Dissolved oxygen stratification in two micro-tidal partially-mixed estuaries

Lin, Jing; Xie, Lian; Pietrafesa, L. J.; Shen, Jian; Mallin, Michael A.; Durako, Michael J.

doi:10.1016/j.ecss.2006.06.032

Cited by 48 publications

(29 citation statements)

References 36 publications

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“…Typically, hypoxia conditions in deeper estuarine systems, such as the Neuse River and the Cape Fear Estuary, are abated by wind-induced vertical mixing that disrupts the development of stratification (Buzzelli et al 2002;Lin et al 2006) or prevents it from being prolonged (Lucas et al 2006). The longer fetch distances in these larger systems provide greater exposure to wind mixing than occurs in the much smaller estuarine tributaries of this study.…”

Section: Environmental Variables and Diel-cycling Hypoxiamentioning

confidence: 93%

Temporal and Spatial Dynamics of Diel-Cycling Hypoxia in Estuarine Tributaries

Tyler

Brady

Targett

2008

Estuaries and Coasts

177

138

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The distribution and intensity of hypoxia (low dissolved oxygen) in estuaries is increasing worldwide due to cultural eutrophication. This study quantifies the strength of associations between the duration of diel-cycling severe hypoxia (≤2 mg O 2 l −1 ) in bottom water (∼15 cm above bottom) of a shallow (<2 m) coastal lagoon estuary (Delaware, USA) and abiotic environmental variables (water temperature, insolation, tide, streamflow, and wind) and predicts the duration of severe hypoxia given different combinations of these variables. The intensity and spatial extent and dynamics of diel-cycling severe hypoxia events were defined. Vertical variability in dissolved oxygen (DO) concentration during the daytime was also determined. During the summers of 2001-2005, bottom DO data were collected for periods of weeks to months at multiple sites using automated sondes. Multiple linear regression (MLR) and regression tree analysis (RTA) were used to determine the relative importance of the environmental variables in predicting the number of hours of severe hypoxia per day. Key findings of the study were that severe hypoxia events of minutes to hours in duration occurred frequently in all four tributaries sampled, primarily between 0200 and 1000 hours. Severe hypoxia duration and diel-cycling amplitudes of DO concentration increased in the up-tributary direction. Hierarchically, the duration of severe hypoxia was influenced mostly by the mean daily water temperature, then by preceding days' total insolation, percentage of morning hours (02:00 to 10:00 A.M.) ebb tide, and daily streamflow. Collectively, the variables examined by the MLR and the RTA approaches accounted for 62% and 65% of the variability in the duration of severe hypoxia, respectively. RTA demonstrated that daily mean water temperature above 26.3°C and previous day's total insolation below 13.6 kW m −2 were associated with the longest lasting severe hypoxic events (9.56 h). The environmental variables and combinations of conditions that modulate or augment diel-cycling hypoxia presented in this paper enhance understanding of this widespread and growing phenomenon and provide additional insight regarding the extent to which it can impact food webs in very shallow estuarine waters that often serve as nursery habitat.

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Section: Environmental Variables and Diel-cycling Hypoxiamentioning

confidence: 93%

Temporal and Spatial Dynamics of Diel-Cycling Hypoxia in Estuarine Tributaries

Tyler

Brady

Targett

2008

Estuaries and Coasts

177

138

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“…Depleted levels of dissolved oxygen (DO) occur in many Asian estuaries (Fang and Lin 2002;Dai et al 2006;Ni et al 2007), North American estuaries (Engle et al 1999;Borsuk et al 2001;Hagy et al 2004;Benoit et al 2006;Lin et al 2006), and European estuaries (Uncles et al 1998;Garnier et al 2001). These zones of hypoxia (DO concentration<2 mg l −1 ) greatly degrade environmental conditions for benthic and pelagic fauna and alter redox conditions, which changes the cycling of nutrients and partitioning of pollutants throughout the estuary (de Jonge and Villerius 1989;Diaz and Rosenburg 1995;Nestlerode and Diaz 1998;Fang and Lin 2002).…”

Section: Introductionmentioning

confidence: 98%

An Idealized Model and Systematic Process Study of Oxygen Depletion in Highly Turbid Estuaries

Talke

Swart

Jonge

2009

Estuaries and Coasts

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The sensitivity of oxygen depletion in turbid estuaries to parameters like freshwater discharge, depth, and sediment availability is investigated using an idealized model. The model describes tidally averaged circulation and suspended sediment concentration (SSC), which are input into an advection-diffusion sink module of dissolved oxygen (DO). Based on the analysis of field data collected in the Ems estuary, the modeled oxygen depletion rates are proportional to SSC. The model is calibrated to the observed variation of DO with SSC and temperature. Modeled DO closely tracks changes to the estuarine turbidity zone (ETZ): increased channel depth, decreased freshwater discharge, and decreased mixing move the ETZ upstream, amplify SSCs, and decrease DO. Summertime temperatures produce lower DO than cooler periods. Model results are consistent with historical measurements in the Ems, which indicate that hypoxic events (DO concentrations<2 mg l −1 ) have occurred more frequently after deepening from 5 to 7 m.

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“…Density differentials between 2 water layers frequently arise from differences in salinity, temperature, or a combination of both (Lin et al 2006, Kim et al 2012. Our study sites exhibited apparent vertical changes in temperature and salinity, with more significant changes in temperature (Fig.…”

Section: Nature Of Hypoxiamentioning

confidence: 99%

Pelagic oxycline and damage potential of hypoxia to the Pacific oyster Crassostrea gigas suspended in longline aquaculture systems

Lee¹,

Jo²,

Han³

et al. 2017

Aquacult. Environ. Interact.

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Depletion in dissolved oxygen (DO) occurred in 2 semi-enclosed shallow bays in Korea in which Crassostrea gigas were suspended for aquaculture. DO depletion started at the bottom and expanded rapidly upwards for days until it was blocked by a temperature-driven density differential. This resulted in the formation of pelagic oxyclines at a depth of 2-4 m in one bay (Hypoxic Site 1, HS-1) and 2-5 m in the other (Hypoxic Site 2, HS-2). Water above the oxycline was normoxic (> 4 mg l ). The oxyclines were accompanied by significant changes in environmental variables and phytoplankton composition, but these changes were not fatal to the oysters. However, the oxyclines themselves caused oyster mortality: complete mortality below the oxyclines and depth-dependent mortality within the oxycline. Interestingly, mortality was observed in a significant number of oysters above the oxyclines compared with the reference site, and greater mortality was ob served in HS-1 than HS-2. These findings suggest the existence of toxic compounds that diffuse up from below the oxycline in shallow waters and exert effects that overshadow those of DO. The higher mortalities in the HS-1 normoxic layer supported this influence from the bottom layer. In a subsequent experiment, we observed additional mortalities among the surviving oysters in the upper normoxic waters after the bays had completely reoxygenated during fall turnover. These data provide useful observations of hypoxia in highly sheltered shallow waters and can be used to guide site selection for oyster longline aquaculture.

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Dissolved oxygen stratification in two micro-tidal partially-mixed estuaries

Cited by 48 publications

References 36 publications

Temporal and Spatial Dynamics of Diel-Cycling Hypoxia in Estuarine Tributaries

Temporal and Spatial Dynamics of Diel-Cycling Hypoxia in Estuarine Tributaries

An Idealized Model and Systematic Process Study of Oxygen Depletion in Highly Turbid Estuaries

Pelagic oxycline and damage potential of hypoxia to the Pacific oyster Crassostrea gigas suspended in longline aquaculture systems

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