Climate Change Brings New Threat To Oceans: Toxic Mercury Levels Could Rise If Land Runoff Increases
Rising temperatures and precipitation driven by climate change would trigger heavy runoff into oceans and the resulting pollution will shoot up mercury levels in all oceanic creatures and harm the food chain.
A new study said the impact will be quite high on the bottom level zooplanktons, fish, and to humans who consume the fish. The mercury levels are expected to rise seven times the current rate.
It said zooplankton will see a massive spurt in toxic mercury by 300 to 600 percent if runoff goes up by 15 to 30 percent triggered by higher rainfall.
"With climate change, we expect increased precipitation in many areas in the Northern Hemisphere, leading to more runoff," said Jeffra K. Schaefer, co-author of the study and assistant research professor in Department Of Environmental Sciences at Rutgers University.
The threat of mercury escalation comes from the discharge of mercury and organic carbon to ecosystems in coastal regions, which will take the mercury to the small animals living there.
The study was published in Science Advances.
Damage To Food Chain
The research traced the new route by which the rising warming would shoot up mercury toxin levels in sea creatures. Rising rainfall would drive up the amount of organic material flowing into the sea and will add serious implications on the food chain by the addition of an extra layer of organisms to the chain.
"When bacteria become abundant in the water there is also a growth of a new type of predators that feed on bacteria," said lead author Erik Bjorn of the Umea University in Sweden.
That is like adding a new step in the food chain and methylmercury being enriched to a bigger factor in the food web, he added.
For humans, exposure to high mercury content will be from eating fish containing methylmercury, which is generated by the reaction of bacteria with mercury in water, soil, or plants. The toxic methylmercury is very harmful to nervous, digestive, and immune systems.
Carbon Matter Runoff
The study also said, in a climate scenario of rising temperatures, the organic matter outflow into seas will increase by an average 15-20 percent by the close of the century. Correspondingly, the methylmercury levels in zooplankton will zoom by seven fold.
The worst hit by the "mercury invasion" will be coastal waters and lakes the Northern Hemisphere with sharp increases of methylmercury in fish.
At the same time, the regions that see a reduction in mercury levels will include central United States, Southern Africa, and the Mediterranean.
In the lab, the researchers ran a simulated model of Bothnian sea estuary for testing the emerging scenario. They discovered that rising temperatures could trigger high runoff of organic matter into the world's oceans and lakes.
To study the impact of mercury on zooplankton and other organisms, the researchers collected sediment cores from the estuary, mixed water, mercury, and nutrients and tested for the impact levels.
The model predicted the impact of climate change on mercury accumulation and methylmercury production.
Rising Mercury Levels
Mercury levels in the world's ecosystems have jumped between 200 and 500 percent after the Industrial revolution as the use of fossil fuels such as coal became entrenched.
To curb the dispersal of mercury into the environment, an international treaty has come up. Named as Minamata Convention, it has 136 countries as signatories.
The study was also hailed by some experts for unraveling new facts that were previously unknown.
"This work experimentally proves that climate change will have a significant effect on methylmercury budgets in coastal waters and its concentrations in fish," said Milena Horvat of Slovenia's Jozef Stefan Institute.