Tuesday, February 14, 2023

Look Who's Fighting Ocean Acidification



(Hello folks, Brian here btw)

I was doing some light reading of the 200-page Feasibility Assessment: Sea Otter Reintroduction to the Pacific Coast by our friendly government staff at US Fish and Wildlife. It's actually surprisingly readable, unless like me you need to plow through the legal aspects.

Anyway, one interesting piece of information from the study is that otters can create localized reductions in ocean acidification. It's the identical process for taking carbon dioxide out of the water column, which might have been obvious but I would've guessed there would be too much water exchange to have localized effects. The process is that otters indirectly promote the growth of kelp, in rocky areas, and sea grass, in estuaries. For kelp it's pretty simple, they eat the things that eat kelp. For sea grass, they eat crabs that eat slug like animals that eat the algae that grows on sea grass and limit its growth. All that removes carbon dioxide from the water column, enough to have temporarily reduced the acidification in the area. Kelp is the ocean equivalent of a forest and seagrass the ocean equivalent of grass meadows (surprise), so the environmental benefits from otter reintroduction extend far beyond carbon and acidification.

It would be helpful to get some quantification of the reduced acidification and its biological significance, but given how bad it's getting, I'd assume anything is helpful. This could also be relevant because one of the few adverse economic effects of reintroducing otters is they reduce some shellfish levels to low (but healthy) levels so that fisheries can no longer rely on them. With acidification coming, however, that might be the fate of those fisheries regardless.

The point I'd like to make is that the study underplays the benefit of reduced acidification, only describing it as "locally" beneficial. Yet for carbon sequestration, they acknowledge otters can't significantly contribute to reducing carbon globally but local sequestration "is important as all such changes are cumulative and collectively they are necessary" (page 77). Well, the same holds true for ocean acidification, anything that helps to collectively address the problem is cumulatively important.

As for whether otter reintroduction does happen, I certainly hope so. I think it's mainly a political problem at this point.

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