19 Sep 2016:
Arctic Sea Ice Extent in 2016 Ties
As Second Lowest in the Satellite Record
Arctic sea ice extent shrank to 1.6 million square miles earlier this month — tying 2016 with 2007 as the second lowest sea ice minimum since satellite records began.
Sea ice extent in September 2016.
The lowest year remains 2012. The new measurements follow a decades-long trend of declining sea ice extent in the Arctic as global temperatures rise. According to NASA
, “September Arctic sea ice is now declining at a rate of 13.4 percent per decade, relative to the 1981 to 2010 average.” The ten lowest sea ice extents have all happened in the last ten years
. Since 2016 is considered likely to be the warmest year on record, scientists had anticipated an even worse year for sea ice. But “unusually cool, cloudy conditions” in the region for much of the summer helped reduce ice melt, the National Oceanic and Atmospheric Administration said
15 Sep 2016:
Obama Announces First
Marine Protected Area off U.S. East Coast
President Obama is creating a 4,913-square-mile marine monument off the New England coast, adding to a long list of marine protected areas established in recent years by the Obama and Bush administrations. The Northeast Canyons and Seamounts Marine National Monument, 130 miles southeast of Cape Cod, contains massive undersea canyons and towering seamounts and is the first fully protected federal marine reserve off the eastern seaboard. The area is home to deep-sea corals, sharks, deep-diving marine mammals, whales, and sea turtles, and is a rich fishing ground. The fishing industry objected to the creation of the marine monument, arguing that existing fisheries management laws were sufficient to protect the area. Under the new designation, commercial fishing will be phased out over seven years. Obama has also recently created massive marine reserves off Hawaii and the U.S. West Coast, and today a quarter of U.S. waters are under strong federal protection.
12 Sep 2016:
Dolphins Speak in Ways Similar
To Human Conversation, Finds New Study
Dolphins communicate in a way very similar to how humans talk, saying up to five complex “words” in a sentence and pausing to listen to each other before speaking, according to a new study
. Researchers at the T. I. Vyazemsky Karadag Scientific Station in Russia observed the conversation
in two Black Sea bottlenose dolphins, known as Yasha and Yana. “The dolphins took turns producing pulse packs [words and phrases] and did not interrupt each other, which gives reason to believe that each of the dolphins listened to the other's pulses before producing its own,” the scientists wrote in the study. “This language exhibits all the design features present in human spoken language, [indicating] a high level of intelligence and consciousness in dolphins.”
02 Sep 2016:
Scientists Have Found
Another Massive Reef In Australia
Scientists have discovered a massive, deepwater reef
along the outer edge of the Great Barrier Reef in northeastern Australia. The newly charted,
A newly mapped bioherm reef in Australia.
1.5 million-acre marine ecosystem contains thousands of donut-shaped rings known as bioherms, built by the green algae Halimeda
, each of which measure 650 to 1,000 feet across and 66 feet thick. Scientists have known the rings were there since the 1970s, but had no idea how extensive the reef was, said Robin Beaman
, a marine geologist at James Cook University and one of the co-authors of the research. Using LiDAR surveying technology, the Australian scientists found the bioherm reef is three times larger than previously estimated. The structures have likely been built over the past 10,000 years, the scientists said, and will provide clues on how the environment has changed over that time. The research was published in the journal Coral Reefs
24 Aug 2016:
How Elephant Seals Are
Helping Scientists Study Climate Change
A group of southern elephant seals is helping scientists monitor
how climate change is impacting Antarctica by tracking water temperature, depth, and salinity as they swim and dive around the frozen continent.
An elephant seal wearing a data tracker.
Most recently, data from the seals — which routinely dive to depths of 1,000 to 2,000 feet — showed that water melting off the Antarctic ice sheet is causing the surrounding seas to become less salty, disrupting a conveyor belt-like system that transfers heat and nutrients around the globe. The new findings were published this week in the journal Nature Communications
. The elephant seal data, as well as records from monitoring devices on other marine mammals, have generated more than 500,000 vertical profiles of temperature and salinity in the world’s oceans and helped inform nearly 100 scientific studies. “"At the moment it's all about filling gaps” in the environmental records, lead author Guy Williams of the University of Tasmania told the Australian Broadcasting Corporation
. “The [seals] have gone to areas where we've never had an observation before."
18 Aug 2016:
Urine From Large Fish Critical
To Reef Health—And Fishing Is Reducing It
Studies have shown that large fish such as grouper, snapper, and barracuda release key nutrients essential for healthy coral reefs through their urine and body tissue.
A barracuda swims along a Caribbean coral reef.
Now, new research in Nature Communications
has found that in areas where fishing occurs, nearly half of these nutrients are missing from the reefs, threatening their well-being. The study was conducted by four U.S. scientists, who surveyed 143 fish species at 110 sites across 43 Caribbean coral reefs, with varying levels of fishing activity, from marine preserves where anglers are banned to heavily fished reefs. “This study is useful to understand alternative ways fishing is affecting coral reef ecosystems,” said Jacob Allgeier
, an ecologist at the University of Washington and lead author of the new study. “Simply stated, fish biomass in coral reefs is being reduced by fishing pressure. If biomass is shrinking, there are fewer fish to pee.”
15 Aug 2016:
Researchers Discover Ocean
Crust Dating Back 340 Million Years
Scientists have found what they believe is the world’s oldest piece of ocean floor — dating to more than 300 million years ago — in the Mediterranean Sea.
The Herodotus Basin in the eastern Mediterranean Sea.
Because shifting tectonic plates continuously drag seafloor rock into the earth’s mantle, most ocean crust is younger than 200 million years. The new discovery, found in the Herodotus Basin between Cyprus, Crete, and Egypt, indicates that area of seafloor is likely a remnant of the Tethys Ocean, which existed at the time of the Pangaea supercontinent, according to a new study in the journal Nature Geoscience
. To determine the rock’s age, scientists dragged a magnetometer
behind a research vessel on four different trips, measuring the magnetic signals in the underlying seafloor, and comparing them to signals of the African continental plate and the earth’s shifting magnetic alignment over millions of years. They determined that the oceanic crust in the Herodotus Basin is between 315 and 365 million years old.
11 Aug 2016:
Shipping Noise Causes Whales
To Dive More Slowly and Forage Less
Ocean noise caused by shipping can cause humpback whales to dive more slowly and forage less frequently, according to new research
in the journal Biology Letters
A humpback whale diving.
A team of U.S. and U.K. researchers tagged 10 humpbacks in Stellwagen Bank National Marine Sanctuary, off the coast of Massachusetts, with devices that simultaneously tracked the whales’ movements and underwater noise. They found that as ship noise increased
, the whales dove 15 percent more slowly and did one-third fewer side-roll feedings, a foraging technique humpbacks use to catch fish near the seafloor. The findings are the latest addition to a growing list of negative impacts
from ocean noise on marine mammals, including disrupted communication, higher stress levels, and increased vulnerability as acoustic pollution masks predator movement. “Chronic impacts of even small reductions in foraging efficiency could affect individual fitness and translate to population-level effects on humpback whales,” the scientists wrote.
04 Aug 2016:
UNESCO Moves To Expand
World Heritage Sites Into the Deep Ocean
UNESCO has launched a campaign
to include deep-sea ecosystems in its list of World Heritage Sites. Previously, only sites within national jurisdiction,
A Dumbo octopus in the deep sea.
either on land or close to shore, could be given heritage status and UNESCO protection. But ecosystems within the open ocean, which covers more than half the planet, deserve similar classification, UNESCO says. In a new report, World Heritage in the High Seas: An Idea Whose Time Has Come
, the organization presents five biodiversity hotspots—many of which are at risk from climate change, pollution, over-fishing, and deep-sea mining—worthy of recognition: the Costa Rica Thermal Dome; the White Shark Café, a shark gathering point in the Pacific Ocean; the Sargasso Sea; the Lost City Hydrothermal Field, with its 200-foot carbonate towers, in the Atlantic Ocean; and the Atlantis Bank, a sunken fossil island, in the Indian Ocean.
03 Aug 2016:
Roughly 2 Percent of U.S. Homes
At Risk from Sea Level Rise, Report Finds
Almost 1.9 million homes in the U.S. — roughly 2 percent of the nation’s housing stock, worth $882 billion — could be underwater by 2100 with six feet of sea level rise,
Boston homes at risk of flooding.
according to a new report by Zillow
, an online real estate database. One in eight Florida homes, representing $413 billion in property value, could flood by the end of the century. In Hawaii, one in 10 homes are at risk and in New Jersey, one in 13. The new analysis is based on climate projections and mapping from the National Oceanic and Atmospheric Administration, as well as Zillow’s database of 100 million U.S. properties. It found coastal cities, such as Miami and Honolulu, are particularly vulnerable to sea level rise. More than 1 in 6 Boston homes could be underwater by 2100. These estimates don’t include commercial buildings or government properties.
01 Aug 2016:
Bacteria in Sea Ice Could Play
Role in Mercury Pollution in Oceans
Scientists have discovered bacteria living in Antarctic sea ice that could play a role in mercury contamination of fish, birds, and other marine species.
Antarctic sea ice.
The bacteria, Nitrospina
, can transform mercury found in sea ice — originating from sources such as coal-fired power plants — into the more toxic methylmercury. The heavy metal pollutant—which impacts brain development and can cause mental and physical ailments—accumulates in higher concentrations in marine life as it moves up through the food chain. The findings were published Monday in the journal Nature Microbiology
by scientists at the University of Melborne, the U.S. Geological Survey, and Lawrence Livermore National Lab. John Moreau, a geomicrobiologist at the University of Melbourne who helped lead the study, said in a statement
that the findings beg further study into the sources and behavior of mercury in the oceans, "particularly in a warming climate and when depleted fish stocks means more seafood companies are looking south."
21 Jul 2016:
South Africa’s Great White
Shark Population At Risk of Extinction
South Africa’s great white sharks are at risk of disappearing due to pollution, human interference, and a limited gene pool, according to a new study in the journal Marine Ecology Progress Series
A great white shark.
Scientists from Stellenbosch University spent six years tracking great white populations in Gansbaai, a fishing town and shark hotspot in western South Africa. They estimated there are 350 to 520 great whites remaining along the country’s coastline — 52 percent fewer than previously thought. "The numbers… are extremely low. If the situation stays the same, South Africa's great white sharks are heading for possible extinction," Sara Andreotti, a marine biologist and lead author of the study, said in a statement
. The scientists said shark nets, poaching, habitat encroachment, pollution, and loss of food were all to blame for the sharks’ demise. Low genetic diversity among the remaining sharks would make it difficult for the population to bounce back, they said.
At Ground Zero for Rising Seas,
A TV Weatherman Talks Climate
John Morales is part of a new breed of TV weather forecasters seeking to educate viewers on climate change and the threat it poses.
In South Florida, where porous limestone geology and sea level rise are already causing periodic flooding, he has a rapt audience. The chief meteorologist of the NBC affiliate station in Miami, Morales uses his broadcasts and Twitter feed to tie weather trends in South Florida to the broader influences of climate change. In an interview with Yale Environment 360
, Morales discusses a heartening shift away from climate change skepticism among the nation’s television weather forecasters, the positive public reaction to his discussion of climate change, and the daunting threats facing the Miami area, ranked as one of the regions in the world most vulnerable
to sea level rise.
Read the interview.
13 Jul 2016:
Six Years After BP Spill,
Remaining Oil More Toxic Than Ever To Fish
Six years after the Deepwater Horizon drilling rig spilled nearly three million barrels of crude oil into the Gulf of Mexico, scientists have found that ultraviolet light
is transforming the remaining oil
into a more toxic substance that hinders the development of heart, eye, and brain function in fish. The research, led by scientists at the University of California, Riverside and the University of Miami, exposed embryos and larvae of mahi-mahi from the Gulf of Mexico to what they called weathered (exposed to years of sunlight) and un-weathered oil (taken from the drilling site) from the Deepwater Horizon spill in 2010. Compared to fish exposed to un-weathered oil, the fish exposed to the weathered oil experienced impaired eye and neurological function, reduced heart rates, and a buildup of excess fluid in the heart.
06 Jul 2016:
As Oceans Become More Acidic,
Mussels Could Lose Ability to Hang On
Rising carbon dioxide emissions have caused the world’s oceans to become 30 percent more acidic
since the Industrial Revolution, affecting everything from marine life’s ability to build shells
Trossulus byssus mussels.
to the pH level of fishes’ blood. Now, scientists have discovered that more acidic water also prevents mussels from attaching
to rocks and other surfaces, which could have ramifications on the global food chain, the economy, and ecosystem health. Oceans today have a pH of about 8.1. When the pH drops below 7.6, the adhesive plaque that cements mussels to hard surfaces becomes weaker, according to the new research by scientists at the University of Washington. Unattached mussels are easy prey for predators like crabs, fish, and sea stars. Mussels play an important role in filtering pollutants from waterways. They are also a critical food source for coastal communities, with the industry worth an estimated $1.4 billion.
23 Jun 2016:
Scientists Discover Contagious
Cancer in More Species of Shellfish
Last year, scientists discovered a type of contagious cancer in soft-shell clams in which free-floating cells transmitted the disease from one animal to another.
Now, a team of Columbia University researchers is reporting that contagious cancers in the ocean may be more common than previously thought
and can not only jump from animal to animal, but across species. According to the new study published in Nature, the leukemia-like cancer, known as disseminated neoplasia, has been found in three more species of bivalves: mussels, cockles, and golden carpet shell clams. The cancer cells were genetically distinct from their hosts, indicating they originated elsewhere. Transmissible cancer had previously been found in Tasmanian devils
and dogs, but there’s no indication that humans are at risk. “I would only worry deeply if I was a mollusk,” Stephen P. Goff, a molecular biologist at Columbia University and co-author of the study, told The New York Times
Unable to Endure Rising Seas,
Alaskan Villages Stuck in Limbo
A number of Alaska Native villages have been impacted so severely by sea-level rise and other climate-induced threats, they have decided to relocate.
But there is no U.S. agency designated to help pay for and implement an entire community’s move. Robin Bronen, a senior scientist with The Institute of Arctic Biology
at the University of Alaska, says that’s a huge problem. In an interview with Yale Environment 360
, she explains that because there is no government process to facilitate such relocations, none of these villages have been able to move, despite their resolve to do so. And in a bureaucratic Catch-22, these communities no longer receive the infrastructure repair funds they were once entitled to. Pointing to future sea level rise along U.S. coasts, Bronen says that “if we don't figure out how to create this relocation institutional framework, we're talking about humanitarian crises for millions of people living in the United States.”
Read the interview.
16 Jun 2016:
Some Coral Reef “Bright Spots”
Remain, Despite Devastating Bleaching
After decades of being overfished and mismanaged, and the worst bleaching event on record this year, scientists reported in the journal Nature this week
that there remain some “bright spots” among the world’s coral reefs
Coral reef on the Palmyra Atoll in the Pacific.
– systems that are doing better than anyone expected. The study examined 18 different factors at 2,514 reefs in 46 nations, including water depth, tourism, fishing, and population density. Those systems that were still thriving — defined by the scientists as having more fish than expected — tended to be managed by, and accessible only to, local fishermen and indigenous groups. This included reefs in places like the Solomon Islands, parts of Indonesia, Papua New Guinea, and Kiribati. “There’s been a narrative about local involvement, but it’s often very token,” Joshua Cinner, a research fellow at James Cook University in Australia and lead author of the study, told The Atlantic
. He said there should be more opportunity for “communities to creatively confront their own challenges.”
09 Jun 2016:
Fish Can Recognize Human
Faces, According to One New Study
Fish now join humans, monkeys, primates, and birds as one of the few animals able to distinguish faces, according to new research published in the journal Scientific Reports
James St. John/Wikimedia
The skill requires a sophisticated combination of perception and memory
— and generally, a neocortex. But scientists at the University of Oxford in England and the University of Queensland in Australia were able to train archerfish to recognize human faces, despite the fact that these tropical fish don’t have complex brain structures. Archerfish typically feed by spitting water at prey, like insects. So the scientists taught the fish to spray water at images of particular human faces in exchange for food. Archerfish identified the correct person 81 percent of the time.
08 Jun 2016:
Sea Ice Hits New Spring Low
In the Arctic, Says Federal Agency
Sea ice extent in the Arctic hit a new record spring low last month, measuring 537,000 square miles below average — an area twice the size of Texas, the National Snow and Ice Data Center announced this week
Sea ice breaking up in the Beaufort Sea in May.
Last month’s Arctic sea ice extent was the lowest May sea ice measurement since satellite monitoring began 38 years ago and follows a string of record low ice this winter. “We didn’t just break the old May record, we’re way below the previous one,” NSIDC Director Mark Serreze told Climate Central
. The Arctic’s snow cover also hit record lows this year, with April having the lowest snow cover for that month on record and May the fourth lowest. The Arctic has warmed twice as fast as the rest of the world in recent decades, but scientists say that this year’s strong El Niño in the Pacific Ocean could be ramping up temperatures even more. Temperatures at the pole have been 4 to 11 degrees F above average
this winter. “Will we end up with very low sea ice extent this September?” Serreze said. “I think pretty much absolutely.”
06 Jun 2016:
Fish Choose Plastic Over
Zooplankton in Polluted Waters
Fish that grow up in waters full of plastic particles develop a taste for trash, choosing to eat plastic over zooplankton, their natural food source, according to a study published in the journal Science
The research, by ecologists at Uppsala University in Swedish, found larval perch from the Baltic Sea exposed to microplastic pollution (less than 5mm in size) had stunted growth, were less active, ignored the smell of predators, and experienced increased mortality rates. Plastic pollution has become a major problem in the world’s oceans, but scientists are just beginning to understand how these fragments can affect the health of marine species. “If early life-history stages of other species are similarly affected by microplastics, and this translates to increased mortality rates, the effects on aquatic ecosystems could be profound,” said ecologist Oona Lönnstedt
, lead author of the study.
03 Jun 2016:
Increasing Hurricane Damage
Could Strain U.S. Emergency Relief Budget
As hurricane season in the U.S. officially got underway this week, federal financial experts warned that damage from tropical storms will “increase significantly in the coming decades” due to human-driven climate change, and that such a trend could threaten the national emergency relief budget.
New Jersey National Guard
“Over time, the costs associated with hurricane damage will increase more rapidly than the economy will grow,” the report from the U.S. Congressional Budget Office states
. Right now, damage from hurricanes amounts to 0.16 percent of the U.S. GDP, or about $28 billion. As sea levels rise, intense storms become more frequent, and coastal development continues, the report estimates this share could reach .25 percent ($45 billion in today’s economy) by 2075. The federal agency suggested that one way to cut costs is “a coordinated effort to significantly reduce global emissions.”
19 May 2016:
Brewing Company Creates
Edible Six-Pack Rings to Save Wildlife
Plastic six-pack rings have long been a nuisance to wildlife and ecosystems, fouling oceans and shorelines, and entangling and choking wildlife.
Now, a brewery in Florida has developed an edible version from the byproducts of making beer
, including wheat and barely. If not eaten by marine creatures, the six-pack ring biodegrades. Saltwater Brewery
3-D printed 500 of the holders in April and plans to scale up production to package all of its 400,000 cans of beer per month in the edible rings. The material is just as strong as traditional plastics, the brewery says, but is more expensive. The price would drop, however, as more companies use the edible rings, the brewery said. “We want to influence the big guys,” Chris Goves, president of Saltwater Brewery, said in a video about the new project. “And hopefully inspire them to get on board.”
17 May 2016:
Norwegian Company Building
The World’s Largest Floating Wind Farm
Scotland is about to get the world’s largest floating wind farm, with five 6-megawatt turbines bobbing 15 miles offshore in the North Sea.
The project—which is being developed by Statoil, a Norwegian energy company—marks a shift in offshore wind technology. Most ocean-based turbines to date have been rooted to the sea floor by concrete and steel foundations, similar to oil and gas rigs. But this design limits the projects to shallower waters. Statoil’s floating turbines, known at Hywind, consist of a steel cylinder filled with ballast water and stones, and are tethered to the sea floor by a series of cables. The company, which was granted a lease to build the wind farm this week
, will install the Scotland project in water more than 300 feet deep. The plan is for the wind farm to start generating electricity by the end of 2017.
09 May 2016:
Pacific Northwest Starfish Seem
Set for Comeback After Deadly Disease
Two years after a virus devastated colonies of starfish
along the U.S. west coast, the population is showing early signs of a comeback, at least in some areas.
The number of juveniles in the Pacific Northwest is “off the charts,” said Bruce Menge
, a marine biologist at Oregon State University. “Higher than we’d ever seen — as much as 300 times normal,” Menge said. Young starfish usually have to compete with adults for food. But with up to 84 percent of the adult population wiped out from an outbreak of “sea star wasting disease” two years ago, juveniles have had abundant resources to thrive, Menge and his colleagues reported in a recent PLOS ONE
journal. However, the researchers warn starfish populations aren’t entirely in the clear. “Whether they can make it into adulthood and replenish the population without succumbing to sea star wasting disease is the big question,” Menge said in a statement.
03 May 2016:
A Sea Urchin's Mouth Could
Make it Easier to Study Distant Planets
Sea urchins have long inspired awe among scientists for their ability to chew through almost anything, from entire kelp forests to rocks. Their mouths — comprised of a ring of intricate muscles and five curved, pointed teeth —
UC San Diego
operate like a giant claw in an arcade game. Now scientists have designed a new space-exploration device based on the urchins’ teeth
that will make it easier to collect sediment samples on other planets, like Mars. “Our goal was a bio-inspired device that's more precise and efficient at grabbing ground samples, and won't disturb the surrounding area like a shovel" — the tool space vehicles like the Mars rovers currently use, said
Michael Frank, an engineer at the University of California, San Diego. The technology, based on 3D scans of pink sea urchins, has five claws with beveled edges that gather and trap material in a smooth, quick motion.
28 Apr 2016:
Half of All Farmed Fish Have
Deformed Ear Bones That Cause Hearing Loss
Farmed fish have become an increasingly larger share of the world’s seafood market in recent decades—now accounting for 50 percent of global seafood consumption.
At the same time, however, debate about the ethics, safety and health of farmed fish versus their wild counterparts has also intensified. A new study
published in the journal Nature Scientific Reports
finds that half of all farmed Atlantic salmon have deformed ear bones that lead to hearing loss. These salmon are 10 times more likely to have the deformity than wild fish. The findings “raise questions about the welfare of farmed animals," said
Tim Dempster, a biologist at the University of Melbourne involved in the study. It may also explain why efforts to boost wild populations by releasing farmed juveniles have proven unsuccessful. Hearing loss would prevent farmed fish from detecting predators, or restrict their ability to navigate to breeding sites, the scientists said.
From Mass Coral Bleaching,
A Scientist Looks for Lessons
Twice a year, Georgia Tech climate scientist Kim Cobb travels to Christmas Island in the middle of the Pacific Ocean to collect samples from coral reefs to better understand past and future climate change.
But when Cobb arrived on the island earlier this month, she was stunned. The corals she had spent the past 18 years studying were largely dead or dying. The scene has become a familiar one across the Pacific and Indian oceans this year as a record-breaking El Niño drove up water temperatures and caused fragile coral reef systems to bleach from stress or die. In an interview with Yale Environment 360
, Cobb talked about the recent bleaching event, the race to make reefs more resilient, and how coral records could improve short-term climate projections. “What you think reefs might be experiencing in 20 years,” she says, “they're experiencing now.” Read the interview.
20 Apr 2016:
Entries Invited for Third
Annual Yale Environment 360 Video Contest
The third annual Yale Environment 360
Video Contest is now accepting entries. The contest honors the year's best environmental videos. Submissions must focus on an environmental issue or theme, have not been widely viewed online, and be a maximum of 15 minutes in length. Videos that are funded by an organization or company and are primarily about that organization or company are not eligible. The first-place winner will receive $2,000, and two runners-up will each receive $500. The winning entries will be posted on Yale Environment 360
. The contest judges will be Yale Environment 360
editor Roger Cohn, New Yorker
writer and e360
contributor Elizabeth Kolbert, and documentary filmmaker Thomas Lennon. Deadline for entries is June 10, 2016. Read More.
12 Apr 2016:
Scientists Reimagine The
Tree of Life With New Microbe Knowledge
Following years of intense exploration and research into the microbial world, scientists have reimagined the tree of life
—the iconic visual representation of the living world first proposed by Charles Darwin in 1859.
The new tree of life.
The project was led by researchers at the University of California, Berkeley, who over the last decade have been gathering DNA from across the globe—from everywhere from meadow soils and river mud to deep sea vents—to reconstruct genomes and describe thousands of new microbial species. Curious how their findings fit into the tree of life, the scientists used a supercomputer
to visualize how more than 3,000 new and known species related to one another. They discovered that eukaryotes, the group that includes humans, exist on a thin twig compared to the microbial branch of the tree. “The tree of life as we know it has dramatically expanded due to new genomic sampling of previously enigmatic or unknown microbial lineages,” the authors wrote