GIS database of hypoxia (low oxygen) conditions in Corpus Christi Bay




Morehead, Sally
Montagna, Paul A.
Simanek, Carol

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Hypoxia (low oxygen conditions) has been documented in the southeastern region of Corpus Christi Bay, Texas every summer since 1988. Hypoxia is a serious water quality condition because all aerobic organisms require oxygen to live. Hypoxia in Corpus Christi Bay occurs only in bottom waters, within 1 - 2 meters above bottom, so effects are mostly on benthic organisms. The objectives of the current study were to determine the spatial and temporal extent of hypoxia in Corpus Christi Bay, Texas, as well as to generate a GIS database for existing data to aid in management. Continuous oxygen recorders were deployed and water quality was surveyed during summer to measure the extent of hypoxia. Water column profiles measured during spatial surveys revealed benthic oxygen depletion with and without salinity stratification. Continuous oxygen monitoring captured numerous hypoxic events, many of which were of short duration (less than 1 hr) and high intensity (between 1 and 2mg 1⁻¹). Other archival data from resource agencies was also obtained for analysis. The trends in the hydrographic data indicate that hypoxia in Corpus Christi Bay is a transient event in the southeastern region and is caused by a combination of biotic processes (i.e., respiration) and abiotic processes (i.e., low mixing potential because of sluggish currents, a small tidal range, and high temperatures). Temperature has increased in this region of Corpus Christi Bay over the last 20 years, presumably due to global warming. Trends in the data indicate that extent and intensity of hypoxia is increasing over time. This increase in hypoxia is primarily due to increases in temperature, because nutrients have not increased.



Final report to: Coastal Coordination Council ... Austin, Texas
Coastal Management Program Grant number: 01-214
March 31, 2002