BENTHIC INFAUNA 



INTRODUCTION 



The benthic infauna are relatively small inconspicuous organisms that inhabit intertidal beach and 

 subtidal bottom sediments. Infaunal communities are generally composed of worms (polychaetes and 

 oligochaetes), clams and small crustaceans and collectively, they play a vital role in maintaining ecosystem 

 productivity. For instance, many infaunal organisms are important prey species for demersal fishes 

 (Woodin 1982; Moeller et al. 1985; Witman 1985; I,e Mao 1986) and thus form an important linlc tn 

 energy transfer pathways in the food chain. Their contribution to primary production in marine 

 environments, though less conspicuous, is of equal importance. Many studies have described the 

 influence of infaunal feeding, burrowing and tube building activities on nutrient recycling (Goldhaber et 

 al. 1977; Aller 1978; Hylleberg and Maurer 1980; Raine and Patching 1980). The importance of this 

 recycling process was documented by Zeitzschel (1980), who estimated that 30-100% of the nutrients 

 required by shallow-water phytoplankton are derived from the sediment; the activities of the benthos 

 often enhance this nutrient release. 



Infaunal organisms are also useful environmental monitoring tools. These species are relatively 

 sedentary and thus are often exposed to and cannot escape the anthropogenic stress. Further, the 

 manner in which infaunal communities respond to stress is highly predictable (Boesch 1973; Reish 1973; 

 Sanders et al. 1980; Boesch and Rosenberg 1982; Young and Young 1982; Rees 1984). For example, 

 a physically stressed community is usually comprised of a few characteristically abundant species (e.g, 

 Polydora ligni, Capitella spp. and Mediomastus ambisetd) which rapidly invade after disturbance or are 

 capable of tolerating environmental stress (McCall 1977; Reish et al. 1980; Sanders et al. 1980). 



To evaluate impacts based on the abundance and species composition of infaunal communities 

 assumes that the organization of natural, undisturbed communities can be established, and that the 

 direction and extent of any natural trends can be identified (Nichols 1985). Many studies have shown 

 that cold winters (Beukema 1979), storms (Boesch et al. 1976), or heavy rainfall (Jordan and Sutton 

 1985; Flint 1985) and changes in such biological factors as competition and predation (l^vinton and 



