Toxic trace elements like lead, mercury, arsenic, and cadmium are naturally found in small amounts in coastal waters. However, human endeavors, particularly in industry and agriculture, add much larger quantities. A recent study has explored how climate change is currently altering the distribution and accumulation of these elements and the potential future impacts. One key finding is that climate-driven natural events are releasing higher levels of contaminants, creating health risks for both humans and animals. Yet, there remains a lack of understanding about how these pollutants will behave moving forward.
Climate change is causing the ocean to warm, become more acidic, and lose oxygen—these effects are widely recognized. However, less attention has been given to how these changes are influencing contaminants in marine environments. A recent study titled “Impacts of Climate Change on the Transport, Fate, and Biogeochemistry of Contaminants in Coastal Marine Ecosystems” delves into the relationship between trace elements and climate change. The results of this research have been published in the journal Communications Earth & Environment.
Climate Events are Releasing More Contaminants
According to Dr. Rebecca Zitoun, a marine chemist at the GEOMAR Helmholtz Centre for Ocean Research Kiel and co-lead author of the study along with her Croatian colleague Dr. SaÅ¡a Marcinek from the RuÄ‘er BoÅ¡ković Institute in Zagreb, “We aimed to analyze how climate change impacts trace elements, an area that has been under-researched until now.” The research examined both human-induced and natural sources of these elements. Lead, mercury, and cadmium enter ocean waters not just from human activities like industry and fossil fuel combustion but also increasingly from natural sources affected by climate change, including rising sea levels, floods, receding glaciers, and thawing permafrost—all of which help release and increase contaminant flow.
The study encompasses findings from a working group of the UN Joint Group of Experts on the Scientific Aspects of Marine Environmental Protection (GESAMP), focusing on metallic contaminants in oceanic environments. This 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 his expertise.
Dr. Sander elaborates: “Our group concentrated on how climate change and greenhouse gases affect marine contaminants.” One notable example is the increasing mercury levels in Arctic waters. As glaciers melt, permafrost thaws, and coastal erosion occurs, more mercury is being discharged from natural sources. This presents a serious risk to communities reliant on traditional fishing, as mercury can accumulate in the food chain and ultimately reach our plates through contaminated fish consumption.
Human Sources of Toxic Metals
Professor Sander further points out, “Human activities have augmented the global flow of toxic metals—lead levels have surged tenfold while mercury levels have tripled to septupled when compared to pre-industrial figures.” She also notes that toxic elements like silver are increasingly found in coastal waters, stemming from coal burning and the rising use of silver nanoparticles in antimicrobial products. Moreover, shipping and the proliferation of plastics are contributing to the distribution of heavy metals, as plastics can bind with metals like copper, zinc, and lead in water. These bonded contaminants are also vulnerable to entering the food chain.
In the future, the human-induced influx of heavy metals could escalate further due to the growing exploitation of marine resources.
Trace Elements in Seawater are Sensitive to Climate Change
Climate changes—including elevated sea temperatures, ocean acidification, and reduced oxygen levels—affect trace elements in various ways.
For instance, increased water temperatures enhance the bioavailability and uptake of trace elements like mercury by marine life. Higher temperatures can elevate metabolic rates, lower oxygen solubility, and increase gill ventilation, which enables more metals to enter organisms and accumulate within their bodies.
As the ocean absorbs a significant portion of the carbon dioxide (CO2) released by human activities, its acidity rises, lowering the pH level. This shift increases the solubility and bioavailability of metals like copper, zinc, or iron, especially copper, which can become highly toxic to numerous marine species at elevated concentrations.
Furthermore, the significant depletion of oxygen, especially in coastal regions and on the ocean floor, amplifies the harmful effects of trace elements, placing stress on organisms that dwell on or within the seabed, such as mussels, crabs, and other crustaceans.
Double Burden: Pollutants and Climate Change
Human activities contribute to environmental contaminants in coastal areas in two primary ways: directly through the emission of pollutants and indirectly through the consequences of climate change on natural sources.
The study also indicates that there is still a significant knowledge gap regarding how climate change impacts ocean contaminants. The working group emphasizes the need for more research on newly emerging and lesser-studied contaminants. In addition, enhanced models and revised legislation are needed to improve oversight of pollutants in marine ecosystems.
Dr. Rebecca Zitoun states, “To better grasp the impacts on ecosystems and human health, we must close the knowledge gaps concerning the interactions between pollutants and climate change and develop standardized methods that yield globally comparable data.” Addressing these issues is vital for bolstering marine protection and formulating sustainable solutions for at-risk coastal regions.
