collected during the period of Octo- 

 ber 1978 to June 1979. Development of 

 this data and information from var- 

 ious other sources is presented in 

 "Freshwater Needs of Fish and Wild- 

 life Resources of Nueces-Corpus 

 Christi Bay Area, Texas" (Henley and 

 Rauschuber 1981) . 



MATERIALS AND METHODS 



Spartina spartinae , Monanthocloe lit - 

 toralis , Borrichia f rutescens , and 

 Distichlis 



spicata. 



Annual net 



STUDY AREA 



The selected study site, the 

 Nueces deltaic marsh, lies in a broad 

 basin flanked by bluffs on each side 

 approximately 5-10 miles north and 

 west of Corpus Christi, Texas (Fig- 

 ures 1 and 2). Flooding and drainage 

 of the marsh occurs mainly through 

 the Rincon Bayou, although two smal- 

 ler channels, one dredged and one na- 

 tural, also serve this function. The 

 marsh is crossed by a few old shell 

 roads, used in earlier years during 

 oil and gas drilling activities, and 

 by a railroad right-of-way. The marsh 

 is bounded on the north and east by 

 areas of considerable agricultural 

 and pastoral activity and on the 

 south by a heavy industrial zone 

 along Corpus Christi harbor (cater- 

 ing mainly to shipping and oil sto- 

 rage). 



The areal extent of the marsh 

 has been estimated at 12,300 acres 

 (4,990 ha) and is composed of algal- 

 covered mud flats and emergent marsh 

 vegetation (Benton et al. 1975). 

 Dominant vegetation found in the 

 marsh is generally characteristic of 

 vegetation found in other Texas estu- 

 arine systems. Dominant species are 

 Batis maritima , Salicornia virginica , 



above-ground primary production for 

 the 12,330 acres of marsh has been 

 estimated at 92.4 million pounds (dry 

 weight) per year (42,000 metric tons/ 

 year) in previous studies (Espey, 

 Huston, and Associates 1977). Most 

 of this production is contributed by 

 Borrichia f rutescens and Spartina 

 spartinae , as determined in our con- 

 current studies of marsh primary pro- 

 duction. Mean annual tidal ampli- 

 tudes in the marsh normally range 

 from to 24 inches (0 to 60 cm) and 

 salinities usually vary from 7 to 

 25 ppt. 



MEASUREMENT OF WATER EXCHANGE 



AND SAMPLING 



Flow rates into and out of the 

 Nueces deltaic marsh were measured 

 during the period February 1979 to 

 June 1979. Flow rates for October, 

 November, and December of 1978 were 

 not measured dirctly but were esti- 

 mated using regression analysis of 

 historical rainfall and tide flow 

 data generated by the United States 

 Geological Survey in Corpus Christi, 

 Texas . 



Water samples were taken at mid- 

 depth in the Rincon Bayou using a 4- 

 liter Van Dorn water sampler and im- 

 mediately placed on ice for transport 

 to the laboratory. Triplicate 1- 

 liter water samples were taken over a 

 24-hour tide cycle during each sam- 

 pling trip. Normally there were 4 

 cycling events during a tide cycle: 

 high slack tide, mean high tide, low 

 slack tide and mean low tide. Each 

 cycle usually lasted 2 to 8 hours. 

 Tide cycle times for the Gulf of 



473 



