Small changes in oxygen levels have big implications for ocean life

Small changes in oxygen levels have big implications for ocean life

Oceanographers at the University of Rhode Island have found that even slight levels of ocean oxygen loss, or deoxygenation, have big consequences for tiny marine organisms called zooplankton.

Zooplankton are important components of the food web in the expanse of deep, open ocean called the midwater. Within this slice of ocean below the surface and above the seafloor are oxygen minimum zones (OMZs), large regions of very low oxygen. Unlike coastal “dead zones” where oxygen levels can suddenly plummet and kill marine life not acclimated to the conditions, zooplankton in OMZs are specially adapted to live where other organisms — especially predators — cannot. But OMZs are expanding due to climate change, and even slight changes to the low oxygen levels can push zooplankton beyond their extraordinary physiological limits.

“Although the animals in the ocean’s oxygen minimum zone have adapted over millions of years to the very low oxygen of this extreme and widespread midwater habitat, they are living at the very limits of their physiological capability,” said Karen Wishner, a professor of oceanography at URI’s Graduate School of Oceanography and lead author of a new paper on deoxygenation and zooplankton in the Eastern Tropical North Pacific OMZ. “Our research shows that they are sensitive to very small changes in oxygen, and decrease in abundance when oxygen gets just a little bit lower.”

The research team, which this week published their findings in Science Advances, found more natural variability in oxygen levels in the OMZ than previously known. This has a direct effect on the distribution of many types of zooplankton because, as the team discovered, the organisms respond to a less than 1 percent reduction in oxygen levels.

While zooplankton have had millions of years to adapt to conditions in the OMZ, these low oxygen zones may expand rapidly due to climate change, leading to major unanticipated changes to midwater ecosystems. For example, an expansion of the OMZ into shallower waters may make zooplankton more susceptible to predators like fish. If this leads to a zooplankton population crash, it will have impacts all the way up the food chain.

“Further loss of oxygen in ocean waters is predicted in the future as a result of global warming, and these animals may be unable to adapt and persist,” Wishner said. “They are important components of the food web of oceanic ecosystems, and their loss could potentially impact top predators, including whales and commercially important fisheries.”

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What could cause the Mississippi Bight to become hypoxic?

What could cause the Mississippi Bight to become hypoxic?

Coastal regions with low dissolved oxygen (known as hypoxia) can lead to poor water quality and harm regional fisheries. These areas of low dissolved oxygen are expanding and expected to continue growing in coming years due to human impacts on the environment.

A recent article published in Continental Shelf Research explores aspects of the environmental conditions that can potentially lead to hypoxia in the Mississippi Bight region of the northern Gulf of Mexico. This area extends from Apalachicola in Florida to the Mississippi River Delta.

Dr. Brian Dzwonkowski of the Dauphin Island Sea Lab and University of South Alabama worked with several other research groups to synthesize a range of data sets. The article, “Tracking sea surface salinity and dissolved oxygen on a river-influenced, seasonally stratified shelf, Mississippi Bight, northern Gulf of Mexico” was published in September 2018.

Understanding the Dead Zone

The northern Gulf of Mexico is home to the second largest hypoxic zone in the world, also known as the “Dead Zone,” however, there is no part of the country or the world that is immune. Researchers have directly linked the northern Gulf of Mexico “Dead Zone” to discharge from the Mississippi River. The river water delivers excess nutrients to the region and creates a fresher layer of water at the surface that prevents oxygen from reaching the bottom layer. This leads to a depletion of oxygen over the summer season.

The historic and current focus on “Dead Zone” research and management is centered on the Louisiana and Texas shelf region of the northern Gulf of Mexico, a region to the west of the Mississippi Delta.

The Research

Using satellite sea surface salinity data from 2010 to 2016, Dr. Dzwonkowski and his colleagues demonstrated the region to the east of the delta is similarly impacted by river discharge. Accompanying field data from the July of 2016, showed evidence of widespread areas of low bottom dissolved oxygen (and hypoxic conditions in some areas) across the Mississippi Bight region.

As a result, there are potentially large regions of hypoxic and low dissolved oxygen zones that are not included in the yearly estimate of the “Dead Zone.”

Furthermore, the low dissolved oxygen levels observed, as well as the extensive freshwater surface layer, suggest this region is highly susceptible to becoming hypoxic should there be changes to background environmental conditions (e.g., increased ocean warming), regional watershed land use (e.g., coastal urbanization), and/or diversion pathways of the Mississippi River (e.g., increased discharge through spillways).

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Mars may have enough oxygen underneath its surface for life

Mars may have enough oxygen underneath its surface for life


NASA/JPL/Malin Space Science Systems

The possibility of life on Mars has been a tantalizing possibility for years, and recent discoveries have only increased excitement about whether we’ll find life on the red planet. Now, a new study in Nature Geoscience posits that it’s possible that Mars may have enough oxygen to harbor life under its surface.

The team was led by Vlada Stamenković from NASA’s Jet Propulsion Laboratory (JPL), and their findings stemmed from two different discoveries. We know there’s a possibility that there are subsurface lakes of briny water on Mars; one in particular may be located under the Martian polar ice cap. This means there’s a lot of potential for oxygen within these lakes, if they exist.

Back in 2016, the Mars Curiosity rover discovered that Mars may once have had an oxygen-rich atmosphere, but the loss of its magnetic field meant that the bulk of its surface oxygen escaped. However, there is still oxygen within the planet’s rocks which means that it may be present underneath the surface of the planet.

Given both these discoveries, the JPL-led team took a look at how much oxygen could exist in these subsurface briny lakes, and whether it would be enough to support life. The team found that it was indeed possible, especially in the polar regions because the lower temperatures in these regions means that it’s easier for oxygen to enter these briny lakes.

There are a lot of caveats and unknowns with this research — after all, the existence of these briny subsurface lakes hasn’t yet been proven. But it’s the next step forward in showing how life could exist on the red planet, given what we think we know about Mars. What’s more, it also shows us how life could exists on other planets without photosynthesis.

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Weaponizing oxygen to kill infections and disease

Weaponizing oxygen to kill infections and disease

The life-threatening bacteria MRSA can cripple a medical facility since it is resistant to treatment. But scientists report that they are now making advances in a new technique that avoids antibiotics, instead using light to activate oxygen, which wipes out bacteria. The method also could be used to treat other microbial infections, and possibly even cancer.

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Bacteria engineered to create fertilizer out of thin air

Bacteria engineered to create fertilizer out of thin air,

Researchers have created a bacteria that uses photosynthesis to create oxygen during the day, and at night, uses nitrogen to create chlorophyll for photosynthesis. This development could lead to plants that do the same, eliminating the use of some — or possibly all — human-made fertilizer, which has a high environmental cost.

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An ATM that dispenses antioxidants

An ATM that dispenses antioxidants,

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Method of Making Oxygen from Water in Zero Gravity Raises Hope for Long-Distance Space Travel

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One of the main challenges with long-distance space flight is transporting enough oxygen for astronauts to breathe and enough fuel to power complex electronics

— Read more on ScientificAmerican.com

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Oxygen levels on early Earth rose, fell several times before great oxidation even

Oxygen levels on early Earth rose, fell several times before great oxidation even,

Earth’s oxygen levels rose and fell more than once hundreds of millions of years before the planetwide success of the Great Oxidation Event about 2.4 billion years ago, new research shows.

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Further drivers of ocean deoxygenation identified

Further drivers of ocean deoxygenation identified,

Measurements as well as model calculations equally show that the oxygen inventory of the oceans is decreasing. However, the models underestimate this decrease significantly making projections into the future problematic.

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Gulf of Mexico ‘dead zone’ forecasted to exceed the size of Connecticut

Gulf of Mexico ‘dead zone’ forecasted to exceed the size of Connecticut

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Scientists have predicted the dead zone, or area with little to no oxygen in the northern Gulf of Mexico, will become larger than the state of Connecticut by the end of July, according to a new report. While there are more than 500 dead zones around the world, the northern Gulf of Mexico dead zone is the second largest human-caused coastal hypoxic area in the world.

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Five hundred and forty million years ago, during the Cambrian period, life suddenly went nuts. ‘Blossomed’ is far too mild a word: instead, geologists call this sudden diversification an ‘explosion.’ But what exactly sparked the Cambrian explosion?

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Warming, acidification, eutrophication, the loss of oxygen — examples of major changes being observed or expected for the future in coastal zones around the world. These processes are occurring in the Baltic Sea at a much faster pace than in other regions. But the Baltic also provides useful lessons for how negative trends can be reversed by protective measures. Researchers promote the Baltic Sea as a time machine for coastal areas worldwide.

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