News

NOAA, USGS and partners predict larger summer ‘dead zone’ for the Chesapeake Bay

"Scientists expect this year’s summer Chesapeake Bay hypoxic or “dead zone” — an area of low to no oxygen that can kill fish and aquatic life — will be larger than average, approximately 1.89 cubic miles, or nearly the volume of 3.2 million Olympic-size swimming pools.

Measurements for the Bay’s dead zone go back to 1950, and the 30-year mean maximum dead zone volume is 1.74 cubic miles. [...]"

Source: U.S. Geological Survey

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Stormy waters: the salmon farmer trying to limit fishing and save the ocean

"There’s trouble brewing in Tasmania’s waterways once again.

In the 1980s, protests over the proposed Franklin River hydroelectric dam threw the Apple Isle’s conservation plight onto the national stage. This time, it is the state’s salmon farming industry that is under a cloud. The relatively young industry is worth over $700m a year and now outpaces all other farming activities on the island but environmental campaigners are worried about its impact on the region’s pristine waters. [...]"

Source: The Guardian

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Environmental Research in Macquarie Harbour (Progress Report)

"This report provides an update on the status of dissolved oxygen and benthic conditions in Macquarie Harbour. It follows on from the results reported in the IMAS report released in January 2017 which described the deterioration of benthic and water column conditions in Macquarie Harbour in spring 2016. This report presents the results and preliminary interpretation of oxygen monitoring data up until the end of March 2017, and a repeat survey of benthic communities in January/February 2017. [...]"

Source: The Institute for Marine and Antarctic Studies
Authors: Jeff Ross and Catriona Macleod

Full report (PDF)


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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Nutrients that limit growth in the ocean

Abstract.

"Phytoplankton form the basis of the marine food web and are responsible for approximately half of global carbon dioxide (CO2) fixation (∼ 50 Pg of carbon per year). Thus, these microscopic, photosynthetic organisms are vital in controlling the atmospheric CO2 concentration and Earth’s climate. Phytoplankton are dependent on sunlight and their CO2-fixation activity is therefore restricted to the upper, sunlit surface ocean (that is, the euphotic zone). CO2 usually does not limit phytoplankton growth due to its high concentration in seawater. [...]"

Source: Current Biology
Authors: Laura A. Bristow
DOI: 10.1016/j.cub.2017.03.030

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As CO2 Goes Up, Ocean Health Goes Down

"June 8th is World Oceans Day, a day to raise awareness of the ocean’s importance to the planet. 93 percent of the excess heat absorbed by the climate system goes into our oceans, creating major consequences. While more extreme storms and rising sea levels are some of the impacts of warmer oceans, rising CO2 levels and the resulting warmer oceans are impacting ocean health itself. The most well­known effects are coral bleaching and ocean acidification, but an emerging issue is the decreasing oxygen levels in the warming waters. [...]"

Source: Climate Central

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Less oxygen in a warmer ocean

"Climate warming should decrease the concentration of dissolved oxygen (O2) in the surface ocean, for a variety of reasons. This trend, predicted on theoretical grounds and by ocean models, has been difficult to detect within the much greater range of natural variability, though. Ito et al. analyzed existing measurements of O2 in the ocean collected from 1958 to 2015, and they report that a widespread negative O2 trend has begun to emerge. Further work will be needed to understand which mechanisms are responsible for the global and regional trends, however.

Geophys. Res. Lett. 10.1002/2017GL073613 (2017)."

Source: Science
Author: H. Jesse Smith
DOI: 10.1126/science.356.6341.919-g

Link to article


Seasonal monitoring of deep-sea megabenthos in Barkley Canyon cold seep by internet operated vehicle (IOV)

Abstract.

"Knowledge of the processes shaping deep-sea benthic communities at seasonal scales in cold-seep environments is incomplete. Cold seeps within highly dynamic regions, such as submarine canyons, where variable current regimes may occur, are particularly understudied. Novel Internet Operated Vehicles (IOVs), such as tracked crawlers, provide new techniques for investigating these ecosystems over prolonged periods. In this study a benthic crawler connected to the NEPTUNE cabled infrastructure operated by Ocean Networks Canada was used to monitor community changes across 60 m2 of a cold-seep area of the Barkley Canyon, North East Pacific, at ~890 m depth within an Oxygen Minimum Zone (OMZ). [...]"

Source: PLoS ONE
Authors: Carolina Doya et al.
DOI: 10.1371/journal.pone.0176917

Full article


Light penetration structures the deep acoustic scattering layers in the global ocean

Abstract.

"The deep scattering layer (DSL) is a ubiquitous acoustic signature found across all oceans and arguably the dominant feature structuring the pelagic open ocean ecosystem. It is formed by mesopelagic fishes and pelagic invertebrates. The DSL animals are an important food source for marine megafauna and contribute to the biological carbon pump through the active flux of organic carbon transported in their daily vertical migrations. They occupy depths from 200 to 1000 m at daytime and migrate to a varying degree into surface waters at nighttime. Their daytime depth, which determines the migration amplitude, varies across the global ocean in concert with water mass properties, in particular the oxygen regime, but the causal underpinning of these correlations has been unclear. [...]"

Source: Science Advances
Author: Dag L. Aksnes et al.
DOI: 10.1126/sciadv.1602468

Full article


Persistent spatial structuring of coastal ocean acidification in the California Current System

Abstract.

"The near-term progression of ocean acidification (OA) is projected to bring about sharp changes in the chemistry of coastal upwelling ecosystems. The distribution of OA exposure across these early-impact systems, however, is highly uncertain and limits our understanding of whether and how spatial management actions can be deployed to ameliorate future impacts. Through a novel coastal OA observing network, we have uncovered a remarkably persistent spatial mosaic in the penetration of acidified waters into ecologically-important nearshore habitats across 1,000 km of the California Current Large Marine Ecosystem.  [...]"

Source: Scientific Reports
Authors: F. Chan et al.
DOI: 10.1038/s41598-017-02777-y

Full article


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