Skip to main content

Pollutants invade remotest place on earth; Mariana Trench highly contaminated (downtoearth,)

Even the bottom of the ocean is not safe from human pollution. A joint study by the researchers at the James Hutton Institute and University of Aberdeen found “extraordinary” levels of contamination in the form of Polychlorinated biphenyls (PCBs) in two of the deepest trenches in the ocean—Mariana Trench in the North Pacific and Kermadec Trench in the South Pacific

The PCBs, which are created by electrical equipment and during waste incineration, were banned in 1979 as these ‘tough chemicals’ had increased cancer risk and other health issues. These persistent organic pollutants (POPs) have not only resisted degradation but also spread far and wide, reaching the Arctic and Antarctic.

During two expeditions in 2014, a team of researchers collected wildlife from these trenches. On analysing shrimplike crustaceans, called amphipods, many kinds of PCBs were detected. The most contaminated samples from the Mariana Trench—which is nearly 11 kilometres deep—had PCB concentrations 50 times greater than crabs studied in a highly polluted Chinese river.


The concentrations of key PCBs and polybrominated diphenyl ethers (PBDEs) in multiple endemic crustaceans from across the deepest trenches were measured after the samples were obtained using traps deployed on deep-sea landers. Both PCBs and PBDEs were present in all samples across all species at all depths in both the trenches. These chemicals were previously found at high levels in Inuit people in the Canadian Arctic and also in killer whales and dolphins in Western Europe.

The level of contamination was considerably higher than what is documented in nearby regions of heavy industrialisation. It not only indicates bioaccumulation of persistent organic pollutants in the deepest ocean fauna, but also infers that these pollutants are “pervasive across the world’s oceans and to full ocean depth”.

Origin of this pollution

From the 1930s to the 1970s, when PCB production ceased, the total global production was about 1.3 million tonnes. Approximately 65 per cent of it is thought to be contained in landfills or within electrical equipment. The other 35 per cent are residing in coastal sediments and open oceans. These pollutants are not prone to natural degradation and persist in the environment for decades. As persistent organic pollutants, they are highly detrimental to health of organisms through their endocrine disrupting properties. They also affect reproductive ability. Moreover, they can spread great distances such as Polar Regions and the open ocean.

Why is the study important?

Earlier studies on deep-sea organisms have reported higher concentrations f pollutants than in nearby surface-water species. Although these studies are described as ‘deep sea’, they rarely extend beyond the continental shelf (less than 2,000 metres). Hence, contamination at greater distances from shore and at extreme depths was hitherto unknown.


While we think that deep ocean is pristine and safe from human impact, the research shows that this notion is further from the truth. “The very bottom of the deep trenches like the Mariana are inhabited by incredibly efficient scavenging animals, like the 2cm-long amphipods we sampled, so any little bit of organic material that falls down, these guys turn up in huge numbers and devour it,” said Alan Jamieson of Newcastle University in the UK, who led the research.

Jamieson will now assess the impact of PCBs and other POPs on hardy trench creatures, which survive heavy water pressures and freezing temperature. More importantly, he will also examine deep sea animals for evidence of plastic pollution, feared to be widespread in the oceans.


Popular posts from this blog

Khar’s experimentation with Himalayan nettle brings recognition (downtoearth)

Nature never fails to surprise us. In many parts of the world, natural resources are the only source of livelihood opportunities available to people. They can be in the form of wild shrubs like Daphne papyracea and Daphne bholua (paper plant) that are used to make paper or Gossypium spp (cotton) that forms the backbone of the textile industry.

Nothing can compete with the dynamism of biological resources. Recently, Girardinia diversifolia (Himalayan nettle), a fibre-yielding plant, has become an important livelihood option for people living in the remote mountainous villages of the Hindu Kush Himalaya.

There is a community in Khar, a hamlet in Darchula district in far-western Nepal, which produces fabrics from Himalayan nettle. The fabric and the things made from it are sold in local as well as national and international markets as high-end products.

A Himalayan nettle value chain development initiative implemented by the Kailash Sacred Landscape Conservation and Development Initiati…

SC asks Centre to strike a balance on Rohingya issue (.hindu)

Supreme Court orally indicates that the government should not deport Rohingya “now” as the Centre prevails over it to not record any such views in its formal order, citing “international ramifications”.

The Supreme Court on Friday came close to ordering the government not to deport the Rohingya.

It finally settled on merely observing that a balance should be struck between humanitarian concern for the community and the country's national security and economic interests.

The court was hearing a bunch of petitions, one filed by persons within the Rohingya community, against a proposed move to deport over 40,000 Rohingya refugees. A three-judge Bench, led by Chief Justice of India Dipak Misra, began by orally indicating that the government should not deport Rohingya “now”, but the government prevailed on the court to not pass any formal order, citing “international ramifications”. With this, the status quo continues even though the court gave the community liberty to approach it in …

Cloud seeding

Demonstrating the function of the flare rack that carries silver iodide for cloud-seeding through an aircraft. 
Water is essential for life on the earth. Precipitation from the skies is the only source for it. India and the rest of Asia are dependent on the monsoons for rains. While the South West Monsoon is the main source for India as a whole, Tamil Nadu and coastal areas of South Andhra Pradesh get the benefit of the North East Monsoon, which is just a less dependable beat on the reversal of the South West Monsoon winds.