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Seabird die-off 'has no precedent' – Futurity: Research News

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Why did nearly one million common murres wash ashore dead from California to Alaska in 2015 and 2016? “The blob,” caused this seabird die-off, say researchers.

Although the common murre must eat about half of its body weight in prey each day, common murres are experts at catching the small “forage fish” they need to survive. Herring, sardines, anchovies, and even juvenile salmon are no match for a hungry murre.

“The magnitude and scale of this failure has no precedent.”

So the die-off was unprecedented—both for murres, and across all bird species worldwide. Scientists blame an unexpected squeeze on the ecosystem’s food supply, brought on by a severe and long-lasting marine heat wave known as “the blob.”

Their findings appear in the journal PLOS ONE.

“Think of it as a run on the grocery stores at the same time that the delivery trucks to the stores stopped coming so often,” explains second author Julia Parrish, professor in the University of Washington School of Aquatic and Fishery Sciences. “We believe that the smoking gun for common murres—beyond the marine heat wave itself—was an ecosystem squeeze: fewer forage fish and smaller prey in general, at the same time that competition from big fish predators like walleye, pollock, and Pacific cod greatly increased.”

three rows of 5 dead murres on beach
Common murres washing onto beaches in the Homer, Alaska area were so abundant in early 2016 that COASST beach surveyors were forced to collect and photograph them in batches. (Credit: COASST via U. Washington)

Seabird die-off

Common murres nest in colonies along cliffs and rocky ledges overlooking the ocean. The adult birds, about one foot in length, are mostly black with white bellies, and can dive more than two football fields below the ocean’s surface in search of prey.

Warmer surface water temperatures off the Pacific coast—a phenomenon known as “the blob”—first occurred in the fall and winter of 2013, and persisted through 2014 and 2015. Warming increased with the arrival of a powerful El Niño in 2015-2016. A number of other species experienced mass die-offs during this period, including tufted puffins, Cassin’s auklets, sea lions, and baleen whales. But the common murre die-off was by far the largest any way you measure it.

From May 2015 to April 2016, about 62,000 murre carcasses were found on beaches from central California north through Alaska. Citizen scientists in Alaska monitoring long-term sites counted numbers that reached 1,000 times more than normal for their beaches. Scientists estimate that the actual number of deaths was likely close to one million, since only a fraction of birds that die will wash to shore, and only a fraction of those will be in places that people can access.

Many of the birds that died were breeding-age adults. With massive shifts in food availability, murre breeding colonies across the entire region failed to produce chicks for the years during and after the marine heat wave event, the researchers find.

“The magnitude and scale of this failure has no precedent,” says lead author John Piatt, a research biologist at the US Geological Survey’s Alaska Science Center and an affiliate professor in the University of Washington School of Aquatic and Fishery Sciences. “It was astonishing and alarming, and a red-flag warning about the tremendous impact sustained ocean warming can have on the marine ecosystem.”

Trouble in the food chain

From a review of fisheries studies conducted during the heat wave period, the research team concluded that persistent warm ocean temperatures associated with “the blob” increased the metabolism of cold-blooded organisms from zooplankton and small forage fish up through larger predatory fish like salmon and pollock. With predatory fish eating more than usual, the demand for food at the top of the food chain was unsustainable. As a result, the once-plentiful schools of forage fish that murres rely on became harder to find.

“Food demands of large commercial groundfish like cod, pollock, halibut, and hake were predicted to increase dramatically with the level of warming observed with the blob, and since they eat many of the same prey as murres, this competition likely compounded the food supply problem for murres, leading to mass mortality events from starvation,” Piatt says.

As the largest mass die-off of seabirds in recorded history, the common murre event may help explain the other die-offs that occurred during the northeast Pacific marine heat wave, and also serve as a warning for what could happen during future marine heat waves, the researchers say.

University of Washington scientists recently identified another marine heatwave forming off the Washington coast and up into the Gulf of Alaska.

“All of this—as with the Cassin’s auklet mass mortality and the tufted puffin mass mortality—demonstrates that a warmer ocean world is a very different environment and a very different coastal ecosystem for many marine species,” says Parrish, who is also the executive director of the Coastal Observation and Seabird Survey Team, known as COASST. “Seabirds, as highly visible members of that system, are bellwethers of that change.”

Additional coauthors are from the University of Washington, the US Geological Survey, the US Fish and Wildlife Service, Farallon Institute, International Bird Rescue, Humboldt State University, the National Park Service, NOAA Fisheries, Moss Landing Marine Laboratories, NOAA Greater Farallones National Marine Sanctuary, and Point Blue Conservation Science.

Funding for the work came from the USGS Ecosystems Mission Area, the North Pacific Research Board, the National Science Foundation, and the Washington Department of Fish and Wildlife.

Source: University of Washington

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Lake Huron sinkhole surprise: The rise of oxygen on early Earth linked to changing planetary rotation rate – Phys.org

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A scuba diver observes the purple, white and green microbes covering rocks in Lake Huron’s Middle Island Sinkhole. Credit: Phil Hartmeyer, NOAA Thunder Bay National Marine Sanctuary.

The rise of oxygen levels early in Earth’s history paved the way for the spectacular diversity of animal life. But for decades, scientists have struggled to explain the factors that controlled this gradual and stepwise process, which unfolded over nearly 2 billion years.

Now an international research team is proposing that increasing on the early Earth—the spinning of the young planet gradually slowed over time, making the days longer—may have boosted the amount of oxygen released by photosynthetic cyanobacteria, thereby shaping the timing of Earth’s oxygenation.

Their conclusion was inspired by a study of present-day microbial communities growing under extreme conditions at the bottom of a submerged Lake Huron sinkhole, 80 feet below the water’s surface. The water in the Middle Island Sinkhole is rich in sulfur and low in oxygen, and the brightly colored bacteria that thrive there are considered good analogs for the single-celled organisms that formed mat-like colonies billions of years ago, carpeting both land and seafloor surfaces.

The researchers show that longer day length increases the amount of oxygen released by photosynthetic microbial mats. That finding, in turn, points to a previously unconsidered link between Earth’s oxygenation history and its . While the Earth now spins on its axis once every 24 hours, day length was possibly as brief as 6 hours during the planet’s infancy.

The team’s findings are scheduled for publication Aug. 2 in the journal Nature Geoscience.

Lead authors are Judith Klatt of the Max Planck Institute for Marine Microbiology and Arjun Chennu of the Leibniz Centre for Tropical Marine Research. Klatt is a former postdoctoral researcher in the lab of University of Michigan geomicrobiologist Gregory Dick, who is one of the study’s two corresponding authors. The other co-authors are from U-M and Grand Valley State University.

“An enduring question in the Earth sciences has been how did Earth’s atmosphere get its oxygen, and what factors controlled when this oxygenation took place,” Dick said from the deck of the R/V Storm, a 50-foot NOAA research vessel that carried a team of scientists and scuba divers on a sample-collection trip from the town of Alpena, Michigan, to the Middle Island Sinkhole, several miles offshore.

“Our research suggests that the rate at which the Earth is spinning—in other words, its day length—may have had an important effect on the pattern and timing of Earth’s oxygenation,” said Dick, a professor in the U-M Department of Earth and Environmental Sciences.

The researchers simulated the gradual slowing of Earth’s rotation rate and showed that longer days would have boosted the amount of oxygen released by early cyanobacterial mats in a manner that helps explain the planet’s two great oxygenation events.

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The project began when co-author Brian Arbic, a physical oceanographer in the U-M Department of Earth and Environmental Sciences, heard a public lecture about Klatt’s work and noted that day length changes could play a role, over geological time, in the photosynthesis story that Dick’s lab was developing.

Cyanobacteria get a bad rap these days because they are the main culprits behind the unsightly and toxic algal blooms that plague Lake Erie and other water bodies around the world.

But these microbes, formerly known as blue-green algae, have been around for billions of years and were the first organisms to figure out how to capture energy from sunlight and use it to produce organic compounds through photosynthesis—releasing oxygen as a byproduct.

Masses of these simple organisms living in primeval seas are credited with releasing oxygen that later allowed for the emergence of multicellular animals. The planet was slowly transformed from one with vanishingly small amounts of oxygen to present-day atmospheric levels of around 21%.

At the Middle Island Sinkhole in Lake Huron, purple oxygen-producing cyanobacteria compete with white sulfur-oxidizing bacteria that use sulfur, not sunlight, as their main energy source.

In a microbial dance repeated daily at the bottom of the Middle Island Sinkhole, filmy sheets of purple and white microbes jockey for position as the day progresses and as environmental conditions slowly shift. The white sulfur-eating bacteria physically cover the purple cyanobacteria in the morning and evening, blocking their access to sunlight and preventing them from carrying out oxygen-producing photosynthesis.

But when sunlight levels increase to a critical threshold, the sulfur-oxidizing bacteria migrate back down below the photosynthetic cyanobacteria, enabling them to start producing oxygen.

New theory: Earth's longer days kick-started oxygen growth
This June 19, 2019 photo provided by NOAA Thunder Bay National Marine Sanctuary shows purple microbial mats in the Middle Island Sinkhole in Lake Huron, Mich. Small hills and “fingers” like this one in the mats are caused by gases like methane and hydrogen sulfide bubbling up beneath them. Feel like days are just getting longer? They are and it’s a good thing because we wouldn’t have much to breathe if they weren’t, according to a new explanation for how Earth’s oxygen rich atmosphere may have developed because of Earth’s rotation slowing. Scientists provided evidence for this new hypothesis by lab testing gooey smelly purple bacteria from a deep sinkhole in Lake Huron. Credit: Phil Hartmeyer/NOAA Thunder Bay National Marine Sanctuary

The vertical migration of sulfur-oxidizing bacteria has been observed before. What’s new is that the authors of the Nature Geoscience study are the first to link these microbial movements, and the resultant rates of oxygen production, to changing day length throughout Earth’s history.

“Two groups of microbes in the Middle Island Sinkhole mats compete for the uppermost position, with sulfur-oxidizing bacteria sometimes shading the photosynthetically active cyanobacteria,” Klatt said while processing a core sample from Middle Island Sinkhole microbial mats in an Alpena laboratory. “It’s possible that a similar type of competition between microbes contributed to the delay in oxygen production on the early Earth.”

A key to understanding the proposed link between changing day length and Earth’s oxygenation is that longer days extend the afternoon high-light period, allowing photosynthetic cyanobacteria to crank out more oxygen.

“The idea is that with a shorter day length and shorter window for high-light conditions in the afternoon, those white sulfur-eating bacteria would be on top of the photosynthetic bacteria for larger portions of the day, limiting oxygen production,” Dick said as the boat rocked on choppy waters, moored a couple hundred yards from Middle Island.

The present-day Lake Huron microbes are believed to be good analogs for ancient organisms in part because the extreme environment at the bottom of the Middle Island Sinkhole likely resembles the harsh conditions that prevailed in the shallow seas of early Earth.

Lake Huron is underlain by 400-million-year-old limestone, dolomite and gypsum bedrock that formed from the saltwater seas that once covered the continent. Over time, the movement of groundwater dissolved some of that bedrock, forming caves and cracks that later collapsed to create both on-land and submerged sinkholes near Alpena.

Cold, oxygen-poor, sulfur-rich groundwater seeps into the bottom of the 300-foot-diameter Middle Island Sinkhole today, driving away most plants and animals but creating an ideal home for certain specialized microbes.

Dick’s team, in collaboration with co-author Bopaiah Biddanda of the Annis Water Resources Institute at Grand Valley State University, has been studying the microbial mats on the floor of Middle Island Sinkhole for several years, using a variety of techniques. With the help of scuba divers from NOAA’s Thunder Bay National Marine Sanctuary—which is best known for its shipwrecks but is also home to the Middle Island Sinkhole and several others like it—the researchers deployed instruments to the lake floor to study the chemistry and biology there.

They also brought mat samples to the lab to conduct experiments under controlled conditions.

Klatt hypothesized that the link between day length and oxygen release can be generalized to any given mat ecosystem, based on the physics of oxygen transport. She teamed up with Chennu to conduct detailed modeling studies to relate microbial mat processes to Earth-scale patterns over geological timescales.

The modeling studies revealed that day length does, in fact, shape oxygen release from the mats.

“Simply speaking, there is just less time for the oxygen to leave the mat in shorter days,” Klatt said.

This led the researchers to posit a possible link between longer day lengths and increasing atmospheric oxygen levels. The models show that this proposed mechanism might help explain the distinctive stepwise pattern of Earth’s oxygenation, as well as the persistence of low-oxygen periods through most of the planet’s history.

Throughout most of Earth’s history, atmospheric oxygen was only sparsely available and is believed to have increased in two broad steps. The Great Oxidation Event occurred about 2.4 billion years ago and has generally been credited to the earliest photosynthesizing cyanobacteria. Nearly 2 billion years later a second surge in , known as the Neoproterozoic Oxygenation Event, occurred.

Earth’s rotation rate has been slowly decreasing since the planet formed about 4.6 billion years ago due to the relentless tug of the moon’s gravity, which creates tidal friction.


Explore further

Researchers find oxygen spike coincided with ancient global extinction


More information:
Possible link between Earth’s rotation rate and oxygenation, Nature Geoscience (2021). DOI: 10.1038/s41561-021-00784-3 , www.nature.com/articles/s41561-021-00784-3

Citation:
Lake Huron sinkhole surprise: The rise of oxygen on early Earth linked to changing planetary rotation rate (2021, August 2)
retrieved 2 August 2021
from https://phys.org/news/2021-08-lake-huron-sinkhole-oxygen-early.html

This document is subject to copyright. Apart from any fair dealing for the purpose of private study or research, no
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Astronomers spot light behind a black hole for the first time, reaffirming Einstein's theory of general relativity – TechSpot

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Something to look forward to: An international team of astronomers have observed light from behind a black hole for the first time. Future observatories, like the Advanced Telescope for High Energy Astrophysics (Athena) should provider even higher resolution images with much shorter observation times.1

Led by Stanford University’s Dan Wilkins, the team focused on a black hole that is 10 million times as massive as our sun and located 1,800 million light years away in a galaxy called I Zwicky.

Armed with the European Space Agency’s XMM-Newton and NASA’s NuSTAR space telescopes, the astronomers observed bright flares of X-ray light coming from around the black hole. The X-ray flares echoed off of gas that was falling into the black hole, and as the flares were subsiding, the telescopes were remarkably able to pick up smaller flashes of X-rays that were different “colors.” These were the echoes bouncing off the gas behind the black hole.

“Any light that goes into that black hole doesn’t come out, so we shouldn’t be able to see anything that’s behind the black hole,” Wilkins said. “The reason we can see that is because that black hole is warping space, bending light and twisting magnetic fields around itself,” he added.

The black hole’s gravitational pull is responsible for the warping of space.

This is the first time that astronomers have directly observed light from behind a black hole, and it also matches Einstein’s theory of general relativity, yet again confirming his predictions.

The team’s findings were recently published in the scientific journal Nature.

Image credit Dan Wilkins

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Russian cosmonauts give video tour of module that jolted space station – Euronews

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MOSCOW – Russian cosmonauts have given a video tour of the interior of a research module which briefly threw the International Space Station out of control on Thursday a few hours after docking.

Russian space officials said a software glitch and possible lapse in human attention were to blame for the mishap that caused the entire space station to pitch out of its normal flight position 250 miles above the Earth with seven crew members aboard.

Footage published late on Saturday showed cosmonauts Oleg Novitsky and Pyotr Dubrov opening the hatches and giving a short tour inside the Nauka module, the Russian space agency Roscosmos said.

According to NASA‘s account of Thursday’s incident, the mission flight director immediately declared a spaceflight emergency as engineers on the ground struggled to restore stability to the sprawling research satellite.

NASA and Roscosmos each said that the seven crew members – two Russian cosmonauts, three U.S. astronauts and two others from Japan and France – were never in any immediate danger.

Roscosmos, which this week spoke of plans to launch another Russian module to the station in November, has suffered a series of mishaps and corruption scandals, including during the construction of the Vostochny Cosmodrome in the country’s far east where contractors were accused of embezzling state funds.

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