[Coral-List] Acidification & Boring Erosion

Michael Risk riskmj at mcmaster.ca
Fri Dec 7 21:39:28 EST 2012

Hello Andrew.

Yes, you have hit the nail on the head. Acidification will certainly accelerate bioerosion. 

Many of the common bioeroding critters employ chemical dissolution as part of the process. The most common, ubiquitous eroders in photic waters are the boring algae. There is no piece of reef coral that does not contain boring algae. They bore purely by chemical means, seeking out the crystal surfaces with the highest free energy and secreting a variety of organic acids. In sponges, a protoplasmic loop secretes carbonic anhydrase, etching the perimeter of a chip-amoebocytes then rip that chip off the surface. The actual chemical part of the process is only a few %, but will obviously be accelerated.

Sadly, there is still a dearth of research in this field: although bioerosion is a process which is volumetrically more important in reef carbonate budgets than coral growth, the coral reef community continues to pay little attention. Fortunately there is some good work on acidification appearing now-I especially recommend papers by Christine Schoneberg and Max Wisshak.

On 2012-12-07, at 11:21 AM, andrew ross wrote:

> List,
> With discussion about acidification related reef erosion is there an elephant in the room in boring organisms? Admittedly my experience is primarily in very broken systems, but for me it's common to be able to tear chunks of hard reef away with my hands. When I look inside the hole I've made I see little but sponge, plus scrambling cryptic beasties. This has been my observation in obviously "enriched" locations like Montego Bay (Jamaica) and on less obvious sites such as St. Mary to the East, where our recent visitor Hurricane Sandy demonstrated the issue on a much larger and messier scale. I found this condition particularly notable when I could not break bits off at the more remote Pedro Banks this past spring. 
> Can we expect that boring erosion be increased under a reduced ocean pH? Can we expect this to occur additively, or might these processes work in synergy?
> Should this be part of our climate change adaptation planning?
> Andrew Ross
> UWI (Mona)
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Michael Risk
riskmj at mcmaster.ca

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