Bacteria

Overview

Fecal coliform bacteria are used as the primary indicator for determining whether surface water is contaminated by animal or human waste. Presence of coliform bacteria suggests that potentially dangerous pathogens could also be present.

Elevated bacteria concentrations are typically associated with slow flowing bayous concentrated on the western side of Galveston Bay where most of the human development is situated. Water samples taken from open bay waters show substantially lower fecal coliform concentrations. Elevated levels of fecal coliform contamination prompt:

• The restriction or prohibition of portions of Galveston Bay waters to the harvest of shellfish 
• A number of local bayous to be the subject of Total Maximum Daily Load studies

  A Description of the Indicator

The Status and Trends Project compares concentrations of three bacterial parameters in Galveston Bay surface waters to Texas Commission on Environmental Quality (TCEQ) screening levels for contact recreation (e.g. swimming). The three bacterial parameters are:

Water and sediment sampling stations. Click for a larger map.

• Fecal coliform bacteria
• E. coli (in freshwater)
• Enterococci (in saltwater)

Major subbays and tributaries of the bay are rated based on the percentage of samples exceeding current TCEQ screening levels. Samples are collected by the TCEQ and Texas Department of State Health Services (DSHS) during the period 1999-2006.

What the Indicator Says

The indicator below compares bacterial contamination in the 1970s to the present decade. Pathogen concentrations are highest in the bayous that serve as tributaries to Upper and Lower Galveston Bay. Over the last 30 years, the five subbays of Galveston Bay have rated "Good" for pathogenic bacteria with nine percent or less of the samples exceeding the fecal coliform bacteria screening level. The major water quality problems with regards to bacteria are found in six bayous currently rate poor for fecal coliform bacteria: Dickinson Bay/Bayou, Clear Creek, Armand Bayou, the Houston Ship Channel, Buffalo Bayou, and Cedar Bayou. Chocolate Bayou/Bay, Oyster Bayou, and the San Jacinto River are currently rated as moderate, the remaining areas rate good.

View water quality trends and download water quality data from the Water Sediment Quality Data Portal.