Science and the Sea Podcast

• Big-Beaked Dolphins

  The Franciscana dolphin has quite the schnozz. Its beak is longer in relation to the size of its body than that of any other dolphin or whale—up to 15 percent of the animal’s total length. The Franciscana has another distinction: It’s the only “river dolphin” that doesn’t actually live in freshwater rivers. Instead, it lives in saltwater. It’s found along the coast of South America, from southern Brazil to central Argentina. It’s in bays and estuaries, and up to a few miles out to sea in the Atlantic Ocean. Franciscana dolphins have several other names. The most common is La Plata, for a region of Brazil where it’s abundant. The dolphins are among the smallest of all dolphin species—no more than six feet long, and weighing up to a hundred pounds or so. They’re grayish brown on top, and lighter underneath. As they age, though, they turn gray-white, so fishermen have given them yet another name: “white ghosts.” That’s not just because of their color. Franciscanas move through the water slowly and quietly, perhaps to avoid attracting the attention of killer whales and other predators. But those aren’t their greatest threats. Hundreds of the dolphins are caught in fishing nets every year. Coastal pollution, habitat destruction, and other human activities are also problems. So while no one knows the exact population, Franciscanas are listed as “vulnerable”—threatened by people who can’t keep their own schnozzes out of the dolphins’ business. The post Big-Beaked Dolphins appeared first on Marine Science Institute. The University of Texas at Austin..

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• Harmless Invasion

  A type of damsel fish from the other side of the world has invaded the Gulf of Mexico. But it doesn’t appear to be doing much harm to the fish that were already there—at least not so far. The Regal Damselfish comes from the Indian and western Pacific oceans. It’s only about four inches long, and it lives on coral reefs, in shallow coastal waters. The invader was first seen in the Gulf in 2013. It probably hitchhiked on an oil platform that was moved from the eastern hemisphere. A recent study looked at how the fish spread across the Gulf through 2021. It also looked at how other types of fish fared—especially those that compete with the invaders for resources. Researchers from the University of Texas Marine Science Institute and elsewhere counted the fish found in sections of five reef systems along the coast of Mexico. They then used mathematical models to estimate the total populations of the entire system. The invading damsel fish spread across all the reefs in the study area. At the same time, the populations of its competitors dropped. But so did the populations of some of the other species of fish that don’t compete with the invaders. That suggests that the dip in the number of competing fish had some other cause. One possibility is loss of habitat caused by human activities. One of the reefs in the study is near a busy port that’s growing bigger. So that might be damaging the reefs more than the invasion of the damsel fish. The post Harmless Invasion appeared first on Marine Science Institute. The University of Texas at Austin..

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• Dietary Problems

  The wolves on a small island in Alaska have a diet problem. They’ve wolfed down dangerously high levels of mercury—a result of eating sea otters. Pleasant Island is a mile off the coast of Glacier Bay National Park, in Alaska’s panhandle. Wolves have decimated the island’s population of deer, which used to be their main prey. So the wolves started eating sea otters. In fact, otters now make up about two-thirds of their diet. Biologists have been studying the wolves for years. When a pack member died in 2020, they found that its tissues held extremely high levels of mercury—a nasty toxin. So they compared mercury levels of the island’s wolves to the wolves along the adjacent coastline and in the middle of Alaska. The mainland wolves eat mainly moose and deer. The island wolves have much higher levels of mercury. Some of the levels were the highest ever seen in any wolves anywhere in the world. Mercury builds up in marine organisms. Larger organisms eat lots of smaller ones, allowing the mercury concentration to grow as it moves up the food web. Sea otters are near the top of the web, so they build up a lot of mercury. And when the wolves eat the otters, they get high doses of mercury as well.             The population of sea otters on the coast of Alaska and British Columbia has been increasing. And wolves along the coast appear to be incorporating more otters into their diets. So wolf populations could face greater mercury-contamination problems in the years ahead. The post Dietary Problems appeared first on Marine Science Institute. The University of Texas at Austin..

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• Deep Trash

  In July of 2022, two scientists descended to the Challenger Deep—the deepest spot in the oceans. The first thing they saw on the bottom wasn’t a new species of life or some other exotic wonder. It was a glass beer bottle—sitting seven miles deep. Litter isn’t limited to the giant “garbage patches” on the ocean surface. It’s found on the bottom as well—even in the deepest of all locations. It’s been seen on the floors of all the oceans and seas, including the Arctic and Southern oceans. A recent study, for example, used video cameras to survey a portion of the Calypso Deep—a three-mile-deep spot in the Mediterranean Sea, near Greece. The cameras recorded about 150 items of trash: paper bags and cartons, glass bottles and jars, and lots and lots of plastic—bags, crates, bottles, fishing gear, and more. Based on that sample, researchers calculated the region should average about 70 thousand pieces of trash per square mile. The spots with the highest estimated density of trash yet recorded are a couple of mile-deep canyons in the South China Sea: 135 thousand pieces per square mile. Trash washes out to sea from rivers, is lost from ships, or is deliberately dumped. And it’s a menace to any organisms on the sea floor. It can entangle them, or strangle or poison them if they try to eat it. And with an estimated seven million tons of trash added to the oceans every year, the problem will only get worse in the years ahead. The post Deep Trash appeared first on Marine Science Institute. The University of Texas at Austin..

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• Drowning Marshes

  Here’s an old saying about nature: Drown a salt marsh, drown a coastline. Okay, we made that one up. But it’s true. And you might hear it more in the future because marshes are threatened by rising sea levels. But a team of researchers has developed a way to know that a marsh is in trouble before it vanishes—providing time to preserve and restore threatened systems. Coastal salt marshes offer many benefits. They store carbon, filter the water, and provide habitat for wildlife and fishing grounds for people. And they act as a barrier against storm surges and rising sea level. As sea level rises, they build more extensive root networks that trap more sediments, elevating the entire bed. But when the water level climbs too fast, or stays high for too long, it can drown the roots. So while the vegetation looks healthy, its days are numbered. The researchers developed a computer model that assesses the health of the roots. The model used observations by a satellite and other details. They applied the model to the marshes along the coast of Georgia. And they compared their findings to surveys made on the ground. They found that the root systems had been declining by about one percent per year over most of the study area—even though the amount of the plants above ground had been going up. It takes a while for what’s happening in the roots to show up above ground. So the study provides an early warning—and time to save the marsh, save the coastline. The post Drowning Marshes appeared first on Marine Science Institute. The University of Texas at Austin..

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