A new study identifies rapidly emerging ocean threats.

 A global study released on Thursday outlines new, potentially unexpected threats to ocean ecosystems and vulnerable coastal communities over the next five to ten years, on top of the already harmful effects of overfishing, pollution, and global warming.

On August 4, 2019, a worker collects sand contaminated by an oil spill at a shoreline in Karawang, West Java, Indonesia. via Andrew Gal/NurPhoto
On August 4, 2019, a worker collects sand contaminated by an oil spill at a shoreline in Karawang, West Java, Indonesia. via Andrew Gal/NurPhoto

The goal of what the research team refers to as a horizon scan is to try to avoid ecological disasters. Many of the emerging threats are linked to global warmings, such as runoff from wildfire-ravaged areas, the potentially toxic effects of new biodegradable materials intended to replace plastics, lithium mining from ocean-bottom brine deposits, and an increase in toxic metal contamination caused by ocean acidification.

The study, which was published in the journal Nature Ecology and Evolution, also warns that many fish will migrate away from the hottest equatorial ocean regions, creating a dead zone that will reduce food security for millions of people in developing countries who rely on fish for daily nutrition. Where fish do remain, global warming appears to reduce their nutritional content because plankton produce fewer fatty acids for the fish to consume in warmer oceans.

According to Omar Defeo, a co-author and researcher in coastal ecology and small-scale fisheries at Uruguay's University of the Republic, the study's list of 15 issues "are multidimensional and connected."

"There are no isolated effects; they work in a cascading manner," he explained, "and we will see that this affects already vulnerable communities the most."

As a small-scale fisheries expert, Defeo is well aware of the interconnected nature of social and environmental issues. He claims that as ocean temperatures rise, the redistribution of fish species has an impact on fishing communities and food supplies.

"The fish in the tropics will not be able to stay where the temperature exceeds their physical tolerance," he said, "changing the species richness in this area." "This ultimately affects small-scale fisheries in the tropics, where social inequity already exists." As a result, these communities are now facing economic, social, and nutritional challenges."

According to Defeo, without a greater global effort to implement policies that slow the impacts of these emerging issues, countries vulnerable to environmental and economic volatility will bear the greatest burden.

According to co-author Ann Thornton, a biologist at the University of Cambridge, "understanding and highlighting the new threats helps guide monitoring and policies to protect marine and coastal environments." Similar global scans have been conducted since 2009, but this is the first to focus solely on marine and coastal issues, she added.

The 2009 scan identified ocean plastic pollution as an emerging threat that quickly escalated into a global crisis, prompting an emergency response, but only after significant damage to marine ecosystems had occurred. She believes that heeding the warning 20 years ago could have prevented some of the consequences.

The research team consisted of 30 experts from 11 different countries who collaborated to identify emerging changes in marine and coastal habitats. Using a technique known as horizon scanning, scientists submitted 75 new ocean issues that have only recently appeared on the science radar.

Through several rounds of reading and voting, the entire team of marine and coastal scientists, practitioners, and policymakers narrowed and divided the list of issues into three main categories: ecosystem impacts, resource exploitation, and novel technologies.

The researchers realized that it would take 10 to 15 years to fully understand "whether or not these issues are going to come to provenance," according to Thornton. "We believe it provides an opportunity for policymakers and practitioners to think about it and say, 'Hang on, we haven't thought of that.'"

According to Mark Spalding, senior marine scientist at The Nature Conservancy, the emphasis on soft robotics could be beneficial.

"The concept of robot swarms mapping ocean habitats is intriguing," he said. Given that we currently have no idea what lies beneath the seabed below the depths that satellites can see, which range from 10 to 30 meters, such mapping is critical.

The new study's call to focus research on marine collagen extraction, which is used in health products, is "certainly a good example of where stepping in, in a timely manner, could be quite powerful to steer a potentially important production in a sustainable fashion," he said. "If done correctly, it has the potential to be a highly effective use of fish waste."

A Carbon Pump in the Deep Sea

For example, Thornton believes that the anticipated increase in large-scale harvesting of mesopelagic fish living between 200 and 1,000 meters deep in the ocean could provide an option for increased nutrition and food supply during a time of global food insecurity.

"But the underlying issue is that we don't know how much carbon these species sequester," she explained. "That is only now coming to light, so before we start taking these species from this depth, we need to pause and ask, 'Hang on a minute, what are the broader consequences on the ecosystem and on our overall ability to reduce carbon in the atmosphere?"

According to recent research, those fish act as "a massive carbon sequestration pump," she said. "That was previously unacknowledged simply because no one had investigated it."

As scientists discover marine life in deep ocean brine pools, they warn that lithium extraction from the pools must be regulated in order to avoid further biodiversity loss in the oceans.  Credit: NOAA
As scientists discover marine life in deep ocean brine pools, they warn that lithium extraction from the pools must be regulated in order to avoid further biodiversity loss in the oceans.  Credit: NOAA

The mesopelagic species usually lurk on the deep ocean floor, catching prey with bioluminescent lures and other baubles, but the new research cited in the horizon scan suggests otherwise.

They are thought to make the longest daily vertical migration of any fish species to feed on plankton at the surface.

"I was really excited about this because these are bug-ugly fish with spotlights, lanterns, and angler fish." "I just find them completely fascinating," Thornton said.

Researchers are realizing how much of the ocean biomass is contained in these species, with high densities detected in places like the Arabian Sea, the Mediterranean, and the North Atlantic, thanks to improved surveys. The densities appear to be lower in the southern oceans, but this could be due to the fact that the sampling area is so large that they have yet to be accurately counted, she added.

"They take the carbon in the phytoplankton and algae they eat and, defecating at depth, the carbon sinks to the ocean floor and gets sequestered," Thornton said. They consume calcium carbonate by consuming surface species, "which, to put it bluntly, makes their poo heavier and sinks." However, their role in carbon storage at the ocean floor is only now becoming clear because scientists "didn't appreciate the sheer numbers and biomass of these species," she said.

"You get these situations where it's jaw-dropping, and you think, my goodness, we never thought of that," she explained. "The majority of the people on the panel had that jaw-dropping moment as a result of all 15 issues we identified."

The newfound understanding of the importance of deep sea fish populations also demonstrates how deep-ocean research lags behind terrestrial biodiversity research, partly due to technical difficulties and high costs, and partly due to the sheer size of the ocean, she said.

"We simply don't know what the benefits of these deep sea lithium pools are in terms of planetary regulation," Thornton said. "They have to be doing something." We don't yet know what services the deep sea offers, and we're only now beginning to exploit it."

Despite the fact that the initial scientific canvassing did not include specific climate-related questions, global warming emerged as a common theme connecting many of the issues identified, according to co-author James Herbert-Read, a biologist at the University of Cambridge.

"That really emphasizes that climate change is the most serious threat to biodiversity," he said. However, he claims that climate change will have other, lesser-known effects on the oceans. Increased wildfires; coastal darkening, or a reduction in the amount of light that penetrates upper ocean layers; and even increased pollution from toxic heavy metals mobilized by rising ocean acidity are among these.

List of Laundry Effects

Another major potential threat to ocean biodiversity is the increasing demand for lithium, which is used in renewable energy technology such as batteries. According to Herbert-Read, lithium in deep sea brine pools with high salt concentrations could be attractive targets for extraction, but recent deep sea surveys have revealed that they may support a surprising amount of marine life.

"We don't know what we're losing if we don't look at what's there and understand the diversity of life there before extracting from these places." "Let's not lose things we didn't even know we had," he said.

Irene Schloss, Argentine Arctic Institute co-author and biological oceanographer, echoed Herbert-message Reed's about lithium and its unintended consequences.

"On the lithium issue, it's fantastic to have electric cars, but it's well known that lithium mining can disrupt the ocean, it can disrupt the fauna," she said, adding that "we have to think of every single step and up to the last drop of the ocean, if it has any consequence."

The study also demonstrates how hasty emergency policy and market responses to environmental crises can simply exacerbate the problem, according to Herbert-Read. This includes replacing plastic derived from fossil fuels with so-called biodegradable plastic derived from plant-based starches.

The issue is that those materials do not biodegrade in natural conditions, he claims. They're designed to degrade in yet another industrial process, and as these plastic-replacing materials reach the ocean, they're causing a new set of issues.

Only about a dozen eco-toxicological studies on the effects of those materials have been conducted, with half of the studies indicating that they are harmful to ocean life. He claims that they can contain chemicals as toxic as those found in conventional plastics, and that some research indicates that they can reduce species abundance and richness, slow fish growth rates, and disrupt organism physiology. Even less is known about the long-term effects of these chemicals.

"There is a big push for these materials as part of the circular economy," he said, "but we don't want to push something if we don't understand the negative effects."

Coastal Darkening

Many different types of human impacts combine to cause coastal darkening, which affects plankton at the bottom of the ocean food chain, as well as algae, kelp, and seagrass, all of which play important roles in absorbing carbon dioxide.

"Increased precipitation, storms, permafrost thawing, and coastal erosion have resulted in 'browning' of freshwater ecosystems due to elevated organic carbon, iron, and particles, all of which are eventually discharged into the ocean," the researchers wrote.

Increasing wildfires are also a factor, as rain washes soil away from burned areas, contributing to coastal darkening. When soot particles from wildfires reach the ocean, they can promote the growth of algae and plankton.

These changes have an impact on ocean chemistry, including photochemical decomposition of dissolved organic carbon and the production of toxic chemicals. The combined effects could have a significant impact on ocean ecosystems, changing the composition, distribution, and behavior of species in affected areas, as well as degrading coastal habitats and their ecological functions, such as carbon sequestration.

While large-scale coastal darkening is likely to harm ocean ecosystems, the same phenomenon at lower levels may "have some positive impacts such as limiting coral bleaching on shallow reefs," according to the authors.

Schloss wants people to see the study as "a step that has to continue, a step through a long walk," not just a step forward.

Defeo believes something positive can come out of this study, despite his difficulty in being optimistic. "The positivity will be measured by the management of all the issues listed," he said. "A positive outcome is possible, but it will depend on all of us."


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