News

Chesapeake Bay dead zone this summer worst since 2014

In June, federal scientists predicted a bigger-than-average oxygen-deprived dead zone in the Chesapeake Bay this summer, and it turns out they were right.

Researchers with the Virginia Institute of Marine Science who study bay hypoxia announced Monday that the total amount of dead zones this summer was the worst since 2014, and a 10 percent increase over last year.

Source: Daily Press

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Low Oxygen Dead Zones in the Pacific Ocean are Growing

"Every year, we see wildfires wreak havoc on large regions of the West United States, and each year scientists attempt to forecast exactly how bad the upcoming fire season is going to be by assessing things like weather, moisture levels, and a bevy of different factors. [...]"

Source: Mind Guild

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Oxic-anoxic regime shifts mediated by feedbacks between biogeochemical processes and microbial community dynamics

Abstract.

"Although regime shifts are known from various ecosystems, the involvement of microbial communities is poorly understood. Here we show that gradual environmental changes induced by, for example, eutrophication or global warming can induce major oxic-anoxic regime shifts. We first investigate a mathematical model describing interactions between microbial communities and biogeochemical oxidation-reduction reactions. [...]"

Source: Nature Communications
Authors: Timothy Bush et al.
DOI: 10.1038/s41467-017-00912-x

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Oceanic uptake of oxygen during deep convection events through diffusive and bubble mediated gas exchange

Abstract.

"The concentration of dissolved oxygen (O2) plays fundamental roles in diverse chemical and biological processes throughout the oceans. The balance between the physical supply and the biological consumption controls the O2 level of the interior ocean, and the O2 supply to the deep waters can only occur through deep convection in the polar oceans. [...]"

Source: Global Biogeochemical Cycles
Authors: Daoxun Sun, Takamitsu Ito, Annalisa Bracco
DOI: 10.1002/2017GB005716

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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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What Scientists Are Learning About the Impact of an Acidifying Ocean

"The effects of ocean acidification on marine life have only become widely recognized in the past decade. Now researchers are rapidly expanding the scope of investigations into what falling pH means for ocean ecosystems."

Source: NewsDeeply: Oceans Deeply

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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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Sound physiological knowledge and principles in modeling shrinking of fishes under climate change

Abstract.

"One of the main expected responses of marine fishes to ocean warming is decrease in body size, as supported by evidence from empirical data and theoretical modeling. The theoretical underpinning for fish shrinking is that the oxygen supply to large fish size cannot be met by their gills, whose surface area cannot keep up with the oxygen demand by their three-dimensional bodies. [...]"

Source: Global Change Biology
Authors: Daniel Pauly, William W. L. Cheung
DOI: 10.1111/gcb.13831

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Macroalgal Blooms on the Rise along the Coast of China

Abstract.

"A broad spectrum of events that come under the category of macroalgal blooms are recognized world-wide as a response to elevated levels of eutrophication in coastal areas. In the Yellow Sea of China, green tides have consecutively occurred 10 years, which is considered as the world’s largest Ulva blooms. However, in recently years, golden tides caused by Sargassum seaweed have also been on the rapid rise, resulting in dramatic damage to the environment and economy again.  [...]"

Source: Oceanography & Fisheries
Authors: Jianheng Zhang, Yuanzi Huo and Peimin He 
DOI: 10.19080/OFOAJ.2017.04.555646

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