of Beulah and the effects of these 

 rains were therefore confounded and 

 not totally interpretable. 



The logic involved in focusing 

 on the dynamics of populations on 

 the sea floor for this study in- 

 cluded the fact that because of the 

 sedentary nature of these fauna, they 

 represent a potential barometer in- 

 dicating changes to the system unlike 

 fish and many planktonic fauna which 

 are relatively mobile and able to 

 avoid adverse conditions prevailing 

 over a preceding point. Furthermore, 

 the benthos represents an important 

 component of the estuarine ecosystem 

 not only because of their trophic re- 

 lationships with important fisheries 

 but also because their activities and 

 functioning within the sediments play 

 a large role in material fluxes from 

 the sediment sinks, including the nu- 

 trients which potentially drive the 

 production of the system. 



Unlike the few previous studies 

 documenting accounts of effects of 

 freshwater flooding on the estuarine 

 benthos (Stone and Reish 1965; Boesch 

 et al. 1976), the results of this 

 study suggest that the inflow event 

 had a positive impact on the func- 

 tioning of the ecosystem. Stone and 

 Reish (1965) reported mortalities of 

 benthic invertebrates resulting from 

 heavy rainfalls in the upper portions 

 of some California estuaries. Wells 

 (1961) reported effects of freshwater 

 inflow from a series of successive 

 hurricanes on oyster reef fauna of 

 the Newport River estuary in North 

 Carolina indicating mass mortalities 

 and community structure changes. In 

 a similar fashion, Thomas and White 

 (1969) observed high invertebrate 

 mortality following an unusually 

 heavy spring thaw discharge into 

 the Bedford River, Prince Edward Is- 

 land. 



In contrast to the above reports 

 concerning small estuarine systems 

 which do not have the volume of water 

 to buffer against dramatic salinity 

 changes, two studies in large estua- 

 ries also showed either high mortali- 

 ties and community structure changes 

 or that salinity changes simply de- 

 termined the distribution of fauna. 

 Boesch et al. (1976) observed the 

 benthos in the lower Chesapeake Bay 

 after Hurricane Agnes and found that 

 many abundant species were eliminated 

 from the shallow bottoms and several 

 species were eliminated or reduced in 

 abundance in the deeper waters after 

 extensive freshwater intrusion into 

 the estuary. Fradette and Bourget 

 (1980) found that numbers of organ- 

 isms and biomass decreased markedly 

 from higher salinity areas to areas 

 affected by freshwater inflows in the 

 Gulf of St. Lawrence. 



In the present study, from the 

 cluster analysis results it would ap- 

 pear that community structure changes 

 had occurred after freshwater inflow 

 (Figure 6 and 7). In fact a few spe- 

 cies did occur which had not been 

 present previously increasing the 

 number of species present in the bay 

 (Figure 4) . The most striking ben- 

 thic changes that occurred, however, 

 were the tremendous increases in 

 densities (Figure 4) which had a pro- 

 found effect on the clustering tech- 

 niques employed. The dominant fauna 

 did not disappear or change, as was 

 observed in other studies. These 

 fauna simply increased their produc- 

 tion of biomass and numbers to rec- 

 ords never observed before, in res- 

 pect to the historical data base. 



There is a possibility that in 

 the previous studies cited above, 

 either because of the smallness of 

 the estuary or becuase the salinity 

 changes after freshwater inflow were 

 so dramatic (Boesch et al. 1976) that 



506 



