Patterns and drivers of global riverine hypoxia
Abstract
Hypoxia in riverine ecosystems has been noted in the literature since the beginning of the 20th century, yet our understanding of the spatial extent and prevalence of hypoxic events in rivers at a global scale is limited. Characterization of the prevalence of hypoxic events in inland waters at broad spatial scales has only recently become possible with the widespread deployment of high-frequency dissolved oxygen sensors and the creation of publicly available databases of historical point measurements. To determine the distribution, frequency, and extent of global riverine hypoxic events, we compiled dissolved oxygen and water temperature measurements from 45,101 sites across the globe. We found that of sites with at least 10 measurements, 4% had dissolved oxygen concentrations of less than 2 mg/L (consensus threshold for hypoxia classification) for more than 10% of the time series. We predicted that the dominant drivers of hypoxic events in rivers include variables that influence gas exchange, including river geomorphology, as well as water temperature and biochemical oxygen demand, estimated as ecosystem respiration (ER). We developed a model of the probability of hypoxia occurring under these conditions and validated our predictions using modeled estimates of ER and gas exchange from rivers with time series of greater than a year. We extrapolated this model to our global database using estimates of instantaneous ER and gas exchange to evaluate the relative variation in the dominant drivers. This synthesis of hypoxic events in rivers at a global scale provides new insight into riverine ecosystem processes and responses to increasing pressure from global environmental change.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2019
- Bibcode:
- 2019AGUFM.B53D..02B
- Keywords:
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- 0414 Biogeochemical cycles;
- processes;
- and modeling;
- BIOGEOSCIENCES;
- 0439 Ecosystems;
- structure and dynamics;
- BIOGEOSCIENCES;
- 0452 Instruments and techniques;
- BIOGEOSCIENCES;
- 1895 Instruments and techniques: monitoring;
- HYDROLOGY