ocean bottom

Biodiversity And Trawling Bans | Earth Wise

June 7, 2021 By EarthWise Leave a Comment

Trawling is a method of commercial fishing that involves pulling or dragging a fishing net – called a trawl – through the water or across the seabed in hopes of catching fish. Commercial fishing companies favor towing trawl nets because large quantities of fish can be caught in one go.

However, the trouble with trawling is that it’s destructive to the seafloor and indiscriminate in what it catches. When towing these large trawl nets, the largest of which is reportedly big enough to catch thirteen 747 jets, everything that happens to be in the way gets caught. As a result, trawling results in lots of bycatch, a fishing industry term used to describe the deaths of non target species during the process.

In 2012, the Hong Kong government implemented a territory-wide trawling ban in its waters in hopes of rehabilitating the marine benthic habitat. The benthic zone refers to the ecological region at the bottom of the ocean.

Researchers from City University of Hong Kong collected sediment samples from 28 locations six months before the trawl ban and two and a half years after the trawl ban to see whether such interventions can facilitate ecosystem recovery.

According to the study, which was recently published in the journal Communications Biology, the ban on trawling significantly improved marine biodiversity. The researchers observed substantial increases in the richness of species and the abundance of benthic marine organisms following the trawling ban. And since small benthic organisms are the main source of food for large species like fish and crabs, the trawling ban actually helps support fisheries.

More governments should consider a trawl ban to promote sustainable fisheries and marine biodiversity conservation.

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Research confirms trawl ban substantially increases the abundance of marine organisms

Photo, posted December 4, 2018, courtesy of John via Flickr.

Earth Wise is a production of WAMC Northeast Public Radio.

Even The Deep Sea Is Warming | Earth Wise

November 17, 2020 By EarthWise Leave a Comment

Approximately 75% of the area covered by ocean is deep, dark, and cold. This is known as the deep sea. But even in these remote regions of the planet things are heating up.

According to a new study published in the journal Geophysical Research Letters, researchers analyzed a decade of hourly temperature readings at four depths in the Atlantic Ocean’s Argentine Basin, off the coast of Uruguay. The research team selected recording depths that would best represent the average depth of the ocean, which is just over 12,000 feet.

The researchers found that deep sea temperatures fluctuate more than was previously known. They also detected a warming trend at the bottom of the ocean. In fact, all recordings indicated a warming trend of 0.02 to 0.04 degrees Celsius per decade between 2009 and 2019. This is a significant warming trend in the deep sea because temperature fluctuations are typically measured in thousandths of a degree.

Researchers say this increase is consistent with warming trends in the shallow ocean associated with anthropogenic climate change. However, they say more research is needed to better understand what is driving the warming temperatures in the deep sea.

A better understanding of what is driving these changes could have far-reaching implications. Since oceans absorb a significant amount of the world’s heat, learning about the oceans’ temperature trends could help researchers better understand temperature fluctuations in the atmosphere as well.

The researchers hope their findings will demonstrate the need to survey deep ocean temperatures annually in order to better identify the long-term trends.

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The deep sea is slowly warming

Photo, posted July 1, 2018, courtesy of NOAA Ocean Exploration and Research via Flickr.

Earth Wise is a production of WAMC Northeast Public Radio.

Artificial Reefs As Havens For Marine Predators | Earth Wise

October 28, 2020 By EarthWise Leave a Comment

Climate change, pollution, development and other stresses have accelerated the decline of reef ecosystems across much of the world’s oceans in recent years. Large predators such as sharks, mackerels, barracudas, jacks and others that formerly fed around reefs have had to venture outside their normal migratory routes in search of suitable alternatives.

According to a new study by Duke University, marine predators have taken up residence at shipwrecks and other artificial reefs. The study surveyed 30 sites along the North Carolina coast and found that predator densities were up to five times larger at the 14 artificial reefs surveyed than at the 16 natural reefs in the survey.

Shipwrecks, particularly those that rose between 4 and 10 meters up into the water column, were a big favorite of the fishes. Some of those sites supported predator densities up to 11 times larger than natural reefs or low-profile artificial reefs. The shipwrecks are basically high-rise timeshares in the sea.

The findings of the survey show that artificial reefs can support large predators, supplementing natural reefs if the design and placement of the artificial reefs are appropriate. In addition, when it comes to designing artificial reefs, there appears to be a height advantage. So, reefs either made from sunken ships or at least made to resemble them would be desirable.

Because undersea predators help maintain healthy and sustainable populations of species lower in the food web, providing suitable habitat for the predators is extremely important. Based on the study, it appears that the strategic use of artificial reefs can be an effective way to help counter the increasing loss of natural habitat on the ocean bottom.

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Artificial Reefs Take on a Towering Presence as Havens for Marine Predators

Photo, posted July 29, 2014, courtesy of NOAA Photo Library via Flickr. Photo credit: Flower Garden Banks National Marine Sanctuary

Earth Wise is a production of WAMC Northeast Public Radio.