First Biologically Derived Global Map Reveals High Mercury Concentrations in North Pacific and Atlantic Oceans

First biologically based map of ocean mercury uses 11,000 seabird samples to show high pollution in the North Pacific and Atlantic.

By: AXL Media

Published: Apr 10, 2026, 9:09 AM EDT

Source: Information for this report was sourced from Nagoya University

A Biological Lens on Global Marine Pollution

For the first time, researchers have moved beyond theoretical simulations to map mercury distribution using direct biological evidence from the world’s oceans. Traditionally, scientists relied on biogeochemical models to estimate how mercury, largely released through coal combustion since the Industrial Revolution, settles into marine environments. However, a study led by Professor Akiko Shoji and Researcher Jumpei Okado of Nagoya University has shifted the focus to seabirds as living sensors. By analyzing blood mercury levels across 108 different species, the team has produced a dataset that reflects actual dietary intake and biological accumulation, offering a more grounded perspective on the health of global waters.

The Strategic Advantages of Avian Blood Sampling

The methodology relied on the efficient collection of blood samples from adult seabirds when they return to shore for breeding. According to the researchers, these samples provide a high-resolution snapshot of mercury exposure within the specific two-month window prior to collection. This approach allows for a precise correlation between toxic concentrations and specific foraging locations, which is often difficult to achieve with other types of tissue. Furthermore, the process is minimally invasive and causes little harm to the birds, making it a sustainable choice for long-term environmental monitoring across diverse habitats ranging from tropical zones to the polar regions.

Bioaccumulation Factors and Foraging Depth

The study identified several critical biological drivers that dictate how much mercury a bird will eventually carry in its system. Analysis showed that mercury levels are significantly higher in birds that occupy higher trophic levels, such as those preying on larger fish, and in species with greater body mass. Interestingly, the depth at which a bird hunts also plays a pivotal role, with those feeding on prey from depths between 200 and 1,000 meters exhibiting elevated concentrations. This suggests that mercury may be more concentrated or more easily methylated into its toxic form in deeper, mid-water zones compared to the immediate surface.