Imagine you live hundreds of meters deep in the sea to hide from predators. But every night you swim upward to find food in nutrient-rich surface waters and descend again before dawn. And to do it, you swim the equivalent of eighty miles in the course of a night.
You would be a pteropod. A pyramid-shaped pteropod, Clio pyramidata, swims 400 meters up and down every night. It’s one centimeter long. That would be like me—at five and a half feet—swimming over eighty miles in the course of a night. To top it off, the diminutive world-class swimmer belies the very category of its existence: it’s a snail.
I had a chance to shadow the research of one of the world’s experts on pteropods, Dr. Amy Maas, on a Bermuda Institute of Ocean Sciences (BIOS) expedition led by Dr. Maureen Conte. Maas studies how climate change impacts biochemical cycles in the ocean, especially how pteropods respond to ocean acidification. Maas was assisted by Dr. Andrea Miccoli and Jordan Wingate. Miccoli worked with Maas on respiration experiments which shed light on the role of pteropods in carbon sequestration. Wingate worked on a study of pteropod locomotion to understand the mechanics of their remarkable swimming speed for underwater robotics applications.
Pteropods are “pelagic snails,” the oceanic counterpart of terrestrial snails you might find in a backyard or a forest. They are a type of plankton called zooplankton—tiny organisms that drift in the ocean or larger creatures in early development like fish larvae.
Zooplankton basically means “animal plankton.” It’s derived from the Greek word, zoon, meaning animal, and planktos, the Greek word for wanderer or drifter. Diminutive as they might be, some only visible under a microscope, zooplankton are nevertheless animals. They breath, eat, avoid being eaten, and some, like the pteropod, swim at impressive speeds.
The “little animals” migrate up and down every night in every sea of the world. They make up what’s called the deep scattering layer which was discovered in the 1940s. Military sonar operators were flummoxed by what looked like gigantic portions of the sea floor rising from the depths. In one instance, the commander of the Atlantic Task Force, Admiral John S. Thatch, sent frantic SOS signals, stating a huge “cloud” in the sea was wreaking havoc with the ship’s sonar. The frightful “moving sea bottoms” turned out to be vast swathes of microscopic and near-microscopic living creatures on the move, migrating to feed.
Twice a year Maas collects samples in the Sargasso Sea, about 75 kilometers southeast of Bermuda in the western part of the North Atlantic gyre. Our boat, the R/V Atlantic Explorer, was equipped with labs for processing samples. In the opposite lab, Maureen Conte headed up the Oceanic Flux Program, which for over forty years has analyzed samples from as deep as 14,000 feet, making innumerable contributions to the understanding of ocean ecosystems. The OFP has continuously collected and analyzed that data for over forty years—the longest time-series of its kind.
Maas warned me ahead of time, “You’ll be working graveyard.” Mass collected her samples at night, because that’s when the pteropods are closest to the surface.
My first night on the boat I bolted awake from a nap when my alarm went off and banged my head on the low-lying bunk ceiling. I groggily made my way down the stairs to the main deck, clutching the railing. “The seas,” the captain, George Gunther, had explained earlier, “were a bit confused.” Translation: we were in a high-pressure zone between a macro-scale extratropical cyclone (“Nor’easter) and a hurricane.
Miccoli, Mass, and Wingate were already at work. The zooplankton are collected by trolling with a Reeve net, which looked like an oversized butterfly net attached to a large bucket, or a high-tech net called the MOCNESS equipped with an elaborate array of remote controls and sensors. The boat trolls with the net in the water for about three hours. Then Maas, assisted by Miccoli and Wingate, meticulously sort and store the samples in the lab for experiments until almost dawn.
Amy occasionally dropped a few pteropods and other zooplankton in a glass dish for me to look at under a dissection microscope which was lashed to a counter with thick straps and ratchet buckles. The boat gyrated back and forth so much, it was hard to keep my eyes next to the eyepieces. Wingate politely reminded me to keep my hand on the dish, lest the boat surge and send it flying off the table.
The iridescent creatures swam frantically in the small dish, their world suddenly illuminated and confined. They too were blurry-eyed, their circadian rhythms rudely interrupted. Watching them, I felt something shift in me.
Truths are truths. You know something, you believe it. Evidence shows it. But sometimes an experience comes along that drives that truth home with a strength that leaves your awareness irreversibly changed.
The transparent, jewel-like creatures yanked from the dark open ocean had so much to tell us about our world. The truths of the pteropod’s world—the “world according to pteropod”—are not some arcane oceanographic footnote, they are crucial for all of us.
Pteropod shells are starting to thin and fray. They are less able to form their shells because of ocean acidification—the fact that the carbon dioxide we’ve pumped into the atmosphere has made the seas 30% more acidic in the last 200 years. That sharp drop in pH is more dramatic than any change in ocean chemistry in the last 50 million years.
So, what’s the big deal about a drop in pH? Well, in your body or mine, a blood pH drop of 0.2 or 0.3 can cause seizures and comas, even death. That’s what makes this question so chilling: What will this do to biological cycles in the ocean? To living creatures? To food chains?
As ocean acidification progresses, the survival of pteropods and other creatures that form shells and skeletons—coral, oysters, starfish—becomes even more uncertain. Pteropods are nicknamed the “potato chips of the sea,” because they are essential food for everything from juvenile fish to herring, mackerel, rays, seabirds and whales. Like cutting a link in a chain, the loss or decline of pteropods and similar organisms can disrupt the entire food chain.
The pteropod’s world is also deeply connected to the biological cycles by which the ocean sequesters carbon. Like powerful brakes on a Mac truck driving down a steep incline, the seas have put an enormous brake on climate change, sequestering over 25% of the carbon dioxide we’ve pumped into the atmosphere. Just how much carbon is that? It’s 525 billion tons, continuing at a current rate of 22 million tons a day.
Like all zooplankton, pteropods breathe. When they exhale carbon dioxide at depth it stays there. That carbon dioxide is sequestered along with the carbon in their bodies that sink when they die. Their fecal pellets sequester even more carbon.
If the biological cycles by which carbon is sequestered are seriously disrupted or collapse, so too will the ocean’s ability to put a brake on climate change. That takes us to the runaway climate change scenarios that we need to do everything in our power to avoid.
“We know the chemistry, what we don’t know is how resilient the biology is,” Dr. Maas told me. “We keep adding more to the situation, more temperature, more acidity, and we are not sure when we are going to hit what we call a tipping point—the biological tipping point both for individual species and for the whole ecosystem.”
It’s like an errant EKG for the health of the planet. The ethereal, wing-footed creatures who are endangered speak to our own endangerment, that the life of our planet as we know it is in grave danger.
But real hope starts with truth and action. And pteropods exemplify another truth, key to our survival—their world speaks legions about the interconnected nature of life. Understanding that connectedness through science is key to charting a better future. And each of us is a part of that interconnected web—every time one of us acknowledges that climate change is a global emergency, that reducing our carbon imprint is imperative, we push the needle toward a better future.
Liz Cunningham’s mission is to be a voice for the life of the seas and the people who are working to save it, to inspire and empower others to join the effort to save our seas and forge a sustainable future. She writes and speaks to audiences about ocean conservation and the traits we need to be effective stewards of our seas and life on this planet—among others, courage, an engaged, active hope, and the ability to work together to find solutions. She is the author of the award-winning book, Ocean Country with a foreword by Carl Safina. More information about her work is available at: http://www.lizcunningham.net
Links to learn more:
The top 100 solutions to counter climate change. Project Drawdown reviews, analyses, and identifies the most viable global climate solutions: https://www.drawdown.org
An Interview with Dr. Amy Maas
http://www.bios.edu/currents/scientist-at-work-a-conversation-with-bios-biologist-amy-maas
The Bermuda Institute of Ocean Sciences
http://www.bios.edu/#!/who-we-are
The Oceanic Flux Program:
https://www.mbl.edu/ecosystems/conte/ofp/
The ocean’s role as a carbon sink: “Carbon Dioxide and Our Ocean Legacy,” by Richard A. Feely, Christopher L. Sabine, and Victoria J. Fabry
https://www.pmel.noaa.gov/pubs/PDF/feel2899/feel2899.pdf
This piece was prepared online by Panuruji Kenta, Publisher, SEVENSEAS Media