Table 5-7: Composition of the meiofauna community. 



Taxa 



Percent 



Nematoda 

 Copepoda 

 Other metazoa 

 Insects 

 Protozoa 



71,10 

 9.39 

 4.17 

 0.02 



15.32 



DISCUSSION 



Macrofauna and Meiofauna 



The upper Nueces Delta is an unusual marsh, with 

 extreme environmental variability. The variability is 

 evidenced by wide ranges in salinity (from to 

 160 ppt), high temperatures (12 to 40 °C) and a 

 tendency toward reverse salinity gradients, with higher 

 salinity concentrations in the upper marsh area. These 

 environmental extremes drive the response patterns of 

 benthic resources. Macrofauna diversity in Rincon 

 Bayou was generally lower than found in either Nueces 

 Bay or Corpus Chris ti Bay. The average number of 

 dominant species (diversity index Nl) per station was 

 only 1.8 in Rincon Bayou, whUe, in contrast, the 

 average Nl value was 3.5 in Nueces Bay stations 



(Mannino and Montagna 1997) and 7.0 in Corpus 

 Christi Bay (Ritter and Montagna 1999). For 

 comparison, hypoxic stations in Corpus Christi Bay 

 averaged an Nl value of 1.5 (Ritter and Montagna 

 1999). The low diversity in Rincon Bayou reflects a 

 relatively greater degree of stress on benthos caused by 

 the higher environmental variability, particularly in 

 salimty extremes. 



Macrofaunal abundance and biomass, which are 

 indicators of productivity, were in a range typically 

 found in Nueces and Corpus Christi bays. This 

 observation indicates that environmental variability 

 affected benthic community structure but was not 

 likely to affect secondary productivit}'. However, 

 marsh habitats typically have greater productivity than 

 open bay habitats (Day et al. 1989), so it was not 

 known if production in the Nueces marsh was optimal 

 or suboptimal. 



Overall, there is strong evidence that the demon- 

 stration project increased producti^^ty and ameliorated 

 stresses on biodiversity. These positive effects were 

 caused by increased opportunities for freshwater 

 inflow into the marsh and responses of the benthos to 

 this inflow. Seasonal increases of biomass occurred in 

 spring, when salinity values were lowest and water 



100000 



ri"" 80000 



E 



(]} 

 o 



g 60000 



C 



J3 

 CD 



ro 



c 



O 

 03 



40000 



20000 



- Macrofauna 



- Meiofauna 



I- 4000 E 



o 



5000 



X 



c, 



0) 



o 



c 



03 



■o 



X) 

 03 



03 



c 



03 



1000 -§ 



- 3000 



- 2000 



1995 



1996 



1997 



1998 



1999 



2000 



Figure 5-12: Marsh-wide average abundance of meiofauna and macrofauna. 



Chapter Five ♦ 5-21 



