What are heavy metals and how do they enter the ocean?
Heavy metals, such as lead, zinc, mercury, copper, arsenic, and chromium, are naturally present in the marine environment. They can originate from geological processes such as volcanic eruptions, hydrothermal activity associated with new ocean floor formation or are transported into the marine environment from rock and soil weathering and through atmospheric deposition (e.g., dust, volcanic gases).
In addition to these natural sources, heavy metal concentrations in the marine environment are often increased by human activities, including industrial discharge, mining runoff, and urban wastewater.
How do heavy metals behave in the marine environment?
Once in the marine environment, the cycling of metals is driven by complex interactions with biological and chemical factors, and they can undergo various transformations. Heavy metals dissolve in seawater, where they are available for uptake by organisms, or bind to particles and accumulate in sediments, forming a long-term environmental reservoir. Changes in environmental conditions, such as shifts in pH, oxygen levels, or microbial activity, or human disturbances of the seafloor, can remobilize metals from the sediment. This process releases them back into the water column, effectively turning sediments from a sink into a source of heavy metals.
Why are heavy metals a concern?
While some heavy metals, such as zinc and copper, are essential in trace amounts for marine organisms, excessive concentrations can be toxic, posing risks to marine life and the broader marine ecosystem. Metals can bioaccumulate in marine organisms and magnify up the food chain, which poses a serious threat to marine life. Long-term exposure to elevated heavy metal levels can lead to ecosystem degradation, reduce fishery and aquaculture productivity, and pose significant risks to human health and the marine economy.
Understanding how heavy metals interact with sediments, biogeochemical processes, and the ecosystem is crucial as it allows us to predict pollution impacts and develop effective remediation and management strategies, which are vital for protecting our oceans.
What capabilities does NOC have for investigating heavy metals?
The National Oceanography Centre has a range of capabilities that provide the means to investigate heavy metal pollution in the marine environment.
What projects is NOC conducting on heavy metals?
FOCUS (Future States of the Global Coastal Ocean) concentrates on understanding the effects of climate change and multiple human pressures on coastal ecosystems. These pressures include nutrient pollution, urban impacts. In FOCUS we are specifically looking at the pathways of mining waste from land to the ocean and its distribution in the marine environment.
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