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Increased atmospheric CO2 concentration is leading to changes in the carbonate chemistry and the temperature of the ocean. The impact of these processes on marine organisms will depend on their ability to cope with those changes, particularly the maintenance of calcium carbonate structures. Both a laboratory experiment (long-term exposure to decreased pH and increased temperature) and collections of individuals from natural environments characterized by low pH levels (individuals from intertidal pools and around a CO2 seep) were here coupled to comprehensively study the impact of near-future conditions of pH and temperature on the mechanical properties of the skeleton of the euechinoid sea urchin Paracentrotus lividus. To assess skeletal mechanical properties, we characterized the fracture force, Young's modulus, second moment of area, material nanohardness, and specific Young's modulus of sea urchin test plates. None of these parameters were significantly affected by low pH and/or increased temperature in the laboratory experiment and by low pH only in the individuals chronically exposed to lowered pH from the CO2 seeps. In tidal pools, the fracture force was higher and the Young's modulus lower in ambital plates of individuals from the rock pool characterized by the largest pH variations but also a dominance of calcifying algae, which might explain some of the variation. Thus, decreases of pH to levels expected for 2100 did not directly alter the mechanical properties of the test of P. lividus. Since the maintenance of test integrity is a question of survival for sea urchins and since weakened tests would increase the sea urchins' risk of predation, our findings indicate that the decreasing seawater pH and increasing seawater temperature expected for the end of the century should not represent an immediate threat to sea urchins vulnerability. [ABSTRACT FROM AUTHOR]

Fernández-Boán, M., Freire, J., Parma, A. M., Fernández, L., and Orensanz, J. M. 2013. Monitoring the fishing process in the sea urchin diving fishery of Galicia – ICES Journal of Marine Science, 70: 604–617.The assessment and management of small-scale benthic fisheries requires attention to the spatial structure of stocks and patterns of effort allocation. Spatial information helps in the interpretation of fisheries data, and is required for designing spatially explicit management strategies, often prescribed in the case of benthic fisheries. Monitoring of boats with GPS, combined with port interviews, was evaluated as an approach to investigate the spatial pattern of fishing intensity and catch per unit of effort (CPUE) in the sea urchin (Paracentrotus lividus) diving fishery from Galicia, Spain. Fishing opportunities (FOs), relatively small regions of high fishing intensity, were identified and mapped at a fine scale. New FOs were first visited at an approximately constant rate. Concentration analysis shows that effort intensity was not uniformly distributed within FOs. CPUE did not exhibit a significant trend throughout the season, either at the scale of the aggregated fishery or within individual FOs. Catch per area and area covered per unit of diving time were inversely related, indicating that fishers stay longer in high-density patches. While abundance is the primary driver of effort allocation, other factors contributing to suitability were identified. Based on these results, we discuss realistic options for the monitoring of this and comparable fisheries. [ABSTRACT FROM PUBLISHER]