29 



and emigrate or die, and the tubes 

 become darkened by sedimentary 

 sulfides. Bacterial degradation of the 

 tubes results in tube fragmentation. 

 Although the tubes remain 

 identifiable, it is clear from their 

 condition that such populations have 

 experienced local extinction. This is 

 an example of being able to recognize 

 retrograde succession (decreased 

 secondary production) from a death 

 assemblage. 



There also may be statistical 

 uncertainty about the 

 representativeness of samples. 

 REMOTS® surveys need to be designed 

 to account for both small and large- 

 scale spatial variability. Because field 

 sampling is efficient and analysis costs 

 are a fraction of those associated with 

 traditional benthic sampling, both 

 instantaneous replicates (to 

 characterize within-station variability) 

 and multiple stations along transects 

 across disposal mounds (to determine 

 gradients and characterize large-scale 

 variability) are taken. It is important 

 that a sufficient number of stations be 

 spread-out over the entire surface of a 

 disposal mound and not limited just to 

 the mound apex. The top of a disposal 

 mound may experience scour, 

 resulting in an accumulation of coarse 

 shell and sediment. This scour surface 

 is not typical of the overall disposal 

 mound, so it is important that the 

 REMOTS® sampling locations be 

 selected to account for this patchiness 

 in sediment textures. 



42 A Three-Tiered Monitoring Protocol for 

 Unconfined Disposal Mounds 



As stated in the section above, the 



focus of the monitoring effort is to 

 determine the effect of disposal on the 

 secondary benthic production. The 

 overall null hypothesis being tested is: 



H : On an unconfined disposal 

 mound, dredged material 

 disposal will result in benthic 

 population density (a surrogate 

 for production) greater than the 

 ambient condition. 



The objective of this hypothesis is to 

 verify that the disposed sediments are 

 not having toxic effects as predicted 

 during the initial sediment evaluation 

 (permitting) process. 



A three-level tiered monitoring 

 protocol was designed (Figure 2). The 

 first tier relates biological responses to 

 disposal on a population and 

 successional level. These processes are 

 measured against a reference 

 condition on the ambient bottom. The 

 second tier involves the potential for 

 sediment physical factors (mass 

 properties, scour, deposition) to affect 

 colonization. The third tier is focused 

 on the potential for sediment 

 chemistry to affect colonization rates 

 and population density. 



4.2.1 Tier One: Biological Processes and 

 Related Management Decisions 



Box 2.1 "Assess Stage I Population 



Density..... " 



Most dredging and disposal at the 

 three Long Island Sound DAMOS 

 disposal sites takes place in the winter 

 and early spring months to avoid 

 apparent conflict with reproduction 



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



