26 



assumption is that if the rate of 

 secondary production of prey species 

 on the disposal mound is equal to or 

 greater than the ambient bottom, the 

 foraging value of the bottom will not 

 have been compromised by disposal. 



Secondary productivity of prey 

 species is used here to mean the 

 change in benthic biomass per unit 

 time following cessation of disposal. A 

 corollary to this definition is that if 

 these benthic invertebrates are eaten 

 by demersal species, the prey are 

 replenished rapidly by recruitment. 



Quantification of secondary benthic 

 production is a very time-consuming 

 and costly task involving time-series 

 sampling of the bottom for 

 determination of the dry weight and 

 shell-free biomass (and/or caloric 

 content) of colonizing species. Because 

 of the need for rapid data turnaround 

 at reasonable cost, the DAMOS TAG 

 adopted a surrogate measure of 

 secondary production involving the 

 enumeration of colonizing polychaetes 

 (Stage I sere) from REMOTS® images 

 and relating these abundances to 

 known turnover rates of these species 

 (McCall, 1977 and Rhoads, McCall, and 

 Yingst, 1978). This task is made 

 relatively easy because only a few 

 species participate in early succession. 



Earlier research studies in Long 

 Island Sound by McCall (1977) and 

 Rhoads et al. (1978) showed that rates 

 of secondary benthic production 

 (gm/m 2 /day) on areas of "disturbed" 

 seafloor was 2 to 6 times greater than 

 on the ambient bottom. Further, most 

 of this enhanced production is related 

 to the massive sets of larvae of spionid, 



capitellid, or oweniid polychaetes that 

 initially colonize disturbed habitats 

 (Stage I seres). The basic assumption is 

 that the productivity of the bottom can 

 be deduced or inferred from the 

 standing stock densities of pioneering 

 polychaetes. The densities of these 

 polychaetes can be estimated from 

 REMOTS® images by counting the 

 number of tubes projecting above the 

 sediment surface (number per linear 

 centimeter across the 15 cm width of 

 the optical window). This number 

 squared and expressed as number of 

 tubes per cm 2 can be used as the unit 

 of comparison for making estimates of 

 secondary production in space and 

 time. It is assumed that all or most of 

 the tubes contain living polychaetes 

 and that these polychaetes provide a 

 major potential fraction of the food for 

 foraging fish and crustaceans. This 

 assumption also is based on 

 observations from laboratory 

 microcosm experiments (Germano, 

 1983) that abandoned tubes 

 disintegrate rapidly. However, if the 

 status of the tubes is questionable, 

 some limited grab sampling can be 

 done to resolve this question. 



In addition to the phenomenon of 

 larval recruitment, the variables 

 including the physical properties of 

 disposed sediment, sedimentary 

 processes, and the chemistry of 

 disposed materials which also can 

 affect rates of colonization and 

 secondary production must be 

 included as "feedback" factors in the 

 monitoring of disposal site biological 

 impacts. The assumption here is that 

 the rate of recruitment of the bottom 

 (and hence rate of succession) is 

 limited by physical and chemical 



An Integrated, Tiered Approach to Monitoring and Management of Dredged Material Disposal Sites 



