Christi area with tropical storm- 

 intensity rains that reached as much 

 as a 33 cm accumulation in 24 hours. 

 The results of this intensive storm 

 produced a large amount of riverine 

 input and land runoff to the estua- 

 rine system associated with the Ar- 

 ansas Pass Inlet and Corpus Christi 

 Ship Channel (Figure 1). The impact 

 of this massive freshwater inflow 

 event to the system was reflected 

 by an extensive period of continual 

 low salinities measured in the Corpus 

 Christi Bay estuarine system. This 

 prolonged period of lowered salinity 

 measurements ranging around 18 parts 

 per thousand occurred from approxi- 

 mately 20 September to 27 September 

 1979. Salinities remained well below 

 expected seasonal levels through the 

 middle of October 1979. This storm 

 event, with its associated high 

 freshwater inflow to the estuaries, 

 proved to be relatively unique to the 

 area with freshwater inputs having 

 not occurred with such intensity 

 since Hurricane Beulah in 1967. 



At the time of this event, we 

 had recently completed a five-year 

 survey (1974 to 1979) based upon 

 monthly sampling to investigate the 

 community structure and dynamics of 

 the estuarine benthos in the area of 

 Corpus Christi Bay as illustrated 

 in Figure 1 . This provided us with 

 an extensive baseline of data on ben- 

 thic macrofauna ecology preceding the 

 climatic events described above. By 

 continuing the basic sampling design 

 in this area after September 1979, we 

 were able to compare the events in 

 the benthos that occurred after the 

 storm with the historical data base 

 and to infer the effects of freshwa- 

 ter inflow on the fisheries of the 

 area. Specifically, we resampled two 

 stations (1 and 4) from the original 

 sampling design; Stations 1 and 4 

 represented two different habitats as 

 evidenced by our five previous years 

 of benthic data collection. 



METHODS 



Monthly collections were con- 

 tinued at stations 1 and 4 (Figure 1) 

 as they had been for the previous 

 five years (Flint and Younk in 

 press). The sampling months includ- 

 ed October-December 1979 and January 

 -April 1980. 



Benthic samples were obtained 

 from the stations during each month 

 of sampling duration using a 0.09m 

 modified Petersen grab. Triplicate 

 samples were taken at each collection 

 site during the study period. The 

 contents of the grabs were washed 

 through a 500 u mesh screen and the 

 retained material preserved in a 10 

 percent formalin solution. Benthic 

 macroinvertebrates were separated 

 from the debris in the laboratory by 

 examination under a stereo dissecting 

 microscope, identified to lowest pos- 

 sible taxa, and counted. Wet weight 

 biomass was measured for each total 

 sample plus individually for the dom- 

 inant taxa. A 15 percent weight cor- 

 rection was done to compensate for 

 increase in weight due to preserva- 

 tive effects (Mills and Fournier 

 1979). 



The measure of species diversity 

 based upon species listed for each 

 station during each sampling interval 

 was calculated by the Shannon-Wiener 

 diversity index (Pielou 1966) using 

 log 10 and equitability (Lloyd and 

 Ghelardi 1964). By combining a di- 

 versity index with measures of rich- 

 ness (numbers of species) and even- 

 ness (distribution of relative abun- 

 dance of the species) a reasonable 

 comparison between communities could 

 be accomplished. 



Species composition of individ- 

 ual sampling sites over time was com- 

 pared, using the numerical classifi- 

 cation technique of cluster analysis. 

 The cluster analysis grouped together 



491 



