Water Quality and Microbial Ecology of Upper Barataria Estuary in Southeast Louisiana, USA

Nicole Eddlemon and Raj Boopathy



The waterways in the upper Barataria Estuary are important throughout the estuary because they receive large amounts of nutrients, such as nitrates and phosphates, through runoff from agriculture fields and natural swamp land. Although nutrients can stimulate increased microbial activity, large amounts of nutrients can be detrimental to the system. To develop effective managerial methods, it is becoming important to understand how factors within a system work together at the microbial level. Samples from five sites in the upper Barataria Estuary were collected bi-weekly to measure the bacterial load and to identify the bacterial communities. Dissolved nitrate, dissolved phosphate, organic carbon, and dissolved oxygen were measured bi-weekly. Sample collection started on 20 July 2007 and ended on 21 June 2008. Additional samples were taken 6 days after Hurricane Gustav on 7 September 2008. Statistical analysis was used to investigate seasonal and spatial variations among sample sites. Rainfall leading to floodplain inundation and runoff was suspected to be one of the main seasonal factors affecting the analyzed parameters. Among sampling sites, runoff from human dominated areas was suspected to be the primary factor affecting, pH, dissolved oxygen, dissolved nitrate, and dissolved phosphate. As expected, the high levels of organic carbon after Hurricane Gustav caused a significant decrease in the dissolved oxygen levels in the upper Barataria Estuary which led to a massive fill kill. The upper Barataria Estuary may be better managed by decreasing the amount of runoff into the upper Barataria Estuary.

Keywords: Upper Barataria Bay; fish kill; nutrient run-off; organic carbon; nitrogen; hypoxia; Hurricane Gustav