50 -, 



45 



40 



35 -] 



E 30 - 



^ 25 4 



C 



OJ 20 



15 



10 



5 



J 



5000 



- 140 



1995 



1996 



1997 



1998 



1999 2000 



^m Total flow into Rincon Bayou 



I Total rainfall 

 ▼• • Average salinity: Reference Site (Stations A and B) 

 -o— Average salinity; upper Rincon Bayou Site (Stations C and D) 

 -a — Average salinity: central Rincon Bayou Site (stations E and F) 



Figure 5-4: Marsh-wide average salinity at each sampling site for each sampling date. Cumulative daily rainfall and 

 inflow/ into Rincon Bayou also plotted for each quarterly period betw/een sampling dates. 



Dissolved Oxygen 



Dissolved oxygen (DO) concentrations varied widely 

 during the study period, from hypoxic (< 2 rng/l) to 

 super-saturated (Figure 5-5). Stations A and B were 

 most likely to be hypoxic. These stations have sea 

 grasses, so decay of organic matter or night time 

 respiration likely caused the hypoxia, which was mostly 

 likely to occur in summer. The solubility of oxygen in 

 sea water decreases with increasing temperature and 

 salinity, both of which increased in summer. 



Benthos 



To indicate the importance of freshwater inflow, the 

 average salinity at all stations (instead of at each site) 

 was evaluated against many organismal response 

 variables. 



Macroinfauna 



There was a strong significant interaction (P = 0.0001) 

 between stations and dates for both log-transformed 

 biomass and log-transformed abundance. Station C, 

 the most directiy affected by diversion from the 

 Nueces Overflow Channel, had the highest biomass 

 and abundance of macrofauna (Table 5-2). However, 

 because of the significant interactions, differences 

 among stations means could not be determined with a 

 simple post hoc comparison, and examination of the 

 interaction itself was necessary. 



At various times. Stations E and F had the lowest 

 biomass, or Stations A and B had the lowest 

 (Figure 5-6a). Station C had the highest abundance of 

 all stations during periods of peak biomass blooms. 

 Station C was the station most directly influenced by 

 inflow from the project. There was a strong seasonal 



5-8 



Benthk Communities 



