Coastal lagoon transitioning from healthy marine life to mercury-polluted environment.

Is Your Seafood Safe? Unmasking Mercury's Hidden Dangers in Coastal Lagoons

Kai Mendoza in Climate & Environment August 2025 • 4 min read.

"Dive into the alarming science of mercury pollution and how eutrophication intensifies the threat in our beloved marine environments."

Imagine biting into a succulent piece of grilled fish, savoring the taste of the ocean. But what if that delicious meal contained a hidden threat? Mercury, a pervasive and toxic metal, lurks in our aquatic ecosystems, silently accumulating in the seafood we love. While mercury naturally occurs, human activities have significantly amplified its presence, turning our coastal lagoons into potential danger zones.

Coastal lagoons, those shimmering bodies of water nestled between land and sea, are particularly vulnerable. These ecosystems are biodiversity hotspots, teeming with life and supporting countless communities. However, they also act as sinks for pollutants, trapping mercury and other contaminants that wash in from surrounding areas. This sets the stage for a complex and concerning cycle of mercury accumulation and biomagnification.

But there is new research that has shone a light on the concerning relationship between eutrophication—the excessive enrichment of water with nutrients—and mercury cycling. This article will explore the intricate details of this research, revealing how eutrophication exacerbates mercury contamination in coastal lagoons and what this means for the safety of our seafood and the health of our environment.

Eutrophication: How Nutrient Pollution Supercharges Mercury's Threat

Coastal lagoon transitioning from healthy marine life to mercury-polluted environment.

Eutrophication, often driven by agricultural runoff and sewage discharge, throws aquatic ecosystems out of balance. Excess nutrients, like nitrogen and phosphorus, fuel algal blooms, those unsightly and often toxic overgrowths that suffocate marine life. But the consequences extend far beyond the visible, influencing the very chemistry of the water and sediments, and, crucially, impacting the behavior of mercury.

The study reveals that eutrophication and related shifts in oxygen levels dramatically alter mercury's speciation, mobility, and bioavailability. Under oxygen-rich conditions, mercury tends to bind to iron oxides, effectively immobilizing it in the sediment. However, as eutrophication depletes oxygen, these iron oxides dissolve, releasing mercury back into the water column, where it can be converted into methylmercury, its most toxic form.

Increased Methylation: Eutrophication creates an environment ripe for methylmercury production, a process driven by anaerobic bacteria.
Enhanced Bioaccumulation: Methylmercury readily accumulates in aquatic organisms, magnifying as it moves up the food web, ultimately posing a threat to human consumers.
Altered Sediment Dynamics: Eutrophication disrupts sediment chemistry, impacting mercury's long-term fate and potential for release.

These findings paint a concerning picture: eutrophication acts as a catalyst, transforming relatively benign forms of mercury into a highly toxic and readily bioavailable threat. This not only jeopardizes the health of aquatic ecosystems but also increases the risk of mercury contamination in seafood, impacting human health.

Safeguarding Our Coasts: What Can Be Done?

The findings underscore the urgent need for integrated management strategies that address both eutrophication and mercury pollution in coastal lagoons. By tackling nutrient pollution, we can not only restore the health of these vital ecosystems but also mitigate the risk of mercury contamination in seafood. This requires a multi-pronged approach:

About this Article -

This article was crafted using a human-AI hybrid and collaborative approach. AI assisted our team with initial drafting, research insights, identifying key questions, and image generation. Our human editors guided topic selection, defined the angle, structured the content, ensured factual accuracy and relevance, refined the tone, and conducted thorough editing to deliver helpful, high-quality information.See our About page for more information.

This article is based on research published under:

DOI-LINK: 10.3389/fmars.2018.00291, Alternate LINK

Title: Modeling The Influence Of Eutrophication And Redox Conditions On Mercury Cycling At The Sediment-Water Interface In The Berre Lagoon

Subject: Ocean Engineering

Journal: Frontiers in Marine Science

Publisher: Frontiers Media SA

Authors: Svetlana Pakhomova, Evgeniy Yakushev, Elizaveta Protsenko, Sylvain Rigaud, Daniel Cossa, Joel Knoery, Raoul-Marie Couture, Olivier Radakovitch, Shamil Yakubov, Dominika Krzeminska, Alice Newton

Published: 2018-08-21

Everything You Need To Know

How does eutrophication affect mercury levels in coastal lagoons, and what is the primary concern?

Eutrophication, driven by excess nutrients like nitrogen and phosphorus from sources like agricultural runoff and sewage, disrupts the balance in coastal lagoons. This leads to algal blooms and oxygen depletion. The depletion of oxygen changes the behavior of mercury, facilitating the conversion of mercury into methylmercury, a highly toxic form that accumulates in aquatic organisms. This ultimately elevates the risk of mercury contamination in seafood.

What are the specific mechanisms by which eutrophication intensifies mercury contamination in coastal lagoons?

Eutrophication exacerbates mercury contamination through several key mechanisms. First, it increases methylation by creating environments ripe for methylmercury production, driven by anaerobic bacteria. Second, it enhances bioaccumulation, allowing methylmercury to readily accumulate in aquatic organisms. Finally, eutrophication alters sediment dynamics, impacting mercury's long-term fate and potential release, ultimately increasing the risk of mercury contamination in seafood and impacting human health.

In what ways do human activities contribute to mercury levels in coastal lagoons, and how does this affect the safety of seafood?

Human activities, such as agriculture and sewage discharge, introduce excessive nutrients into coastal lagoons, leading to eutrophication. This eutrophication, in turn, intensifies mercury pollution by altering mercury's speciation and bioavailability. The release of mercury from sediments, combined with enhanced methylmercury production, elevates the risk of mercury contamination in seafood. Reducing nutrient pollution can help to restore the health of these vital ecosystems and mitigate the risk of mercury contamination.

What integrated management strategies can be implemented to safeguard coastal lagoons from mercury contamination and eutrophication?

Integrated management strategies are crucial. These strategies need to address both eutrophication and mercury pollution in coastal lagoons. Tackling nutrient pollution, often from agricultural runoff and sewage discharge, helps restore the health of these vital ecosystems. This reduces algal blooms and subsequent oxygen depletion, which in turn, minimizes the conversion of mercury into its toxic form, methylmercury, and reduces its accumulation in seafood.

Besides mercury and eutrophication, what other pollutants might affect coastal lagoons, and how could these interact and affect the ecosystem?

While the focus is on mercury, it's important to consider that coastal lagoons are also affected by other pollutants, such as heavy metals, pesticides, and plastics. These pollutants can interact with mercury and eutrophication processes, further complicating the dynamics of contamination and potentially amplifying the risks to both ecosystems and human health. Further research is needed to understand the complex interactions between multiple pollutants and their combined impacts.