<p><strong>Abstract.</strong> The design and evaluation of replicated artificial mesocosms are presented in the context of a thirteen month experiment on the effects of ocean acidification on tropical coral reefs. They are defined here as (semi)-closed (i.e. with or without water change from the reef) mesocosms in the laboratory with a more realistic physico-chemical environment than microcosms. Important physico-chemical parameters (i.e. pH, <i>p</i>O<sub>2</sub>, <i>p</i>CO<sub>2</sub>, total alkalinity, temperature, salinity, total alkaline earth metals and nutrients availability) were successfully monitored and controlled. Daily variations of irradiance and pH were applied to approach field conditions. Results highlighted that it was possible to maintain realistic physico-chemical parameters, including daily changes, into artificial mesocosms. On the other hand, the two identical artificial mesocosms evolved differently in terms of global community oxygen budgets although the initial biological communities and physico-chemical parameters were comparable. Artificial reef mesocosms seem to leave enough degrees of freedom to the enclosed community of living organisms to organize and change along possibly diverging pathways.</p>
The transportation of live coral nubbins is a major constraint of the coral trade. Corals must be transported within a timeframe of <20 hours using concentrated oxygen to avoid high post-transportation mortality. To understand the effects of transportation water quality on coral nubbin growth and post-transportation mortality, a series of transportation simulations were performed on Seriatopora hystrix. Different water volumes (dry method, 125 ml, 190 ml, and 325 ml) and oxygen concentrations in the gas phase (21 %, 40 %, and 85 %) were tested, and a 24 LED Handy Lamp was added to provide light irradiance of >100 µmol m-2 s-1 in the transportation box. During transportation nubbins extracted calcium carbonate for growth reducing water alkalinity and consequently pH to 6.67. Dissolved oxygen concentration also rapidly decreased to 0.19 mg L-1. The concentration of inorganic nitrogen, particularly ammonium ions, increased after 24 hours and reached very high concentrations after 48 hours. Before 48 hours, the larger the water volume and oxygen concentration, the faster the nubbin growth after transportation. Beyond 48 hours, in all cases, reduction in water quality became critical for nubbins and resulted in partial mortality. Illuminating the transportation box improved water quality for 72 hours using normal air.
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