Nutrients

Overview

Nutrients are essential compounds required for plant and animal life. The bay’s food web is supported by primary producers that require adequate amounts of nutrients to convert inorganic compounds and sunlight into biomass. Without an adequate amount of nutrients, Galveston Bay would not be the productive ecosystem that it is today.

At high concentrations nutrients can cause eutrophication (nutrient over-enrichment), a water quality condition that can lead to harmful algal blooms, low dissolved oxygen levels (hypoxia), and fish kills.

Elevated levels of nutrients are often associated with non-point sources of pollution which cannot be traced back to a single source. Non-point sources include yards, pastures, agricultural fields, roads and parking lots. When rainfall flows off of these areas, the stormwater carries nutrients and other compounds directly to bayous and ultimately into the bay. Nutrients can also enter the bay and its tributaries via atmospheric deposition.

A Description of the Indicator

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

The Status and Trends Project compares concentrations of four nutrients 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:

• Total phosphorus
• Ammonia
• Nitrate-nitrite
• Chlorophyll-a (an indicator of phytoplankton biomass in the water)

Samples were collected by the TCEQ during the period 1999-2006.

What the Indicator Says

Many areas of Galveston Bay appear to have experienced an overall improvement in nutrient concentrations since the 1970s. Several urbanized tributaries to the bay such as Armand Bayou, Buffalo Bayou, and the Houston Ship Channel now rate “Moderate” in terms of nutrient enrichment. All other subbays and tributaries rate "Good" or "Very Good".  While these improvements are heartening, it is important to note that many tributaries around the bay continue to experience high nutrient concentrations episodically. 

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