Todd McLeish: Could a tough N.E. hard coral help save tropical corals?

Northern Star Coral is found in the waters along the Rhode Island coastline. In this photo, the northern star coral is attached to a rock and near green alga, commonly called sea lettuce, and red alga.

— ecoRI News photo

From ecoRI News (ecori.org)

The ongoing decline of tropical coral reefs around the world is causing a domino effect that could impact the quarter of marine life that depends on this ecosystem. Reefs are becoming bleached and dying as warming waters force corals to expel the algae that live in their tissues and produce sugars to provide food for the coral.

A Rhode Island scientist is co-leading a collaborative effort to determine if New England’s only hard coral species — a variety that can survive bleaching — could provide a solution to the coral-bleaching problem in the tropics.

Northern Star Coral is found in a range that extends from the Gulf of Mexico to Cape Cod.

“Some corals in Florida can have hundreds to thousands of individuals in one colony, and they can be 10 to 20 feet high. Here in Rhode Island, most of our coral colonies are about the size of a silver dollar. They don’t get big, mainly because they don’t grow during the winter,” said Koty Sharp, Roger Williams University associate professor of biology, marine biology and environmental science. “They’re also not super charismatic; they’re not as visually impressive. But under a microscope we see beautiful structures, tentacles, mouths, different colors.”

Sharp believes that the Northern Star Coral’s adaptability to life in both temperate and tropical waters may provide insight into how corals handle the stress of changing environmental conditions, which could ultimately help tropical corals be resilient to the climate crisis.

“Because the Northern Star Coral lives in this large latitudinal range, individuals of the same species experience really different temperature changes and really different environmental shifts throughout the year,” she said. “They’re exposed to different thermal regimes — drastic shifts up here and stable temperature conditions down south. That gives us the flexibility to learn more about how an individual’s history or experience of temperatures and water-quality conditions may influence the physiology of the organism and how that influences its resilience.”

Sharp and colleagues from throughout the species’ range are conducting a variety of experiments to learn about the symbiotic relationship between algae and Northern Star Coral, as well as investigations of its thermal resilience, tolerance for heavy metals, and how it responds to other threats. Sharp’s focus is on the bacteria that live in and on the coral.

“The peculiar thing about this species is that because it goes through winters where water temperatures drop to 2 degrees Celsius, they go through a period of dormancy in winter when they retract into their skeleton and shut up for the winter,” she said. “We don’t know much about what happens during that period of inactivity, but from our bacterial data, it looks like there is very little regulation of the surface microbiome of the coral in winter, and then in spring there is a reorganization of the microbiome.

“We’re focused on finding the processes that happen so they can have this spring awakening. Every New Englander can relate to this; what do we do to regroup and reboot? That’s the key to coral’s resilience to such extreme temperatures and conditions that are unfavorable to most coral species.”

Sharp and a team of Roger Williams University undergraduates are conducting several laboratory experiments designed to identify the factors that influence coral health and its relationship with its algal partners. They are also using DNA sequencing to identify the types of bacteria that live in the corals, culturing those bacteria, and determining what role each plays.

“We’re finding there are bacteria in and on the coral that we think are very important for defense against marine diseases,” Sharp said. “Some are actively inhibiting the growth of potential coral pathogens.’’

How the results of Sharp’s research can be transferred to helping tropical corals become resilient to warming temperatures is uncertain

“We’re hoping to learn more about how corals recover from disturbance, whether a thermal disturbance like a warming event or a winter event up here in New England,” Sharp said. “My lab is interested in what that recovery looks like from a microbial perspective. But it’s not necessarily the goal to apply microbes from New England to tropical reefs. What’s more broadly useful is identifying the mechanisms they use for recovery.

“If bacteria provide the ability to resist or recover from stress, then what’s the biochemistry of that success? It may be as simple as the production of certain chemicals that kill other pathogens. It may be that there are certain compounds the bacteria make in the springtime that support the growth of the coral host. We just don’t know a lot about the functional significance of associated bacteria, but we’re excited to learn more about the partnership and how it can be translated to corals in the tropics.”

Sharp is pleased with each of the small successes she and her students are achieving, like their recent ability to spawn corals in the lab and create the conditions the larval corals need to settle on a rock and start to grow. This will enable her to grow multiple generations of larval corals that her colleagues around the country can use in their own studies.

“It’s a New England coral that we can learn a lot from about coastal ecosystems in New England, but we also want to translate our findings to the tropics in new and powerful ways,” she said. “We need all the information we can get.”

Rhode Island resident and author Todd McLeish, a frequent EcoRI News contributor runs a wildlife blog.

Frank Carini: Microplastic pollution imperils corals

A recent study found that northern star coral polyps routinely consumed microplastics, shown above in blue, over brine shrimp eggs, shown in yellow.

— Photo by Rotjan Marine Ecology Lab at Boston University

From ecoRI News

Coral reefs form the most biodiverse habitats in the ocean, and their health is essential to the survival of thousands of other marine species. Unfortunately, these vital underwater ecosystems are beginning to get a taste for plastic.

A Roger Williams University professor, working with a team of researchers, recently published a study that found corals will choose to eat plastic over natural food sources. Unsurprisingly, it’s not good for their health, as it can lead to illness and death from pathogenic microbes attached to microscopic plastics. It also adds to the stress already being applied to coral reefs worldwide, by acidifying and warming oceans, other pollution sources, development, and harmful fishing practices, such as dynamiting and bleaching to capture fish for aquariums.

The project grew from concern about the 6,350 million to 245,000 million metric tons of plastic in the world’s oceans, and the 4.8 million to 12.7 million metric tons of new plastic that enter annually.

Photographs and news reports have documented dead whales and seabirds found with stomachs full of plastic and of sea turtles suffocating from plastic straws clogging their nostrils. At least two-thirds of the world’s fish stocks are suffering from plastic ingestion, according to estimates, as much of the planet’s plastic pollution eventually makes its way into the ocean.

Roger Williams University associate professor of marine biology Koty Sharp recently told ecoRI News that plastic pollution presents a growing problem for both water- and land-based ecosystems.

“It’s a huge problem,” she said. “There’s really nowhere left on the planet that hasn’t been touched by plastics. We’re finding plastics in every organism we study.”

As much as plastic proliferation is a problem, Sharp is even more concerned about the impacts of a changing climate and how humans are using natural resources. She pointed to the manmade damage being done to Australia’s Great Barrier Reef as an example.

“We need to quickly and dramatically decrease our dependency on plastics and fossil fuels,” the microbiologist said. “This isn’t a problem a few people can fix.”

The study that Sharp helped author was published recently in London’s science journal, Proceedings of the Royal Society B: Biological Sciences. It is the first of its kind to identify that corals inhabiting the East Coast of the United States are “consuming a staggering amount of microplastics,” which alters their feeding behavior and has the potential to deliver fatal pathogenic bacteria.

In their samples of northern star coral, collected off the coast of Jamestown, R.I., each coral polyp — about the size of a pin head — contained more than 100 particles of microplastics, according to the collaborative research team that included Sharp, Randi Rotjan, a research assistant professor of biology at Boston University, and colleagues from UMass Boston, Boston Children’s Hospital Division of Gastroenterology, Harvard Medical School, and the New England Aquarium.

Northern star coral can be found from Buzzards Bay to the Gulf of Mexico. Since it can be found along the coast of most East Coast urban areas, Sharp said it is a “powerful tool” in helping to understand microplastic pollution.

Although this study is the first to document microplastics in wild corals, previous research had found that this same coral species consumed plastic in a laboratory setting. A 2018 study found plastic pollution can promote microbial colonization by pathogens implicated in outbreaks of disease in the ocean.

The study co-authored by Rotjan and Sharp produced similar lab results. When the researchers conducted experiments of feeding microbeads to the corals in their labs, Sharp said they found that the coral would more often choose the fossil-fuel derivative when given the choice between plastic and food of similar sizes and shapes, such as brine shrimp eggs.

In fact, every single polyp, or mouth, that was given the choice ate almost twice as many microbeads as brine shrimp eggs. After the polyps had filled their stomachs with plastic junk food with no nutritional value, they stopped eating the shrimp eggs altogether.

The study showed that bacteria can “ride in” on the microbeads. In the case of the bacteria they used in the lab — the intestinal bacterium E. coli — the microplastic-delivered bacteria killed the polyps that ingested them and their neighboring polyps within weeks, even though the polyps spit the microbeads out after about 48 hours. The E. coli bacterium persisted inside their digestive cavity.

“Research has shown that there are virtually no marine habitats that are untouched by plastics,” said Sharp, noting that research abounds demonstrating that nearly all ocean water contains plastic pollution. “Because of that, it’s critical that we understand the impact of plastics pollution. Microplastics pollution is a matter of global health — ecosystem health and human health.”

She noted that the problem of plastic pollution extends far beyond what can be seen. Plastics never fully degrade in seawater, breaking down into smaller and smaller pieces. Invisible to the naked eye, microplastics remain suspended in the water column, and this is what corals and other filter-feeding animals take in to get their food, she said.

The researchers had anticipated they would find microplastics in wild corals, but they were shocked by the volume present in their samples, according to Sharp.

Another invisible factor is the presence of microbes that hitch rides with plastics floating in the ocean, winding up in the stomachs of many creatures. These plastic-riding microbes are growing in number and upending the delicate balance of ecosystems.

Sharp said the problem is being made worse by human-induced climate change, which is helping bacteria to proliferate. She noted that microplastics in the ocean are coated with microbes.

“We know that plastic particles provide an enriching habitat for bacteria that are not usually in very high numbers in seawater,” Sharp said. “The microbial aspect of microplastics pollution is largely underexplored — it’s critical that we learn more about how plastics can affect the dynamics, abundance, and transport of microbes through our ecosystems and food webs. Alteration of microbiomes in our marine ecosystems by human-induced threats like plastics pollution and climate change holds great potential to impact marine environments on a global scale.”

To help mitigate the problem of plastic pollution, Sharp offered some tips:

Minimize single-use plastics. Use reusable bags and mugs. Buy groceries in bulk. Decline a straw if you don’t need one.

Take a day to count. How many times in one day do you use single-use plastics. What is unnecessary and what can be eliminated or replaced with more sustainable products?

Demand lower-impact packaging and support products with sustainable packaging.

Support and advocate for legislation and lawmakers that promote innovative solutions and alternatives for sustainable packaging.

“Given that plastics pollution is an ongoing threat co-occurring with climate change, it’s critical that we do more research to understand how they impact marine ecosystems together,” Sharp said, “and take immediate actions to minimize human impacts on the world’s oceans.”

Frank Carini is editor of ecoRI News.