where numbers/m of A. tonsa were 

 negatively correlated with streamflow 

 (r = -0.32, p£ 0.05), correlations 

 at Stations 38-2, 200-2, and 54-3 

 were not significant. A. tonsa was 

 collected every month at each station 

 except in October 1973 at Station 

 44-2. The lowest numbers of A. 

 tonsa were associated with high peaks 

 of freshwater inflow at Stations 38-2 

 in July 1973 (30/m ) , October 1973 

 (0/m ), and September 1974 (21/m ); 

 at Station 44-2 in June 1973 (0/m ), 

 September 1973 (90/m ) , and September 

 1974 (29/m ); and at Station 54-3 in 

 October 19,74 (25/m ) and September 



1974 (67/m ). 

 numbers of A. 



No obvious declines in 

 tonsa were seen in as- 



sociation with freshwater inflow at 

 Station 200-2. Following incursions 

 of fresh water, populations of A. 

 tonsa showed rapid recovery, usually 

 to greater numbers than before flood- 

 ing even though salinities may have 

 remained low. 



DISCUSSION 



Although local rainfall was sig- 

 nificant and negatively correlated 

 with salinity at Stations 38-2, 

 200-2, 44-2, and 54-3 a stronger cor- 

 relation (or higher absolute value of 

 r) was obtained when streamflow was 

 correlated with salinity at each sta- 

 tion. Fluctuations in salinity re- 

 sulting from freshwater inflow to the 

 estuaries are dependent not only on 

 local rainfall but also on precipi- 

 tation and run-off from inland areas. 

 The higher overall salinities record- 

 ed during this study in the Nueces- 

 Corpus Christi Bay system indicate 

 that this area is affected by tidal 

 incursions of higher salinity Gulf 

 water more than the Copano-Aransas 

 area. While salinities in the upper 

 Nueces Bay (Station 38-2) tend to 

 remain low for an extended period 

 following freshwater inflows, the 

 area near the mouth of Oso Bay (Sta- 



tion 200-2) shows a rapid return to 

 higher salinity following freshwater 

 inflows, due to tidal flushing with 

 higher salinity gulf water. The re- 

 moteness of Copano Stations 44-2 and 

 54-3 from the Aransas Pass Inlet re- 

 sults in a long flushing time and 

 very little mixing with gulf water, 

 accounting for the overall lower 

 salinities in this area. 



The initial effects of increased 

 freshwater inflow near the observa- 

 tion points of the study result in 

 the physical displacement of estua- 

 rine water with freshwater. Fresh- 

 water zooplankton populations re- 

 place estuarine zooplankton for 

 short periods until mixing with es- 

 tuarine water raises salinities to 

 levels which allow estuarine species 

 to recover. 



The euryhaline copepod, A. 

 tonsa, the most dominant calanoid 

 copepod throughout this study and 

 other studies along the Texas coast 

 (Gilmore et al. 1976; Holland et al. 

 1974, 1975; Matthews et al. 1975; 

 McAden 1977; Rennie 1975; Sritha- 

 vatch 1973; Texas Dept. of Water Re- 

 sources 1980) , is a very important 

 link in the estuarine food chain. A. 

 tonsa , after initially being dis- 

 placed by freshwater species during 

 high inflow, is very tolerant to low 

 salinities and is able to repopulate 

 a low salinity area very quickly. It 

 is speculated that the success of 

 large populations of A. tonsa follow- 

 ing peak inflows can probably be at- 

 tributed to influx of nutrients, 

 food, and a decrease in higher sali- 

 nity predators . 



CONCLUSIONS AND RECOMMENDATIONS 



1 . Salinity fluctuations in the 

 study area were negatively correlated 



469 



