Novel microcosm system for investigating the effects of elevated carbon dioxide and temperature on intertidal organisms

In addition to the predicted rise in temperature, a recognised consequence of increased atmospheric CO2 is ocean acidification. The response of marine organisms to the stresses associated with acidification is still not understood, and a number of recent experiments have addressed this problem. The starting point for many of these studies has been the development of a system by which seawater pH can be altered and then maintained. The current paper presents details of a temperature- and pH-controlled microcosm system, which enables the establishment of a tidal regime, for the experimental investigation of intertidal organisms. Two climate scenarios were simulated to evaluate the system's precision and accuracy; Year 2008 ('low' [CO2]: 380 ppm and 14 degrees C) conditions and Year 2100 ('high' [CO2]) conditions (based on the IPCC-Intergovernmental Panel on Climate Change-2007 A2 scenario, 'high' [CO2]: 1250 ppm and 2.0 to 5.4 degrees C warming). The temperature and seawater carbonate chemistry were reliably maintained for 30 d during which time newly settled barnacle cyprids were allowed to metamorphose into juveniles, then grow and develop. The pH and [CO2] had 95% confidence intervals of 0.03 units and 17 ppm, respectively, under low [CO2] conditions, and of 0.02 units and 43 ppm, respectively, under high [CO2] conditions. The tidal regime is fully adjustable, and on this occasion was set to a 6 h cycle. These microcosms have proved ideal for studying benthic organisms from a variety of near-surface environments and at different stages of their life-cycle.