Stop Feeding Sardines To The Cat: Let Fish Poop Save The World!


Sardines...With Tomatoes and Rosemary Image credit:Urban Sardines, On Food And Wine, blog

Ok, I admit the title is hyperbole. But the science is certain, important, timely, and fascinating, I promise.

A newly published research paper describes how bony marine fishes have been found to sequester significant amounts of carbon, as calcium carbonate, a.k.a. "gut rocks." Marine fish pooping 'gut rocks' are estimated to drop "3 to 15% of total oceanic carbonate production" of the oceans - right on Neptune's rug. Read on mermaids and mermales. It gets weird.The paper describing the 'gut rocks' phenomenon, Contribution of Fish to the Marine Inorganic Carbon Cycle, was recently published in Science Magazine. See the full abstract in Science, 16 January 2009: Vol. 323. no. 5912, pp. 359 - 362 here.

The sequestration effect discussed in this paper appears not to be about filter-feeding fish consuming carbonate-forming plankton and then excreting said planktonic carbonates. It looks, instead, to be an entirely separate biochemical transformation accomplished inside every marine fish, producing something the authors refer to as "gut rocks."

As a friend explained to me:

A test was done in the study, placing a fish in freshwater where fish don't drink water and seeing no 'gut rocks;' then, into salt water and it immediately began excreting carbonate. Fish do this to manage the overdose of calcium they drink in as it is managed/eliminated and precipitated into the gut as calcium carbonate.
Whatever. Just know that ocean fish poop out "gut rocks," that fall toward the bottom. (Some of the ancillary magnesium carbonate also formed in this process is thought to redissolve on the way down.)

The 'gut rocks' effect is anticipated become more pronounced over time, "in response to future environmental changes in carbon dioxide, and thus become an increasingly important component of the inorganic carbon cycle."

Where from marine calcium in the first place?
The weathering of mountains dissolves calcium sulfate, carrying it to the sea, where a very dilute calcium sulfate switches to calcium carbonate, or "gut rocks," inside fish, thereafter falling to the bottom to become sedimentary calcite or "limestone" (over millions of years). The earth is continuously heaving, compressing, and heating, shoving the calcite back up to the sun;; from which we start all over again - with fish poop - in the passing of geologic time.

Keep in mind that the gut-rock effect happens in fish of all sorts, but that small plankton eating fish are more voluminous, and therefore more important to the earth's climate in this respect.

Small, voluminous plankton-eating fish that we humans do feed on directly are: anchovy; herring; and, sprat or sardine. Sardines and such often end up as cat food: hence the silly title.

Darkness at the end of the tunnel.
If, after wiping out all the fish-eating predators like tuna and swordfish and salmon (which we humans are increasingly close to accomplishing), the fishing industry concentrates its predation on the small planktivores, helping society feed on them indirectly by grinding them up as a food supplement for hogs and chickens, and pet cats, sufficient to wipe out the plankton eaters as well as the tuna, why, we would be destroying our climate ever more rapidly.

Something fishy and confusing, this way comes.
Writing this made me so hungry I think I'll go have a can of sardines. None for the cat, either. It's way too good.

Or, should I become a vegetarian?

Eat naturally produced meats only?

Protest to my congress critter?

Eat plankton cakes, and just keep still?

Seed plankton, with iron sulfate, so the little fishes have more to eat and become more numerous?

So many choices...so little time.

Image credit:Nowhere Man, Beatles, Yellow Submarine

See more sea food stories in our archive.
CleanFish: Supplying Sustainable Seafood for All
Seafood Choices Alliance- Sustainable Seafood Database
Hong Kong Chefs Join Sustainable Seafood Initiative..
FishPhone: Get Your Sustainable Seafood Report On the Go
Pocket Guide to Good Fish Choices.

Tags: Carbon Sequestration