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Trouble for clownfishes

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Clownfishes or anemonefishes are colorful saltwater fishes that mainly inhabit coral reefs in the warm and tropical waters of the Indo-Pacific.  Clownfishes have a symbiotic and mutually beneficial relationship with sea anemones, which they rely on for shelter and protection from predators. In turn, clownfishes will protect the anemone from anemone-eating fish, as well as clean and fan them.  The popular film Finding Nemo is about a clownfish who lives in a secluded sea anemone.

The Red Sea, circled by Middle Eastern deserts, is home to marine life that is accustomed to very warm water – often 85 to 90 degrees during the summer.  However, in the past three years marine heat waves have made the Red Sea even hotter.  The rising sea temperatures have caused a breakdown in the symbiotic relationship between clownfish and anemones.

Anemones have a symbiotic relationship of their own with the same microscopic algae that pair with coral.   Just as is the case with coral, anemones expel the algae from their tissues during periods of high heat, causing them to bleach.  Prolonged bleaching can result in the death of the anemone and, in turn, exposes the clownfish to danger.

Researchers from Boston University monitoring three Red Sea reefs over a three-year period found that the marine heatwave in 2023 resulted in the death of 94 to 100% of the clownfish and 66-94% of the anemones.  Rising ocean temperatures can be devastating for many sea creatures.

Anemones are not as well-studied as coral, so it is not clear whether their populations can recover, particularly once the clownfish are gone, making them much more vulnerable to their own predators.

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Clownfish and Anemones Are Disappearing Because of Climate Change

Photo, posted March 9, 2016, courtesy of John Voo via Flickr.

Earth Wise is a production of WAMC Northeast Public Radio

The Great Atlantic Sargassum Belt

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Sargassum is a free-floating brown seaweed that can drift together in vast mats, sometimes stretching for miles across the ocean’s surface. For centuries, these blooms have been a natural part of the Atlantic, creating food and shelter for many marine creatures.  Sargassum was once thought to be confined mainly to the Sargasso Sea in the western Atlantic, but scientists now know it grows rapidly and spreads widely, driven both by natural forces and by nutrients from human activities.

Scientists at Florida Atlantic University have reviewed 40 years of data on sargassum seaweed. Their study, which was recently published in the journal Harmful Algae, points to the rise of what is now called the Great Atlantic Sargassum Belt – a massive seaweed bloom stretching from West Africa to the Gulf of Mexico. First spotted in 2011, it has since appeared every year except in 2013.  This past May, the bloom reached a record 37.5 million tons, a number that does not include the 7.3 million tons in the Sargasso Sea.

Sargassum thrives in nutrient-rich waters.  Under ideal conditions, controlled studies found sargassum can double its biomass in just eleven days!  According to the scientists, nutrient pollution from agriculture and wastewater has fueled these record blooms.

In the ocean, sargassum provides habitat for fish, turtles, and other marine life.  But along the coast, it piles up in smelly heaps, clogs waterways, disrupts tourism, and can even threaten power plants.

Understanding why sargassum is spreading so rapidly is key to tackling a problem that now spans an entire ocean.

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A monster seaweed bloom is taking over the Atlantic

Photo, posted December 24, 2014, courtesy of Roban Kramer via Flickr.

Earth Wise is a production of WAMC Northeast Public Radio

Marine heatwaves are spreading

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Sea surface temperatures broke records in 2024 and a quarter of the world’s oceans are experiencing temperatures that qualify as a marine heatwave.  A marine heatwave is a prolonged period during which ocean temperatures are significantly warmer than average for that specific location and time of year. 

Unusual heatwaves have occurred in all the major ocean basins around the planet in recent years and some have become so intense that they are being called super marine heatwaves.

The seas off the coasts of the UK and Ireland experienced an unusually intense and long-lasting marine heatwave starting in April.  Australia was recently struck by heatwaves on two coasts.

Hotter oceans are causing drastic changes to marine life, sea levels, and weather patterns.  Some of the most apparent casualties of ocean warming have been coral reefs.  About 84% of reefs worldwide experienced bleaching-level heat stress at some point between January 2023 and March 2025.

Excess heat in the oceans can affect weather patterns, making hurricanes more likely to rapidly intensify and become more destructive.

A recent study published in Proceedings of the National Academy of Sciences concluded that climate change has been responsible for the overwhelming majority of marine heatwaves in recent decades.

People are learning to forecast these events.  Eventually, parts of the ocean might enter a constant state of marine heatwave, at least by how it is defined today.  Studying what is going on in the oceans today may provide insights into the future of the world’s oceans and provide guidance on how to try to achieve different outcomes.

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See How Marine Heat Waves Are Spreading Across the Globe

Photo, posted December 5, 2015, courtesy of Susanne Nilsson via Flickr.

Earth Wise is a production of WAMC Northeast Public Radio

More trouble from sea urchins

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Sea Urchins are real troublemakers.  On the West Coast, the sea urchin population exploded when the sunflower sea stars that eat them were decimated by a wasting disease.  Urchins devour kelp and they ate up 96% of the region’s kelp forests.  Kelp forests serve as shelter and food for a vast array of marine life and kelp sequesters as much as 20 times more carbon than terrestrial forests.

A new study by researchers at North Carolina State University looked at the health of the coral reef in Honaunau Bay on Hawaii’s Big Island and found that ballooning sea urchin populations are endangering the survival of the reef.

Fishing in these areas has greatly reduced the numbers of fish that feed on sea urchins and urchin populations have grown significantly.   There are areas of the reef where there are 51 sea urchins in every square meter.

The reef is already not growing at a healthy rate as a result of water pollution and overheating created by climate change.  These result in a poor environment for coral to reproduce and grow, which leaves the reef unable to keep up with the pace of erosion caused by urchins.

Reef growth is measured in terms of net carbonate production – namely the amount of calcium carbonate produced over time.  In the 1980s, healthy reefs in Hawaii produced about 15 kilograms of carbonate a year per square meter.  The Honaunau Reef today shows an average net carbonate production of only 0.5 kilograms per square meter.  The reef is growing very slowly and can’t keep up with urchin erosion.

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Huge sea-urchin populations are overwhelming Hawaii’s coral reefs

Photo, posted October 29, 2017, courtesy of Rickard Zerpe via Flickr.

Earth Wise is a production of WAMC Northeast Public Radio

Toxic algae and West Coast marine life

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Over the first several months of this year, hundreds of sea lions, dolphins, and seabirds have fallen ill or died after eating sardines or anchovies that had been feeding on an algal bloom along the California coast since winter.  The biotoxin in the algae accumulates in the feeder fish.

Two cases of whales dying from the biotoxin have been confirmed by two nonprofit organizations tasked with testing dead mammals.  These were a humpback that washed ashore in Huntington Beach in January and a minke whale found dead in Long Beach in April.

This is the fourth year a row that California has experienced major algal blooms.  Warmer waters are causing blooms to be bigger and more damaging than they have been before.  They enter into new areas and contaminate the food web for longer.  The warmer waters accelerate algae growth that is further fueled by nutrients that rise to the surface from deeper colder waters driven by winds that blow parallel to the coast.  This year’s algae event started earlier than usual and is lasting longer than normal.

More than a dozen animal rescue and rehabilitation groups that form NOAA’s West Coast Marine Mammal Stranding Network are providing resources to try to respond to the situation.  At the Marine Mammal Care Center in Los Angeles, more than 80 sea lions and seals were being treated for domoic acid poisoning, the result of ingesting algae neurotoxin.  Since February, it has cared for more than 300 poisoned animals.

Marine mammals are sentinel species for humans who also consume seafood.  The West Coast ocean ecosystem is currently filled with toxins.

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California Toxic Algal Bloom Blamed for Months-long Marine Life Poisoning

Photo, posted March 26, 2025, courtesy of Marnee Jill via Flickr.

Earth Wise is a production of WAMC Northeast Public Radio

Fighting harmful algal blooms with harmful algal blooms

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Harmful algal blooms – HABs – occur when colonies of algae grow out of control and produce toxic or harmful effects on people, marine life, and birds.  HABs occur naturally but their frequency and intensity are often associated with increased nutrient loading (mainly phosphorous and nitrogen) in bodies of water that is the result of runoff from sources like lawncare and agriculture.

Researchers at Florida Atlantic University have developed a technique for transforming cyanobacteria – also known as blue-green algae and a prime HAB material – into an effective material for removing phosphorous from water.

Their process converts blue-green algal biomass – essentially hazardous waste – into a custom-made adsorbent material that can pull harmful phosphorous from water.  The algae is first quickly heated up using microwaves and then it is modified by adding lanthanum chloride. 

The study took blue-green algae from Florida’s Lake Okeechobee, synthesized the adsorbent material in minutes, and using only small amounts of it could remove 90% of the phosphorous present in only half an hour.  It worked perfectly well in the presence of natural organic matter.  Using the harmful algae itself to prevent algal growth in bodies of water is an innovative way to reduce its further occurrence.

Phosphorous is a major contributor to the occurrence of harmful algal blooms, which can lead to toxic water conditions, loss of aquatic life, and significant economic losses for the fishing and tourism industries.  This technique could prove to be an essential tool for managing the growing problem of nutrient pollution.

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FAU Engineering Develops New Weapon Against Harmful Algal Blooms

Photo, posted October 27, 2010, courtesy of Jennifer L. Graham / U.S. Geological Survey via Flickr.

Earth Wise is a production of WAMC Northeast Public Radio

Sharks and rays in a warming world

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Sharks and rays belong to a group of cartilaginous fish called elasmobranchs, which have been swimming in the world’s oceans for 450 million years. The resilient species have survived five mass extinction events, and are older than dinosaurs, trees, and Mount Everest. 

But despite their resilience, many species of sharks and rays today are threatened by human activities, including overfishing, habitat loss, and climate change.  In fact, according to a new study led by researchers from the University of Vienna in Austria, more than one third of the shark and ray species known today are severely under threat. 

The study, which was recently published in the journal Biology, found that higher carbon dioxide levels were having a negative effect on sharks and rays, ranging from impacts on the animals’ senses to changes in the skeleton during embryonic development.  An examination of fossil records found that higher CO2 levels had contributed to the extinction of individual shark and ray species in the past. 

But the study also found that global warming could be creating opportunities for sharks and rays.  Rising sea levels and higher temperatures have historically expanded shallow coastal habitats and warm waters, supporting species biodiversity.

But according to the research team, the rapid environmental changes, combined with the impacts from human activities, outpace the ability of sharks and rays to adapt, making it unlikely that they will benefit from global warming.

Protecting sharks and rays is crucial not only for their survival but also for maintaining entire ocean ecosystems. Without top predators, these ecosystems could collapse, impacting both marine life and the people and industries that depend on it.

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Sharks and rays benefit from global warming – but not from CO2 in the Oceans

Myths About Sharks and Rays

Photo, posted November 27, 2007, courtesy of Laszlo Ilyes via Flickr.

Earth Wise is a production of WAMC Northeast Public Radio

Corals and climate change

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Climate change is a major threat to coral reefs around the world.  Ocean warming triggers coral bleaching – a stress response where corals expel the symbiotic algae essential for their survival.  If coral bleaching is severe, it can lead to coral death.

A new study led by scientists from Newcastle University in England suggests that corals are unlikely to adapt to ocean warming quickly enough to keep pace with global warming, unless there are rapid reductions in global greenhouse gas emissions.

The study, which was recently published in the journal Science, found that coral heat tolerance adaptation via natural selection could keep pace with ocean warming, but only if the climate goals of the Paris Agreement are realized.  In the Paris Agreement, countries agreed to limit global warming by the end of the century to two degrees Celsius above pre-industrial levels.  

However, current climate policies around the world have the globe on track to warm by three degrees Celsius.  According to the research team, this could lead to significant reductions in reef health, elevated risks of local coral extinctions, and considerable uncertainty in the so-called “evolvability” of corals. 

Coral reefs are among the most biologically diverse ecosystems on Earth.  They are often referred to as the “rainforests of the sea” because they support an incredible variety of marine life.  They provide essential ecosystem services, such as protecting coastlines from erosion and storm surges, supporting fisheries, and serving as a source of income through tourism. Coral reef health is vital for the health of the planet.

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Coral adaptation unlikely to keep pace with global warming

Photo, posted June 9, 2012, courtesy of Bokissa Private Island Resort via Flickr.

Earth Wise is a production of WAMC Northeast Public Radio

Warming estuaries

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Estuaries and their surrounding wetlands are bodies of water where freshwater from rivers and streams mixes with salt water from the ocean to create brackish water.  These brackish ecosystems support many unique plant and animal communities around the world. 

But ocean water temperature around the world continues to warm.  In fact, from 1901 to 2023, the average sea surface temperature has increased by 0.14°F per decade, and 2023 was the warmest year on record.

While sea surface temperatures are on the rise, the problem is more pronounced in South Florida’s estuaries.  According to a new study by researchers from the University of South Florida College of Marine Science and the National Park Service, estuaries have experienced rapid warming over the past two decades. 

In fact, the research team found that sea surface temperature in four estuaries in South Florida – Florida Bay, Tampa Bay, St. Lucie Estuary and Caloosahatchee River Estuary- has risen around 70% faster than the Gulf of Mexico, and 500% faster than the global oceans. 

Their findings, which were recently published in the journals Environmental Research Letters and Estuaries and Coasts, paint a troubling picture for the marine life that calls South Florida’s estuaries home.

The research team has speculated about the possible causes of the rapid rate of warming, including evaporation, water capacity, and residence time, but no single factor has been revealed as dominant. 

The researchers hope to partner with colleagues at the Florida Fish and Wildlife Conservation Commission and NOAA to explore the potential impacts of water temperatures on seagrass and coral populations in South Florida.

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Estuaries in South Florida are warming faster than the Gulf of Mexico and global ocean

What is an estuary?

Photo, posted August 18, 2016, courtesy of City of St. Pete via Flickr.

Earth Wise is a production of WAMC Northeast Public Radio

Floating cities

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About 40% of the world‘s population lives in coastal regions.  People really like ocean-front property.  But worldwide, rising sea levels mean that more and more people want to live on land that may someday be swallowed up by the sea.

One possible solution to the problem is to build cities on top of the water.  It sounds pretty futuristic and impractical, but it is starting to happen.  There have long been floating communities in places like the Netherlands, but these are for the most part clusters of houseboats moored close together.

But there are far more ambitious projects underway.  The Maldives Floating City, already under construction, will eventually have 5,000 houses located in a lagoon that is a 15-minute boat ride from the capital city of Male.  The housing units will be tethered to the lagoon floor and linked together. 

A new project, located off Busan, South Korea, will combine high and low technology to create a large-scale, on-water town, that can house more than 10,000 people.

The town will be built on enormous concrete platforms suspended on the water.  The platforms float because they are rounded hexagonal boxes that are buoyed up by Archimedes’’ principle.  They can’t sink.  Such structures will attract marine life, providing places for oysters and mussels, for example, to grow. 

The initial development will cover 15 acres and the infrastructure will handle power, water, waste, and even some food.  The goal is even to produce enough energy to provide some to the nearby community.  A bridge will link the community to the land.

The project is scheduled to be completed in 2028.  Future expansion could end up housing 150,000 people.

Floating cities could soon no longer be exotic or futuristic.

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Are Floating Cities the Solution to Rising Seas?

Photo, posted June 5, 2012, courtesy of Raymond Bucko via Flickr.

Earth Wise is a production of WAMC Northeast Public Radio

Artificial reefs

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The coral reefs that surround tropical islands are a refuge for a wide variety of marine life and also form a natural buffer against stormy seas.  The changing climate is bleaching coral reefs and breaking them down.  Extreme weather events are becoming more common and are threatening coastal communities with flooding and erosion.

Researchers at MIT are designing architected reefs – sustainable offshore structures that mimic the wave-buffering effects of natural reefs and can also provide habitats for fish and other marine life.

There are already artificial reefs in a number of places used to protect coastlines.  These are typically made from sunken ships, retired oil and gas platforms, and even assemblies of concrete, metal, car tires, and stones.  Generally, it takes quite a lot of material to form an effective barrier to waves.

The MIT group has developed a cylindrical structure surrounded by four rudder-like slats.  Their experiments have shown that when this structure stands in the way of a wave, it efficiently breaks the wave and creates turbulent jets that dissipate the energy in the wave.  The engineers calculated that the new design could reduce as much wave energy as existing artificial reefs but use 10 times less material.

Based on the initial experiments with lab-scale prototypes, these artificial reefs would reduce the energy of incoming waves by more than 95%.

Coral reefs are only found in tropical waters, whereas these artificial reefs don’t depend on temperature and could be placed along any coastline for protection.  In a time of rising seas and increasingly frequent storms, these artificial reefs may be just what coastlines need.

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Artificial reef designed by MIT engineers could protect marine life, reduce storm damage

Photo, posted December 9, 2010, courtesy of Phoenix Wolf-Ray via Flickr.

Earth Wise is a production of WAMC Northeast Public Radio

Major species turnover forecasted for North American cities

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Climate change affects animal species in many ways.  It induces habitat loss, disrupts migration and breeding patterns, threatens marine life, and facilitates an increased spread of disease.  It may also affect where animals can be found in the future. 

According to a new study led by researchers from the University of Toronto Mississauga and Apex Resource Management Solutions in Canada, climate change may dramatically affect the animal species observed in North American cities by the end of the century.

The researchers used species distribution data combined with machine learning to study the impact of human-caused climate change on more than 2,000 animal species historically found in the 60 most populous North American cities. 

According to the research team, changes in biodiversity are brewing for almost every city it studied by the year 2100.  In fact, cities with a rich history of biodiversity are predicted to have the largest declines and fewest gains in species. Cooler and wetter cities like Quebec, Ottawa, Winnipeg, Kansas City, and Omaha are expected to welcome the most new species.  Warmer cities with higher precipitation – like cities in coastal California – are projected to lose the most species. 

More than 95% of bird and insect species are predicted to experience a change in the number of cities they call home.  Canines, most amphibians, and aquatic birds are expected to experience the greatest losses.  Toads, turtles, mice and pelicans are projected to become more common overall. 

The researchers hope their findings will encourage more efforts to protect biodiversity.

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North American cities may see a major species turnover by the end of the century

Photo, posted September 29, 2013, courtesy of Jonathan Kriz via Flickr.

Earth Wise is a production of WAMC Northeast Public Radio

A Below-Average Dead Zone In The Gulf of Mexico | Earth Wise

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The Gulf of Mexico dead zone, or hypoxic area, is an area of low oxygen content that can kill fish and other marine life.  It occurs every summer and is mostly a result of excess nutrient pollution from human activities in cities and farms throughout the Mississippi River watershed.  The nutrients carried by the river into the gulf stimulate an overgrowth of algae, which eventually die and decompose, which depletes oxygen in the water as the algae sink to the bottom.

The resultant low oxygen levels near the bottom of the gulf cannot support most marine life.  Fish and shrimp often leave the area seeking better places to be.  Animals that can’t swim away – like mussels and crabs – can be stressed by the low oxygen level or even killed.

The National Oceanic and Atmospheric Administration produces a dead zone forecast each year based on a suite of models developed by NOAA and partners at multiple universities. 

The latest forecast, completed in May, found that the discharge of nutrients in the rivers was about one-third below the long-term average between 1980 and 2022.  Nitrate loads were down 42% and phosphorous levels down 5%.

Based on these measurements, the scientists forecast a summer dead zone that will cover an estimated 4,155 square miles, which is 22% lower than the 36-year average of 5,364 square miles.  Ongoing efforts by the Interagency Mississippi River and Gulf of Mexico Hypoxia Task Force to reduce nutrient levels seem to be paying off.

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NOAA forecasts below-average summer ‘dead zone’ in Gulf of Mexico

Photo, posted September 6, 2013, courtesy of NOAA Photo Library via Flickr.

Earth Wise is a production of WAMC Northeast Public Radio

A New Deep-Sea Reef In The Galapagos | Earth Wise

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Like in many other places around the world, ocean warming has mostly destroyed the shallow-water reefs in the Galapagos Islands.  The islands are some of the most carefully protected places in the world, but they can’t escape the effects of a warming planet.

Recently, however, scientists have discovered a healthy, sprawling coral reef hidden deep under the sea in the Galapagos.  More than 1,300 feet underwater, the reef extends for several miles along the ridge of a previously unknown volcano in the Galapagos Marine Preserve.

The reef is pristine and is teeming with all sorts of marine life including pink octopus, batfish, squat lobsters, and a variety of deep-sea fish, sharks, and rays.

The expedition that discovered the new reef was led by the University of Essex in the UK.  Prior to this discovery, scientists thought that coral reefs were all but gone from the Galapagos.  A period of ocean warming in 1982 through 1983 wiped out more than 95% of the corals in the archipelago.  Only a few reefs in shallow waters remained.  The newly discovered reefs are sheltered deep under the sea and would have been protected from the deadly heat.

According to the scientists from the expedition, the newly discovered reef potentially has global significance because it represents a site that can be monitored over time to see how such a pristine habitat evolves with the ongoing climate crisis.  Reefs like this are clearly very old because coral reefs take a long time to grow. Finding this one means that it is likely that there are more healthy reefs across different depths that are waiting to be discovered.

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Pristine Deep-Sea Reef Discovered in the Galápagos

Photo, posted March 28, 2009, courtesy of Derek Keats via Flickr.

Earth Wise is a production of WAMC Northeast Public Radio

Reef Insurance | Earth Wise

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Coral reefs around the world face multiple dangers from warming waters, acidification, human activity, and more.  Powerful storms often cause tremendous damage to reefs.  When possible, snorkelers and divers are deployed to try to repair damage to reefs.  But philanthropy and government grants are basically the only resources available to fund such actions.

Three years ago, tourist businesses and the government in the Mexican state of Quintana Roo purchased an insurance policy to offset costs of protecting the local parts of the Mesoamerican Reef.  The environmental group the MAR Fund later took out an insurance policy on the rest of the reef in Mexico, Belize, Guatemala, and Honduras. 

With this precedent, the Nature Conservancy recently purchased an insurance policy on behalf of the state of Hawaii to help offset repair work on its coral reefs.  It is the first U.S. coral insurance contract.

Coral reefs are more than just hosts for marine life.  They provide barriers against ocean storm surges, which is a major financial incentive for protecting them and hence an incentive to invest in insurance.

The new Hawaiian insurance policy has a premium of $110,000 a year and will provide $2 million in protection.  Payouts occur when wind speeds go above 50 knots.  No further proof of damage is required.

The Nature Conservancy has created teams called ‘Reef Brigades’ composed of snorkelers and divers who recover reef fragments, store them in ocean or shore-based nurseries, and then re-attach them when conditions are safe.  It can be very expensive to do this sort of work, particularly when new corals grown in a nursery are required.

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Analysis: First U.S. coral insurance marks the rise of the reef brigades

Photo, posted September 14, 2011, courtesy of Greg McFall/NOAA Office of National Marine Sanctuaries via Flickr.

Earth Wise is a production of WAMC Northeast Public Radio

Better Marine Protected Areas | Earth Wise

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Marine protected areas are regions of seas, oceans, estuaries, and in the US, the Great Lakes, that are afforded special protections.  MPAs restrict human activity for conservation purposes, generally in order to protect natural or possibly cultural resources.   MPAs may limit such things as development, fishing practices, fishing seasons, catch limits, moorings, and removal or disruption of marine life.

A new study by the University of Plymouth in the UK looked at the effectiveness of MPAs in increasing the total abundance of reef species.  It looked at the MPAs in Lyme Bay, off the south coast of England, where two of them are co-located but governed by different constraints.

The study found that whole-site management of an MPA can increase the total abundance of reef species within its borders by up to 95%.  This is in contrast to the MPA where only known features are conserved and human activity is otherwise allowed to continue unchecked.  In that place, species abundance increased by only 15%.

The whole-site MPAs were observed to have other benefits as well.   They show higher levels of functional redundancy, meaning that when there are species losses, they are compensated by other species.  Whole-site MPAs also exhibit higher levels of species diversity.

MPAs are increasingly being recognized as a sustainable way to enhance the marine environment even while supporting coastal communities.  The Global Ocean Alliance, a 72-country alliance led by the UK, has set a target of protecting 30% of all marine areas by 2030.  The new study shows that even more important than simply establishing marine protected areas, it is essential that they are effectively implemented.

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Whole-site management of Marine Protected Areas can lead to a 95% increase in reef species

Photo, posted October 28, 2011, courtesy of Benjamin Evans via Flickr.

Earth Wise is a production of WAMC Northeast Public Radio.

Return Of The Fin Whale | Earth Wise

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The fin whale is the second largest whale species and therefore the second largest creature on Earth.  They can grow to more than 80 feet in length.  From 1904 to 1976, there was massive industrial whaling in the Southern Ocean surrounding Antarctica.  During that period, whalers killed about 700,000 fin whales, reducing their population by 99%.  The species was nearly extinct.

In 1982, the International Whaling Commission voted to ban commercial whaling.  Since that time, fin whales started to make a comeback in their historical feeding grounds.

During a nine-week expedition in the waters around the Antarctic Peninsula, researchers encountered the largest gathering of fin whales ever documented.  About 150 fin whales were seen diving and lunging against the water’s surface.  It was a feeding frenzy triggered by large amounts of krill in the water.  The actions of the whales are known as a “whale pump” that drives the krill to the surface.  Not only does it provide huge amounts of food for the whales but also for other animals, including seabirds and seals.

Forty years after the commercial whaling ban, the number of fin whales has been increasing.  Large groups were observed in a 2013 survey.  Aerial surveys in 2018 and 2019 recorded 100 groups of fin whales, usually composed of a just a handful of individuals.  They did document eight large groups of up to 150 individuals.

Not all species of whales have rebounded so successfully since the whaling ban.  The rebound in fin whale population is not only good for the whales, but for the entire ecosystem in the Southern Ocean.  It is a glimmer of good news in a time of great challenges for global biodiversity and for marine life in particular.

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Once Facing Extinction, Massive Fin Whales Have Returned to Antarctic Waters

Photo, posted November 15, 2007, courtesy of Gregory Smith via Flickr.

Earth Wise is a production of WAMC Northeast Public Radio.

Marine Predation And Climate Change | Earth Wise

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Climate change is taking a toll on forests, farms, freshwater resources, and economies all around the world.  But ocean ecosystems remain the center of global warming.

Despite their vast ability to absorb heat and carbon dioxide, oceans are warming.  In fact, according to scientists, the oceans have absorbed 90% of all the warming that has occurred during the past 50 years. 

The ocean’s surface layer, which is home to most marine life, takes most of this heat.  As a result, the top 2,300 feet of global ocean water has warmed approximately 1.5°F since 1901.

Well it turns out that a hotter ocean is also a hungrier ocean.  According to a new study recently published in the journal Science, researchers discovered that predator impacts in the Atlantic and Pacific oceans peak at higher temperatures.  The effects of more intense marine predation could disrupt ecosystem balances that have existed for millennia. 

An international research team led by the Smithsonian Institution and Temple University analyzed predator and prey data collected from 36 sites, running along the Atlantic and Pacific coasts from Alaska in the north to Tierra de Fuego at the tip of South America.  The research team found that, in warmer waters, predators’ more voracious appetites left outsized marks on the prey community.  Total prey biomass plunged in warmer waters when prey were left unprotected.  However, in the coldest zones, leaving prey exposed or protected made nearly no difference at all.  

As the oceans continue to warm, more intense predation will create winners and losers and could jeopardize the overall health of marine ecosystems.  

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As the ocean heats up hungrier predators take control

Photo, posted July 14, 2017, courtesy of Jonathan Chen via Flickr.

Earth Wise is a production of WAMC Northeast Public Radio.

Climate Change And The World’s Fisheries | Earth Wise

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According to a new study, approximately 70% of the world’s oceans could be suffocating from a lack of oxygen by 2080 as a consequence of climate change.  This has the potential to impact marine ecosystems all around the world.  

The study, which was recently published in the journal Geophysical Research Letters, is the first to use climate models to predict how and when deoxygenation will occur throughout the world’s oceans outside of its natural variability. 

According to the findings, significant and potentially irreversible deoxygenation of the ocean’s middle depths began occurring last year.  The models predict that deoxygenation will begin affecting all zones of the ocean by 2080.

According to the study’s models, mid-ocean depths are already losing oxygen at unnatural rates. Globally, the ocean’s middle depth – known as the mesopelagic zone – is home to many of the world’s commercially fished species.  This makes these new findings a potential harbinger of economic hardship, seafood shortages, and environmental disruption. 

Just like land animals, aquatic animals need oxygen to breathe.  As climate change warms the oceans, the water holds less oxygen and is more buoyant than cooler water.  This leads to less mixing of oxygenated water near the surface with deeper waters, which naturally contain less oxygen.  Warmer water also raises oxygen demand among living organisms, resulting in less availability for marine life. 

The researchers also found that oceans closer to both the North Pole and the South Pole are particularly vulnerable to deoxygenation.  While they are not yet sure why, accelerated climate warming could be the culprit. 

These findings should add new urgency to climate change mitigation efforts. 

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Climate change has likely begun to suffocate the world’s fisheries

Photo, posted January 28, 2019, courtesy of Joseph Gage via Flickr.

Earth Wise is a production of WAMC Northeast Public Radio.

Wildfires And Algal Blooms

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Australia is no stranger to wildfires. But the 2019-2020 season proved to be particularly severe: wildfires destroyed 3,100 homes, displaced 65,000 people, and burned more than 72,000 square miles – roughly the same size as Washington State. The season is colloquially referred to as the Black Summer.

According to a new study recently published in the journal Nature, clouds of smoke and ash from these wildfires triggered widespread algal blooms thousands of miles downwind to the east in the Southern Ocean.

The study, which was led by researchers from Duke University, shows that aerosol particles in the smoke and ash fertilized the water as they fell into it.  This provided the nutrients that fueled unprecedented blooms in that region, conclusively linking for the first time a large-scale response in marine life to fertilization by pyrogenic iron aerosols from a wildfire.

This finding raises questions about the role wildfires may play in the growth of phytoplankton, the microscopic marine algae that – through photosynthesis – absorbs large amounts of climate-warming carbon dioxide from Earth’s atmosphere. 

According to the research team, the Australian algal blooms were so extensive that the subsequent increase in photosynthesis may have temporarily offset a substantial portion of the wildfires’ CO2 emissions.  It remains to be seen how much of the absorbed CO2 remains safely stored in the ocean and how much it has been released back into the atmosphere. 

The researchers plan to investigate the fate of the phytoplankton further.  They also plan more research to better predict where and when aerosol deposition will boost phytoplankton growth in the future.  

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Australian wildfires triggered massive algal blooms in Southern Ocean

Photo, posted January 12, 2020, courtesy of BLM-Idaho via Flickr.

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