Imagine you’re on a small boat in the middle of the open ocean, surrounded by what looks like a raft of plastic. Now flip the whole world upside down. You remain comfortably attached to your seat—the abyss towers above you, and all around, stretching up from the water’s surface, is an electric-blue meadow of life. What you thought was plastic is actually a living island. This meadow is made up of a diverse collection of animals. The most abundant are blue buttons and by-the-wind sailors, with bright-blue bodies that dot the sky like suns, and deep-purple snails found in patches so dense one scientist described collecting more than 1,000 in 20 minutes.

This is the neuston, a whole ecosystem living at the ocean’s surface. I once stumbled upon a raft of neuston when a storm blew it ashore in California. Many neustonic animals are vibrant highlighter colors, and the sand was saturated in bright blues and pale pinks. Together, these small creatures may function like upside-down coral reefs: an oasis of shelter and life far out to sea. As far back as the Cold War era, scientists were describing these colorful and important ecosystems, yet they still remain all but unknown. But now, as efforts to clean the ocean of plastic start up, our ignorance is putting this ecosystem at risk.

The neuston is home to more than blue buttons and bright snails. Erupting through the lawn of blue are crackling purple, red, gold, and yellow strands. These are Portuguese man o’ wars, whose tentacles stretch like lightning from the meadows of blue and pink. And among them, dragons roam.

Small nudibranchs, known as blue sea dragons, feast on blue buttons and man o’ wars, using their winglike cerata to grab and hold onto their tentacled prey. There are sea anemones, barnacles, copepods, color-changing crabs, specialized bacteria, even bugs, all living in this inverted reef in the middle of the open ocean. (Organisms that live exclusively by floating at the surface of the water are called pleuston, while neuston is a broader term, referring generally to the sea-surface ecosystem, which is why I chose to use it here.)

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Just like reefs on the seafloor, this ecosystem does not stand apart from the open ocean around it. The neuston is a nursery for multiple species of larval fish and a hunting ground for paper nautilus octopuses. It supports sunfish, leatherback turtles, and diverse ocean grazers, which frequent these islands, relying on them as a food source. At night, soft-bodied jellies rise up to join the neuston, sparkling like fireflies. But all of this, from the blue sea dragons to the by-the-wind sailors, is in peril.

When I learned about the Ocean Cleanup project’s 600-meter-long barrier with a three-meter-deep net, a wall being placed in the open ocean, ostensibly to collect plastic passively as the currents push water through the net, I thought immediately of the neuston. How will it be impacted? But in the 146 pages of the Ocean Cleanup’s environmental-impact assessment , this ecosystem isn’t mentioned once.

I was disturbed by this omission. Though the neuston isn’t known to many people, it is certainly known to marine biologists. Evidence that the Ocean Cleanup knows about the neuston is clear from a table reporting animals in the vicinity of the Ocean Cleanup deployment area, where both blue buttons and by-the-wind sailors are listed. But the ecosystem itself is never discussed. By omitting the neuston from its assessment, the project is overlooking the habitat it could be impacting most, and there is no sense of what the damage might be. Because the impact report didn’t provide any answers, I went looking for my own.

There are few contemporary reviews of whole-ocean neuston ecosystems. I started with smaller studies on specific animals and worked my way through their references. One reference, in Russian Cyrillic, came up again and again. This made sense. I knew the United States and the U.S.S.R. had both developed extensive oceanographic-research programs after World War II, but each region published in its own language, making overlap difficult. I sat with a librarian for nearly an hour, hunting this study down. Finally, we found it: a 1956 study published in the U.S.S.R., in Russian, by an oceanographer named A. I. Savilov. This led us to another study of his from 1968, mercifully translated into English. Savilov spent his career studying the neuston by conducting extensive surveys all across the Pacific and synthesizing this work into a map of the open-ocean surface ecosystems.

Savilov described seven unique neuston meadows in the open ocean, each with its own unique composition of animals. Just as rainforests differ from temperate forests, these neustonic ecosystems are unique. And one of them, Neuston Ecosystem 2, is in exactly the same spots as the “garbage patches” where the Ocean Cleanup plans to operate. This makes sense: The neuston ecosystem is entirely passive—floating just like plastic—and evolved over millions of years to thrive within these regions, where surface-bound objects collect. But these ocean gyres are precisely where the Ocean Cleanup project intends to operate, and where it is currently testing its first system.

The Ocean Cleanup was founded with the vision of clearing the world’s ocean of plastic. The project’s goals are ambitious, and it plans to launch approximately 60 systems to reduce “the amount of plastic in the world’s oceans by at least 90% by 2040 .” It is starting with what’s known as the Great Pacific Garbage Patch, but is already scoping out other targets, too.

Even without an environmental-impact assessment, it’s easy to imagine what will happen if the Ocean Cleanup succeeds. Neuston and plastic co-occur: They’re in the exact same spots. Cleaning up 90 percent of the plastic using the current method means potentially destroying 90 percent of the neuston.

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This reality is built into the project’s design. Plastics mimic the neuston world—it’s buoyant, surface bound, and rubbery. When wind and ocean currents sweep neuston through the project’s barrier, animals such as blue sea dragons will be corralled and confined in a huge trap, their fragile bodies colliding with hard and jagged surfaces. They cannot sink below or swim around. They will be suffocated, crushed, and hauled to landfills.

The fact that we don’t have a solid understanding of the neuston ecosystem is even more worrying: We will have very little “before” data to compare the Ocean Cleanup’s impact against. By deploying its system right now, the project could rob the world of an entire ecosystem that we don’t understand and may never get back.

The Ocean Cleanup says it wants to protect animals at the ocean’s surface from plastic, but neuston is the ecosystem of the ocean’s surface. There is a reason turtles and sunfish eat floating surface plastic: It looks like neuston. Using these wall-like barriers to collect plastic in spite of the neuston is like clear-cutting a canopy in the name of helping a forest. There is no point in collecting plastic if by the end there is nothing left to conserve.

I believe that the founders of the Ocean Cleanup mean well and that the engineers involved are passionate about protecting the ocean. When I shared my concerns about the neuston, the organization was responsive, but said that its assessment had already estimated impacts to relevant groups of animals based on the best data it could find. That’s far from reassuring. We cannot monitor this ecosystem with our current technology, and millions of animals may die and dissolve before the scale of destruction is fully understood.

Here is one alternative solution: Place a modified design closer to plastic sources—river mouths and bays—to catch plastic before it enters the open ocean. Choose a place where it can be monitored and corrected for environmental impact. It seems too great a risk to disrupt the whole surface ocean ecosystem so severely, when it is also one we barely know. The neuston is an alien world, as bizarre as it is beautiful. It’s still possible to avoid destroying this strange ecosystem, wedged between sea and sky.