Our Living Resources — Coasuil & Murine E<<)SYStt'ins 



275 



Galveston Bay cstuarine system, seagrass areal 

 extent deelined from 121 ha (300 aeres) in 1975 

 to 81 ha (200 acres) in 1987, but increased to 

 156 ha (385 acres) by 1989. 



Conclusions 



Losses of seagrasses in the northern Gulf of 

 Mexico have been extensive over the last five 

 decades, with losses varying 20%- 100% for 

 most estuaries of the northern Gulf of Mexico. 

 Only a few locales have experienced increases 

 in seagrasses. The high productivity of the Gulf 

 of Mexico seagrass beds as spawning, nursery, 

 food, and shelter areas increases the importance 

 of the loss of this valuable habitat far beyond 

 the areal extent of the resource. Regionwide, the 

 loss of seagrasses is attributable to natural caus- 

 es (hurricanes, cold-front storms, and increased 

 or decreased salinities) and human-induced 

 effects (increased turbidity and decreases in 

 water quality resulting from dredging, boating 

 activities, and other development pressures), 

 which work in concen to deterioriate the envi- 

 ronmental quality of the habitat. 



References 



Duke. T.W.. and W.L. Kruczynski. eds. 1992. Status and 

 trends of emergent and submerged vegetated habitats of 

 the Gulf of Mexico. Gulf of Mexico Proaiam. U.S. 



HnNironnicntal Protection Agency. Slennis Space Center. 

 MS. 161 pp. 



Evans. M.. and T. Brungardt. 1978. Shoreline analysis of 

 Sarasota County Bay systeins with regard to revegetation 

 activities. Pages 193-206 in D.P. Cole. ed. Proceedings of 

 the Fifth Annual Conference on Restoration of Coastal 

 Vegetation in Florida. Environmental Studies Center. 

 Hillsborough Community College. Tampa. 



Lewis. R.R,. M.J. Durako. M.D. Moftler. and R.C. Phillips. 

 198?. Seagrass meadows of Tampa Bay — a review. Pages 

 210-246 m S.F Treat. J.L. Simon. R.R. Lewis III. and 

 R.L. Whitman. Jr. eds. Proceedings of the Tampa Bay 

 Area Scientific Information Symposium. May 1982. 

 University of South Florida. Tampa. 



Neckles. H.A.. ed. 1993. Seagrass monitoring and research 

 in the Gulf of Mexico: draft report of a workshop held at 

 Mote Manne Laboratory in Sarasota, Florida. January 

 28-29. 1992. National Biological Survey. National 

 Wetlands Research Center. Lafayette. LA. 75 pp. 



Puhch. W.M.. Jr.. and W.A. White. 1991. Decline of sub- 

 merged vegetation in the Galveston Bay system: chronol- 

 ogy and relationship to physical processes. Journal of 

 Coastal Res. (4):1125-1138.' 



White. W.A.. T.A. Tremblay. E.G. Wermund. Jr. and L,R. 

 Handley. 1993. Trends and status of wetland and aquatic 

 habitats in the Galveston Bay system. Texas. The 

 Galveston Bay National Estuary Program. Puhl. 

 GBNEP-31. 225 pp. 



Wolfe. S.H.. and R.D. Drew, eds. 1990. An ecological char- 

 acterization of the Tampa Bay watershed. U.S. Fish and 

 Wildlife Service Biological Rep. 90(20). 334 pp. 



Zieman. J.C. and R.T. Zieman. 1989. The ecology of the 

 seagrass meadows of the west coast of Florida: a com- 

 munity profile. U.S. Fish and Wildlife Service Biological 

 Rep. 85(7.25). 155 pp. 



For further information: 



Lawrence R. Handley 



National Biological Service 



Southern Science Center 



700 Cajundome Blvd. 



Lafayette. LA 70506 



A series of lagoons forms an almost continu- 

 ous fringe of water behind coastal baniers 

 for 500 km (310 mi) from Galveston Bay, 

 Texas, to the Mexican border (Fig. 1). At the 

 northeast end, where river discharge and precip- 

 itation greatly exceed evaporation from the 

 embayments, fringing marshes are the dominant 



wetland type. Toward the southwest, freshwater 

 inputs decrease, fringing marshes are replaced 

 by wind-tidal flats that support highly produc- 

 tive algal mats during periodic inundation, and 

 seagrasses dominate the shallow waters of the 

 embayments (Table). 



Seagrasses are so prevalent in Laguna Madre 

 that they defme the structure of the physical 

 environment, as well as being the source of bio- 

 logical production for the ecosystem. 

 Consequently, seagrass meadows serve a criti- 

 cal nursery function in support of the region's 

 rich fisheries, and one waterfowl species has 

 established an exclusive dependence on Laguna 

 Madre and its most common seagrass. More 

 than 75% of the world population of redhead 

 ducks {Aytliya americana) winters in the greater 

 Laguna Madre ecosystem (inclusive of the 



Seagrass 

 Meadows of 

 the Laguna 

 Madre of 

 Texas 



by 



Christopher P. Oiiiif 



National Biological Service 



Table. Seagrass cover in bays of 

 the Texas coast. 



Fig. 1. Major bay systems along the Texas coast. 



• Adair etal 1994. 



"" Adair and Moore 1990, 



"""Ouammen and Onul 1993, 



