SAN DIEGO, Calif. — Modern DNA testing has helped solve cold cases and reunite long-lost siblings. Now, it’s helping solve mysteries in our ocean.

Scientists at Scripps Institution of Oceanography at UC San Diego, the J. Craig Venter Institute, and the National Oceanic and Atmospheric Administration (NOAA) are using tools of genetics research to evaluate the diversity of marine life in our oceans.

Using a method called metabarcoding, they can now test hundreds to thousands of microscopic organisms at one time. From feeding ecosystems to consuming waste and sequestering carbon, the microbes are essential for the ocean and planet.

The breakthrough technique will help researchers to diagnose conditions at the base of the ocean food web that affects the abundance of commercially important fishes or creates harmful algal blooms. Scientists can also use so-called environmental DNA (eDNA) to evaluate how effectively the oceans can protect the planet from the effects of climate change.

The team reported on the findings in the journal Nature Communications.

RODANTHE, N.C. — The National Park Service says two beach houses have fallen into the waves along North Carolina's coast. The homes, which were unoccupied when they fell into the ocean, were located along Ocean Drive in the Outer Banks community of Rodanthe.

The park service confirmed the collapses on Tuesday and has closed off the areas around the fallen structures. Debris from the first fallen house has spread widely. Officials from the Cape Hatteras National Seashore say they'll be working closely with the homeowner to coordinate cleanup activities. This is the third time a Rodanthe home has fallen into the surf this year.

“Unfortunately, there may be more houses that collapse onto Seashore beaches in the near future,” David Hallac, superintendent of National Parks of Eastern North Carolina, said in a statement obtained by the Associated Press. “We proactively reached out to homeowners along Ocean Drive in Rodanthe after the first house collapse and recommended that actions be taken to prevent collapse and impacts to Cape Hatteras National Seashore.”

The coast of North Carolina is almost entirely made up of narrow, low-lying barrier islands. Hatteras Island is part of what’s known as the Outer Banks.

BUCHAREST, Romania (AP) — Romania's foreign ministry says a tourist has died from a shark attack in Egypt.

It's the second shark attack in Egypt in the past several days.

On Friday, a 68-year-old Austrian woman died after losing an arm and a leg in an attack by a Mako shark while swimming in the Red Sea near the resort town of Hurghada.

Egyptian local media widely reported on the death of a second woman from a shark attack on Sunday.

Incidents with sharks have been relatively rare in Egypt’s Red Sea coastal region in recent years.

In 2010, one European tourist was killed and several others were maimed in a series of shark attacks.

CNN —

Just as Earth's land surface has enormous peaks and valleys, the oceanic world has a similarly varied topography.

Related video above: How Do We Know That the Challenger Deep is the Deepest Part of the Ocean?

Perhaps the most intriguing of these features is the Mariana Trench — a chasm in the western Pacific Ocean that spans more than 1,580 miles and is home to the Challenger Deep, the deepest known point on Earth's underwater surface that plunges more than 36,000 feet down.

That's nearly three times deeper than the site where the wreckage of the RMS Titanic lies in the Atlantic Ocean, and it's deeper than Mount Everest is tall.

Here are some fascinating facts about this deep-sea phenomenon.

1. 'Titanic' director James Cameron is one of the few people who have visited

Few human expeditions have ventured to the Challenger Deep.

The first came in 1960 with the historic dive of the Trieste bathyscaphe, a type of free-diving submersible. During the dive, passengers Jacques Piccard and Don Walsh said they were stunned to see living creatures where scientists once imagined it was impossible for anything to survive.

"Right away, all of our preconceptions about the ocean were blown out the window," Dr. Gene Feldman, an oceanographer emeritus at NASA said. He spent more than 30 years at the space agency.

James Cameron, director of the 1997 film "Titanic," was the next deep-sea explorer to follow. He piloted a submersible — one that he personally had helped design — to about 35,787 feet, setting a world record in 2012.

2. A plastic bag was found in the trench

Another explorer who returned to the site was Victor Vescovo, a Texas investor who journeyed 35,853 feet down and claimed a world record in 2019.

Vescovo gave depressing insight into humankind's impact on these seemingly untouchable remote locations when he observed a plastic bag and candy wrappers at the bottom of the Mariana Trench.

A handful of explorers have trekked to the Challenger Deep since then, but the expeditions are not common — and the journey is extremely dangerous.

For every 33 feet traveled beneath the ocean's surface, the pressure on an object increases by one atmosphere, according to National Oceanic and Atmospheric Administration. An atmosphere is a unit of measure that's 14.7 pounds per square inch. A trip to the Challenger Deep can put a vessel under pressure that is "equivalent to 50 jumbo jets," Feldman noted.

3. It lies in the hadal zone, named for the god of the underworld

Much like the Earth's atmosphere, the ocean can be described in terms of layers.

The uppermost portion is called the epipelagic zone, or the sunlight zone, and extends just 660 feet below the water's surface, according to NOAA.

The mesopelagic zone, or the so-called twilight zone, stretches from the end of the sunlight zone to about 3,300 feet.

Then there's the bathypelagic zone, also called the midnight zone, and, beneath that, the abyssopelagic zone — as in, the abyssal zone — that extends from 13,100 feet to 19,700 feet. That's nearly 4 miles underwater. Within the abyssal zone, few life forms can survive, the water is completely devoid of light, and temperatures are near freezing.

But the Challenger Deep lies even further — in the hadalpelagic zone or the hadal zone. It's named for Hades, the Greek god of the underworld thought to rule over the dead.

4. It's home to unique aquatic life and mud volcanoes

The hadal zone is one of the least explored habitats on Earth. At bone-crushing depths with no sunlight, it was long thought that nothing could survive there.

But that belief has been dispelled.

"Even at the very bottom, life exists. In 2005, tiny single-celled organisms called foraminifera, a type of plankton, were discovered in the Challenger Deep," according to NOAA.

Discoveries at the Challenger Deep have included colorful rocky outcrops and bottom-dwelling sea cucumbers.

A series of undersea mud volcanoes and hydrothermal vents in the Mariana Trench also support unusual life forms, according to NOAA. Despite the highly acidic and infernally hot water produced by hydrothermal vents in mud volcanoes, exotic species, and microscopic organisms there are able to survive.

In the absence of sunlight, the creatures instead benefit from the nutrient-rich waters belched out from hydrothermal vents. The life-supporting medium results from chemical reactions between the seawater and magma rising from beneath the ocean floor.

5. The Mariana Trench was designated as a US national monument in 2009

The Marianas Trench Marine National Monument was established in 2009 in part to protect the rare organisms that thrive within its depths.

Objects of interest include the submerged ecosystem and its life forms, such as deep-sea shrimp and crabs, and — higher up in the water column — stony coral reefs.

"A great diversity of seamount and hydrothermal vent life (is) worth preservation," according to NOAA.

The entire national monument protects about 95,000 square miles.

6. It's difficult to know just how deep the trench goes

The ocean floor remains one of the most mysterious places in the universe.

In fact, "we have better maps of the moon and Mars than we do of our own planet," according to Feldman.

Though people have been exploring the ocean's surface for tens of thousands of years, only about 20% of the seafloor has been mapped, according to 2022 figures from NOAA.

Given the high interest in the Mariana Trench, however, researchers have made several efforts to give increasingly detailed pictures of its features. But that's not easy: Due to the vastness and deepness of the bottommost ocean zone, scientists must rely on sonar, or acoustic, technology to attempt to give a full picture of what's below.

Because instrumentation and technology are constantly improving, the estimated depth of the Challenger Deep has been updated as recently as 2021 to about 35,876 feet.

ANNAPOLIS, Md. — A certain mystique laps upon the shores. Even in the dead of winter on the Chesapeake Bay, there are still plenty of signs of life.

"This time of year, I notice how clear the water is," said Beth McGee, who has spent decades studying the nation's largest estuary.

On the surface, things may look calm here. However, this watershed, which touches six states and spans over 64,000 square miles, is sick.

"All told the bay is still struggling," said McGee, who works for the Chesapeake Bay Foundation.

Every year, the nonprofit gives this waterway a grade based on how healthy it is. This year, it received a D+.

"Climate change is making our restoration efforts more challenging. More severe storms are bringing more pollution into the bay," McGee said.

What’s happening here has become a case study on just how hard it is to clean up and restore vital watersheds and estuaries, as well as reverse the impacts of pollution and global warming even as costly plans are being put in place nationwide to push back against climate change.

Environmentalists first started realizing how polluted the Chesapeake was back in the 1970s. By 2010, government agencies, nonprofits and environmentalists started taking action to clean it up.

"People across the country were saying, 'We need to watch this,' because they are setting themselves up for success. They have plans. They have accountability that no other watershed has had," McGee added.

Thirteen years later, though, progress has been slow.

Across the lower 48 states, there are 78 major watersheds, essentially basins catching water from rivers as they hit the sea. But of the more than 700,000 miles of waterways in the US, nearly 51% are impaired by pollution.

"One hundred years ago, people didn’t give rivers and streams much thought," explained Matt Ehrhart with the Stroud Water Research Center. "Clean fresh water is one of the most vital resources we have."

Ehrhart says that these days, most pollutants in our nation's watersheds come from agriculture. Fertilizers and pesticides used on crops often run off into nearby rivers and streams. There are other causes, like runoff from the road salt we use in the winter.

"It’s critical the way we live on the landscape doesn’t unduly impact those resources," he added.

FIDALGO ISLAND, WA — Hope is a rare term to be applied to the environment these days, but looking off into the horizon, the people who know this land best see a beautiful future in store for coastal communities both here and beyond.

Alana Quintasket and Joe Williams are members of the Swinomish tribe, whose traditions are deeply rooted in coastal life.

Digging for clams and other shellfish is a big part of their identity, as it has been for centuries, but what’s happening on their lands in western Washington is a reflection of what’s happening up, down and across coast lines nationwide.

"Our biologists, our shellfish team have been kind of documenting throughout the Puget Sound. They're noticing a definite decline in that population," said Williams.

The ocean absorbs 30% of the CO2 in the atmosphere. According to the National Ocean and Atmopheric Administration, the excess carbon in the atmosphere has not only led to warmer seas but it changes the ocean’s PH balance, making the water more acidic.

Coastal areas in the country have seen shellfish population drops as large as 85%. Nationally, if nothing changes its predicted that by the end of the century, shellfish populations nationwide will continue to drop by almost half.

"We're under apocalyptic circumstances, where it is a climate crisis and lives are at stake. As indigenous people and indigenous beings of the land, it's our responsibility to do what we can to restore the practices that have been left for us," said Quintasket.

In the face of a crisis, the Swinomish have a plan to restore the shellfish population: build the very clam gardens their ancestors did centuries ago.

In a few weeks, the Swinomish will be building a clam garden, a tough of rocks meant to be the ideal environment for clam and shellfish growth, on a section of coastline. This ancient practice can increase shellfish growth by 400%.

"It's really expanding the area where clams can grow," said Courtney Grenier, a marine ecologist with the Swinomish Tribal Community.

She says while the numbers don’t lie, scientists are still trying to figure out why the clam gardens are so successful.

"It doesn’t have to be confirmed by Western science to acknowledge there has been this technology that has been used and can still be implemented in a way that’s still in harmony with nature," she said.

The Swinomish are not only looking at this as an opportunity to combat climate change, but by making this a community project, they hope to physically reconnect generations after recent history and past tragedies have taken so much.

"Not only are we trying to get through this pandemic to make it an endemic, but we're also thinking of the fear for the climate, and for us to have something to be excited about is just something good for our people," said Quintasket.

As the project is set into motion, the Swinomish hope other coastal communities are listening and watching to see what native practices are already out there that we can use in our collective fight for our environment.

"There are plenty of teachings to help us get through this, this climate change, we just have to pay attention and be at one with our nature," said Williams.

Related video: Glaciers all over the world are melting at a more rapid pace

The National Geographic knows a thing or two about maps: They've been making them since 1915.

Over those 106 years, the famed publication has listed four oceans on Earth — the Atlantic, Pacific, Indian and Arctic. Those maps are now being redrawn.

A fifth ocean has been designated by the magazine: the icy waters surrounding Antarctica below the Earth's southern 60th parallel is officially being named the Southern Ocean.

The move is significant beyond adding one more name for grade school students to remember. The Southern Ocean is fenced from the the northern oceans by a fast current that circles the Earth from west to east around Antarctica in a band centered around a latitude of 60 degrees south.

The waters south of that Antarctic Circumpolar Current are colder and ecologically distinct, the magazine says, making a home for thousands of species that can live nowhere else on Earth.

"The Southern Ocean encompasses unique and fragile marine ecosystems that are home to wonderful marine life such as whales, penguins, and seals," said National Geographic Explorer in Residence Enric Sala said in the announcement.

"Anyone who has been there will struggle to explain what's so mesmerizing about it," Seth Sykora-Bodie, a marine scientist at the National Oceanic and Atmospheric Administration (NOAA) added, "but they'll all agree that the glaciers are bluer, the air colder, the mountains more intimidating, and the landscapes more captivating than anywhere else you can go."

The recognition of the world's fifth ocean, made official on June 8, World Oceans Day, aims to promote conservation in a region where industrial fishing has blighted populations of krill and Patagonian toothfish over the years.

The waters around Antarctica (the Earth's seventh continent) have also been known as the Antarctic Ocean or the Austral Ocean, though the use of Southern Ocean is the most popular in the media and scientific community, and is used by the U.S. Board on Geographic Names and the International Hydrographic Organization and NOAA.

Find the full National Geographic announcement here.