmental success and growth rates were not directly affected by changes in pH or aragonite saturation state but were highly correlated with the availability of carbonate ions. In contrast to previous studies, both developmental success into viable D-shaped larvae and growth rates were not significantly altered as long as carbonate ion concentrations were above aragonite saturation levels, but they strongly decreased below saturation levels. These results suggest that the mechanisms used by these organisms to regulate calcification rates are not efficient enough to compensate for the low availability of carbonate ions under corrosive conditions

Nutrient dynamics in European water systems (a digest from the Eloise results). Available: http://www.eloisegroup.org/themes/nutrients/contents.htm Forsman A, Grimvall A.

Abstract The European ELOISE (European Land Ocean Interaction Studies) cluster (460 projects) is the world's largest research initiative on land -ocean interactions. Beside its scientific goals, ELOISE is also meant to contribute directly to coastal zone management and thus to European coastal policy. Most of the ELOISE results have been gathered in digests that are made available on the Internet to all potential end-users (see http://www.eloisegroup.org/themes/). This paper highlights the contribution of the scientific work within ELOISE to the understanding of the ecological functioning of coastal ecosystems under eutrophication stress and what the implications are for the management of these systems. Our main objectives were (i) to identify the cross-cutting concepts emerging from the scientific studies, (ii) to point out how these concepts changed our view of the intrinsic characteristics of ecosystems and of their responses to man-made disturbance, and (iii) to relate them to issues in ecosystem management. One important conclusion is the crucial issue of spatial and temporal scale for most of the processes controlling the fluxes and impacts of nutrients in water systems. Beside the availability of the appropriate models and databases, necessary tools to bridge the gaps between scales, the main challenge for water systems managers is how to organize a system where appropriate and coordinated actions can be taken at all scales, from local communities to the European level. This study points out some tremendous advances in our understanding of essential processes in nutrient cycling that are triggered by progresses in fundamental scientific knowledge. It follows that continuing efforts at deepening our insight into ecosystem functioning are required to support a sound management for coastal ecosystems