Cold-Water Corals Feeling Laboratory Heat ... and Loving It!
Naumann, M.S., Orejas, C. and Ferrier-Pages, C. 2013. High thermal tolerance of two Mediterranean cold-water coral species maintained in aquaria. Coral Reefs 32: 749-754.
Determined to explore this situation in more detail, Naumann et al. collected live specimens of D. cornigera and D. dianthus of similar skeletal dry weight south of Malta in the Mediterranean Sea with the help of a manned submersible. They then transferred them to two identically equipped and darkened 100-L flow-through aquaria through which Mediterranean subsurface seawater was continuously pumped from a 50-meter depth and supplied to the tanks at a rate of about one liter per minute. This water was maintained at a temperature of 12.5 ± 0.1°C for approximately 30 months prior to initiating the primary phase of their experiment, which was to increase the temperature of one of the aquariums by 0.5°C per day until a value of 17.5 ± 0.1°C was achieved and thereafter maintained for a further 87 days, during which time "daily visual assessments of coral health (i.e. tentacle protrusion, suspension feeding and mortality/survival) and monthly growth measurements by the buoyant weight technique (Davies, 1989) were conducted," the latter or which were ultimately translated into coral dry weight data."
In describing their results, the three researchers say that "over the entire experimental period, both CWC species showed neither differences in tentacle protrusion and suspension feeding nor mortality at ambient (12.5°C) or elevated (17.5°C) seawater temperatures." And they say that "D. cornigera specimens developed a non-quantified number of new polyps at both temperatures suggesting efficient thermal acclimatization." In addition, they report that "D. dianthus exhibited growth rates for ambient and elevated temperatures of 0.23 ± 0.08% per day and 0.19 ± 0.06% per day, whereas D. cornigera grew at 0.05 ± 0.01% per day under ambient and 0.14% ± 0.07% per day under elevated temperature conditions."
In the final sentence of their paper's abstract, Naumann et al. say their findings "suggest that D. dianthus and D. cornigera may be capable of surviving in warmer environments than previously reported, and thus challenge temperature as the paramount limiting environmental factor for the occurrence of some CWC species." And who knows but what other species may be able to beat the heat as well.
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