Zinc from industry and fossil fuel combustion reaches even the most remote oceans, as researchers at ETH Zurich have shown. There, it now exceeds natural inputs, potentially disturbing the balance of marine ecosystems.
In brief
- Even in the extremely remote South Pacific Ocean, zinc from man-made emissions now exceeds natural sources.
- Zinc emitted by humans is carried by aerosols over vast distances and transported to open ocean regions far from civilisation.
- Rising zinc concentrations in seawater could disrupt the delicate balance of plankton communities and the marine food web.
The vast, deserted South Pacific is considered unspoilt nature. But this ocean is not as unspoilt as we would like to think. A new study by a group of researchers from ETH Zurich and the GEOMAR Helmholtz Centre for Ocean Research in Kiel sheds light on this premise.
The researchers have shown that zinc released by the combustion of fossil fuels and by industrial emissions has reached the most remote corners of the ocean and is now far more common in these waters than zinc from natural sources.
"There is no more untouched nature, not even in the South Pacific, which is as far away from the nearest civilisation as the astronauts on the International Space Station," states Tal Ben Altabet, the lead author of the external page study , which has just been published in the journal Nature Communications Earth and Environment. Ben Altabet is a postdoctoral researcher in the group of Derek Vance, Professor of Geochemistry at ETH Zurich.
Zinc and other metals are released into the atmosphere during the combustion of fossil fuels, coal burning and metal smelting. The emitted metals attach to tiny aerosols in the air, which can travel thousands of kilometres before settling on the surface waters of the open ocean. In this way, atmospheric aerosols can transport metals from industrial areas to even the most remote seas.
Plankton needs zinc
Zinc and other trace elements such as iron and copper are essential for marine life. In particular, microscopic marine algae, phytoplankton, need zinc for photosynthesis. Through this process, phytoplankton absorbs carbon dioxide and produces organic matter and oxygen. In this way, these tiny green algae play a central role in regulating the Earth's climate.
In recent years, scientists have begun to measure not only the concentrations of trace metals in seawater but also their isotopic composition.
Isotopes are variants of an element with different weights, and their ratios form a chemical fingerprint. These isotopic fingerprints help identify metal sources and track the processes they undergo in the ocean. Oceanic zinc is relatively enriched in heavier isotopes such as Zn-66, whereas human emissions are typically enriched in lighter isotopes such as Zn-64.
Over the past ten years, marine geochemists have been investigating an unusual isotopic fingerprint in the upper ocean. Some researchers have attributed these anomalies to natural processes in the ocean, such as the adsorption of zinc onto particles in seawater. More recently, others have suspected that the anomalies reflect the input of zinc from human sources, delivered by atmospheric aerosols.
Aerosols transporting zinc to the South Pacific
To resolve this question, the ETH researchers, led by Ben Altabet, investigated one of the most remote marine regions on Earth - the South Pacific. Detecting a zinc fingerprint from human emissions there would highlight just how widespread human pollution is.
The team pursued a novel approach: instead of analysing only the zinc dissolved in seawater, they also investigated the isotopic composition of zinc in particles in seawater and in aerosols from the atmosphere. To better identify human emission sources, the researchers also measured the isotopic composition of lead - an established indicator of environmental pollution.
Almost only zinc from human sources detectable
The results of the study were clear: the researchers found that zinc from human emissions, delivered by aerosols, is the dominant source of zinc in the upper layer of the South Pacific. By contrast, traces of zinc from natural sources were almost undetectable.
"Essentially all of the zinc in the particles from the upper South Pacific is unnatural. These results show that even elements previously thought to be unaffected by human activity are now dominated by industrial pollution, which has reached the most remote parts of the open ocean," Ben Altabet states
Cycle out of balance?
Naturally, the uppermost layer of the ocean is relatively low in zinc and other trace metals, as they are consumed by phytoplankton. For phytoplankton to thrive, these micronutrients must be present in the right proportions in seawater.
The researchers anticipate that continued increases in man-made metal emissions could disturb the delicate nutrient balance. It is difficult to predict, however, exactly how phytoplankton will respond to this. If additional metals such as zinc, iron, copper and cadmium - all of which show signs of accumulation in seawater due to human activity - are introduced into the oceans, the availability of nutrients could change, thereby potentially impacting the entire marine food chain.
Analysing other oceans for zinc isotopes
The researchers now want to conduct further studies to elucidate the isotopic composition of zinc and other biologically essential metals, such as iron and copper, in marine particles from other ocean regions.
"Only by studying different marine systems will we be able to understand trace metal behaviour across the ocean as a whole and how marine organisms respond to shifts in nutrient balances," Ben Altabet explains.
Reference
Benaltabet T, Gosnell KJ, de Souza GF, Jasinski D, Rickli J, O'Sullivan EM, Steiner Z, Achterberg EP, Vance D: Pervasive contamination of the remote open ocean with anthropogenic zinc. Communications Earth & Environment, 25 March 2026, DOI: external page 10.1038/s43247-026-03425-y
