Friday, January 16, 2009

First-ever estimate of global fish biomass and impact on climate change

Via Ocean Acidification:

Fish Carbonate Animation

Are there really plenty of fish in the sea? University of British Columbia fisheries researcher Villy Christensen gives the first-ever estimate of total fish biomass in our oceans: Two billion tonnes.

And fish play a previously unrecognized but significant role in mitigating climate change by maintaining the delicate pH balance of the oceans, according to a study published in tomorrow’s edition of the journal Science, co-authored by Christensen and a team of international scientists.

“By drinking salt water, fish ingest a lot of calcium, which needs to be removed – or they will get renal stones,” says Christensen, an associate professor in the UBC Fisheries Centre.
The team discovered that fish do this by binding the calcium to bicarbonate, and then excreting it as pellets of calcium carbonate, a chalk-like substance also known as “gut rocks,” in a process completely separate from food digestion. For an animation of this process, visit

As the calcium carbonate from these pellets dissolves, it turns the seawater more alkaline, which has relevance for ocean acidification, and is impacted by the ocean’s exchange of carbon dioxide (CO2) with the atmosphere.


“This study really is the first glimpse of the huge impact fish have on our carbon cycle – and why we need them in the ocean,” says Christensen. “We must buck the current trend of clear-cutting of the oceans and foster these unrecognized allies against climate change.”

Brian Lin, EurekAlert, 15 January 2009. Article.

UBC researcher gives first-ever estimate of worldwide fish biomass and impact on climate change
Fri, 16 Jan 2009 08:15:27 GMT

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