Larval fish are eating plastic

Newborn / larval fish are mistaking tiny bits of trash for food. If they die, there’ll be fewer big fish—and that could rattle the food chain.

FISH NURSERIES OFF HAWAII ARE NOW A MICROPLASTIC MESS.  The naturally oily surface slicks in which many ocean fish come of age are rich in plankton and other fish food—and now also in plastics, according to researchers at the National Oceanic and Atmospheric Administration in Honolulu. They’ve been towing fine mesh nets through slicks off the Big Island and analyzing each haul. Here, a scribbled filefish, about 50 days old and two inches long, navigates a soup of plastic.

Not long ago I went snorkeling in the Pacific Ocean, a half mile off the southwest coast of Oahu. The flanks of the Hawaiian island are steep there, and the bottom quickly disappeared beneath us as we motored out to the site. Looking back, I could see the green slopes of the Waianae Range rising to 4,000 feet behind the beach. Normally the mountains shield the water here from the trade winds. But on that day a breeze created a light chop that nearly obscured what I had come to see: a thin, oily slick of surface water, rich in organic particles, in which newborn fish were feeding and struggling to survive their first precarious weeks.

My guides that day, oceanographer Jamison Gove and fish biologist Jonathan Whitney of the National Oceanic and Atmospheric Administration in Honolulu, are nearly three years into a research project that aims to make sense of this chaotic scene. The larval stage is the “black box” of fisheries science: Fertilized eggs go in, and young fish come out—but what happens inside remains sketchy. The larval fish are so small and fragile they’re exceedingly difficult to study. The overwhelming majority will never become adults. Yet fish populations around the world, and the animals that eat them, depend on just how many larval fish make it, and in what condition.

The blue glove hasn’t been in the water long enough to suffer the fate of most ocean plastic, which is to be shredded into small bits, or microplastics, by waves and sunlight. The larval fish below the thumb is a driftfish; the striped one at the base of the index finger is a mahi-mahi.

What Gove and Whitney have found lately—and what David Liittschwager’s photographs of their water samples document—is that fish and wholesome fish food are not the only things collecting in the slicks off Hawaii. Microplastics, tiny shreds of human trash, are there as well, and in such abundance that larval fish are eating them in their first days of life.

For newborn fish, to eat is to live another day; if their first meal is plastic, they’re not consuming the calories they need to sustain them until the second. “They’ve beaten a lot of odds to get this far,” Gove says. “They hatched, they found the slick, they’re feeding and growing. This is one-tenth of one percent that made it this far; they’re the lucky ones. And now plastics are coming in.”

“The most critical moment is that first feeding,” Whitney says. “If they get a piece of plastic, that could be it. A single thread in the stomach of a larval fish is potentially a killer.”

ON THE RIGHT, FISH FOOD. ON THE RIGHT, PLASTIC.A dollop of surface water from the English Channel contains a shrimplike krill, about a third of an inch long; a smaller decapod crustacean; and an orange sea star just emerging from its filmy floating larval stage. The white chip and the fraying red fiber on the right are polyethylene—but to a young fish they too may look like food. Three percent of the larval fish caught for a 2017 study by researchers at Plymouth Marine Laboratory and the University of Plymouth had eaten microplastic fibers.

Plastic waste, mostly from rivers or careless dumping on land, washes into the oceans at an average rate of about nine million tons a year, according to a 2015 study by Jenna Jambeck of the University of Georgia. The visible trash, along with heartbreaking images of its impact on everything from turtles to birds to whales, has generated a public outcry. But sunlight, wind, and waves eventually break down ocean plastic to bits that are barely visible. One of the biggest unknowns—and concerns—is the effect that these microplastics, smaller than a fifth of an inch, might be having on fish.

Fish provide critical protein to nearly three billion people and countless seabirds and other marine animals. But fish stocks worldwide have fallen by half since 1970, surveys show. Populations of the largest predatory fish, such as tuna, have fallen even more. The decline is largely because of overfishing, but pollution and waters warmed and acidified by climate change are having a growing impact.

As long ago as the early 1970s, scientists were finding plastic pellets—the material used to manufacture plastic goods—in the stomachs of fish caught off New England and Great Britain. More recent studies have documented the presence of even smaller microplastic particles in a growing array of adult fish. Larval fish have been studied much less but are likely to be more vulnerable to microplastics, as they are to everything else. “Any stressor will likely have more of an impact on early life stages than later life stages,” says Susanne Brander, a toxicologist at Oregon State University who is studying how plastics might affect the growth of fish.

A grid painted on a petri dish helps a NOAA technician sort through a sample and identify tiny organisms, such as the larval sergeant major damselfish on the left, just outside the middle row. The squares are one centimeter (.39 inch) across.

Most ocean fish are terrible parents. A few species guard their eggs on the seafloor; others protect them inside their mouths. But most fish release thousands or even millions of eggs and sperm into the wide ocean and never see their offspring. When eggs hatch a day or two later, the newborn fish are on their own.

Newborn fish look misshapen, heads oversize, tails barely formed. They have to eat like crazy to grow into their body. Whereas human babies develop in the shelter of the uterus, fish mainly develop after they emerge into an unforgiving world.

Predators or starvation will get most of them. “That’s why fish spawn so many eggs,” says Su Sponaugle, an Oregon State University marine ecologist who specializes in the early life stages of fish. “They have to hedge their bets.”

The larval phase is treacherous every step of the way—starting with the need for the larvae to find food, which they do in a surface slick. Surface slicks form mostly in coastal regions around the world, wherever currents, tides, or subsurface waves cause water to converge and concentrate the organic gunk that floats in it. Slicks can be seen by satellite as long, squiggly ribbons that run parallel to coasts.

Some larval fish swim to slicks, some drift, as do eggs not yet hatched. Predators converge on slicks too. If a baby fish manages to avoid being eaten and to find enough food, it will be about two inches long when it heads back to its permanent habitat—a reef, say. The right current will transport it there, the wrong one out to sea.

“If you miss an island, good luck with that. If there’s no reef, you cannot complete your life cycle,” Sponaugle says. Life for newborn fish was a crapshoot even before they met our plastic trash.

Off Hawaii, a single eight-minute tow of the NOAA team’s net yields a plethora of living organisms and plastic.

Pushed into a surface slick by converging currents, they’re separated in the lab by a technician with tweezers. A computer program counts the plastic pieces and measures each one; the technician uses a microscope to identify the creatures.

Alarm as study shows how microplastics are blown across the world 

Microplastics are raining down on even remote mountaintops, a new study has revealed, with winds having the capacity to carry the pollution “anywhere and everywhere”.

The scientists were astounded by the quantities of microplastic falling from the sky in a supposedly pristine place such as the French stretch of the Pyrenees mountains. Researchers are now finding microplastics everywhere they look; in rivers, the deepest oceans and soils around the world.

Other recent studies have found microplastics in farmland soils near Shanghai, China, in the Galápagos Islands, a Unesco world heritage site, and in rivers in the Czech Republic. Humans and other animals are known to consume the tiny plastic particles via food and water, but the potential health effects on people and ecosystems are as yet unknown.

However the ubiquity of the pollution means it needs to be taken very seriously, said Steve Allen, at the EcoLab research institute near Toulouse and who led the new work in the Pyrenees: “If it is going to be a problem, it is going to be a very big problem. I don’t think there is an organism on Earth that is immune to this.”

About 335m tonnes of plastic is produced each year – while it degrades extremely slowly, it can be broken into smaller and smaller pieces. Microplastic pollution in rivers and oceans is now well known but just two previous studies have looked at its presence in the air, one in Paris, France, and another in Dongguan, China. Both found a steady fall of particles.

The new study, published in Nature Communications, is the first to show microplastic is raining down just as hard in remote environments and that it can travel across significant distances through wind. The team collected samples from high altitudes in the Pyrenees that were far from sources of plastic waste – the nearest village was 6km away, the nearest town 25km, and the nearest city 120km.

An inverse image of a plastic fibre. Microplastics can travel through the atmosphere and end up in regions far from their original emission source.
They found an average of 365 plastic particles, fibres and films were deposited per square metre every day. “It’s astounding and worrying that so many particles were found,” said Allen.

“It is comparable to what was found in the centre of Paris and Dongguan, and those are megacities where a lot of pollution is expected,” said Deonie Allen, also at EcoLab and part of the team. “Because we were on the top of a remote mountain, and there is no close source, there is the potential for microplastic to be anywhere and everywhere.”

 An inverse image of a plastic fibre. Microplastics can travel through the atmosphere and end up in regions far from their original emission source. Photograph: Allen et al/Nature

The most common microplastics found were polystyrene and polyethylene, both widely used in single-use packaging and plastic bags. The samples were collected during winter and it is possible that even more microplastic may fall in summer, when drier weather means particles are more easily lifted from the ground by the wind.

Microplastics have been shown to harm marine life when mistaken for food and were found inside every marine mammal studied in a recent UK survey. They were revealed in 2017 to have contaminated tap water around the worldand in October to have been consumed by people in Europe, Japan and Russia.

Many scientists are concerned about the potential health impacts of microplastics, which easily absorb toxic chemicals and can host harmful bacteria, with some even suggesting people are breathing the particles. The new research shows microplastics can remain airborne.

Professor Stefan Krause, at the University of Birmingham, UK, and not part of the team, said the new Pyrenees research was convincing: “These findings surely highlight the need for more detailed studies.”

“Frankly we are only at the start of understanding [microplastic pollution],” he said. Krause is leading a project called 100 Plastic Rivers which will produce the first systematic, global analysis of microplastics in freshwater ecosystems. He said the particles pose a range of potential dangers, from affecting soils and food production and carrying toxic chemicals and microbes far and wide.

Featured image: Scientists found that winds can carry plastic pollution ‘anywhere and everywhere’. Photograph: Teresa Short/Getty Images


By Damian Carrington, Environment editor, The Guardian,

April 15, 2019