2000 



Figure 5-5: Dissolved oxygen at all benthic stations (A through F) for each sampling date. 



trend, as the highest biomass occurred in spring 

 (April), and lowest biomass in summer (July) or fall 

 (October). 



There was also a strong significant interaction (P = 

 0.0001) between stations and dates for log-transformed 

 macro fauna abundance (Figure 5-6b). The nature of 

 this interaction was much more complex than for 

 biomass. No one station appeared to have the highest 

 peaks, but Stations A and B (reference site) had almost 

 always the lowest values. Again, low values had a 

 tendency to occur in summer and higher abundances in 

 fall or winter. This result indicated that Stations A and 

 B, most removed from demonstration project effects, 

 suffered from the consequences of evaporation and 

 concomitant high salinity concentrations. 



Macrofauna diversity was very low, ranging from zero 

 to 11 species found at a station (Figure 5-6c). Because 

 diversity was so low, all three replicates were pooled 

 for species analyses lea\'ing no replication. An 

 interaction between stations and dates was e'vident. 

 However, in 13 of 21 sampling periods. Stations A or 

 B had the highest diversit}'. Diversity was highest 

 when abundance was highest. 



The seasonal and inter-annual trends were most 

 evident when all samples at all stations were averaged 

 together to form a marsh-wide average biomass (Figure 

 5-7a), or marsh-wide average abundance (Figure 5-7b). 

 The marsh-wide averages were most useful because 

 station differences were obscured by interaction effects 

 with sampUng dates. VCTien the marsh- wide averages 

 were compared to average sahnit}', the effect of inflow 

 became apparent. VCTien salinit)^ values were high, 

 biomass decreased, often to near zero. During periods 

 following salinit\' declines due to inflow, biomass 

 increased as ex'idenced in the summer through fall of 

 1997 and 1998. In contrast, salinit}' declines due to 

 rainfall alone did not have the same effect. During 

 April 1997, there was a large local rainfall event but 

 Htde inflow (Table 5-1, Figure 5-4). Biomass continued 

 to decline during spring and summer 1997. In 

 contrast, when salinity declined due to an inflow event 

 in fall 1997 (Event 18), biomass increased. There was 

 a strong seasonal signal, with highest biomasses in 

 January' or April of each year, and lowest biomasses in 

 July of each year. Another important trend was less 

 variability in biomass fluctuations through time as the 

 demonstration project progressed. 



The marsh-wide average abundance trend (Figure 5-7b) 

 was very similar to the biomass trend described 



5-10 



Benthic Communities 



