How microbes can detoxify heavy metal pollution in the ocean

Worsening heavy metal pollution in the ocean

Researchers have recently found that heavy metal pollution levels in the ocean are getting worse. They mentioned climate change as a primary driver.

Climate change altering heavy metal distribution and concentration

Scientists know climate change is making the ocean warmer and more acidic while causing oxygen loss. However, a lesser-studied aspect of climate change is how it affects the heavy metals already present in trace amounts.

A research team examined this issue by evaluating the natural and human-induced impacts of climate change and whether they cause changes in heavy metals. One of the findings was that global flows of some heavy metals from human activities are at least seven times greater now than during preindustrial times, and shipping and plastic use increases the dispersion.

Additionally, the researchers noted environmental changes — including glacier melt and thawing permafrost — have increased mercury levels in the Arctic Ocean, sometimes causing mercury-contaminated fish in food supply chains.

Although the researchers noted this topic requires more research, their work uncovered concerning conclusions about heavy metal pollution in the ocean.

For example, warmer waters increase the bioavailability and uptake of trace elements by marine creatures. Additionally, as the water becomes more acidic, the bioavailability and solubility of some heavy metals increases. The team said copper is particularly vulnerable to this effect. Finally, oxygen depletion makes trace heavy metals more toxic, especially to organisms living on or near the seabed.

Heavy metal content climbing in Arctic fjords

During an interdisciplinary cooperation project, researchers learned how climate change affects brown macroalgae called kelps, which are foundational to the Arctic Ocean’s coastal ecosystems.

The group determined that melting glaciers change the composition of coastal runoff plumes, primarily when freshwater reduces the salinity or introduces washed-in sediments. When the team investigated the impacts of heavy metals on this Arctic ecosystem, they found that trace elements become more concentrated as runoff intensifies

One conclusion was that kelps affected by runoff plumes had 72% higher mercury content than those in the control group. While the scientists recognized that some nutrients in the runoff benefit the kelps, the mercury contamination had adverse effects on the ocean dwellers that rely on the kelps for sustenance. For example, those that ingested the mercury-affected macroalgae had reduced development, reproduction, and growth rates, and researchers said those impacts could spread across the food web.

Reducing pollution with microbes

The above studies highlight the urgent need to remain aware of heavy metal pollution and its potentially far-reaching effects on the ocean, its inhabitants, and humans who eat seafood.

Although research is ongoing, many pollution-reduction efforts for soil and wastewater have centered on microbes for bioremediation. That work may also shape how people tackle the severe and growing problem of heavy metal ocean pollution.

Researchers find fungi to remove mercury from saltwater

Some studies not directly related to ocean pollution may hold clues to improve the matter. A good example came from a group that genetically engineered fungi to improve their mercury detoxification capabilities. Although their work involved using it on crops, the team also discovered that this approach removed mercury from fresh- and saltwater, potentially making it worth further investigation to treat ocean pollution.

The fungi made crops planted in mercury-polluted soil grow normally and remain safe to eat because they did not draw up the heavy metal into their fibers. Researchers initially became interested in using this fungus for mercury removal after genetic sequencing showed it contained two genes also present in a bacterium known to remediate the metal.

Since it grows ubiquitously, the team believes their approach is an efficient and cost-effective way to address mercury contamination. Although water purification was not the primary focus of this work, they see their findings as useful for cleaning mercury-filled waterways.

Efforts continue to make wastewater treatment more effective

People continually search for industrial wastewater treatment methods that may be more sustainable and offer equal or better effectiveness than currently deployed options. If leaders could get the desired effects while using fewer resources, they may be more willing to make widespread process changes.

In one case, researchers found that an organic coagulant lowered heavy metal content in a steel mill’s wastewater. The main challenges with inorganic counterparts are that they are costly to import and produce large amounts of sludge. Organic alternatives may overcome those obstacles.

Another example involved a team that discovered that simple microorganisms may improve wastewater treatment efficiency by working together. This group targeted the active sludge method of wastewater treatment, which uses electricity to produce the flow of oxygen that feeds bacteria and other microorganisms that process the liquid. Adding green algae to conduct photosynthesis made the process more energy-efficient, but low carbon dioxide prevented healthy growth in that addition.

Fortunately, the researchers learned that a particular kind of carbon dioxide-producing yeast balanced things out by helping the algae thrive and keep the wastewater treatment processes maximally efficient. Additionally, this combination made the algae better able to absorb materials in the wastewater while creating opportunities for people to simultaneously create useful compounds during the treatment.

Although these examples do not directly connect to ocean pollution, the progress made in these treatment efforts could influence researchers’ efforts in other areas, especially when they find out more about how microbes and other aspects present in the natural environment may support bioremediation.

Artificial intelligence quantifies pollutants’ effects

Many researchers have realized how artificial intelligence could reduce their workloads by helping them find patterns in data faster and draw informed conclusions. One recent effort involved using AI to study water and biofilm samples from 52 of England’s freshwater lakes. The goal was to determine which pollutants caused the most adverse effects on the biodiversity of those local ecosystems.

The research indicated that insecticides and fungicides had the largest impacts, but 43 other physicochemical aspects — including heavy metals — also played a role. People performing such studies have previously used DNA analyses to estimate these changes, but that approach was overly narrow, often requiring people to determine individual aspects rather than seeing the interconnectedness that can cause complex interactions.

Identifying the areas most affected by heavy metals or other contaminants could encourage researchers to find microbes or other effective methods of reducing pollution. If experiments show the approach works well in freshwater environments, the evidence might cause people to adapt it to the ocean, too.

Microbes can reduce ocean microplastics

Although the studies above highlight the current and worsening heavy metal problem in oceans, this issue exists alongside other pollution. In particular, researchers have spotlighted the negative impacts of microplastics — findings indicate they comprise 80% of ocean trash, and plastics take thousands of years to degrade.

As people learn more about microbes to address heavy metal pollution in the world’s oceans, they may also come across possibilities to manage the microplastic problem. In one case, researchers discovered through a lab model study that a particular bacteria present in the ocean eats and digests microplastics.

The researchers cautioned that this finding is not a solution to ocean-related microplastics. Even so, it is useful for them to know about this aspect, especially because it helps them understand what has happened to previously unaccounted-for pollutants. The models indicated the bacteria can break down approximately 1% of the microplastics it consumes annually, turning them into CO2 and harmless substances.

Sunlight is also an important component in the process because previous studies showed that ultraviolet rays break the plastics down into small enough chunks for the bacteria to digest. The researchers also confirmed that the 1% estimate that the bacteria consumes is probably an underestimate, but it is difficult to separate the degradation that occurs due to sunlight versus the bacteria.

Harnessing ocean microbes for heavy metal reductions

Learning more about already-present microbes could accelerate people’s research into other bioremediation efforts, including those involving heavy metals. Scientists are already learning more about using marine microorganisms to reduce those contaminants. However, most of that work has involved sites isolated from oceans, such as ponds or wastewater plants.

Although those familiar with the topic have documented successful attempts, they also note several limitations. For example, scientists must optimize the environment to control microbial growth and accelerate degradation rates. Additionally, some chemicals resist microbial treatments, meaning even if researchers find some that reduce heavy metals, they may need to target other contaminants in different ways.

Additionally, if people introduce microbes into controlled environments, such as by injecting them into wells, this approach could cause an overabundance of microbiological growth. However, the more individuals learn about this approach, the easier it should be to achieve progressively better outcomes. Even if people do not use microbes as large-scale options for heavy metal detoxification in the world’s oceans, they may find feasible ways to address the problem on a smaller scale.

Making progress with microbial detoxification strategies

As scientists continue documenting ocean pollution and how climate change exacerbates existing heavy metal contamination, microbes will remain important for unlocking new possibilities and improving results. Many lab-based discoveries will contain the details researchers need to identify what they could do to tackle pollution. Additionally, they will learn about how microbes might complement other methods of keeping oceans cleaner.