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European sea bass show chronic impairment after exposure to crude oil

"The new study tested the capacity of European sea bass to perform not just in typical seawater but also in low-oxygen level sea water. Researchers used a novel integrated respiratory assessment paradigm (IRAP) to screen both the fish's aerobic capacity and tolerance for low-oxygen (hypoxic) levels, grouping the fish into hypoxia tolerant and hypoxia sensitive phenotypic groups. They then exposed the fish to dispersed crude oil for 48 hours. [...]"

Source: Phys.org

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Exposure of European sea bass [...] to chemically dispersed oil has a chronic residual effect on hypoxia tolerance but not aerobic sc

Abstract.

"We tested the hypothesis that the chronic residual effects of an acute exposure of European sea bass (Dicentrarchus labrax) to chemically dispersed crude oil is manifest in indices of hypoxic performance rather than aerobic performance. Sea bass were pre-screened with a hypoxia challenge test to establish their incipient lethal oxygen saturation (ILOS), but on discovering a wide breadth for individual ILOS values (2.6–11.0% O2 saturation), fish were subsequently subdivided into either hypoxia sensitive (HS) or hypoxia tolerant (HT) phenotypes, traits that were shown to be experimentally repeatable. [...]"

Source: Aquatic Toxicology
Authors: YangfanZhang et al.
DOI: 10.1016/j.aquatox.2017.07.020

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Ecophysiological limits to aerobic metabolism in hypoxia determine epibenthic distributions and energy sequestration in the northeast Pacific ocean

Abstract.

"Expansion of oxygen deficient waters (hypoxia) in the northeast Pacific Ocean (NEP) will have marked impacts on marine life. The response of the resident communities will be a function of their ecophysiological constraints in low oxygen, although this remains untested in the NEP due to a lack of integrative studies. Here, we combine in situ surveys and lab-based respirometry experiments were conducted on three indicator species [...] of seasonally hypoxic systems in the NEP to test if metabolic constraints determine distributions and energy sequestration in a hypoxic setting.  [...]"

Source: Limonology and Oceanography
Authors: Jackson W. F. Chu, Katie S. P. Gale
DOI: 10.1002/lno.10370

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Biodiversity response to natural gradients of multiple stressors on continental margins

Abstract.

"Sharp increases in atmospheric CO2 are resulting in ocean warming, acidification and deoxygenation that threaten marine organisms on continental margins and their ecological functions and resulting ecosystem services. The relative influence of these stressors on biodiversity remains unclear, as well as the threshold levels for change and when secondary stressors become important.  [...]"

Source: Proceedings of the Royal Society B
Authors: Erik A. Sperling, Christina A. Frieder, Lisa A. Levin
DOI: 10.1098/rspb.2016.0637

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Meat industry blamed for largest-ever 'dead zone' in Gulf of Mexico

"The global meat industry, already implicated in driving global warming and deforestation, has now been blamed for fueling what is expected to be the worst “dead zone” on record in the Gulf of Mexico.

Toxins from manure and fertiliser pouring into waterways are exacerbating huge, harmful algal blooms that create oxygen-deprived stretches of the gulf, the Great Lakes and Chesapeake Bay, according to a new report by Mighty, an environmental group chaired by former congressman Henry Waxman. [...]"

Source: The Guardian

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Gulf of Mexico ‘dead zone’ is the largest ever measured

"Scientists have determined this year’s Gulf of Mexico “dead zone,” an area of low oxygen that can kill fish and marine life, is 8,776 square miles, an area about the size of New Jersey. It is the largest measured since dead zone mapping began there in 1985." 

Source: National Oceanic and Atmospheric Administration (NOAA)

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Ensemble modeling informs hypoxia management in the northern Gulf of Mexico

Abstract.

"A large region of low-dissolved-oxygen bottom waters (hypoxia) forms nearly every summer in the northern Gulf of Mexico because of nutrient inputs from the Mississippi River Basin and water column stratification. Policymakers developed goals to reduce the area of hypoxic extent because of its ecological, economic, and commercial fisheries impacts. However, the goals remain elusive after 30 y of research and monitoring and 15 y of goal-setting and assessment because there has been little change in river nitrogen concentrations. [...]"

Source: Proceeding of the National Academy of Sciences of the United States of America (PNAS)
Authors: Donald Scavia et al.
DOI: 10.1073/pnas.1705293114 

 

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Historical records of coastal eutrophication-induced hypoxia

Abstract.

"Under certain conditions, sediment cores from coastal settings subject to hypoxia can yield records of environmental changes over time scales ranging from decades to millennia, sometimes with a resolution of as little as a few years. A variety of biological and geochemical indicators (proxies) derived from such cores have been used to reconstruct the development of eutrophication and hypoxic conditions over time. [...]"

Source: Biogeosciences
Authors: A. J. Gooday et al.
DOI: 10.5194/bg-6-1707-2009

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Coastal hypoxia and sediment biogeochemistry

Abstract.

"The intensity, duration and frequency of coastal hypoxia (oxygen concentration <63 μM) are increasing due to human alteration of coastal ecosystems and changes in oceanographic conditions due to global warming. Here we provide a concise review of the consequences of coastal hypoxia for sediment biogeochemistry. Changes in bottom-water oxygen levels have consequences for early diagenetic pathways (more anaerobic at expense of aerobic pathways), the efficiency of re-oxidation of reduced metabolites and the nature, direction and magnitude of sediment-water exchange fluxes. Hypoxia may also lead to more organic matter accumulation and burial and the organic matter eventually buried is also of higher quality, i.e. less degraded. [...]"

Source: Biogeosciences (2009)
Authors: J. J. Middelburg and L. A. Levin
DOI: 10.5194/bg-6-1273-2009

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Eutrophication-Driven Deoxygenation in the Coastal Ocean

Abstract.

"Human activities, especially increased nutrient loads that set in motion a cascading chain of events related to eutrophication, accelerate development of hypoxia (lower oxygen concentration) in many areas of the world’s coastal ocean. Climate changes and extreme weather events may modify hypoxia. Organismal and fisheries effects are at the heart of the coastal hypoxia issue, but more subtle regime shifts and trophic interactions are also cause for concern. The chemical milieu associated with declining dissolved oxygen concentrations affects the biogeochemical cycling of oxygen, carbon, nitrogen, phosphorus, silica, trace metals, and sulfide as observed in water column processes, shifts in sediment biogeochemistry, and increases in carbon, nitrogen, and sulfur, as well as shifts in their stable isotopes, in recently accumulated sediments."

Source: Oceanography Volume 27 (2014)
Authors: Nancy N. Rabalais et al.
DOI: 10.5670/oceanog.2014.21

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