Another use for fish (and another reason not to eat them)

This was a pretty amazing article. I've been familiar with the ways in which the oceanic carbonate system maintains its balance, or gets knocked off kilter (absorption or degassing of atmospheric CO2 or dissolved CO2; biomineralization, i.e. calcification, by corals, coccoliths, foraminifers, pteropods and heteropods; organic matter remineralization in the deep sea; dissolution of calcium carbonate sediments; even the shift in the Ca/Mg balance as waters rush through the deep-sea hydrothermal systems) -- OK, fine, but I never heard of piscine "gut rocks" before!!

First-Ever Estimate Of Worldwide Fish Biomass And Impact On Climate Change

"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.

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."

The study also estimates the total biomass of fish in the ocean at two million tonnes. From another article:

Fish 'gut-rocks' solve ocean puzzle

" - Wilson estimated the total biomass of bony fish in the world's oceans as between 812 million and 2050 million tonnes, leading to a total carbonate production of around 110 million tonnes. "

Now, there MUST be pictures of gut rocks on the Internet. Let's go find 'em.

Took me a few minutes, but I found the following. Also has another good reference.

Eat fish and acidify the oceans