Climate change is affecting the oceans in any number of unpredictable ways. For example, under pressure from rising ocean temperatures (and toxic waste), coral reefs — those glorious engines of biodiversity — are degrading. I knew that.

But this one was new to me: They also become breeding grounds for poisonous algae. And that poison accumulates in the big fish that eat the little fish that eat the algae — making coral-dwelling fish toxic and sometimes even deadly for humans. So reports AP environmental writer Michael Casey in a recent piece.

If we reach a point where coral-dwelling fish become inedible, this will count as yet another instance in which climate change, caused mainly by emissions in the global north, falls most heavily on people in the global south.

One scientist tells AP that:

Worldwide, we have a much bigger problem with toxins from algae in seafood than we had 20 or 30 years ago … We have more toxins, more species of algae producing the toxins and more areas affected around the world.

Some may find poetic justice in this. Much of the fish marketed from coral-reef zones is “exotic” — rare breeds that fetch a high price in wealthy places like Hong Kong. It might seem perversely right that a rich person dropping $50 per pound for rare breeds like Napoleon wrasse shipped from great distances should risk death. After all, overfishing threatens to wipe out such breeds altogether.

But the problem goes deeper than that. Sure, there’s no justifying the global fish trade in an age of declining fish stocks and climate change; it clearly needs to end immediately, as the viability of the oceans as fish habitat is very much in jeopardy.

But for all of human history, people who live near oceans have sustainably harvested fish. In that context, fish represent a cheap and powerful form of human nutrition — and an important part of culture. It’s one thing to ask wealthy businessmen to stop having exotic breeds of fish shipped in from across the globe, refrigerated the whole time. It’s another to eliminate fish from the diets of coastal peoples who make their living from the sea.

And that’s exactly what climate change and ocean pollution are conspiring to do. The AP article states that ciguatera — the toxin that accumulates in coral-dwelling fish — has always been present in low levels in warm seas like the South Pacific and the Caribbean. People there have long known how to avoid it — by testing fish on dogs, for example.

But now ciguatera’s presence is both intensifying and expanding.

Given the direct link with climate change, one way to think about the situation is this: We’re on the verge of sacrificing a cheap, relatively low-impact form of protein and nutrition — coral-dwelling fish — for a crude and byzantine form: feedlot meat production, which is a huge driver of climate change.