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Is life in the open ocean homogenously spread?

Is life in the open ocean homogenously spread?


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Obviously around land masses or in shallow water where reefs and coral may grow, life is diverse and numerous. But how spread out is sea life in the open ocean (for example, half-way between Hawaii and California) where there is no land mass or shallow depths for hundreds or thousands of miles?

Does life exist in clusters with large swaths of oceanic desert in between or is it relatively homogenously spread?


This is sort of a partial answer, but here is a map using chloryphyl density to map the global distribution of marine life. As you would expect, most is clustered around costal regions, but you can also see some pretty distinct zones in open ocean, with more primary production apparently in the northern and southern latitudes. Not sure how much this map projection distorts apparent distances, but it should help give you an idea.

Here's where I found this map.

And here's one of the links they references, which looks to have some more resources to explore.


An ancient 'Great Leap Forward' for life in the open ocean

It has long been believed that the appearance of complex multicellular life towards the end of the Precambrian (the geologic interval lasting up until 541 million years ago) was facilitated by an increase in oxygen, as revealed in the geological record. However, it has remained a mystery as to why oxygen increased at this particular time and what its relationship was to 'Snowball Earth' – the most extreme climatic changes the Earth has ever experienced – which were also taking place around then.

This new study shows that it could in fact be what was happening to nitrogen at this time that helps solve the mystery.

The researchers, led by Dr Patricia Sanchez-Baracaldo of the University of Bristol, used genomic data to reconstruct the relationships between those cyanobacteria whose photosynthesis in the open ocean provided oxygen in quantities sufficient to be fundamental in the development of complex life on Earth.

Some of these cyanobacteria were also able to transform atmospheric nitrogen into bioavailable nitrogen in sufficient quantities to contribute to the marine nitrogen cycle, delivering 'nitrogen fertiliser' to the ecosystem.

Using molecular techniques, the team were able to date when these species first appeared in the geological record to around 800 million years ago.

Dr Sanchez-Baracaldo, a Royal Society Dorothy Hodgkin Research Fellow in Bristol's Schools of Biological and Geographical Sciences said: "We have known that oxygenic photosynthesis – the process by which microbes fix carbon dioxide into carbohydrates, splitting water and releasing oxygen as a by-product – first evolved in freshwater habitats more than 2.3 billion years ago. But it wasn't until around 800 million years ago that these oxygenating cyanobacteria were able to colonise the vast oceans (two thirds of our planet) and be fertilised by enough bioavailable nitrogen to then produce oxygen – and carbohydrate food – at levels high enough to facilitate the next 'great leap forward' towards complex life.

"Our study suggests that it may have been the fixing of this nitrogen 'fertiliser' in the oceans at this time that played a pivotal role in this key moment in the evolution of life on Earth."

Co-author, Professor Andy Ridgwell said: "The timing of the spread in nitrogen fixers in the open ocean occurs just prior to global glaciations and the appearance of animals. Although further work is required, these evolutionary changes may well have been related to, and perhaps provided a trigger for, the occurrence of extreme glaciation around this time as carbon was now being buried in the sediments on a much larger scale."

Dr Sanchez-Baracaldo added: "It's very exciting to have been able to use state of the art genetic techniques to help solve an age-old mystery concerning one of the most important and pivotal moments in the evolution of life on Earth. In recent years, genomic data has been helping re-tell the story of the origins of life with increasing clarity and accuracy. It is a privilege to be contributing to our understanding of how microorganisms have contributed to make our planet habitable."


Summary

Ocean currents have many profound impacts on marine life, moving not only animals and plants around the ocean but also redistributing heat and nutrients. While some of these impacts have been well known for many decades, there have been major recent developments in this area. Biologists are increasingly collaborating with physical oceanographers. At the same time, methods to accurately predict ocean currents and their variability have improved over a broad range of spatial and temporal scales. Emerging from these initiatives is an understanding of how currents impact the connectivity of marine populations, how they influence the migration of strong swimmers, including whales and turtles, and how changing currents, as part of global climate change, may re-shape entire communities.


Marine Communities

Download and print these marine community illustrations to learn about the organisms that live in different ocean environments.

Biology, Earth Science, Oceanography

This set of marine community illustrations can be used as visual aids during formal or informal instruction while teaching about the marine realm. There are three versions of each illustration:

  • unlabeled illustration
  • titled, unlabeled illustration
  • titled, labeled illustration

The three different versions were created in order to provide materials that best suit the needs of any educational situation.

Different areas of the ocean can be classified as different types of marine ecosystems. An ecosystem is defined as "a community and the interactions of living and nonliving things in an area." Marine ecosystems have distinct organisms and characteristics that result from the unique combination of physical factors that create them. Marine ecosystems include: the abyssal plain (areas like deep sea coral, whale falls, and brine pools), polar regions such as the Antarctic and Arctic, coral reefs, the deep sea (such as the community found in the abyssal water column), hydrothermal vents, kelp forests, mangroves, the open ocean, rocky shores, salt marshes and mudflats, and sandy shores.

The hydrosphere connects all freshwater and saltwater systems. Salinity, or high salt content, and global circulation make marine ecosystems different from other aquatic ecosystems. Other physical factors that determine the distribution of marine ecosystems are geology, temperature, tides, light availability, and geography.

Some marine ecosystems are very productive. Near-shore regions, including estuaries, salt marshes, and mangrove forests, teem with life. Others, like the abyssal plain at the bottom of the ocean, contain pockets of life that are spread far apart from one another. Some marine ecosystems, like the deep sea, are in constant darkness where photosynthesis cannot occur. Other ecosystems, like rocky shores, go through extreme changes in temperature, light availability, oxygen levels, and other factors on a daily basis. The organisms that inhabit various marine ecosystems are as diverse as the ecosystems themselves. They must be highly adapted to the physical conditions of the ecosystem in which they live. For example, organisms that live in the deep sea have adapted to the darkness by creating their own light source—photophores are cells on their bodies that light up to attract prey or potential mates. Many parts of the ocean remain unexplored and much still remains to be learned about marine ecosystems.


Why Are Marine Environments Important?

Marine environments are crucial to the entire planet for several reasons. Firstly, although estimates vary it is widely agreed that marine photosynthesizers, most notably tiny phytoplankton, create over 50 percent of the globe’s oxygen. This means that the health of these ocean organisms is integral to the continued breathability and temperature of the Earth they also sequester carbon dioxide, the greenhouse gas, during photosynthesis. When these ecosystems are destroyed billions of tons of carbon dioxide are released into the atmosphere, accelerating global heating.

If that was not crucial enough, there are further reasons marine environments are important. They help regulate the planet’s climate and weather systems, and the warming of the oceans may lead to a higher incidence of extreme weather events like hurricanes and tsunamis, which are often deadly, and the El Niño and La Niña weather events which cause starvation in Asian and Pacific countries like Timor Leste.

Degrading marine environments actually endangers the 40 percent of global communities who live on the coast. Ecosystems on coasts, like mangroves, often provide services of flood and storm protection for adjacent human settlements. The destruction of marine environments can wreck people’s livelihoods. This is true for fisherman and tourist industries, like those anchored to marine wonders like the Great Barrier Reef, over half of which has died due to rising ocean temperatures. Even more alarming are those island nations which may be swallowed up as global warming melts the ice caps and ocean levels rise, and many have already had to evacuate their homes to escape the rising ocean, a bleak omen of what could occur if climate change proceeds unchecked.


Oceanic Dead Zones Continue to Spread

More bad news for the world's oceans: Dead zones&mdashareas of bottom waters too oxygen depleted to support most ocean life&mdashare spreading, dotting nearly the entire east and south coasts of the U.S. as well as several west coast river outlets.

According to a new study in Science, the rest of the world fares no better&mdashthere are now 405 identified dead zones worldwide, up from 49 in the 1960s&mdashand the world's largest dead zone remains the Baltic Sea, whose bottom waters now lack oxygen year-round.

This is no small economic matter. A single low-oxygen event (known scientifically as hypoxia) off the coasts of New York State and New Jersey in 1976 covering a mere 385 square miles (1,000 square kilometers) of seabed ended up costing commercial and recreational fisheries in the region more than $500 million. As it stands, roughly 83,000 tons (75,000 metric tons) of fish and other ocean life are lost to the Chesapeake Bay dead zone each year&mdashenough to feed half the commercial crab catch for a year.

"More than 212,000 metric tons [235,000 tons] of food is lost to hypoxia in the Gulf of Mexico," says marine biologist Robert Diaz of The College of William & Mary in Williamsburg, Va., who surveyed the dead zones along with marine ecologist Rutger Rosenberg of the University of Gothenburg in Sweden. "That's enough to feed 75 percent of the average brown shrimp harvest from the Louisiana gulf. If there was no hypoxia and there was that much more food, don't you think the shrimp and crabs would be happier? They would certainly be fatter."

Only a few dead zones have ever recovered, such as the Black Sea, which rebounded quickly in the 1990s with the collapse of the Soviet Union and a massive reduction in fertilizer runoff from fields in Russia and Ukraine. Fertilizer contains large amounts of nitrogen, and it runs off of agricultural fields in water and into rivers, and eventually into oceans.

This fertilizer runoff, instead of contributing to more corn or wheat, feeds massive algae blooms in the coastal oceans. This algae, in turn, dies and sinks to the bottom where it is consumed by microbes, which consume oxygen in the process. More algae means more oxygen-burning, and thereby less oxygen in the water, resulting in a massive flight by those fish, crustaceans and other ocean-dwellers able to relocate as well as the mass death of immobile creatures, such as clams or other bottom-dwellers. And that's when the microbes that thrive in oxygen-free environments take over, forming vast bacterial mats that produce hydrogen sulfide, a toxic gas.

"The primary culprit in marine environments is nitrogen and, nowadays, the biggest contributor of nitrogen to marine systems is agriculture. It's the same scenario all over the world," Diaz says. "Farmers are not doing it on purpose. They'd prefer to have it stick on the land."

In addition to fertilizers, the other primary culprit is the consumption of fossil fuels. Burning gasoline and diesel results in smog-forming nitrogen oxides, which subsequently clear when rain washes the nitrogen out of the sky and, ultimately, into the ocean.

Technological improvements, such as electric or hydrogen cars, could solve that problem but the agricultural question is trickier. "Nitrogen is very slippery it's very difficult to keep it on land," Diaz notes. "We need to find a technology to keep nitrogen from leaving the soil."

Or farmers can reduce the overall amount of nitrogen required by employing new biotechnologies, such as the nitrogen use efficiency (NUE) improvements offered by Arcadia Biosciences. By engineering crops to overexpress a gene that allows roots to absorb more nitrogen, Arcadia scientists have shown that "it's possible for NUE crops to produce the same yield with half as much fertilizer," president and CEO, Eric Rey, says. "In canola, we saw a two-thirds reduction."

Seeds bearing the technology have already been licensed to agricultural giants Monsanto Company and Dupont's Pioneer Hi-Bred International in the case of canola and corn, respectively&mdashand even grass seed from Scotts Miracle-Gro Company may one day employ it. Although field trials over the last four years have proved the genetic changes effectiveness, further testing and government approval means that such crops will not be grown before 2012.

"It's a big economic benefit for farmers if they use only half as much nitrogen as well a big beneficial impact on nitrogen runoff into waterways," says Rey, who hopes that this product will be adopted as quickly as herbicide-resistant crops, which only took five years from introduction in 1998 to become nearly 70 percent of the corn grown in the U.S., and is now nearly 90 percent. "A reasonable expectation is that there would be a dramatic reduction, maybe by 2018."

But that still might not solve the dead zone problem. So much nitrogen is now reaching these coastal waters that much of it ends up buried in sediment, Diaz says, even when new nitrogen sources are removed those sediments release that nitrogen over time, perpetuating the cycle.

That inability to recover is driven not only by the nitrogen buried in the sediment but also by water layers that don't mix with one another, despite the massive flow of rivers like the Mississippi. Instead, warmer, fresher water on the surface sits on top of cooler, denser, saltier water and it takes the energy of multiple powerful hurricanes to blend the two.

For example, as Hurricane Katrina bore down on the Louisiana coast with its powerful winds blowing faster than 130 miles (210 kilometers) per hour, the monstrous tropical storm delivered a benefit: it mixed the warm, oxygen-rich surface waters with the colder, almost oxygen-free waters beneath, dispelling the largest dead zone in the U.S. for a time. Hurricane Rita followed and finished the work, ending early the seasonal dead zone that forms each year at the mouth of the Mississippi.

That dead zone&mdashwhich last year stretched over roughly 8,500 square miles (22,000 square kilometers), an area the size of New Jersey, and is predicted to grow even more extensive in 2008, thanks to the early summer floods&mdashforms because of the rich load of nitrogen and phosphorus the Mississippi carries down from the farm fields of the U.S. Midwest.

Hoping for hurricanes is neither popular nor sensible, so scientists in the Baltic Sea nations, desperate for solutions, are considering so-called geoengineering options: large-scale human interventions into natural systems. In this case, air would be bubbled into some of the smaller bays to assess what happens. "If you look at agricultural ponds, you can aerate them to prevent low oxygen," Diaz says. "But that's a pond. We're talking about open systems with tides. The water doesn't just stay there."

Ultimately, it may take revolutions in agriculture and transportation, along with the energy of hurricanes to bring life back to dead zones. "If you can't mix a dead zone with the energy of a hurricane," Diaz adds, "I don't see how geoengineering is going to do it."


Like a body rising from the dead, biology came back to life around the 1400s. This was the beginning of the Renaissance in Europe. It marked the end of the Early Middle Ages and the start of new learning. Art, books, and science all became popular once again. Biologists during this time focused on learning more about the human body. That meant studying dead ones.

During the Renaissance in Europe, biologists dissected the human body to try to learn about how it works. Click to enlarge.

Dissection was one of the major ways biologists discovered how the body worked. They would put a dead body on a table and slice it open. This way, they could see everything that lets humans run around. Not many people had studied the inside of the human body before. Now they saw veins, nerves, bones, and muscles. Biologists poked around everything. Afterward, they drew pictures of what they found. This helped them understand how it all connected.


Ancient 'Great Leap Forward' for Life in the Open Ocean

It has long been believed that the appearance of complex multicellular life towards the end of the Precambrian (the geologic interval lasting up until 541 million years ago) was facilitated by an increase in oxygen, as revealed in the geological record. However, it has remained a mystery as to why oxygen increased at this particular time and what its relationship was to ‘Snowball Earth’ &ndash the most extreme climatic changes the Earth has ever experienced &ndash which were also taking place around then.

This new study shows that it could in fact be what was happening to nitrogen at this time that helps solve the mystery.

The researchers, led by Dr Patricia Sanchez-Baracaldo of the University of Bristol, used genomic data to reconstruct the relationships between those cyanobacteria whose photosynthesis in the open ocean provided oxygen in quantities sufficient to be fundamental in the development of complex life on Earth.

Some of these cyanobacteria were also able to transform atmospheric nitrogen into bioavailable nitrogen in sufficient quantities to contribute to the marine nitrogen cycle, delivering ‘nitrogen fertiliser’ to the ecosystem.

Using molecular techniques, the team were able to date when these species first appeared in the geological record to around 800 million years ago.

Dr Sanchez-Baracaldo, a Royal Society Dorothy Hodgkin Research Fellow in Bristol’s Schools of Biological and Geographical Sciences said: "We have known that oxygenic photosynthesis &ndash the process by which microbes fix carbon dioxide into carbohydrates, splitting water and releasing oxygen as a by-product &ndash first evolved in freshwater habitats more than 2.3 billion years ago. But it wasn’t until around 800 million years ago that these oxygenating cyanobacteria were able to colonise the vast oceans (two thirds of our planet) and be fertilised by enough bioavailable nitrogen to then produce oxygen &ndash and carbohydrate food &ndash at levels high enough to facilitate the next ‘great leap forward’ towards complex life.

"Our study suggests that it may have been the fixing of this nitrogen ‘fertiliser’ in the oceans at this time that played a pivotal role in this key moment in the evolution of life on Earth."

Co-author, Professor Andy Ridgwell said: "The timing of the spread in nitrogen fixers in the open ocean occurs just prior to global glaciations and the appearance of animals. Although further work is required, these evolutionary changes may well have been related to, and perhaps provided a trigger for, the occurrence of extreme glaciation around this time as carbon was now being buried in the sediments on a much larger scale."

Dr Sanchez-Baracaldo added: "It’s very exciting to have been able to use state of the art genetic techniques to help solve an age-old mystery concerning one of the most important and pivotal moments in the evolution of life on Earth. In recent years, genomic data has been helping re-tell the story of the origins of life with increasing clarity and accuracy. It is a privilege to be contributing to our understanding of how microorganisms have contributed to make our planet habitable."

Publication of press-releases or other out-sourced content does not signify endorsement or affiliation of any kind.


Water world

At the outset of the Late Ordovician event about 450 million years ago, the world was a very different place than it is today or was even in the age of the dinosaurs. The vast majority of life occurred exclusively in the oceans, with plants having just begun to appear on land. Most of the modern-day continents were jammed together as a single super-continent, dubbed Gondwana.

An initial pulse of extinctions began due to global cooling that gripped much of Gondwana under glaciers. By approximately 444 million year ago, a second pulse of extinction then set in at the boundary between the Hirnantian and Rhuddanian geological stages largely – albeit inconclusively – attributed to ocean anoxia. Around 85 percent of marine species vanished from the fossil record by the time the Late Ordovician event ultimately passed.

The Stanford researchers and their study colleagues looked specifically at the second pulse of extinction. The team sought to constrain uncertainty regarding where in Earth’s seas a dearth of dissolved oxygen – as critical for oceanic biology then as it is now – occurred, as well as to what extent and for how long. Prior studies have inferred ocean oxygen concentrations through analyses of ancient sediments containing isotopes of metals such as uranium and molybdenum, which undergo different chemical reactions in anoxic versus well-oxygenated conditions.


‘A Really Bad Time to Be Alive’ – Ocean Deoxygenation Linked to Ancient Die-Off

Researchers present new evidence that the deoxygenation of the ocean wiped out biodiversity during one of the “Big Five” mass extinctions in Earth’s history – relevant information as climate change contributes to decreasing oxygen in the oceans today.

In a new study, Stanford researchers have strongly bolstered the theory that a lack of oxygen in Earth’s oceans contributed to a devastating die-off approximately 444 million years ago. The new results further indicate that these anoxic (little- to no-oxygen) conditions lasted over 3 million years – significantly longer than similar biodiversity-crushing spells in our planet’s history.

Beyond deepening understandings of ancient mass extinction events, the findings have relevance for today: Global climate change is contributing to declining oxygen levels in the open ocean and coastal waters, a process that likely spells doom for a variety of species.

“Our study has squeezed out a lot of the remaining uncertainty over the extent and intensity of the anoxic conditions during a mass die-off that occurred hundreds of millions of years ago,” said lead author Richard George Stockey, a graduate student in the lab of study co-author Erik Sperling, an assistant professor of geological sciences at Stanford’s School of Earth, Energy & Environmental Sciences (Stanford Earth). “But the findings are not limited to that one biological cataclysm.”

The study, published in Nature Communications April 14, centered on an event known as the Late Ordovician Mass Extinction. It is recognized as one of the “Big Five” great dyings in Earth’s history, with the most famous being the Cretaceous-Paleogene event that wiped out all non-avian dinosaurs some 65 million years ago.

Water world

At the outset of the Late Ordovician event about 450 million years ago, the world was a very different place than it is today or was even in the age of the dinosaurs. The vast majority of life occurred exclusively in the oceans, with plants having just begun to appear on land. Most of the modern-day continents were jammed together as a single super-continent, dubbed Gondwana.

An initial pulse of extinctions began due to global cooling that gripped much of Gondwana under glaciers. By approximately 444 million year ago, a second pulse of extinction then set in at the boundary between the Hirnantian and Rhuddanian geological stages largely – albeit inconclusively – attributed to ocean anoxia. Around 85 percent of marine species vanished from the fossil record by the time the Late Ordovician event ultimately passed.

Laminated black shales and cherts exposed on the Peel River, Yukon, Canada, that were deposited during the late Ordovician and earliest Silurian. These sediments show no evidence of organisms living on the seafloor due to anoxic conditions at the seabed. Researchers estimated the global extent of low-oxygen conditions during this time period using new trace metal isotope data and uncertainty modeling. Credit: Erik Sperling

The Stanford researchers and their study colleagues looked specifically at the second pulse of extinction. The team sought to constrain uncertainty regarding where in Earth’s seas a dearth of dissolved oxygen – as critical for oceanic biology then as it is now – occurred, as well as to what extent and for how long. Prior studies have inferred ocean oxygen concentrations through analyses of ancient sediments containing isotopes of metals such as uranium and molybdenum, which undergo different chemical reactions in anoxic versus well-oxygenated conditions.

Elemental evidence

Stockey led the construction of a novel model that incorporated previously published metal isotope data, as well as new data from samples of black shale hailing from the Murzuq Basin in Libya, deposited in the geological record during the mass extinction. The model cast a wide net, taking into account 31 different variables related to the metals, including the amounts of uranium and molybdenum that leach off land and reach the oceans via rivers to settle into the seafloor.

The model’s conclusion: In any reasonable scenario, severe and prolonged ocean anoxia must have occurred across large volumes of Earth’s ocean bottoms. “Thanks to this model, we can confidently say a long and profound global anoxic event is linked to the second pulse of mass extinction in the Late Ordovician,” Sperling said. “For most ocean life, the Hirnantian-Rhuddanian boundary was indeed a really bad time to be alive.”

Effects on biodiversity

The lessons of the past suggest that the deoxygenation increasingly documented in the modern oceans, particularly in the upper slopes of the continental shelves that bracket major landmasses, will put strain on many organism types – possibly to the brink of extinction. “There is no way that low oxygen conditions are not going to have a severe effect on diversity,” Stockey said.

In this way, in addition to shedding light on Earth of a distant yester-eon, the study’s findings could help researchers better model the planet as it is now.

“We actually have a big problem modeling oxygenation in the modern ocean,” Sperling said. “And by expanding our thinking of how oceans have behaved in the past, we could gain some insights into the oceans today.”

Reference: “Persistent global marine euxinia in the early Silurian” by Richard G. Stockey, Devon B. Cole, Noah J. Planavsky, David K. Loydell, Jiří Frýda and Erik A. Sperling, 14 April 2020, Nature Communications.
DOI: 10.1038/s41467-020-15400-y

Co-authors on the study are with the Georgia Institute of Technology, Yale University, University of Portsmouth and Czech University of Life Sciences Prague.

The research was supported by the Alfred P. Sloan Foundation, National Science Foundation, Packard Foundation and NASA.


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