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Point Source-Driven Seasonal Hypoxia Signals Habitat Fragmentation and Ecosystem Change in River Ganga


Affiliations
1 Ganga River Ecology Research Laboratory, Environmental Science Division, Centre of Advanced Study in Botany, Institute of Science, Banaras Hindu University, Varanasi 221 005, India
2 Department of Botany, Mahatma Gandhi Kashividyapith University, Varanasi 221 002, India
 

The development of dissolved oxygen deficit (DOD; hypoxia) has been reported to expand over 2.45 × 105 km2 area of the ocean from over 400 different areas worldwide1. Although cultural eutrophication has greatly accelerated DOD in estuaries and semi-enclosed seas2,3, it is not a common phenomenon in large rivers4. Hydrological continuum reinforces oxygenation, and therefore, development of hypoxia (dissolved oxygen (DO) < 2.0 mg l–1) is less critical in large rivers. River ecosystems usually respond to gradual changes in a smooth manner. However, smooth and continuous changes can be interrupted by sudden abrupt switches to a mosaic of alternative states leading to loss of resilience5. Such shifts are most often driven externally, for instance, point source flushing, but they can trigger internal feedbacks leading the system to behave chaostically even in the absence of external forcing6.
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  • Point Source-Driven Seasonal Hypoxia Signals Habitat Fragmentation and Ecosystem Change in River Ganga

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Authors

Jitendra Pandey
Ganga River Ecology Research Laboratory, Environmental Science Division, Centre of Advanced Study in Botany, Institute of Science, Banaras Hindu University, Varanasi 221 005, India
Deepa Jaiswal
Ganga River Ecology Research Laboratory, Environmental Science Division, Centre of Advanced Study in Botany, Institute of Science, Banaras Hindu University, Varanasi 221 005, India
Usha Pandey
Department of Botany, Mahatma Gandhi Kashividyapith University, Varanasi 221 002, India

Abstract


The development of dissolved oxygen deficit (DOD; hypoxia) has been reported to expand over 2.45 × 105 km2 area of the ocean from over 400 different areas worldwide1. Although cultural eutrophication has greatly accelerated DOD in estuaries and semi-enclosed seas2,3, it is not a common phenomenon in large rivers4. Hydrological continuum reinforces oxygenation, and therefore, development of hypoxia (dissolved oxygen (DO) < 2.0 mg l–1) is less critical in large rivers. River ecosystems usually respond to gradual changes in a smooth manner. However, smooth and continuous changes can be interrupted by sudden abrupt switches to a mosaic of alternative states leading to loss of resilience5. Such shifts are most often driven externally, for instance, point source flushing, but they can trigger internal feedbacks leading the system to behave chaostically even in the absence of external forcing6.

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DOI: https://doi.org/10.18520/cs%2Fv117%2Fi12%2F1947-1949