A big problem made of tiny pieces - new research shows microplastics may be even more ubiquitous in our oceans than most people think
Sarah-Lyn Wilson’s office is a little more open plan than most - in her case, it’s the entire Hauraki Gulf, on which she guides boatloads of breath-bated whale watchers as a skipper for Auckland Dolphin & Whale Safari.
From the boat she scans the water for sign of the 22 different marine mammals that call the Gulf home. She’s seen everything from leopard and fur seals to orca and pygmy blue whales.
Despite its proximity to New Zealand’s biggest city, the Gulf is a thriving and diverse ecosystem - albeit one that could be on the precipice of change due to the continuing effects of pollution and climate change.
One of the area’s main stars is the Bryde’s whale - filter-feeding behemoths of between 13 and 15 metres that call the shallow waters of the Gulf home. The safaris see them about half the time.
But with a population of around 140 to 200 left in the region and a nationally critical status in New Zealand, these huge creatures could play the canary in the coal mine when it comes to showing humans the unseen ramifications of what we do on land.
The whales are sentinel animals, studied by scientists to provide advance warning of dangers such as changes to the environment.
Scientists looking to pick up samples out on the Gulf or get access to data on marine life often get in touch with Auckland Dolphin & Whale Safari, and between the two groups they may have collected the most exhaustive data for the region.
The latest instalment directly concerns the Bryde’s Whale.
A recent study from the University of Auckland found Bryde’s and sei whales in the Gulf are consuming huge amounts of microplastics each day.
But what really surprised researchers was exactly where the whales were getting the microplastics from.
By comparing previously studied levels of microplastics in the water with the amount that showed up in the scat of the whales, the study confirmed around 99.9 percent of the microplastics came from the zooplankton that forms the staple diet of baleen whales, rather than picked up directly from the water.
This means previous measurements of microplastic levels in the Gulf may be underestimating its omnipresence by up to four orders of magnitude.
A tiny problem on a big scale
Since the rise of the plastics industry in the 1950s, humankind has generated an estimated 8.3 billion tonnes of plastic.
It’s useful stuff, to be sure - cheap, moldable, lightweight and durable. It’s that uncanny knack for long-lastingness that eventually visited a curse upon the planet.
Plastic hangs around long after it's been useful to us, and as a result, beaches and coastlines around the world are strewn with bags and bottles that aren’t going anywhere quickly. If they end up in the ocean, their eventual fate may be in one of the great ocean gyres, which draw floating trash in like rings of dust around a spinning planet.
The Great Pacific Garbage Patch has been the antagonist of countless documentaries and news reports, swirling ominously as every viewer contemplates their own complicity somewhere down the line in the accumulative wages of the sin of littering.
But a huge proportion of the plastic in the oceans is less visible to the human eye.
Earlier this year, scientists trawling the upper oceans found plastic the equivalent of around 30 billion 500-ml plastic water bottles - all less than 5 mm in size.
And while scientists are still getting their heads around how much plastic could be expected to be in any given cupful of ocean water, researchers from New Zealand have found an important factor they need to consider - just how much of this plastic is tied up in marine life.
Professor Rochelle Constantine from the University of Auckland is no stranger to the marine megafauna swimming the waters within spitting distance of New Zealand’s biggest city, having previously published work showing how the whales feed continuously through the daylight hours.
As part of an international team of researchers led by Dr Emma Carroll and in collaboration with Auckland Dolphin & Whale Safari, Constantine set out to collect whale faeces to measure microplastic levels and compare with what was already known about the Hauraki Gulf.
Luckily, whale shit floats.
The team was able to sight it from the boat and collect a sample from the surface of the water. And Constantine said the story that the samples told stopped them in their tracks.
“"We expected microplastics to be found. Microplastics are everywhere, from the poles to the tropics, on land and at sea - but we were surprised at how many,” she said.
The whales feed by taking huge gulps of water which contain their favourite varieties of plankton, before filtering most of it out through their baleen. Each gulp is about 15 metres cubed, and each one has around 24,000 microplastics.
And for a whale to get its fill, it takes around 140 of these gulps a day - a daily diet that comes with more than three million tiny bits of plastic.
Most of these seem to come from the tiny zooplankton eating the microplastics, which is significant because they are at right at the bottom of the food chain - meaning the microplastics can amplify up the food chain and end up in the bodies of other animals, even if they don’t swallow a lot of plastic-strewn water.
“Often when we measure microplastics in the water, environmental agencies will take water samples,” Constantine said. “But our work here has shown this grossly underestimates the amount of microplastics in the water and we should probably be looking at zooplankton instead.”
As water samples are the quickest and easiest way to look into microplastic levels, as a general rule they are the most common method used around the world - suggesting our oceans could be even more plastic-choked than previously thought.
“There’s probably not a single animal in the Hauraki Gulf without microplastics in them,” Constantine said. “Which is a really disappointing thought.”
What does this mean for marine life?
So what does sending your life eating food filled with tiny bits of plastic do to you?
Science is still out on the effect of microplastics on larger animals. It is known that small creatures like filter-feeding shellfish can have their systems clogged up by the accumulation of plastic, which can lead to malnutrition or death - but for a whale, studies are ongoing.
Scientists believe contaminants attached to the plastics can harmfully impact larger animals, but the real threat to the whales may still be on its way if the problem of microplastics is not addressed.
While the microplastics are too big to cross from the stomach into the bloodstream of most larger animals, smaller nanoplastics can. These are fragments of plastic that have degraded even further until they reach a microscopic scale. Many nanoplastics come from products we use, but some come from the degradation of microplastics into an even smaller state.
The pesky durability of plastic means the five millimetre long bits of plastic in the Gulf right now may one day be small enough to cross the membrane into an animal’s bloodstream.
“Microplastics don’t just go away, they abrade and decay and get smaller and smaller. Virtually none of them are ever entirely gone from the system,” said Constantine. “And the more we produce, the more of these we put into the system.”
What can be done?
From his home on Waiheke Island, lifelong conservationist and former Auckland councillor Mike Lee has a particular focus on what’s going on in the Hauraki Gulf.
As chair for Friends of Hauraki Gulf, an organisation calling for renewed conservation efforts in the region, he sees plastic pollution as one of many threats to marine life, with overfishing, toxic run-off from urban development and intensified agriculture.
“But it must be remembered that whales and marine mammals in the Gulf are only a 10 percent remnant of what was originally here. Other species, fish in particular, are being killed directly, over killed - by humans,” he said. “The smartest thing we can do now is to start to build a more resilient ecosystem to preserve and rebuild marine life, so that it can survive these threats, including climate change.”
The group is calling for the creation of a 2300 ha sanctuary for the hard-pressed marine life of the Gulf. The area in question is a noted, important breeding ground for marine mammals.
Constantine said it was a good time for a moment of reflection about how what people do on land goes on to affect life under the surface of the water.
“This is not just a Hauraki Gulf problem,” she said. “Is this the thriving ocean environment that we would envision? The ecosystem is already contaminated with these plastics at the very beginning of the food chain - that’s worth stopping and thinking about.”
Wilson has only recently got back out on the boat for Auckland Dolphin & Whale Safari, after months of being grounded due to lockdown.
But while the Bryde’s whales will still be there waiting, she hopes studies like Constantine’s will bring attention to their vulnerability to the actions of humans.
“Most people in Auckland don’t even realise the whales are there,” she said.
“Hopefully this will bring the fact that these microplastics are everywhere to people’s attention. It’s not something that’s removed, it’s happening right now.”
