Gulf of Mexico 



conditionally approved waters in these 

 states. 



Pollution Sources Affecting Shell- 

 fish-Growing Waters. Pollution 

 sources affecting the region's shell- 

 fish-growing waters reflect urbaniza- 

 tion and industrialization around port 

 cities, and the suburban and rural land 

 uses which characterize about 95 

 percent of the region's estuarine 

 drainage areas (NOAA, 1990). 

 Nonpoint and upstream sources of 

 pollution affect more harvest-limited 

 shellfish-growing waters in the Gulf of 

 Mexico than in any other region. 

 Table 14 shows major categories of 

 pollution sources affecting harvest- 

 limited waters in the region. Data on 

 pollution sources aggregated by 

 estuary are given in Appendix D. 



Among nonpoint sources, septic 

 systems affect the most (48 percent) 

 harvest-limited shellfish-growing 

 waters. This is indicative of the many 

 small communities in the region. 

 Direct urban runoff affects 35 percent 

 of the harvest-limited shellfish-growing 

 waters and upstream urban runoff 

 affects 22 percent, attributable to 

 urbanization, high freshwater inflow, 

 and low tidal influence. In addition, 

 wildlife affects 30 percent of harvest- 

 limited waters. NOAA estimates that 

 over 80 percent of fecal coliform loads 

 in the Gulf of Mexico are from 

 nonpoint sources (Office of Technol- 

 ogy Assessment, 1987). 



Although nonpoint pollution affects the 

 most harvest-limited waters, estuarine 

 drainage areas in the Gulf of Mexico 

 contain the greatest number of point 



sources among the regions, over 

 3,700, or 41 percent of the Nation's 

 total. Point sources of pollution affect 

 only about 14 percent of harvest- 

 limited waters regionwide. Over half 

 of the point sources are industrial 

 facilities, many associated with the 

 petrochemical industry and thus are 

 concentrated around port cities. 

 Galveston Bay, for example, contains 

 747 industrial point sources, the 

 largest concentration in any estuary 

 nationwide. Galveston Bay also 

 contains 566 sewage treatment 

 plants, 45 percent of the regional total. 



Sewage treatment plants affect 27 

 percent of the region's harvest-limited 

 waters, but are a major factor only in 

 the most developed estuaries (about a 

 third), such as Tampa Bay, Mobile 

 Bay, Mississippi Sound, the Missis- 

 sippi Delta Region, and Galveston 

 Bay. Direct discharges are a major 

 pollution factor, affecting 25 percent 

 of harvest-limited waters. These are 

 located primarily in sparsely populated 

 areas of Louisiana, where small 

 camps accommodate hunting and 

 fishing activities. 



Although most of the region's estuar- 

 ies are rural, only eight percent of the 

 harvest-limited shellfish-growing 

 waters were affected by agricultural 

 runoff. The amount of harvest-limited 

 shellfish-growing waters affected by 

 agricultural runoff is not expected to 

 change greatly over the next five 

 years, although urban, industrial and 

 recreational sources of pollution are 

 expected to increase. Between 1970 

 and 1990 the region's coastal popula- 

 tion increased by 30 percent, and is 



37 



