How climate change affects pollutants in the ocean.
The ocean is warming, acidifying, and losing oxygen—well-documented consequences of climate change. However, less attention has been given to how these changes impact contaminants in the marine environment.
A new study has investigated the interaction of trace elements with climate change. The findings have been published in the Nature journal Communications Earth & Environment.
Climate Events are Releasing More Contaminants
“We wanted to understand how trace elements are being affected by climate change – an area that has seen very little research so far,” explains Dr. Rebecca Zitoun, marine chemist at GEOMAR Helmholtz Centre for Ocean Research Kiel and co-lead author of the study alongside her Croatian colleague Dr. Saša Marcinek from the Ruđer Bošković Institute in Zagreb. “We examined both human-induced and natural sources.”
Metals such as lead, mercury, and cadmium enter the oceans not only through human activities such as industry or fossil fuel burning. Natural sources are also changing due to climate change: rising sea levels, rivers overflowing or drying up, melting sea ice and glaciers – all these processes mobilize and increase contaminant flows.
The study summarises the findings of a working group of the UN Joint Group of Experts on the Scientific Aspects of Marine Environmental Protection (GESAMP) focusing on metal contaminants in the ocean. The working group was initiated by Dr Sylvia Sander, Professor of Marine Mineral Resources at GEOMAR and former head of the Marine Environmental Studies Laboratories at the International Atomic Energy Agency (IAEA) in Monaco. Christoph Völker from the Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Research (AWI) is also contributing from Germany.
“Our working group has focused on the effects of climate change and greenhouse gases on contaminants in the ocean,” explains Dr Sander. One example of these impacts is rising mercury levels in Arctic waters: melting glaciers, thawing permafrost, and coastal erosion are releasing more mercury from natural sources. This poses a particular threat to communities that rely on traditional fishing, as mercury accumulates in the food chain and can end up on our plates through the consumption of contaminated fish.
Human Sources of Toxic Metals
“Human activities have increased the global flow of toxic metals such as lead by tenfold and mercury by three to seven times compared to pre-industrial levels,” says Professor Sander, highlighting another example. “Toxic elements like silver are increasingly detectable in coastal waters, originating from coal combustion and the growing use of silver nanoparticles in antibacterial products.” Additionally, shipping and the use of plastics contribute to the spread of heavy metals. Plastics can bind metals such as copper, zinc, and lead from the water. These bound contaminants can also enter the food chain.
In the future, the human contribution of heavy metals could rise further due to the increasing exploitation of the oceans.
Trace Elements in Seawater are Sensitive to Climate Change
Climate changes, such as rising sea temperatures, ocean acidification, and oxygen depletion, impact trace elements in various ways.
Higher water temperatures increase the bioavailability and uptake of trace elements such as mercury by marine organisms. This happens because higher temperatures boost metabolism, reduce oxygen solubility, and increase gill ventilation, leading to more metals entering organisms and accumulating in their bodies.
As the ocean absorbs most of the carbon dioxide (CO2) released by humans, it becomes more acidic – the pH level drops. This increases the solubility and bioavailability of metals such as copper, zinc, or iron. The effect is particularly pronounced with copper, which is highly toxic to many marine organisms at higher concentrations.
Furthermore, the growing depletion of oxygen, especially in coastal zones and on the seabed, enhances the toxic effects of trace elements. This stresses organisms that live directly in or on the seabed, such as mussels, crabs, and other crustaceans.
Double Burden: Pollutants and Climate Change
Human activities influence the amount of contaminants in coastal regions in two ways: directly through the release of pollutants into the environment, and indirectly through the impacts of human-induced climate change on natural sources.
However, the study also reveals that there is still insufficient data on how climate change influences contaminants in the ocean. The working group calls for increased research into new and under-studied contaminants. Additionally, better models should be developed, and legislation adjusted to improve control over the impact of contaminants in the seas.
Dr. Rebecca Zitoun: “To better understand the impacts on ecosystems and human health, we need to close knowledge gaps on the interactions between pollutants and climate change and develop standardized methods that provide globally comparable data.” This is a crucial step towards strengthening marine protection and developing sustainable solutions for vulnerable coastal areas.
Reference: “Climate change driven effects on transport, fate and biogeochemistry of trace element contaminants in coastal marine ecosystems” by Rebecca Zitoun, Saša Marcinek, Vanessa Hatje, Sylvia G. Sander, Christoph Völker, Manmohan Sarin and Dario Omanović, 4 October 2024, Communications Earth & Environment.
DOI: 10.1038/s43247-024-01679-y
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15 Comments
“The ocean is warming, acidifying, and losing oxygen …”
Has the average open-ocean pH changed more than the diurnal or seasonal changes?
“… rising sea levels, rivers overflowing or drying up, melting sea ice and glaciers – all these processes mobilize and increase contaminant flows.”
I would expect that a river drying up would DECREASE contaminant flows. What am I missing?
“… rising mercury levels in Arctic waters: melting glaciers, thawing permafrost, and coastal erosion are releasing more mercury from natural sources. This poses a particular threat to communities that rely on traditional fishing, as mercury accumulates in the food chain and can end up on our plates through the consumption of contaminated fish.”
One should probably be concerned about mercury released by Black Smokers on the bottom of the oceans! Strangely nothing is said about the different types of ‘mercury.’ Metallic mercury and mercury sulfide are of relatively little concern in cold environments. It is when anaerobic bacteria convert elemental mercury in oxygen-poor environments to methylmercury, that one needs to be concerned because it is the form that is soluble in fat and concentrates as it moves up the food chain. However, methylmercury is volatile, and cooking removes most of it. I suspect that traditional aboriginal methods of preserving fish, by freeze-drying it in the wind, will also reduce the methylmercury significantly. However, instead of investigating the efficacy of freeze-drying, the government just banned fish showing high levels of methylmercury in the raw fish.
I once came across a couple of blokes who used liquid metallic mercury to extract gold from ground-up quartz by rubbing it around in their gold pans using their bare hands, before boiling the mercury off as a vapour from tin cans slung over an open fire in their huts. Both as mad as the proverbial Mad Hatter and very violent men. Nothing methyl about that mercury.
One might imagine dried-up rivers could be rather dusty places; all that fine loose sediment etc. plus in certain countries where people engage in “artisinal” mining of river gravels and the use of mercury to extract gold………..I can just see the denizens of Detroit freeze-drying fish caught in the Great Lakes, or hanging it on their washing lines to reduce the methylmercury content…………..You expect the US Government to do that?
Mercury vapors are particularly dangerous because they are taken into the lungs, which are designed to move gases directly into the bloodstream. However, high levels of mercury vapor are almost never encountered naturally. In Almaden, Spain, with metallic mercury encountered in confined, hot tunnels, it takes its toll on the miners. Formerly, the miners would be retired when they could no longer sign their pay checks. However, that took about 30 years of chronic exposure.
My generation frequently handled metallic mercury as children, with no apparent side effects. It was more likely the vapors from the heated amalgam that was the problem for the ‘blokes’ you mentioned.
Metallic mercury is almost as dense as gold, and would be difficult to find on the surface because it would be found in deeper sands and gravels with particles described as being their hydraulic equivalent, or particles with similar settling velocities. Even if it were somehow lifted from the ground, it would be the first to settle out and not travel far. You are stretching.
No, I don’t expect the government to do anything sensible. Most bureaucrats are poorly educated in anything related to surviving in the real world. The methylmercury content of fish in the Great Lakes is not particularly high. I’d expect denizens of Detroit to just cook their fish.
“Toxic elements like silver are increasingly detectable in coastal waters, originating from coal combustion and the growing use of silver nanoparticles in antibacterial products.”
There is a distinct and important difference between something being “detectable” and being toxic. As Paracelsus observed, “The poison is in the dose.”
The question is that certain heavy metals may languish in the body, building up over time from detectable to damaging i.e. toxic. Mercury is one; arsenic is another; as is lead. Copper does the same although I don’t know much about its toxicity. Paracelsus should have modified his statement; “Poison is in the accumulated dose.”
I’m unaware of any toxins that the body isn’t capable of excreting, and usually does. The issue is the rate of accumulation versus the rate of excretion. When exposed to high doses, the body isn’t able to excrete toxins rapidly enough without medical intervention and it accumulates — hence the remark by Paracelsus. Swallowing a slug of lead or mercury probably would not be life threatening because it would be passed out of the intestinal tract before the stomach acid could dissolve much. The key is bio-availability, which is a function of the solubility in weak acid. Thus, chronic exposure is the main problem, when the daily dose is larger than what can be excreted. The ancient Greeks and Romans added lead acetate to their wine as a sweetener. It may have had some impact on the richer people, but inbreeding was probably a more important factor. In any event, it didn’t prevent the Romans from acquiring a reputation for being superb engineers. Arsenic is another issue entirely; however, because native arsenic is rather rare in nature, it is usually an issue again with chronic exposure from drinking water. Most acute problems are related to industrial chemicals. None of these issues are related to climate change.
I wasn’t discussing climate change, just commenting on some of your comments. Arsenopyrite certainly could be a “dusty riverbed problem” just as it can be a wet riverbed problem; it eventually oxidises, but whether it is the arsenic or the sulphurous/ic acid that does the job of killing the fish may be open to debate. Although perhaps one might have to have had a gold/copper mine upstream at some time. Elizabeth Bay in Bougainville was a nice blue colour some 20 yeas ago and still might be; so was a rather lengthy river in Norway and copper sulphate had wrecked the fishing (no doubt more the sulphate bit than the copper).
It is interesting to note that copper pipes even of short length used to reticulate drinking water into one’s house can introduce enough copper into one’s body to meet and maintain the upper safe limit for copper in one’s blood as designated by the WHO, despite one’s healthy kidneys. I gather that lead pipes are more dangerous although I doubt that anyone in Flint has dropped dead from lead poisoning, but no doubt low-level lead poisoning has some unpleasant effect, long-term. Hence my modification of Paracelsus’ quote.
I wonder what damage low-level intake of lead from lead tetraethyl might have done; it wouldn’t kill people but low-levels of heavy metal poisoning could well have less obvious behavioural effects than the shakes of the Mad Hatter and no doubt would not be obvious enough to worry expensive doctors about. I gather some Romans used lead pans to boil their wine in, hence the lead acetate. At last aluminium no longer is seen the cause of Alzheimer’s disease.
Mercury settling deep in gravels etc not a problem. But floods happen, some remarkably catastrophic, and eventually stuff gets into the sea.
I understand that mercury can be absorbed through the skin, although most certainly breathing mercury vapour would be the quicker way of going ‘mad’.
“As the ocean absorbs most of the carbon dioxide (CO2) released by humans, it becomes more acidic – the pH level drops. This increases the solubility and bioavailability of metals such as copper, zinc, or iron.”
This is an outright lie. Grammatically speaking, something can’t become “more acidic” if it isn’t already acidic. An inorganic acid is defined as a solution with a pH less than 7. According to the famous Stanford geochemist, Konrad Krauskopf, the ocean are not acidic, probably never have been and probably never will be. This is important because water actually has to be acidic to dissolve the metals mentioned. Iron carbonate, the mineral siderite, is not soluble in alkaline ocean waters to any significant extent. It isn’t even particularly reactive to weak acids like dilute carbonic acid. It takes a fairly strong acid to dissolve it. This is either deliberate scare mongering, or someone who is running outside of his lane and doesn’t realize it. Climatology is infested with incompetents who propagate urban legends and don’t even realize it.
https://scitechdaily.com/new-study-reveals-oceans-absorb-more-co2-than-previously-thought/
https://scitechdaily.com/scientists-were-wrong-plants-absorb-31-more-co2-than-previously-thought/
https://www.nasa.gov/centers-and-facilities/goddard/carbon-dioxide-fertilization-greening-earth-study-finds/
“…dissolve the metals…..” . Interesting phrase. One might envisage a lump of lead floating out to sea and dissolving slowly…….. forgive my imagination! Why do you single out siderite for special mention? Just curious.
Pure water being neutral, “more acidic” is indeed a bit of careless grammar. However, one might imagine that the seven seas contain some CO2 and therefore are formed of extremely weak carbonic acid, aided and abetted by those sulphurous emissions from assorted black smokers etcetera, so , “more acidic” might be correct technically; I never did dip litmus paper in the oceans to test them and no doubt that unsophisticated experiment could, and indeed might, lead to spurious results based on local conditions.
Weren’t the oceans supposed to have become acidic enough to knock off certain shelly and other organisms during a least two major extinctions? Which would appear to belie the, “probably never have been and probably never will be”, despite its alleged utterance by an allegedly famous geochemist from Stanford university.
https://en.wikipedia.org/wiki/Konrad_Bates_Krauskopf
We have iron oxides (hematite) that were precipitated out of sea water during the Great Oxygenation Event 2-3 billion years ago and are still around. Siderite, iron carbonate, not an uncommon ore for iron before the huge taconite deposits were found, is not as inert as the oxides. I was using it as an illustration because one might expect it to be sensitive to a decreasing pH — if it got below pH 7.
I believe that “ocean acidification” is more than just carelessness. I believe it was purposely coined to scare people without technical backgrounds because their only acquaintance with acids is the strong battery acid.
Ocean water is strongly buffered by (bi)carbonate and borate buffering systems. Even if the hot water coming out of Black Smokers is acidic, it is probably neutralized within a few inches of its release. Pictures of Black Smokes show abundant sea life living placidly within inches of the obvious vents. The current paradigm is that the pH of open sea water has declined from (a model estimate) pH 8.2 a century ago, to about (a measured) 8.1 today.
What caused the Great Dying (aka Permian End Extinction) is the subject of many theories. It has recently been discovered that the Siberian Traps intruded under and into older coal beds. The dikes and sills in an oxygen poor environment would have resulted in carbon monoxide, toxic coal tars (think benzene), sulfur dioxide, and various other gaseous precursors of hydrochloric acid and hydrofluoric acid, all strong acids and toxic. Land plants and animals started dying long before the marine forms. The death of the land animals would have resulted in an increase in CO2 and hydrogen sulfide, and a decrease in oxygen. It is not necessary to appeal to actual acidification of the oceans to explain the widespread extinctions.
https://scitechdaily.com/coal-burning-in-siberia-250-million-years-ago-led-to-climate-change-caused-the-earths-most-severe-extinction-event/
“The current paradigm is that the pH of open sea water has declined from (a model estimate) pH 8.2 a century ago, to about (a measured) 8.1 today.”
Thanks for the information. Maybe I should grab some litmus paper and head for the beach……..just for the amusement of it. A pH of 8.1 should register ……………and alarm the local Greenies.
Being a bit familiar with the Permo-Tiassic; “The death of the land animals would have resulted in an increase in CO2 and hydrogen sulfide, and a decrease in oxygen” might not have been overly significant given the 60 000 years of the “Great Dying”? However, the other stuff certainly was.
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Should we call it… “toxic oceanity”?
I know… I know…