The Sea Butterfly Is the Most Beautiful, Most Threatened Ocean Animal

These sea snails just want to chill and eat snacks, but their fragile shells are dissolving as the ocean becomes more acidic.


Let’s hear it for the pteropod, or sea butterfly — the tiny creatures that spend their days drifting aimlessly through the ocean. The bad news: Their days could be numbered.

Besides being majestic and mesmerizing, the little guys are a crucial part of the marine food web. Some types create webs of mucous that catch and filter organic particles that rain from the shallow waters above, and ingest them as a food source. As a result, that energy stays in the water column, and is available to the fish, squid, and the like that come along to feast on the pteropods.

But pteropods are in trouble. Some of them have thin, delicate shells that are literally dissolving as the ocean becomes more acidic.

The ocean is becoming acidic because some of the extra carbon dioxide in the atmosphere from fossil fuel burning gets absorbed into the seawater, changing its chemical property. This affects the ability of many organisms to build and maintain shells, and sea snails are particularly vulnerable because they are so small.

Acid has already begun to dissolve this pteropod shell.


Dramatic change for ocean creatures and environments isn’t some far-off fantasy — it’s happening today. And more change is coming — serious climate interventions will slow but not stop or reverse future climate change.

What’s clear is that the oceans of our planet will look very different by the end of the century. What’s not yet clear is what role, if any, the beautiful butterflies of the sea will have in it.

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