Climate change may increase the spread of neurotoxin in the oceans

The researchers’ findings raise concerns about how climate change may affect the levels of methylmercury in fish and shellfish.
Photo Credit: Johnér Bildbyrå AB

Climate-driven oxygen loss in the Black Sea thousands of years ago triggered the expansion of microorganisms capable of producing the potent neurotoxin methylmercury. That is shown in a new study published in Nature Water, led by Eric Capo at Umeå University, which suggests that similar processes could occur in today’s warming oceans.

Methylmercury is a highly toxic compound that accumulates in fish and seafood, posing severe health risks to humans. It is formed when certain microbes convert inorganic mercury under low-oxygen conditions.

Today, climate change is causing such oxygen-depleted areas to expand in coastal marine environments, including parts of the Baltic Sea. Warmer and more stagnant waters mix less efficiently, and increased algal blooms contribute to oxygen loss in deeper layers, creating ideal conditions for these microbes.

Lessons from Ascension’s shark troubles could help boost conservation

Sharks at the coast of Ascension Island.
Photo Credit Kate Downes

Understanding people’s attitudes to interactions with sharks could help halt the global decline of shark numbers, according to new research carried out on Ascension Island.  

In 2017, there were two non-fatal shark attacks at Ascension – a UK territory in the South Atlantic with a population of about 800 people.

Large numbers of sharks – mostly silky and Galapagos sharks – have affected the island’s recreational fishers, who often lose tackle and hooked fish before they can be landed.

The research team, led by the University of Exeter and ZSL, interviewed 34 islanders to assess perceptions of sharks.

“We found that human-shark conflict is driven by lots of different factors beyond just attacks – and understanding this is vital if we want shark conservation to work,” said Dr Claire Collins, from ZSL and the University of Exeter.

Critically endangered shark meat sold in US stores

Image Credit: Gillie Sibrian/UNC-Chapel Hill

Critically endangered shark meat is being sold at American grocery stores — often under misleading labels — according to a new study conducted by researchers at UNC-Chapel Hill.

The researchers purchased and DNA barcoded 29 shark meat products from stores in North Carolina; Washington, D.C.; Florida and Georgia and from online vendors. DNA testing revealed 11 different species of shark, yet 93% of the samples were ambiguously labeled as “shark” or “mako shark” at stores with no species-level identification.

Of the 11 species sold in stores, three are listed as critically endangered by the International Union for the Conservation of Nature — the great hammerhead, scalloped hammerhead and tope. Another species sold in stores, the shortfin mako shark, is listed as endangered by the IUCN.

The U.S. Food and Drug Administration only requires sellers to label shark meat as “shark,” with no specific species name required.

Rare glimpse at understudied ecosystem prompts caution on deep-sea mining

Some of the animals identified in the deep-sea that spend their life in the benthic boundary layer.
Photo Credit: Gabrielle Ellis

An enormous but poorly understood region of the global ocean–referred to as the abyssal benthic boundary layer–lies a few meters above the seafloor and has only been sampled a handful of times. A study by oceanographers at the University of Hawaiʻi at Mānoa provided the first in-depth look at this habitat, revealing a dynamic community that may be more sensitive to seasonal changes than previously understood. The research, published in Limnology and Oceanography, also concluded that deep-sea mining could have significant and unavoidable impacts on biodiversity, regardless of the time of year.

“Given the remoteness of this environment, we have extraordinarily limited knowledge of the animals that inhabit this zone,” said Gabrielle Ellis, lead author of the study and recent oceanography graduate from the UH Mānoa School of Ocean and Earth Science and Technology. “This study represents a significant contribution to our understanding of the benthic boundary layer community, and it starts to unravel temporal dynamics in the abyss.”

What Is: Microplastics

Microplastic
Credit: Scientific Frontline

The Invisible Tide of Plastic

The modern era has been defined, in part, by the versatility and ubiquity of plastic. Yet, this celebrated 20th-century material has given rise to a paradoxical form of pollution—one so pervasive and minute that its scale was largely unrecognized until recently. Microplastics, the synthetic dust of our industrial age, represent a global environmental challenge of unprecedented complexity. These tiny particles, born from the fragmentation of larger debris and the intentional design of microscopic products, have infiltrated every corner of the planet. Scientific expeditions have confirmed their presence from the summit of Mount Everest to the abyssal depths of the Mariana Trench. More alarmingly, this invisible tide has crossed the final frontier, entering the human body itself, with researchers detecting microplastic particles in human blood, lung tissue, and even the placenta.

The ubiquity of microplastics signals a fundamental disruption of planetary systems. They are not merely inert debris but active agents in the environment, interacting with ecosystems and organisms in complex and often detrimental ways. Their journey spans the globe, carried by ocean currents, river systems, and atmospheric winds, connecting the most remote wilderness to the most densely populated urban centers in a shared system of contamination. This report provides a definitive, evidence-based synthesis of the current scientific understanding of microplastics. It aims to dissect the full scope of this issue, beginning with a fundamental definition of the pollutant and a detailed accounting of its myriad sources. It will then trace the environmental fate and transport of these particles through aquatic, terrestrial, and atmospheric systems. Finally, the report will conduct an exhaustive analysis of their multifaceted impacts on ecological integrity and human health, concluding with a critical evaluation of the policies, technologies, and strategies required to mitigate this pervasive threat.

3D-printed shelters increase baby coral survival rates

Researchers place the modules onto experimental tables in Kāneʻohe Bay.
Photo Credit: Jessica Reichert

To dramatically increase coral survival rates, scientists at the University of Hawaiʻi at Mānoa Hawaiʻi Institute of Marine Biology (HIMB) have developed innovative 3D-printed ceramic structures that provide crucial protection for baby corals. These new designs offer a low-cost and scalable solution to enhance reef recovery worldwide.

The discovery, published in Biological Conservation, addresses a critical challenge in reef restoration—the low settlement and survival rates of juvenile corals, which often die before adulthood due to predation, being overgrown by algae or being swept away by waves.

“We developed structures that help baby corals find safe homes in the reef,” said Josh Madin, principal investigator at HIMB’s Geometric Ecology Lab and co-author of the study. “Our new designs, with small spiral-shaped shelters called ‘helix recesses,’ give young corals the protection they need during this critical stage.”

Study first to show if nesting heat affects sea turtle hatchling ‘IQ’

A loggerhead hatchling goes through the Y-maze to test its learning abilities.
Photo Credit: Sarah Milton, Florida Atlantic University

As sand temperatures continue to rise, concerns about the future of sea turtles are growing. Hotter nests not only skew sex ratios – producing more females – but also reduce hatchling survival, slow growth, and increase the likelihood of physical deformities. Yet one important and often overlooked question remains: does this heat also affect cognitive ability – how well hatchlings can learn, adapt and respond to the rapidly changing world they face from the moment they emerge?

A new study by researchers at Florida Atlantic University’s Charles E. Schmidt College of Science offers a surprising glimmer of hope. They are the first to test whether incubation temperature affects cognitive ability in loggerhead (Caretta caretta) hatchlings – how well they can learn, adapt and problem-solve. While animal cognition has been widely studied in birds and mammals, much is yet to be discovered in reptiles.

Using a Y-maze and a visual discrimination task, the researchers trained hatchlings incubated at two female-producing temperatures (88 F and a hotter 91 F) and then tested their ability to “reverse train” when the task rules changed. Eggs were collected during the summers of 2019 and 2020 from nesting beaches in Palm Beach County.

Global ‘Noahʻs Ark’ to safeguard coral reefs, led by UH scientists

Acropora muricata, Heron Island, Australia.
Photo Credit: Claire Lager, Smithsonian

In a landmark effort to combat the devastating effects of climate change, a new global alliance with key leadership from the University of Hawaiʻi at Mānoa has been established to create a “Noahʻs Ark” for coral reefs. The initiative, detailed in a publication in BioScience, focuses on building a worldwide network of coral biorepositories to safeguard the genetic diversity of these vital ecosystems.

The research, led by Mary Hagedorn of the UH Mānoa Hawaiʻi Institute of Marine Biology and Smithsonian’s National Zoo and Conservation Biology Institute, highlights the critical need for a proactive conservation strategy. With global carbon emissions continuing to rise, the alliance aims to provide a critical safeguard against extinction by preserving coral genetic material in biosecure facilities.

Clownfish and Anemones Are Disappearing Because of Climate Change

A Red Sea clownfish (Amphiprion bicinctus) peers out of a bleached sea anemone (Radianthus magnifica) during a record-breaking heat wave in 2023.
Photo Credit: © Morgan Bennett-Smith

A new study led by Boston University marine biologists reveals that heat waves are threatening the future of the fish made famous by Finding Nemo

The Red Sea, circled by desert landscapes, is home to marine life accustomed to the water’s bathtub-like temperatures—often reaching 85 to 90 degrees Fahrenheit in the summer. But in the past three years, marine heat waves have made the Red Sea even hotter. Rising ocean temperatures, there and around the world, have been devastating for many sea creatures, including an iconic ocean duo: clownfish and anemones. 

A new paper from a Boston University–led research team finds that this extreme heat has caused a breakdown in the mutualistic relationship of clownfish—also called anemonefish— and anemones and has resulted in a population collapse in the central Red Sea.

Coral reefs set to stop growing as climate warms

Dead reef crest on Mexico's Caribbean coast.
Photo Credit Chris Perry

Most coral reefs will soon stop growing and may begin to erode – and almost all will do so if global warming hits 2°C, according to a new study in the western Atlantic.

An international team, led by scientists from the University of Exeter, assessed 400 reef sites around Florida, Mexico and Bonaire.

The study, published in the journal Nature, projects that more than 70% of the region’s reefs will stop growing by 2040 – and over 99% will do so by 2100 if warming reaches 2°C or more above pre-industrial levels.

Climate change – along with other issues such as coral disease and deteriorating water quality – reduces overall reef growth by killing corals and impacting colony growth rates.

To understand how changing reef ecology is impacting reef growth potential – in other words, how the balance of living organisms translates into vertical “accretion” (reef-building) – the team analysed fossil reefs from across the tropical western Atlantic region to improve understanding of how reef growth rates vary depending on the types of coral present.

Women of Science: A Legacy of Achievement

Future generations to pursue their passions and break down barriers in the pursuit of knowledge.
Image Credit: Scientific Frontline stock image

Throughout history, women have made groundbreaking contributions to science, despite facing significant societal barriers and a lack of recognition. Their relentless pursuit of knowledge and innovation has shaped our understanding of the world and paved the way for future generations of scientists. This article celebrates the achievements of some of these remarkable women, highlighting their struggles and the impact of their work.

The women featured in this article, along with countless others throughout history, have made invaluable contributions to the advancement of science. Their achievements, often accomplished in the face of adversity and societal barriers, have shaped our understanding of the world and paved the way for future generations of scientists. These women demonstrate the power of perseverance, the importance of challenging established norms, and the profound impact that individual dedication can have on scientific progress. By recognizing and celebrating their legacies, we not only honor their contributions but also inspire future generations to pursue their passions and break down barriers in the pursuit of knowledge.

New technology lights way for accelerating coral reef restoration

Improving coral feeding habits can have a positive domino effect on the marine ecosystem.
Photo Credit: Francesco Ungaro

Scientists have developed a novel tool designed to protect and conserve coral reefs by providing them with an abundance of feeding opportunities. 

The device, dubbed the Underwater Zooplankton Enhancement Light Array (UZELA), is an autonomous, programmable underwater light that works to draw in nearby zooplankton, microscopic organisms that coral feed on. 

After testing the submersible on two species of coral native to Hawaii over six months, researchers found that UZELA could greatly enhance local zooplankton density and increase the feeding rates of both healthy and bleached coral. Importantly, providing coral with greater amounts of food makes them stronger and more likely to be resilient against certain environmental threats, like heat stress or ocean acidification.

This result is impressive, especially at a time when rising ocean temperatures are forcing entire coral reefs to the cusp of collapse, said

Whale poop contains iron that may have helped fertilize past oceans

A blue whale photographed in September 2010.
Photo Credit: NOAA

The blue whale is the largest animal on the planet. It consumes enormous quantities of tiny, shrimp-like animals known as krill to support a body of up to 100 feet (30 meters) long. Blue whales and other baleen whales, which filter seawater through their mouths to feed on small marine life, once teemed in Earth’s oceans. Then over the past century they were hunted almost to extinction for their energy-dense blubber.

As whales were decimated, some thought the krill would proliferate in predator-free waters. But that’s not what happened. Krill populations dropped, too, and neither population has yet recovered.

A recent theory proposes that whales weren’t just predators in the ocean environment. Nutrients that whales excreted may have provided a key fertilizer to these marine ecosystems.

Research led by University of Washington oceanographers supports that theory. It finds that whale excrement contains significant amounts of iron, a vital element that is often scarce in ocean ecosystems, and nontoxic forms of copper, another essential nutrient that in some forms can harm life.

The open-access study, the first to look at the forms of these trace metals in what’s commonly known as whale poop, was published in January in Communications Earth & Environment.

Apex predators in prehistoric Colombian oceans would have snacked on killer whales today

. Illustration of some of the apex predators in the Paja Formation biota with a human for scale.
Illustration Credit: Guillermo Torres, Hace Tiempo, Instituto von Humboldt.

Predators at the top of a marine food chain 130 million years ago ruled with more power than any modern species, McGill research into a marine ecosystem from the Cretaceous period revealed. 

The study, published in the Zoological Journal of the Linnean Society, reconstructs the ecosystem of Colombia’s Paja Formation, and finds it was teeming with marine reptiles reaching over 10 meters in length that inhabited a seventh trophic level.  

Trophic levels are the layers or ranks within a food chain that describe the roles organisms play in an ecosystem based on their source of energy and nutrients. Essentially, they help define who eats whom in an ecosystem. Today’s marine trophic levels cap at six, with creatures like killer whales and great white sharks. 

The discovery of giant marine reptile apex predators occupying a seventh trophic level underscores the Paja ecosystem’s unmatched diversity and complexity, offering a rare view into an evolutionary arms race among predators and prey. 

Deep parts of Great Barrier Reef ‘insulated’ from global warming – for now

Mesophotic corals on the Great Barrier Reef.
Photo Credit Prof Peter Mumby

Some deeper areas of the Great Barrier Reef are insulated from harmful heatwaves – but that protection will be lost if global warming continues, according to new research.

High surface temperatures have caused mass “bleaching” of the Great Barrier Reef in five of the last eight years, with the latest happening now.

Climate change projections for coral reefs are usually based on sea surface temperatures, but this overlooks the fact that deeper water does not necessarily experience the same warming as that at the surface.

The new study – led by the universities of Exeter and Queensland – examined how changing temperatures will affect mesophotic corals (depth 30-50 meters).

It found that separation between warm buoyant surface water and cooler deeper water can insulate reefs from surface heatwaves, but this protection will be lost if global warming exceeds 3°C above pre-industrial levels.

The researchers say similar patterns could occur on other reefs worldwide, but local conditions affecting how the water moves and mixes will mean the degree to which deeper water coral refuges exist and remain insulated from surface heatwaves will vary.

“Coral reefs are the canary in the coalmine, warning us of the many species and ecosystems affected by climate change,” said Dr Jennifer McWhorter, who led the research during a QUEX PhD studentship at the universities of Exeter and Queensland.

Tomorrow's reefs – the importance of environmental awareness in coral restoration

Restoration nursery in the northern Red Sea of smooth cauliflower coral (Stylophora pistillata), almost ready for reef transplantation. Classified as near-threatened, S. pistillata is native to the wider Indo-Pacific region. This nursery is at 5 metres depth, close to the Inter University Institute of Marine Science, Eilat.
Photo Credit: H Nativ/Morris Kahn Marine Research

Around the world, projects are underway to save or rebuild damaged coral reefs. However, many restoration projects fail within just a few years. Giving more consideration to current and future environmental conditions would, in many cases, improve long-term restoration success, say the researchers behind a new article published in Plos Biology.

Coral reefs are extremely valuable. An estimated 25 percent of all plants and animals in the ocean, and 1 billion people worldwide depend on them – for food, income, coastal protection or cultural traditions. But their existence is also threatened by multiple factors, such as climate change, pollution, overfishing and coastal development.

Relying on climate change mitigation alone to ensure the future viability of coral reefs is no longer realistic. Targeted efforts are now needed, and restoration of damaged coral reefs has today become a multimillion-dollar business. Nevertheless, the long-term outcome of many coral restoration projects is highly uncertain.

Shy sea anemones are more likely to survive heatwaves

Photo Credit: Praveen Kenderla

Even in nature, pride can prevail. A study with researchers from the University of Gothenburg shows that sea anemones that react more slowly to change can survive a heatwave better than individuals that change their behavior quickly.

Along the Atlantic coasts of Europe, many species are exposed to abrupt shifts in habitat. Tides, storms and rapid temperature changes are commonplace for the marine species that live there. With climate change, heatwaves are expected to become more frequent, and researchers wanted to find out how coastal marine species cope with extreme water temperatures. They chose to study the sea anemone species Actinia equina, a species that exhibits individual behaviors.

Bold or shy

“We call them animal personalities. They are different behavioral life strategies found in the same species. The anemones we studied have two personality traits, bold and shy, and in extreme heat waves the shy anemones do better,” says Lynne Sneddon, a zoophysiologist at the University of Gothenburg and co-author of the study published in the Journal of Experimental Biology.

AI breakthrough: UH researchers help uncover climate impact on whales

Underside of a humpback whale’s tail fluke which can serve as a “finger-print” for identification.
Photo Credit: Adam Pack

More than 10,000 images of humpback whale tail flukes collected by University of Hawaiʻi researchers have played a pivotal role in revealing both positive and negative impacts on North Pacific humpback whales, positive trends in the historical annual abundance of North Pacific humpback whales, and how a major climate event negatively impacted the population. Adam Pack, who heads the UH Hilo Marine Mammal Laboratory, Lars Bejder, director of the UH Mānoa Marine Mammal Research Program (MMRP) and graduate students Martin van Aswegen and Jens Currie, co-authored a study on humpback whales in the North Pacific Ocean, and the images—along with artificial intelligence (AI)-driven image recognition—were instrumental in tracking individuals and offering insights into their 20% population decline observed in 2012–21.

“The underside of a humpback whales tail fluke has a unique pigmentation pattern and trailing edge that can serve as the ‘finger-print’ for identifying individuals,” said Pack.

‘Back to the Future’ to Forecast the Fate of a Dead Florida Coral Reef

Alex Modys, Ph.D., diving at the coral death assemblage in Pompano Ridge and digging up a subfossil coral, Orbicella annularis.
Photo Credit: Anton Olenik, Ph.D., Florida Atlantic University

Rising temperatures and disease outbreaks are decimating coral reefs throughout the tropics. Evidence suggests that higher latitude marine environments may provide crucial refuges for many at-risk, temperature-sensitive coral species. However, how coral populations expand into new areas and sustain themselves over time is constrained by the limited scope of modern observations. 

What can thousands of years of history tell us about what lies ahead for coral reef communities? A lot. In a new study, Florida Atlantic University researchers and collaborators provide geological insights into coral range expansions by reconstructing the composition of a Late Holocene-aged subfossil coral death assemblage in an unusual location in Southeast Florida and comparing it to modern reefs throughout the region. 

Located off one of the most densely populated and urbanized coastlines in the continental United States, the Late Holocene coral death assemblage known as “Pompano Ridge,” records a northward range expansion of tropical coral communities that occurred during a period of regional climate warming more than 2,000 years ago.

Could this happen again in the face of climate change? Going “back to the future,” this study offers a unique glimpse into what was once a vibrant coral reef assemblage and explores if history can repeat itself.

Hypoxia is widespread and increasing in the ocean off the Pacific Northwest coast

In late August, OSU's Jack Barth and his colleagues deployed a glider that traversed Oregon’s near-shore waters from Astoria to Coos Bay and measured the oxygen levels through the water column, and beamed the data back to OSU computers.
Photo Credit: Courtesy of Jack Barth.

Low oxygen conditions that pose a significant threat to marine life are widespread and increasing in coastal Pacific Northwest ocean waters as the climate warms, a new study shows.

Researchers found that in 2021, more than half the continental shelf off the Pacific Northwest coast experienced the low-oxygen condition known as hypoxia, said the study’s lead author, Jack Barth of Oregon State University.

“We’ve known that low oxygen conditions are increasing based on single points of study in the past, but this confirms that these conditions are occurring across Pacific Northwest coastal waters,” said Barth, an oceanography professor in the College of Earth, Ocean, and Atmospheric Sciences. “The 2021 season was unusually strong compared to past years but with climate change, we are headed in a direction where this may be the norm.”

The new study, published recently in Nature Scientific Reports, is based on data collected by an unprecedented number of research vessels and autonomous underwater gliders that were collecting measurements in the ocean during summer 2021.