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Quantifying the Relative Importance of Riverine and Open‐Ocean Nitrogen Sources for Hypoxia Formation in the Northern Gulf of Mexico

Abstract.

"The Mississippi and Atchafalaya River System discharges large amounts of freshwater and nutrients into the northern Gulf of Mexico (NGoM). These lead to increased stratification and elevate primary production in the outflow region. Consequently, hypoxia (oxygen <62.5 mmol/m3), extending over an area of roughly 15,000 km2, forms every summer in bottom waters. [...]"

Source: JGR Oceans
Authors: Fabian Große et al.
DOI: 10.1029/2019JC015230

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Study tests resilience of the Salish Sea to climate change impacts

"What will the ecology of the Salish Sea look like in the year 2095?

It's an important question for millions of people who live along and near the shores of this intricate, interconnected network of coastal waterways, inlets, bays, and estuaries that encompasses Puget Sound in Washington state and the deep waters of southwest British Columbia. A research team from PNNL found that the inner Salish Sea is resilient, and that future response to climate change—while significant—will be less severe than the open ocean. [...]"

Source: phys.org

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Large ‘dead zone’ measured in Gulf of Mexico

Hurricane Barry dampens initial size predictions

"This year’s Gulf of Mexico “dead zone”— an area of low oxygen that can kill fish and marine life — is approximately 6,952 square miles, according to NOAA-supported scientists. The measured size of the dead zone, also called the hypoxic zone, is the 8th largest in the 33-year record and exceeds the 5,770-square-mile average from the past five years. [...]"

Source: NOAA

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Gulf Dead Zone Looms Large in 2019

"In 2019, predictions indicate that the Gulf of Mexico will retain the dubious distinction of having the second-largest low-oxygen dead zone on Earth (the Baltic Sea remains firmly in first place). By the end of the summer, the hypoxic region on the seafloor at the mouth of the Mississippi River is expected to occupy over 22,000 square kilometers—an area the size of the state of Massachusetts. [...]

Source: Earth & Space Science News
Author: Mary Caperton Morton
DOI: 10.1029/2019EO128019

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Exploring the Susceptibility of Turbid Estuaries to Hypoxia as a Prerequisite to Designing a Pertinent Monitoring Strategy of Dissolved Oxygen

Abstract.

"Globally, there has been a decrease in dissolved oxygen in the oceans, that is more pronounced in coastal waters, resulting in more frequent hypoxia exposure for many marine animals. Managing hypoxia requires an understanding of the dynamics of dissolved oxygen (DO) where it occurs. The French coast facing the Bay of Biscay (N-E Atlantic Ocean) hosts at least a dozen tidal and turbid estuaries, but only the large estuaries of the Gironde and the Loire, are subject to a continuous monitoring. [...]"

Source: Frontiers in Marine Science 
Authors: Sabine Schmidt et al.
DOI: 10.3389/fmars.2019.00352

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Yield stability analysis reveals sources of large-scale nitrogen loss from the US Midwest

Abstract.

"Loss of reactive nitrogen (N) from agricultural fields in the U.S. Midwest is a principal cause of the persistent hypoxic zone in the Gulf of Mexico. We used eight years of high resolution satellite imagery, field boundaries, crop data layers, and yield stability classes to estimate the proportion of N fertilizer removed in harvest (NUE) versus left as surplus N in 8 million corn (Zea mays) fields at subfield resolutions of 30 × 30 m (0.09 ha) across 30 million ha of 10 Midwest states. [...]"

Source: Scientific Reports
Authors: Bruno Basso et al.
DOI: 10.1038/s41598-019-42271-1

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Hypoxic volume is more responsive than hypoxic area to nutrient load reductions in the northern Gulf of Mexico – and it matters to fish and fisheries

Abstract.

"While impacts of low oxygen on marine organisms have been reviewed from physiological and ecological perspectives, relating broad population- and ecosystem-level effects to the areal extent of hypoxia (dissolved oxygen concentration below 64 µM, or 2 mg/l) has proven difficult. We suggest that hypoxic volume is a more appropriate metric compared to hypoxic area because volume better integrates the effects of hypoxia on ecological processes relevant to many marine taxa. [...]"

Source: IOP Science
Authors: Donald Scavia et al.
DOI: 10.1088/1748-9326/aaf938

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Home sweet suboxic home: remarkable hypoxia tolerance in two demersal fish species in the Gulf of California

"Extremophiles – organisms that live in extreme environments – invite us to question our assumptions about the requirements for life. Fish, as a group, are thought to be relatively hypoxia intolerant due to their high metabolic requirements (Vaquer‐Sunyer and Duarte 2008); however, the cusk‐eel, Cherublemma emmelas, and the catshark, Cephalurus cephalus, appear to thrive in one of the most extreme low oxygen marine habitats in the world – the Gulf of California. Here, we describe the behavior and habitat of these extraordinary species that live under conditions commonly thought to be uninhabitable by fish. [...]"

Source: Ecology
Authors: Natalya D. Gallo et al.
DOI: 10.1002/ecy.2539

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The case of the missing oxygen: Foster Scholar Kate Hewett studies hypoxia in national marine sanctuaries

"Not every marine scientist has the same origin story. Some are instantly enthralled by the ocean and its many inhabitants at a ripe young age. For others, a lightbulb goes off while sitting in an undergraduate class. Dr. Nancy Foster Scholar Kate Hewett grew up on the islands of Micronesia, but did not consider a career in marine sciences until graduate school. While working as an environmental engineer in Boston, Massachusetts, she decided to go back to school to develop a deeper understanding of the environmental problems she encountered at work. In her classes, the complicated physics associated with coastal zones pulled at Hewett’s engineering heartstrings. [...]"

Source: NOAA

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Volcanic eruptions once caused mass extinctions in the oceans – could climate change do the same?

"All animals, whether they live on land or in the water, require oxygen to breathe. But today the world’s oceans are losing oxygen, due to a combination of rising temperatures and changing ocean currents. Both factors are driven by human-induced climate change.

This process has the potential to disrupt marine food chains. We already know that large hypoxic, or low-oxygen, zones can be deadly. If hypoxia expands in both size and duration, it is possible to cause widespread extinction of marine life, which has happened previously in Earth’s history. [...]"

Source: TheConversation

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