Elkhorn coral (Acropora palmata) was one of the most important reef-building corals in the Caribbean, growing at an average 5-10 centimetres per year and eventually up to 3.7 metres (12 ft) in diameter. Since 1980 90-95% has been lost and it is now an endangered species.
Elkhorn Coral Problems
There are many intertwined problems for the elkhorn coral including; predation, climate change, storm damage, human activity, coral bleaching, and coral diseases.
These all work together to give a 'synergistic effect' – where they add together and each compounds the problems already caused by the others.
One particular problem highlighted here is 'white pox disease'.
Elkhorn White Pox Disease
Elkhorn Coral (Acropora palmata) being decimated by white pox disease, "with losses of living cover in the Florida Keys typically in excess of 70%", (National Academy of Sciences).
The coral loses tissue very quickly at around 2.5 square centimetres per day on average, but up to 10.5 square centimetres in warm conditions – this destruction per day is more than the annual growth rate!
"In Florida, the spread of white pox fits the contagion model ... we identify a common fecal enterobacterium (Serratia marcescens) as the causal agent of white pox", (National Academy of Sciences).
Human Sewage Killing Coral
Research recently published (PLoS ONE, 2011) takes this story at least one stage further. Sutherland, Shaban et al. have shown that,"human strain PDR60 (of Serratia marcescens) is a coral pathogen".
They go on to suggest that a coral-eating snail (Coralliophila abbreviata) may act as a reserve host for this bacteria, keeping the infection going on when there is little contaminated sewage around.
Florida Keys waste disposal has traditionally involved septic tanks, which have a tendency to leak.
The Florida Keys are situated on porous limestone bedrock, so any septic tank that leaks can send sewage through this bedrock and into the ocean.
Coral Reefs are Important
Ecosystems interact with one another, and the well-being of mangrove forests, seagrasses, and coral reefs are closely intertwined.
More than 4,000 species of fish live on coral reefs, and over 500 million people rely on them for survival – they generate $375 billion each year.
But there is more to it: coral reefs and their fish are beautiful places, and who can put a cash value on that?
Divers and marine aquarists have first hand experience of what makes the reefs and their fish special – perhaps they should be leading conservation efforts.
Sources:
- 'The etiology of white pox, a lethal disease of the Caribbean elkhorn coral, Acropora palmata.', Patterson, Porter et al., The National Academy of Sciences, 2002.
- 'Human Sewage Identified as Coral Killer', Jenny Marder, Scientific American, 2011.
- 'Human Pathogen Shown to Cause Disease in the Threatened Eklhorn Coral Acropora palmata', Sutherland, Shaban et al., PLoS ONE, August 2011.
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