Crustaceans in very deep water also in very deep trouble
The deepest parts of the ocean have long been considered pristine wildernesses.
“Extraordinary levels” of pollutants have accumulated in amphipods living in the world’s deepest ocean trenches, according to new research.
A study, led by Alan Jamieson at the University of Aberdeen in Scotland and published in Nature Ecology and Evolution, found contaminant levels 10 kilometres below the surface were “considerably higher” than those found in much shallower seas bordering nearby heavy industry zones.
Jamieson’s team used a deep sea lander to set baited traps in both the Mariana Trench in the western Pacific and the Kermadec Trench near New Zealand. The traps were used to capture three species of small crustaceans called amphipods that were then tested for 14 different chemical markers. The results revealed that some of the world’s nastiest pollutants have reached “the most remote and inaccessible habitats on Earth”, the researchers report. Of particular concern, they noted, were a class of chemical compounds known as persistent organic pollutants (POPS), known to disrupt endocrine systems.
POPS comprise a broad range of manufactured carbon-based products, all noted for their ability to persist within the environment for very long periods, and for their habit of accumulating in living organisms. The first POP to become the focus of public and scientific concern was the insecticide DDT – the subject of Rachel Carson’s Silent Spring, published in 1962. The POPS of central interest to Jamieson and colleague were polychlorinated biphenyls (PCBS), once widely used as dielectric fluid, and polybrominated diphenyl ethers (PBDES), used as flame retardants.
The research found multiple varieties of both in all samples, across all species, at all depths in both trenches.
“In the Mariana, the highest levels of PCBS were 50 times more contaminated than crabs from paddy fields fed by the Liaohe River, one of the most polluted rivers in China,” say the researchers.
“The only Northwest Pacific location with values comparable to the Mariana
Trench is Suruga Bay (Japan), a highly industrialised area with historically heavy usage of organochlorine chemicals.”
‘ THE RESEARCH FOUND MULITIPLE VARIETIES OF IN ALL SAMPLES, ACROSS ALL SPECIES, AT ALL DEPTHS.’
The scientists offer a few explanations for the presence of pollutants at such extreme depths, known technically as hadal zones. They suggest sinking plastic debris and water-surface carrion consumed by the deep-sea scavengers as potential sources. Whatever the exact mechanism, they add, the findings imply that “that these pollutants are pervasive across the world’s oceans and to full ocean depth.”
Katherine Dafforn, a biologist at the University of New South Wales in Sydney, says the report is startling.
“At more than 6000 metres, hadal trenches are a remote wilderness, largely unexplored and widely considered safe from human disturbance,” writes Dafforn in Nature.
“This [finding] is significant since the hadal trenches are many miles away from any industrial source and suggests that the delivery of these pollutants occurs over long distances despite regulation since the 1970s.”
Humans are adding to our planet’s catalogue of mineral types at a rate never before seen. It’s happening so fast that anthropogenic minerals now total 208 of the 5,208 types recorded by the International Mineralogical Association (IMA) – and there are probably hundreds more currently not acknowledged.
Not all these substances are laboratory curiosities created by bored scientists.
“We make bricks,” explains Robert Hazen, a mineralogist at the Carnegie Institution for Science in Washington DC. “We make cement. We make reinforced concrete. We have porcelain in glassware. We have all sorts of crystals in technology, batteries and magnets. We have pigments and paints and glues and things that include mineral-like crystal substances which never before existed in the history of the world.”
Other substances are created by accident. “Many are associated with mining,” says Edward Grew, a mineralogist and petrologist from the University of Maine, who collaborated with Hazen on a paper published in American Mineralogist.
“Mining disturbs the environment under the earth or at the earth’s surface,” he says, “and that disturbance makes for environments where new minerals can form. Some have been dated from the Bronze Age, but for the most part they are much newer.”
To figure out when minerals first appeared, the scientists went through geological databases, looking for the time when each officially recognised mineral first appeared in the geological record.
“This one formed in a mine tunnel, this one in a shipwreck, and this one in an old Egyptian statue,” Hazen says, adding that his favourite – calclacite –formed in a museum drawer where a mineral specimen reacted with acetic acid from the wood to create an entirely new substance.
The new minerals are important, scientists say, because the only other time in history when there was a remotely comparable growth in the number of mineral types was during the “Great Oxidation,” which occurred when oxygen began to build up in the Earth’s atmosphere about 2.2 billion years ago.
This caused the oxidation of preexisting minerals, producing the first appearances of up to two-thirds of the minerals currently in the IMA’S catalogue. Iron ore is one example.
The Great Oxidation lasted hundreds of millions of years. Today’s minerals have arisen in a tiny fraction of that time. That’s important, Hazen says, because minerals are durable and will outlive the civilisation that produced them.
“They will be preserved for billions of years in the sedimentary record,” he says.
And that, he adds, bolsters the argument for designating modern times as a new geological epoch: the Anthropocene.
Naming epochs might seem arcane, but in the long-run view of geologists it is anything but. The issue, Hazen says, is the sediments laid down in our era.
“Cubic zirconium, laser crystals, silicon chips and stuff like that are very stable materials,” he says. “Future geologists will be able to hammer out chunks of materials and say, ‘Look at this.’”
Other scientists have suggested a similar worldwide stratigraphic layer might be created by fallout from nuclear testing, or from the fumes of leaded gasoline. But that, Hazen argues, is nothing compared to “minerals that are being produced in huge volumes all around the world”.
Other scientists agree. Richard Alley, a geoscientist at Pennsylvania State University, calls the new study “one more demonstration of the large and growing human impact on the planet”.