of various macroinvertebrate species such 

 as Streblospio benedicti and Capi tella 

 capitata . Such organisms are 

 characterized by extremely short life 

 cycles. Rapid reproduction and larval 

 settlement could mask the impact of 

 and biological disturbances, 

 often important features of 

 estuaries. Heavy larval 

 not always followed by 

 a given species, however, 

 habitat suitability 

 also be implicated 



physical 

 which are 

 temperate 

 recruitment is 

 predominance of 

 Other factors such as 

 and competition could 



in the 

 structure. 



determination of community 



At various levels of biological 

 organization in the estuary, the dominant 

 macroinvertebrate populations are 

 opportunistic and are influenced to 

 varying degrees by the high productivity 

 and physical instability of the system. 

 Such populations have adapted well to 

 habitat instability and variability. 

 Response time to disturbance remains 

 little understood, however. Recent 

 experiments in polyhaline portions of the 

 bay system (Livingston et al. 1983) 

 indicate that salinity could be a factor 

 in the influence of predation on benthic 

 infaunal associations. Infaunal 



macroinvertebrates in the field were 

 manipulated using a series of treatments 

 that involved exclusion cages (i.e., 

 predators were kept out), inclusion cages 

 (i.e., predators were returned to 

 exclusion cages), and field controls. 

 These treatments were compared to 

 laboratory microcosms taken from the 

 field. Preliminary results indicate that, 

 over a 6-week period of observation, there 

 were increased numbers of 

 macroinvertebrates in the laboratory 

 microcosms and exclusion cages. Species 

 diversity was reduced in such treatments 

 relative to field controls and inclusion 

 cages. Thus predation in polyhaline areas 

 of high macroinvertebrate diversity and 

 low dominance may affect infaunal 

 macroinvertebrate community structure. 

 The influence of salinity on species 

 diversity and relative dominance could 

 thus be a factor in the relative influence 

 of predation pressure on dominant 

 populations in various portions of the 

 estuary. In areas of low dominance, the 

 influence of predation may be enhanced 

 relative to oligohaline areas where 

 dominance is naturally high. In any case, 

 few generalizations of predation effects 

 can be made without due consideration to 

 local habitat conditions. 



89 



