Stony corals of the genus Porites – such as these greybrown specimens on a reef at Raja Ampat (Indonesia) – look rather unimposing. Among them, yellow, red and violet species glow – for the time being at least… Only a few coral species are able to cope with rising water temperatures and ocean acidification.
Porites might prevail and dominate reefs in the future, according to observations in Papua New Guinea. At some places, volcanic systems below the seafloor release carbon dioxide (CO2) and naturally acidify the water around them. In such environments, stony corals adjust their internal pH and enable themselves to form calcium carbonate and grow just like under “normal” conditions. Because not many species are able to withstand a drop in pH levels, Porites dominates the high-CO2 reefs.
Photo: Solvin Zankl