Biomarkers of hypoxia exposure and reproductive function in Atlantic croaker: A review with some preliminary findings from the northern Gulf of Mexico hypoxic zone

The long-term impacts on marine ecosystems of the recent dramatic worldwide increase in the incidence of coastal hypoxia are unknown. Here, we show widespread reproductive disruption in Atlantic croakers collected from hypoxic sites approximately 120 km apart in the extensive northern Gulf of Mexico continental shelf hypoxic zone. Gonadal growth and gamete production were impaired in croakers from hypoxic sites compared with fish from reference normoxic sites east of the Mississippi River Delta. Male germ cells were detected in approximately 19 per cent of croaker ovaries collected in the hypoxic region, but were absent in ovaries from normoxic sites. In addition, the sex ratio was skewed towards males at the hypoxic sites. The masculinization and other reproductive disruptions were associated with declines in neuroendocrine function, as well as ovarian and brain expression of aromatase (the enzyme that converts androgens to oestrogens). A similar incidence of ovarian masculinization and decline in ovarian aromatase expression were observed in croaker after chronic laboratory hypoxia exposure, indicating that ovarian masculinization is a specific hypoxia response and is due to decreased aromatase activity. The results suggest severe reproductive impairment can occur over large coastal regions in marine fish populations exposed to seasonal hypoxia, with potential long-term impacts on population abundance.

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Molecular and biochemical responses of hypoxia exposure in Atlantic croaker collected from hypoxic regions in the northern Gulf of Mexico

PLoS ONE ◽

10.1371/journal.pone.0184341 ◽

2017 ◽

Vol 12 (9) ◽

pp. e0184341 ◽

Cited By ~ 6

Author(s):

Md Saydur Rahman ◽

Peter Thomas

Keyword(s):

Gulf Of Mexico ◽

Atlantic Croaker ◽

Northern Gulf Of Mexico ◽

Hypoxia Exposure ◽

Biochemical Responses

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Effects of spatial variability on the exposure of fish to hypoxia: a modeling analysis for the Gulf of Mexico

10.5194/bg-2020-51 ◽

2020 ◽

Author(s):

Elizabeth D. LaBone ◽

Kenneth A. Rose ◽

Dubravko Justic ◽

Haosheng Huang ◽

Lixia Wang

Keyword(s):

Gulf Of Mexico ◽

Dissolved Oxygen ◽

Spatial Variability ◽

Multiple Scales ◽

Northern Gulf Of Mexico ◽

Hypoxic Zone ◽

Modeling Analysis

Abstract. The hypoxic zone in the northern Gulf of Mexico varies spatially (area, location) and temporally (onset, duration) on multiple scales. Exposure to hypoxic dissolved oxygen (DO) concentrations (

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Performance of an Ocean Buoyancy Glider in a Coastal Region: Application to the Gulf of Mexico Hypoxic Zone

Marine Technology Society Journal ◽

10.4031/mtsj.51.4.1 ◽

2017 ◽

Vol 51 (4) ◽

pp. 41-51

Author(s):

Elizabeth Ramey ◽

Steven F. DiMarco ◽

Karen Dreger ◽

Heather M. Zimmerle

Keyword(s):

Gulf Of Mexico ◽

Action Plan ◽

Coastal Region ◽

Ocean Bottom ◽

Low Oxygen ◽

Northern Gulf Of Mexico ◽

Hypoxic Zone ◽

Horizontal Stratification ◽

Oxygen Conditions ◽

Oil Gas

AbstractThe Gulf of Mexico Coastal Hypoxia Glider Experiment was designed to assess the feasibility of using ocean glider technology in the coastal hypoxic zone of the northern Gulf of Mexico in Summer/Fall 2014. The objectives were (1) to coordinate and operate multiple autonomous buoyancy ocean gliders in depths less than 50 m and (2) to determine how close to the bottom gliders can reliably reach without making contact. Strong vertical and horizontal stratification gradients, strong coastal currents, and the low-oxygen conditions that occur within the lower water column characterize the coastal area of the northern Gulf of Mexico. These environmental conditions combine with the presence of more than 5,000 surface piercing oil/gas structures to make piloting and navigation in the region challenging. We quantify glider performance to assess the usefulness of buoyancy gliders to address the National Oceanic and Atmospheric Administration Action Plan goal to monitor the spatial extent, duration, and severity of the Gulf hypoxic zone. We find that the gliders, despite the operational challenges, were consistently able to travel from the surface to the oxygen-depleted depths of subpycnocline waters, that is, within 2 m of the ocean bottom. Our assessment is that gliders are able to provide real-time observations suitable to monitor coastal hypoxia.

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Coastal change and hypoxia in the northern Gulf of Mexico: Part I

Hydrology and Earth System Sciences ◽

10.5194/hess-11-180-2007 ◽

2007 ◽

Vol 11 (1) ◽

pp. 180-190 ◽

Cited By ~ 8

Author(s):

E. C. Krug

Keyword(s):

Gulf Of Mexico ◽

Natural Resources ◽

Task Force ◽

Coastal Change ◽

Northern Gulf Of Mexico ◽

Atchafalaya River ◽

European Settlement ◽

Hypoxic Zone ◽

Atchafalaya River Basin ◽

And Control

Abstract. The Committee on Environment and Natural Resources (CENR) has identified the input of nutrient-rich water from the Mississippi/Atchafalaya River Basin (MARB) as the prime cause of hypoxia in the northern Gulf of Mexico and the prime means for its control. A Watershed Nutrient Task Force was formed to solve the hypoxia problem by managing the MARB catchment. However, the hypoxic zone is also experiencing massive physical, hydrological, chemical and biological changes associated with an immense river-switching and delta-building event that occurs here about once a millennium. Coastal change induced hypoxia in the northern Gulf of Mexico prior to European settlement. It is recommended that for further understanding and control of Gulf hypoxia the Watershed Nutrient Task Force adopt a truly holistic environmental approach which includes the full effects of this highly dynamic coastal area.

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