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

Abstract

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 tempera-ture-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°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°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 adjust-able, and on this occasion was set to a 6 h cycle. These microcosms have proved ideal for studying ben-thic organisms from a variety of near-surface environments and at different stages of their life-cycle. © Inter-Research 2008.