ESTUARINE BENTHIC COMMUNITY DYNAMICS RELATED TO FRESHWATER INFLOW 

 TO THE CORPUS CHRISTI BAY ESTUARY 



R. Warren Flint and Steve C. Rabalais 



University of Texas Marine Science Institute 

 Port Aransas Marine Laboratory 

 Port Aransas, Texas 



ABSTRACT 



In September 1979 Corpus Chris- 

 ti Bay was impacted by tropical 

 storm-intensity rains that resulted 

 in an intensive period of freshwater 

 inflow to the bay, dramatically de- 

 creasing salinity below normal levels 

 for more than a month. The existence 

 of an historical data base on benthic 

 infauna for this estuary allowed an 

 investigation to be conducted con- 

 cerning effects of this intensive 

 freshwater inflow on the estuarine 

 benthos. Several months after the 

 inflow event, densities of dominant 

 infaunal populations increased to 

 levels never observed and producti- 

 vity of the benthos, as represented 

 by biomass changes, increased sub- 

 stantially over previous years. We 

 speculated that the nutrients as- 

 sociated with the intensive freshwa- 

 ter inflow increased the primary pro- 

 ductivity of the estuarine ecosystem. 

 This increased productivity was, in 

 turn, eventually reflected by the 

 benthos. These data may provide a 

 missing link in the correlations be- 

 tween freshwater inflow events in 

 south Texas estuaries and yields of 

 some of the important fisheries such 

 as shrimp. 



INTRODUCTION 



Bays and estuaries along the 

 coastline of the northwestern Gulf of 

 Mexico are strongly influenced by 

 freshwater inflow and its associated 

 nutrients. This is true primarily 

 because these bays and estuaries are 

 located in a semi-arid climate re- 

 ceiving usually less than 70 cm of 

 rainfall per year (Flint and Rabalais 

 1981). It is thought that in these 

 hypersaline systems, freshwater in- 

 flow, which is very unpredictable in 

 nature, affects estuarine community 

 species composition, the vitality and 

 productivity of estuarine food 

 chains, and the harvests of many 

 fisheries related to the estuarine 

 ecosystem, such as shrimp. The links 

 between the inflow of fresh water and 

 the resulting effects as reflected by 

 the changes in fishery harvest, how- 

 ever, are presently not well under- 

 stood. 



During the 24-hour period be- 

 ginning with the evening of 18 Sep- 

 tember 1979, an extensive low pres- 

 sure system engulfed the south Texas 

 coast and heavily impacted the Corpus 



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