CHAPTER 6 – STATE OF THE BAY, THIRD EDITION Water and Sediment Quality Written & Revised by Lisa A. Gonzalez The wondrous nature of water, that it is at once the “universal solvent” and the global transport system for molecules and masses of debris alike, also makes it particularly vulnerable to debilitating, sometimes lethal, contamination. —Sylvia A. Earle in Sea Change: A Message of the Oceans (1995) Introduction Water pollution in the Houston-Galveston region first became a public concern in the early 1900s with the recognition that sewage contributed pathogenic bacteria to area waterways. In the 1920s, oil pollution in the Houston Ship Channel prompted local and state officials to voice concerns about industrial contamination (Melosi et al. 2007). In 1967, federal investigators identified the Houston Ship Channel as “the worst example of water pollution … observed in Texas” (Melosi and Pratt 2007). This prompted the Texas Water Quality Board (now the Texas Commission on Environmental Quality, TCEQ) to initiate corrective measures to improve the water quality of the Houston Ship Channel and Galveston Bay even prior to the passage of the Clean Water Act in 1972. The portion of the Houston Ship Channel above Morgan's Point (near La Porte) was later listed among the 10 most polluted water bodies in the United States by the U.S. Environmental Protection Agency (EPA). Stringent discharge goals were established in 1971 for industrial and municipal point sources along Buffalo Bayou and the Houston Ship Channel. All industries discharging to the Houston Ship Channel were required to upgrade their wastewater treatment facilities. Municipal waste treatment facilities discharging to the State of the Bay 2009 Bay the of State – tributaries of Galveston Bay were enhanced and expanded. Ten years later, the EPA recognized that several Texas waterways CHAPTER 1 were getting cleaner and singled out the State of the Bay Houston Ship Channel as "the most notable – 6 improvement, a truly remarkable feat" Figure 6.1. The Houston Ship Channel as seen from the (EPA 1980). top of the San Jacinto Monument. Image courtesy Lisa Gonzalez. CHAPTER 1 For the most part Galveston Bay has been able to maintain good water quality because it is shallow, well-mixed, and well-aerated. The vast majority of water quality problems are concentrated in the western, urban tributaries of the bay where municipal and industrial development is most pronounced. This chapter deals with the historical trends and the present status of water and sediment quality in the bay. Contributions from point and nonpoint sources are discussed. Biological monitoring of contaminants is included since some chemicals can only be detected after they accumulate in organisms living in the Figure 6.2. Galveston Bay segmentation scheme. Modified from (Jones and Neuse 1992; Ward et al. 1992). water or sediment. Indicators of water and sediment quality along with time-series trend graphs will be used to characterize the large-scale spatial and temporal patterns of water and sediment quality parameters in the Galveston Bay system. The indicators were initially developed by the Galveston Bay Indicators Project (Lester et al. 2005) and were updated in 2009 by the Galveston Bay Status and Trends Project. Temporal trends were statistically analyzed using linear regression analyses on data grouped spatially by tributary or subbay. 2 Trends are classified as significant if the coefficient of determination (R ) is greater than 0.25 and for each State of the Bay – year at least 10 samples were collected. Positive and negative trends of parameters indicative of the health 6 of the bay are highlighted in this report. Parameters that exhibit no trend are largely omitted. CHAPTER 2 The indicators and trend graphs presented in this chapter utilize quality assured, long-term monitoring data collected and managed by various state agencies including the TCEQ, Texas Department of State Health Services (TDSHS), and the Texas Parks and Wildlife Department (TPWD). When available, data are combined from Figure 6.3. Bolivar Roads is the entrance to the Houston Ship Channel multiple agencies (e.g., and Galveston Bay and is a major inlet to the bay from the Gulf of data describing water Mexico. Image ©2011 Jarrett Woodrow. temperature is collected by the TCEQ and TPWD). For most water quality parameters, the data record extends back at least 35 years. Data analyses end with the 2009 data year. Spatial variation throughout the Galveston Bay system is addressed by aggregating the data into subregions of the bay (e.g., subbays and tributaries). This is done using a hydrographic segmentation scheme originally developed by Jones and Neuse (1992) and Ward and Armstrong (1992) and later modified by the Galveston Bay Status and Trends Project (Lester et al. 2003) (see Figure 6.2). Water Quality Temperature In the context of water quality, water temperature often determines the rates of many chemical reactions and physical processes. For example, the degradation of organic pollutants occurs faster at higher temperatures, if all other reaction conditions are constant. The solubility of oxygen in water decreases as temperature increases. Additionally, the survival of aquatic organisms is affected by temperature. The incidence of pathogens and parasites such as Vibrio vulnificus (Oliver 2005) and Dermo (Perkinsus marinus) State of the Bay 2009 Bay the of State – (see Chapter 7) are dependent on water temperatures; their populations increase as water temperatures rise. Shallow depths, and mixing by wind, produce water temperatures that are homogeneous with little vertical CHAPTER 1 stratification. The principal source of variation in temperature is seasonal change, as shown in Figure 6.4. As State of the Bay one would expect, average water temperature is highest in the summer months (June, July, and August) at – 6 nearly 30˚Celsius, and lowest in the winter months (December, January, and February) at approximately 14˚C. CHAPTER 3 Figure 6.4. Average seasonal surface water temperature (≤ 1meter); Galveston Bay 1970–2009; all stations. Diamonds and values represent the average (mean). Error bars represent standard error from the mean. Light blue bars depict the number of samples. Data sources: (TPWD 2008; TCEQ 2009; HGAC 2010). The TPWD has documented a rising trend in winter water temperatures in all of the Texas bays south of Galveston Bay (Tolan et al. 2009). Similar trends in the water temperatures of Galveston Bay have not yet been observed. As seen in Figure 6.5, there is no trend in surface (≤ 1 meter in depth) or bottom (> 1 meter in depth) water temperatures from 1970–2009. In the graph, bars represent the number of samples collected each year. The trend line represents the trend in annual average temperature for all samples collected in that year. Trends are significant if R2 is greater than 0.25. Water temperatures in localized areas of the bay can be altered by human actions. Effluents with elevated temperatures are discharged from many industrial facilities that use pass-through cooling water. Elevated water temperatures at discharge sites has been shown to change the composition of the ecosystem in the vicinity of the discharge (Jones et al. 1996), but the effect is localized. State of the Bay – 6 CHAPTER 4 Figure 6.5. Average annual surface water temperature (all depths); Galveston Bay 1970–2009, all stations. Bars represent the number of samples collected each year. The trend line represents the trend in annual average temperature for all samples collected in that year. Trends are significant if R2 is greater than 0.25. Data sources: (HGAC 2010; TCEQ 2010; TPWD 2010)(). pH pH is a measure of the concentration of hydrogen (H+) ions and describes the acidity or alkalinity of a substance. A substance with a pH of 7 is considered neutral; pH < 7 is acidic and pH > 7 is alkaline. pH is measured on a negative logarithmic scale, meaning a pH of 6 is 10 times more acidic than a pH of 7, and 100 times more acidic than a pH of 8. In water, various dissolved compounds, including salts and gases, can State of the Bay 2009 Bay the of State – affect pH. pH determines, in part, the reactivity of water with various pollutants and therefore the toxicity of those pollutants. Seawater has a higher pH than freshwater due to the concentration of bicarbonate ions in CHAPTER 1 seawater. Therefore, pollutants will react differently in seawater as compared to freshwater. It is also State of the Bay – interesting to note that photosynthetic organisms can affect pH during respiration; carbon dioxide expelled 6 during hours of darkness can lower pH at night and in the early morning. CHAPTER 5 The pH of water is critical to the survival of most aquatic plants and animals. Many aquatic species have trouble surviving if the pH levels drop below 5.0 (too acidic) or rise above 9.0 (too alkaline). For example, acidic precipitation in the upper freshwater reaches of an estuary can diminish the survival rate of eggs deposited by spawning fish (EPA 2006). Although pH generally exhibits low variability in coastal environments due to the high buffering capacity of seawater, human activities can cause significant, short-term fluctuations in pH or long-term acidification of a freshwater body. For instance, algal blooms initiated by an overload of nutrients cause pH to fluctuate dramatically over a period of several hours, greatly stressing local organisms. pH data collected by the TCEQ in the Lower Galveston Bay watershed from 1973 through 2009 were analyzed (39,044 records). pH is not collected by the TPWD Coastal Fisheries Division and was therefore not available. Samples collected at all depths and times were analyzed. An analysis of all samples from tributaries collected at all depths yielded no annual average trend in pH. However, plotting all samples collected from subbays at all depths revealed a declining trend (R2 > 0.25; Figure 6.6).