In a series of presentations at the recent 2018 Ocean Science Meeting organised by the American Geophysical Union in Portland, Oregon, US scientists report that everything from Prozac to plastic microbeads and antibiotics are finding their way into the ocean at levels sufficient to cause harm. Most of the risk is to marine animals, but there may also be dangers to marine food webs on which we ourselves depend.
Pharmaceuticals are of particular concern because they are intended to be biologically active, even at low doses, says Elise Granek, an environmental scientist at Portland State University.
Scientists have known for several years that these chemicals are a problem in lakes and rivers, Granek says, but the realisation that they might also be a problem in the ocean is much more recent. When she first started looking at the issue in 2015, she says, there were hundreds of studies about their effects in the narrower confines of fresh-water environments, but “only on the order of dozens in the marine environment”.
The levels of these compounds found in coastal waters, however, are high enough to have significant effects on marine animals. For example, Granek says, fluoxetine (Prozac) affects mussel feeding, growth, and reproduction. It also makes crabs more active and bold around predators. Too bold, it turns out, because they wind up losing limbs or dying because they are more easily preyed upon.
Similarly, antibiotics reduce the growth of algae and the growth and reproduction of mussels, she adds. And findings like that may just be the tip of the iceberg. These “emerging” marine contaminants, she says, are found worldwide and are probably increasing.
Others in her study group are finding similar effects. Graduate student Amy Ehrhart has found pharmaceuticals, including antibiotics and antifungal agents, in Pacific oysters at study sites from the southern Oregon coast to the central Washington coast.
These chemicals get to the ocean, she says, partly because people often flush them down their toilets if they have leftovers. As a way of protecting children from accidental poisonings, that’s effective, but wastewater treatment plants aren’t designed to remove them so allow them to pass through to rivers and eventually the sea.
But that’s not the only problem. Many pharmaceuticals pass through the body unchanged. Excreted in urine, they too wind up in wastewater treatment plants.
Tawnya Peterson, an environmental health researcher at Oregon Health & Science University, has measured the concentrations of metformin, a medicine used to treat type II diabetes, in the Columbia River. From that, she has concluded that each day, 62 to 65 kilograms of the drug are reaching the Pacific Ocean, where coastal eddies can trap it for several days before it eventually disperses.
Sixty-five kilograms may not sound like a lot in one of the biggest rivers in America. But it’s enough to account for 130,000 daily doses in the people peeing it out upstream in a giant watershed whose population isn’t much larger than that of metropolitan Sydney.
“Not much happens to it on its journey from person to sewage treatment plant to water,” Peterson says.
The chemical is known to be an endocrine disrupter in fish — meaning that among other things it can cause the feminisation of male fathead minnows (Pimephales promelas, a freshwater species often used in lake and river studies). And while the levels in the ocean are lower than those studied in fresh water, the fact is that nobody has ever studied their effects. Is there a risk to fish?
“We don’t know,” Peterson says. “But it’s worth thinking about.”
Another problem is plastics, particularly in the form of what scientists call microplastics.
Big chunks of plastic, whether floating or washed ashore, are eyesores. But what really matters to environmental toxicologists are microplastics—bits ranging from microscopic to about five millimetres in size.
Most commonly, scientists have found, these take the form of fibres, such as strands from a fleece jacket which may have migrated from a washing machine to the ocean, via wastewater treatment plants no better designed to deal with this hazard than with pharmaceuticals.
But they can also come from the breakdown of polystyrene foam, which is used not only a packaging material, but also for flotation devices such as buoys designed to mark off oyster farming in parts of Asia.
“This is unprotected Styrofoam degrading into the environment,” says Charles Moore of Algalita Marine Research and Education, Long Beach, California, who has photos of beaches onto which polystyrene foam pellets have washed ashore in enormous quantities.
“If you pick up a handful of sea grass on this beach, it’s half Styrofoam,” he says.
Dorothy Horn, another of Granek’s graduate students, has found that sand crabs easily ingest such substances, apparently mistaking them for food. In a lab experiment, she fed tiny fragments of polyurethane rope fibres (chosen because such ropes are commonly used by boaters and other marine enthusiasts) to the crabs, painstakingly clipping the fibers into one millimetre lengths.
Each crab in the “treatment” group got three of the fibres — a number picked because it matched what she’d found in water samples. A control group wasn’t fed anything plastic, though she later discovered that some of them had already eaten microplastic fragments of various sorts before she brought them into the lab.
All of the crabs were female, carrying fertilised eggs that normally would mature into larvae.
What she found was disturbing. The controls lived an average of 60 days. The ones to which she fed rope fragments lived only 45 days. The ones among the control group that had previously eaten plastics lived only 39 days. Similarly, 60% of the eggs carried by the control group lived long enough to hatch into larvae — compared to only 40% for the crabs to which she’d fed rope fragments, and an even smaller percentage of those that had already eaten plastics before she caught them.
And, she notes, microplastics were in the sand of every single beach she sampled across the northern coast of Oregon — an area that, while not truly remote, does not have a large permanent population to pollute it.
In yet another study, Randi Rotjan of Boston University, Boston, Massachusetts, found that polyps of a common Atlantic Ocean coral will not only happily eat plastic microbeads, when given them in the lab, but will preferentially eat them over one their normal foods, the similar-sized eggs of brine shrimp. And while this didn’t kill them — a better outcome than Horn’s sand-crab study — it appeared that once they’d gotten a taste for microbeads, these coral polyps were no longer interested in eating real food, at least in the form of brine shrimp eggs.
Meanwhile, scientists say, there’s a lot of research to be done. Another study, by Katie Gamble of the University of Delaware, found that in the ocean, waves can cause microplastic particles either to be dispersed or concentrated — somewhat akin to what was seen with oil patches after the 2010 Deepwater Horizon oil spill in the Gulf of Mexico.
Could plastic pollution spell the end of the oyster?
These concentrated patches may draw marine organisms, faked out into thinking the plastic microparticles are food — increasing their consumption of it by a factor of between 10 and 100.
“This is something we really need to consider,” Gamble says.
How (or if) all of this might come back to haunt us humans remains a mystery.
“A big data gap is understanding the human health effects,” says Granek.
But there are things ecologically minded people can do. “Sometimes we are told by pharmacists to flush our pharmaceuticals down the drain,” she says. “This is a perfect pathway for them to enter the ocean. Look for alternative solutions, which include drop boxes at pharmacies, and pick-up locations.”
Britta Baechler, another of Granek’s graduate students, applies the same advice to plastics. “Be a conscientious consumer,” she says. “Minimise single-use plastics. Recycle and purchase recycled products and use your voice to influence plastics policies and packaging norms.”[“Source-cosmosmagazine”]