freshwater species had a positive 

 correlation with streamflow (r = 

 +0.051, p £0.005) while the correla- 

 tion between standing crops of estua- 

 rine species and streamflow was not 

 significant. Freshwater species 

 first occurred at -Station 38-2 in 

 June 1973 (5,168/m ). The highest 

 numbers of freshwater species were 

 associated with a period of exten- 

 sive inflow from June through Novem- 

 ber 1973. During this period numbers 

 of estuarine species were lowest in 

 July (94/m ), October (65/m ) , and 

 November 1973 (247/m ) . Remnants of 

 freshwater populations were evident 

 in December 1973 (1/m ), January 1974 

 (0.3/m ), February 1974 (7/m ) . 

 Freshwater species .increased in Au- 

 gust 1974 (3.679/m ) and September 

 1974 (3,850/m ) with increased in- 

 flows. Low numbers of freshwater 

 species were found in Decemher 1974 

 (8/m ) and January 1975 (1/m ). De- 

 creased estuarine species occurred in 

 July 1973 (94/m ), October 19p (65/ 

 m ), and November 1973 (247/m ), and 

 September 1974 (185/m ) during fresh- 

 water inflow. 



At Station 200-2 standing crops 

 of freshwater zooplankton were posi- 

 tively correlated with streamflow 

 (r = +0.84, pi 0.005) while estu- 

 arine species were not (Figure 6). 

 The greatest effect of streamflow 

 increases on estuarine species stand- 

 ing crop was in September 1973 when 

 numbers dropped to 818/m . In June 



1973 (370/m ), September 1973 (1116/ 

 m ), and October 1973 (638/m ) in- 

 cursions of freshwater zooplankton 

 occurred with increased streamflow. 

 The only other freshwater species 

 observed were in May (1/m ) and June 



1974 (1.5/in ). 



The effects of streamflow on 

 standing crops of estuarine and 

 freshwater zooplankton at Stations 



44-2 and 54-3 in Copano Bay were sim- 

 ilar (Figures 7 and 8). Positive 

 correlations for streamflow versus 

 freshwater species occurred at Sta- 

 tion 44-2 (r = +0.49, p 1 0.005) and 

 Station 54-3 (r - +0.64, pi 0.005). 

 Freshwater species at Station 44-2 

 were most abundant in June 1973 

 (385/m ), July 19J3 (42/ni ) , Septem- 

 ber 1973 (3,045/m ), and October 1973 

 (724/m ), and in September 1974 

 (1,708/m ) during which times stream- 

 flow was greatest. Only low numbers 

 of freshwater zooplankton were asso- 

 ciated with increased streamflow in 

 May 1974 (1/m ) and June 1974 (21/m ) . 



At Station 44-2 the correlation 

 between streamflow and estuarine zoo- 

 plankton standing crops was not sig- 

 nificant. Increased inflows at Sta- 

 tion 44-2 resulted in low standing 

 crops of estuarine zooplankton in 

 June 1973 (177/m ), September 1973 

 (175/m ), and October 1973 (53^/m ), 

 and in September 1974 (104/m ) and 

 October 1974 (388/m ) . 



Incursions of freshwater spe- 

 cies at Station 54-3 occurred in 

 June (416/m ), JuLy (93/m ) , and Oc- 

 tober 1973 (375/m : J, and in Septem- 

 ber 1974 (1,319/m ). A few fresh- 

 water organisms, were found in Novem- 

 ber 1973 (8/m ) and February 1974 

 (3/m ). The correlation of stream- 

 flow and standing crops of estuarine 

 species at Station 54-3 was not sig- 

 nificant. Estuarine standing crops 

 decreased in October 1973 (100/m ) 

 and in September 1974 (176/m ). 



Acartia tonsa , a ubiquitous 

 calanoid occurred at salinities rang- 

 ing from 0.04 ppt at Station 44-2 

 in October 1973 to 35.2 ppt at Sta- 

 tion 200-2 in August 1974. Linear 

 correlations of total numbers/m of 

 A. tonsa with streamflow were cal- 

 culated for each station (Figure 9). 

 With the exception of Station 44-2, 



464 



