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Resolving spatiotemporal characteristics of the seasonal hypoxia cycle in shallow estuarine environments of the Severn River and South River, MD, Chesapeake Bay, USA

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ABSTRACT

The nature of emerging patterns concerning water quality stressors and the evolution of hypoxia within sub-estuaries of the Chesapeake Bay has been an important unresolved question among the Chesapeake Bay community. Elucidation of the nature of hypoxia in the tributaries of the Chesapeake Bay has important ramifications to the successful restoration of the Bay, since much of Bay states population lives within the watersheds of the tributaries. Very little to date, is known about the small sub-estuaries of the Chesapeake Bay due to limited resources and the difficulties in resolving both space and time dimensions on scales that are adequate to resolve this question. We resolve the spatio-temporal domain dilemma by setting up an intense monitoring program of water quality stressors in the Severn and South Rivers, MD. Volume rendered models were constructed to allow for a visual dissection of the water quality times series which illustrates the life cycle of hypoxia and anoxia at the mid to upper portions of the tidal tributaries. The model also shows that unlike their larger Virginian tributary counterparts, there is little to no evidence of severe hypoxic water intrusions from the main-stem of the Chesapeake Bay into these sub-estuaries.

No MeSH data available.


Related in: MedlinePlus

Spatiotemporal model of hypoxic squeezing.
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fig0070: Spatiotemporal model of hypoxic squeezing.

Mentions: The results of the spatiotemporal hypoxia models illustrate important similarities and differences between the Severn and South Rivers. Although the initial timing and location of hypoxia are similar, hypoxia and especially anoxia appears to be stronger and last longer in the Severn River. We hypothesize that the main reason for this is rooted in wind efficiency. The Severn River has high bluffs in the upper reaches of the river effectively blocking the wind. Conversely, the South River has low-lying bluffs allowing for efficient wind mixing. In the case of the South River wind mixing can get all the way to the bottom of the tributary, where in the Severn it usually can only get down to about 3-meters. This creates a hypoxic fencing situation in both rivers as hypoxia and anoxia are recognized in the vertical, horizontal, and temporal domains. This concept of hypoxic fencing or squeezing is illustrated in Fig. 14. In this model of hypoxic fencing, the surface of the water column heats up above 28 °C, while severe hypoxic and anoxic waters grow from the bottom creating vertical hypoxic squeezing. During this vertical hypoxic squeezing, the livable potion of the water column is probably the main cause of the large 2010 fish kill in the upper Severn River during July of 2010. In this case, anoxia coupled with a North-westerly wind during ebb tide significantly reduced the livable portion of this narrow section of the river leading to an estimated 100,000 menhaden fish kill. Hypoxic squeezing can also occur in other dimensions, as up-stream growth of hypoxia an anoxia can cause the creation of a lateral hypoxic fence. In this case, above the fence in the upper estuarine reaches, the hypoxia has reached more than half way up the water column. Downstream sections have healthier oxygen levels throughout the water column. This leaves non-mobile living resources stranded behind the fence such as SAV and oysters. Temporal fencing can occur as hypoxia grows and decays over the summer period leading to points in time where the habitable area has decreased significantly but re-opens after some period.


Resolving spatiotemporal characteristics of the seasonal hypoxia cycle in shallow estuarine environments of the Severn River and South River, MD, Chesapeake Bay, USA
Spatiotemporal model of hypoxic squeezing.
© Copyright Policy - CC BY-NC-ND
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC5037264&req=5

fig0070: Spatiotemporal model of hypoxic squeezing.
Mentions: The results of the spatiotemporal hypoxia models illustrate important similarities and differences between the Severn and South Rivers. Although the initial timing and location of hypoxia are similar, hypoxia and especially anoxia appears to be stronger and last longer in the Severn River. We hypothesize that the main reason for this is rooted in wind efficiency. The Severn River has high bluffs in the upper reaches of the river effectively blocking the wind. Conversely, the South River has low-lying bluffs allowing for efficient wind mixing. In the case of the South River wind mixing can get all the way to the bottom of the tributary, where in the Severn it usually can only get down to about 3-meters. This creates a hypoxic fencing situation in both rivers as hypoxia and anoxia are recognized in the vertical, horizontal, and temporal domains. This concept of hypoxic fencing or squeezing is illustrated in Fig. 14. In this model of hypoxic fencing, the surface of the water column heats up above 28 °C, while severe hypoxic and anoxic waters grow from the bottom creating vertical hypoxic squeezing. During this vertical hypoxic squeezing, the livable potion of the water column is probably the main cause of the large 2010 fish kill in the upper Severn River during July of 2010. In this case, anoxia coupled with a North-westerly wind during ebb tide significantly reduced the livable portion of this narrow section of the river leading to an estimated 100,000 menhaden fish kill. Hypoxic squeezing can also occur in other dimensions, as up-stream growth of hypoxia an anoxia can cause the creation of a lateral hypoxic fence. In this case, above the fence in the upper estuarine reaches, the hypoxia has reached more than half way up the water column. Downstream sections have healthier oxygen levels throughout the water column. This leaves non-mobile living resources stranded behind the fence such as SAV and oysters. Temporal fencing can occur as hypoxia grows and decays over the summer period leading to points in time where the habitable area has decreased significantly but re-opens after some period.

View Article: PubMed Central - PubMed

ABSTRACT

The nature of emerging patterns concerning water quality stressors and the evolution of hypoxia within sub-estuaries of the Chesapeake Bay has been an important unresolved question among the Chesapeake Bay community. Elucidation of the nature of hypoxia in the tributaries of the Chesapeake Bay has important ramifications to the successful restoration of the Bay, since much of Bay states population lives within the watersheds of the tributaries. Very little to date, is known about the small sub-estuaries of the Chesapeake Bay due to limited resources and the difficulties in resolving both space and time dimensions on scales that are adequate to resolve this question. We resolve the spatio-temporal domain dilemma by setting up an intense monitoring program of water quality stressors in the Severn and South Rivers, MD. Volume rendered models were constructed to allow for a visual dissection of the water quality times series which illustrates the life cycle of hypoxia and anoxia at the mid to upper portions of the tidal tributaries. The model also shows that unlike their larger Virginian tributary counterparts, there is little to no evidence of severe hypoxic water intrusions from the main-stem of the Chesapeake Bay into these sub-estuaries.

No MeSH data available.


Related in: MedlinePlus