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4.0 TIERED MONITORING SCHEME 

 FOR UNCONFINED AQUATIC 

 DISPOSAL 



4.1 Background 



Unconfined aquatic disposal in 

 New England takes place in most cases 

 on low kinetic energy, silt-clay bottom 

 types in water depths of 20 to 90 

 meters within a few kilometers of 

 shore. Biological resources of concern 

 tend to be demersal fish and 

 crustaceans (such as lobsters), because 

 they provide a direct link via the food 

 chain to human health. The direct 

 effect of disposal on these commercial 

 resources is difficult to evaluate for 

 two primary reasons: 



• These secondary consumers are 

 mobile (many are migratory); 

 and, 



• They have relatively long life 

 spans. 



This means their physiological 

 condition is a function of the quality 

 of habitats that they have lived in 

 throughout their life history. For this 

 reason, if such species are sampled 

 from a disposal site, it is not possible 

 to attribute their specific condition to 

 disposal activities or disposal materials 

 with any degree or certainty. This is 

 the same reason why disposal site 

 monitoring does not include 

 phytoplankton, zooplankton, or nekton 

 as sentinel monitoring species. 



Demersal nekton species are also 

 difficult to sample quantitatively on 

 disposal sites because of the relatively 

 small area of the bottom that may be 



occupied by disposed material. If 

 sampled, it is not possible to 

 determine how long a sampled 

 specimen has been in residence on the 

 disposal mound. This makes it 

 impossible to evaluate exposure 

 history. 



Finally, the direct effects of disposal 

 activities on the behavior and long- 

 term physiological responses of 

 demersal fish and crabs or lobsters are 

 poorly known. We have no indices or 

 coefficients (e.g. acute toxicity or tests 

 for sublethal effects) that allow one to 

 quantify direct exposure effects on 

 demersal predators. Because of all of 

 the above shortcomings, the effect of 

 disposal on commercial species is best 

 inferred from the effects of disposal on 

 their food (prey) resources. 



4.1.1 Underlying Assumptions 



Because of the difficulties with 

 .measuring the direct effects of disposal 

 on benthic predators, a surrogate 

 "effects" parameter is required. This 

 surrogate parameter is the food 

 sources of demersal fish and 

 crustaceans: sedentary or relatively 

 immobile benthic invertebrates that 

 colonize dredged materials. These 

 species usually are abundant on 

 disposal sites; individuals spend all of 

 their benthic life cycle on disposal 

 mounds and are intimately associated 

 with both the sediment solids and 

 pore waters through burrowing, 

 feeding, and respiratory activities. 

 These prey species are the best time- 

 integrator of habitat quality and site 

 conditions. Because the prey may be 

 consumed by demersal fish and 

 crustaceans, the underlying 



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



