Meet the Pteropods

Robin Just

Image courtesy of Arctic Exploration 2002, Russ Hopcroft, University of Alaska, Fairbanks, NOAA/OER

Sharks need pteropods, and so do you! At the risk of looking at the world through shark-shaped glasses, let me explain.

Pteropods are little mollusks (related to snails, slugs and squid) that drift around in ocean currents, feeding on nutrient-rich plankton. Their rich diet makes them delicious to many fish. Seals eat many fish, and sharks eat seals and fish, so there it is: not even 6 degrees of shark separation. Sharks need pteropods, and so do you.

Pteropods are gorgeous. People get poetic when they talk about them. Pteropods with shells are sometimes called “sea butterflies” and the shell-less ones are deemed “sea angels.” But good luck seeing them. The ones around here are tiny. According to Woods Hole Oceanographic Institution (WHOI) pteropod researcher Amy Maas, the biggest they get is about 1/10 of an inch. Visible to the naked eye, but you probably couldn’t see their little faces. Small though they may be, unimportant they are not. Just ask the sharks.

As tiny sea creatures borne by currents, pteropods are individually delicate. Unfortunately, those with shells are under threat from ocean acidification (OA). I’ll be writing more about OA in the coming months, but here are the basics.

The carbon dioxide we are cranking into the atmosphere in unprecedented quantities does not just hang around heating up the planet, it also changes the chemistry of the oceans. The gases in the ocean must be at equilibrium with the gases in the air, so when CO2 concentrations increase in  the air, some of it dissolves into the ocean to achieve that balance. This forms carbonic acid, which decreases the pH of the water, making it more acidic. Ocean Acidification.

This is not good news for these little mollusks, since the minerals they need to grow shells are less available in the acidic water. WHOI scientist Gareth Lawson and other ocean researchers are trying to figure out exactly what will happen to our “charismatic microfauna” as the ocean pH drops. I’ll keep you posted. For now, check out this site about pteropods and OA (don’t miss the song at the bottom, it’s super catchy)

Carbon pollution and ocean acidification are not just New England issues. Yet, while OA is a global problem, there are things we can do right here, right now, to help.

CLF is working hard to prevent further harm and to give our abundant ocean life a chance to thrive. We are promoting clean energy and reductions in greenhouse gas emissions to help stop OA and other negative effects of climate change. We are supporting a climate friendly modernized public transportation network. And we support our National Ocean Policy which calls for immediate steps to protect critical marine habitats, ensure a sustainable future for our fishing industry and coastal communities, reduce coastal pollution and promote the responsible development of offshore renewable energy.

By the way, according to the Shark Week Countdown Clock, only 231 more days to go!

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