In addition to the population densi- 

 ties being much greater in 1980, the 

 size class structure is slightly dif- 

 ferent. There appears to be a small- 

 er mean size class for the 1980 col- 

 lections suggesting a slower growth 

 rate. Also obvious from Figure 8 is 

 that while the population was almost 

 depleted in number by March 1979, 

 probably from predation, the March 

 1980 population was still quite dense 

 and in fact this population sustained 

 itself through May 1980. 



The preceding discussion of ob- 

 servations made on benthic infauna 

 densities for Corpus Christi Bay af- 

 ter the intensive freshwater inflow 

 event of September 1979 illustrates 

 the magnitude of the effect this 

 event had on the ecosystem. Stand- 

 ing stock (biomass) information for 

 the benthos, however, makes it much 

 easier to infer the importance of 

 these changes to the other components 

 of the ecosystem such as the shrimp 

 populations which derive much of 

 their nutrition from the benthos. 

 Again, as with infaunal total density 

 infaunal biomass exhibited a dramatic 

 increase after the freshwater inflow 

 event, with a similar short lag peri- 

 od (Figure 9). Much of this biomass 

 rise was related to a tremendous in- 

 crease in the productivity of several 

 dominant bivalves in the study area 

 such as Abra aequalis (Figure 8) . 



Unfortunately, we did not mea- 

 sure infaunal biomass prior to July 

 1979. Therefore, the historical 

 pre-event collections do not have 

 comparable data for this important 

 variable. A direct proportion was 

 ..established, however, between mea- 

 ;,J$red biomass and infaunal density 

 Wr the collections after July 1979. 

 This relationship is illustrated in 

 Figure 10. The relationship dif- 

 fered slightly between the data for 

 station 1 and the data for station A. 



Therefore, two regression equations 

 were established (Figure 10). 



We used these regression equa- 

 tions to calculate total biomass for 

 the benthic infauna between September 

 1974 and June 1979, using the mea- 

 sured values for total density. Thus, 

 we were then able to determine the 

 infaunal biomass over the entire 

 study duration for the early fall and 

 winter periods as we did for com- 

 munity structure evaluations (Figure 

 7). The results of these comparisons 

 (Figure 11) illustrated again that 

 there were no major differences in 

 infaunal biomass for any of the early 

 fall periods shown, including the 

 fall of 1979 when the inflow event 

 occurred. In contrast, however, win- 

 ter 1980 exhibited extremely large 

 increases in benthic standing stocks 

 compared to any other winter shown in 

 Figure 11. Again, this presentation 

 of biomass changes during the winter 

 of 1980 provides evidence linking 

 these changes of the benthos directly 

 to the freshwater inflow event which 

 occurred several months previously. 



DISCUSSION 



The Corpus Christi Bay complex 

 and associated waterways (e.g. Cor- 

 pus Christi Channel) have not shown 

 a dramatic shift in salinity concen- 

 trations extending over greater time 

 periods than a diel cycle for more 

 than a decade. Hurricane Beulah 

 which impacted the bay-estuarine 

 complex behind Mustang Island in 

 1967 was the last major natural dis- 

 turbance to the south Texas coastline 

 which significantly altered the sali- 

 nity gradients of this system away 

 from normal regimes. Although heavy 

 rainfalls were observed for this area 

 during 1972, the estuarine system had 

 not totally recovered from the impact 



502 



