Chapter 7 – State of the Bay, Third Edition

CHAPTER 7 – STATE OF THE BAY, THIRD EDITION Key Habitats of the Galveston Bay Watershed Written & Revised by L. James Lester The Gulf coastal plain rises gently from sea level to around 200 feet … Much of the flora is in tall grass and midgrass prairies and cordgrass marshes … The coastal marsh itself is a narrow belt of low wetlands. The fauna is very diverse, with more than three hundred species of birds relying on this area for food and rest on their spring and fall migrations ... Spanish records tell us that there were extensive open prairies of little bluestem, Indian grass, and sedges on the uplands between the many rivers. The bottomland hardwoods were abundant, with sugarberry, pecans, elm, and live oak. Now, most of the land has been plowed and cut into farms and ranches. —Richard Bartlett, in Saving the Best of Texas (1995) Introduction The Galveston Bay system contains a variety of habitat types, ranging from open water areas to wetlands to upland prairie. Regional habitats support numerous plant, fish, and wildlife species and contribute to the tremendous biodiversity found in the watershed. The maintenance of varied, abundant, and appropriate habitat is a requirement for the preservation of the characteristic biodiversity of the Galveston Bay system. Habitat is defined as the ecological or environmental area where organisms live. This chapter provides details on the most State of the Bay 2009 Bay the of State vulnerable habitats found – in and around Galveston Bay; including their location, relative area, CHAPTER 1 biological characteristics, State of the Bay – the ecological services 7 they provide and specific Figure 7.1. Map of habitats and developed lands in the Lower Galveston threats to their Bay watershed. Data source Coastal Change Analysis Program land use- land cover data (NOAA 2006). CHAPTER existence. Terrestrial 1 and aquatic habitats that are common in the Lower Galveston Bay watershed (see Figure 7.1) will be considered, including coastal prairie, riparian forest, wetland, oyster reef, and seagrass meadow. Three of the bay’s aquatic habitats are emphasized because they have been identified in The Galveston Bay Plan (GBNEP 1994) for special conservation and restoration efforts. First, wetlands serve important hydrological and ecological functions in the bay ecosystem, but have experienced significant rates of loss over the past century (White et al. 1993). Second, seagrass meadows are a valuable but now rare habitat in the Galveston Bay system outside the Christmas Bay Complex (Pulich and White 1991; Pulich 1996; Williams 2007). Third, oyster reefs are important as indicators of the overall condition of the ecosystem and are the basis for an important commercial fishery. Oyster-shell reefs were dredged and exploited, with attendant ecological detriment, for many decades (see Chapter 3). Recently, oyster reefs bore the brunt of storm surge effects from Hurricane Ike. Two terrestrial habitats: coastal prairie and riparian forest (including their associated freshwater wetlands), are of special conservation concern in the Lower Galveston Bay watershed. Alteration of these habitats for urban and suburban development has left little of their original area, especially in the case of coastal prairie. Wetlands Wetlands are “lands transitional between terrestrial and aquatic systems where the water table is usually at or near the surface or the land is covered by shallow water” (Cowardin et al. 1979). Wetlands in the Lower Galveston Bay watershed play several key ecological roles in protecting and maintaining the health and productivity of the estuary. In this chapter we will focus on 2 types of wetlands: (1) Fringing marshes are estuarine. They are situated along the edge of Galveston Bay and are intermediate between the aquatic habitats of the bay and the terrestrial habitats that surround it. (2) Freshwater wetlands are palustrine. They lie inland from the bay and may be embedded in coastal prairie, riparian corridors, or forest habitat complexes. State of the Bay – 7 Figure 7.2. Reddish egret at Bolivar Flats. Image ©2010 Jarrett Woodrow. CHAPTER 2 The Origin and Importance of Wetlands Wetlands were formed in Galveston Bay by the long-term interaction of the ecosystem's physical processes (see Chapter 5). These processes occurred throughout geologic time and most still occur today. Rainfall and surface runoff, water table fluctuations, streamflow, evapotranspiration, waves and longshore currents, lunar and wind-driven tides, storms and hurricanes, deposition and erosion, subsidence, faulting, and sea level rise form an array of physical environments that range from being infrequently to permanently inundated with water (White and Paine 1992). The resulting elevations of these habitats range from submerged bay bottom, through the intertidal zone, to the zone above high tide that is infrequently flooded by storms. The continuing action of physical processes and the proximity to saltwater and freshwater sources determine the location and composition of wetland plant communities. In addition to being formed by physical processes, wetlands are important elements of many biological processes that support the bay ecosystem. Hydrologically, fringing marsh and freshwater wetlands are valuable filtering zones for polluted runoff, protecting the bay from excessive organic and sediment loadings from the land. Freshwater wetlands also serve as flood control areas that release rainfall runoff slowly compared to the rapid discharge from man-made drainage systems. Finally, well-established, vegetated wetlands also form a buffer between high-energy water and land, preventing or reducing shoreline erosion. Following the disaster of Hurricane Katrina in 2005, there was general recognition that the diminution of wetland extent seaward from New Orleans permitted the storm surge to reach the city at a greater height than if it had moved over intact wetlands (Day et al. 2007). Wetlands are among the most productive biological systems on the planet (Day et al. 1989; Keddy 2000). They may be more important to the Galveston Bay system than to many other bays (Sheridan et al. 1989). Among the most important of wetland functions is their role in providing habitat for many species of plants, fish, birds, and other wildlife. All of Galveston Bay’s principal commercial and recreational fishery species rely on estuarine wetlands during at least some part of their life cycle. The wetland edge is a particularly important habitat for white and brown shrimp (Whaley and Minello 2002). Other marsh-dwelling species include blue crab, red drum, spotted seatrout, Southern flounder, and Gulf menhaden. In the same way, wetlands are important nurseries to hundreds of non-commercial species that comprise a large part of the bay food web. Bird species, such as snowy egrets, great egrets, reddish egrets (Figure 7.2), roseate spoonbills, tri-colored herons, black-crowned night herons and great blue herons use marsh as feeding habitat. State of the Bay 2009 Bay the of State – Types of Wetlands The distribution of fringing and freshwater wetlands occurs along a generally south-to-north salinity gradient. Fringing marsh (estuarine wetlands) typically occurs in the southern portions of the bay near the Gulf passes, while freshwater wetlands are found inland and at points farther north, along bayous and near CHAPTER 1 State of the Bay the mouths of rivers. The characteristics of these wetland classes are described below. – 7 CHAPTER 3 Estuarine Wetlands Estuarine wetlands exist in the Galveston Bay system across a salinity gradient and are classified into salt marshes and brackish marshes. Estuarine wetlands are often referred to as fringing marshes because they are found near the shoreline of the bay at the land-water interface. Salt Marsh Salt marsh communities (Figure 7.3) are found in high-salinity areas along protected estuarine shorelines. Prevalent species in the salt marsh community include smooth cordgrass (Spartina alterniflora), saltwort (Batis maritima), saltgrass (Distichlis spicata) and glasswort (Salicornia spp.) (White and Paine 1992). Smooth cordgrass, which lives in the intertidal zone, dominates the low salt marsh community (e.g., the portion of the marsh that is most frequently inundated by bay waters). While living, cordgrass is seldom eaten, and then by only a few herbivores. Figure 7.3. Smooth cordgrass (Spartina alterniflora) Once dead it nourishes the large bay food salt marsh located near Bayou Vista. Image © 2007 web as detritus. iStockphoto.com Edges of the salt marsh serve as refuge and nursery for juveniles of many species, especially brown and white shrimp. These habitats are also important feeding grounds for wading birds, such as herons and egrets. At higher elevations, marsh hay (or saltmeadow cordgrass, Spartina patens) and Gulf cordgrass (S. spartinae) occur, although they are more common in brackish marshes (White and Paine 1992). Brackish Marsh This community inhabits the transitional zone between salt marsh and fresh marsh and is affected by highly variable water levels and salinities. As would be expected, a number of species use this habitat, ranging from fresh water to salt-marsh species. In general, the brackish marsh is dominated by marsh hay and saltgrass. Other species include black needlerush (Juncus roemerianus), common reed (Phragmites australis) and State of the Bay – big cordgrass (Spartina cynosuroides), seashore paspalum (Paspalum vaginatum), longtom (Paspalum lividum) in 7 fresher areas, and isolated

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