Turbulence and hypoxia contribute to dense zooplankton scattering layers in Patagonian Fjord System
"Abstract. The Puyuhuapi Fjord is an atypical fjord, with two mouths, located in northern Patagonia (44.7° S). One mouth lies to the south, close to the Pacific Ocean, whilst the second connects with the Jacaf Channel to the north where a shallow sill inhibits deep water ventilation contributing to the hypoxic conditions below ~ 100 m depth. Acoustic Doppler Current Profiler moorings, scientific echo sounder transects, and in-situ abundance measurements were used to study zooplankton assemblages and migration patterns along Puyuhuapi Fjord and Jacaf Channel. […]"
Source: Ocean Science (in review)
Authors: Iván Pérez-Santos et al.
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Exposure to elevated pCO2 does not exacerbate reproductive suppression of Aurelia aurita jellyfish polyps in low oxygen environments
"Eutrophication-induced hypoxia is one of the primary anthropogenic threats to coastal ecosystems. Under hypoxic conditions, a deficit of O2 and a surplus of CO2 will concurrently decrease pH, yet studies of hypoxia have seldom considered the potential interactions with elevated pCO2 (reduced pH). Previous studies on gelatinous organisms concluded that they are fairly robust to low oxygen and reduced pH conditions individually, yet the combination of stressors has only been examined for ephyrae. [...]"
Source: Marine Ecology Progress Series
Authors: Laura M. Treible et al.
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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. [...]"
Exposure of European sea bass [...] to chemically dispersed oil has a chronic residual effect on hypoxia tolerance but not aerobic sc
"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.
Ecophysiological limits to aerobic metabolism in hypoxia determine epibenthic distributions and energy sequestration in the northeast Pacific ocean
"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
Biodiversity response to natural gradients of multiple stressors on continental margins
"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
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
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)
Ensemble modeling informs hypoxia management in the northern Gulf of Mexico
"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.
Historical records of coastal eutrophication-induced hypoxia
"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. [...]"
Authors: A. J. Gooday et al.