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Manatees And Pollution | Earth Wise

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Manatees are large, gentle, and curious marine mammals measuring up to 13 feet long and weighing up to 3,300 lbs.  There are three living species of manatees:  The Amazonian Manatee, the West African Manatee, and the West Indian Manatee, which is commonly found in Florida and the Gulf Coast.  Manatees inhabit the shallow, marshy coastal areas and rivers of the Caribbean Sea, the Gulf of Mexico, the Atlantic coast, the Amazon basin, and West Africa. 

The West Indian Manatee, which includes the Florida Manatee, is protected under the Endangered Species Act.  Today, the range-wide population is estimated to be at least 13,000 manatees, with more than 6,500 in the southeastern United States and Puerto Rico.

In Florida, an uptick in nutrient loading from nonpoint sources is triggering algal blooms in Indian River Lagoon and neighboring areas.  These algal blooms have decimated seagrass, manatees’ primary food source. 

As a result , manatees have starved to death by the hundreds along Florida’s east coast.  The state has recorded 974 manatee deaths in 2021, shattering previous annual all-time highs with still approximately two months to go.  Manatees, which need to eat between 100-200 pounds of seagrass daily, are now eating the seagrass roots, which permanently kills the aquatic plants.

Efforts are being made to replant seagrass and to restore clam and oyster beds so that the mollusks can help clean the water.  But manatees face a myriad of additional threats, including collisions with boats and ships, temperature changes, disease, and crocodile predation.

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Florida lawmakers hear Fish & Wildlife agency response to manatee death ‘catastrophe’

West Indian manatee

Preliminary 2021 Manatee Mortality Table by County

Photo, posted May 7, 2010, courtesy of Jim Reid/USFWS via Flickr.

Earth Wise is a production of WAMC Northeast Public Radio.

Mollusks And Microplastics | Earth Wise

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Plastic debris comes in all different shapes and sizes, but pieces that are less than five millimeters in length are called microplastics.  Microplastics are everywhere, including in the food we eat, the water we drink, and the air we breathe.

Much of the oceanic microplastic pollution comes from the breakdown of plastic litter.  Another source of microplastic pollution is microbeads.  Microbeads, which are sometimes added to cleansing and exfoliating personal care products, pollute the environment when they get flushed down the drain.  

According to a new study by researchers at Hull York Medical School and the University of Hull in the U.K., mussels, oysters and scallops have the highest levels of microplastic contamination among seafood.  The research team examined 50 studies between 2014 and 2020 to determine the levels of microplastic contamination globally in fish and shellfish.  The team found that microplastic content was 0-10.5 microplastics per gram in mollusks, 0.1-8.6 microplastics per gram in crustaceans, and 0-2.9 microplastics per gram in fish.  

The researchers found that mollusks collected off the coasts of Asia were the most heavily contaminated with microplastics.  China, Australia, Canada, Japan and the United States are among the largest consumers of mollusks, followed by Europe and the U.K.

While the human health implications of consuming microplastics are not well understood, early evidence from other studies suggest they do cause harm. 

According to the research team, more data is needed from different parts of the world in order to better understand how microplastics vary between different oceans, seas, and waterways.

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Highest levels of microplastics found in molluscs, new study says

Photo, posted September 3, 2007, courtesy of Andrew Malone via Flickr.

Earth Wise is a production of WAMC Northeast Public Radio.

Climate Change And Global Fisheries

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A Rutgers University-led study published in the journal Science has shown that climate change has taken a toll on many of the world’s fisheries and that over fishing has magnified the problem.

Seafood has become an increasingly important source of nourishment as the global population grows, especially in coastal, developing countries where it provides as much as half of the animal protein eaten.  More than 50 million people worldwide work in the fisheries industry or subsist on fisheries.

Scientists at Rutgers and the National Oceanic and Atmospheric Administration studied the impact of ocean warming on 235 populations of 124 species in 38 ecological regions around the world.  Species included fish, crustaceans such as shrimp, and mollusks such as scallops.  They combined data on fisheries with ocean temperature maps to estimate temperature-driven changes in the sustainable catch over 8 decades.  The data covered about one-third of the global catch.

According to the study, ocean warming has led to an estimated 4.1% drop in sustainable catches, on average around the world, for many species of fish and shellfish from 1930 to 2010.  In five regions that include the East China Sea and the North Sea, the estimated decline was 15 to 35%.

The researchers recommend that fisheries managers eliminate over fishing, rebuild fisheries, and account for climate change in fisheries management decisions.  Over fishing provides a one-two punch to fisheries facing warming waters.   It not only makes fisheries more vulnerable to ocean warming but continued warming will also hinder efforts to rebuild over fished populations.

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Climate Change Shrinks Many Fisheries Globally, Rutgers-Led Study Finds

Photo, posted April 23, 2011, courtesy of Derek Keats via Flickr.

Earth Wise is a production of WAMC Northeast Public Radio.

WAMC Northeast Public Radio

WAMC/Northeast Public Radio is a regional public radio network serving parts of seven northeastern states (more...)