assays and a mussel filtering assay (MFA). The MFA tested for toxicity of the porewaters by 

 observing filtering rates of a native mussel, the deertoe (Truncilla trimcata). 

 2. Methods 



Ceriodaphnia dubia survival/reproduction assays and 48-hour toxicity assays were used 

 the first year to detect sediment toxicity in Reach 15. 

 2.1 . Materials and Methods 

 2.1.1 Sediment and Porewater Collection Procedures 



This study required the collection of sediment from which we extracted porewater for 

 use in the assays. It is important to collect sediment in a manner that disturbs the collection site 

 as little as possible so as to collect a representative sample and increase the likelihood that 

 laboratory experiments conducted with the collected sediments or porewaters simulate 

 experiments conducted in situ, i.e., at the site of collection (ASTM 1991). The collection of 

 sediments with a Ponar grab was considered the most efficient means of collecting a sample 

 with minimum disturbance of the collection site. Sediment samples were collected from 

 designated sample sites within Reach 15 of the Mississippi River (Table 1, Figure 1 ) with a 



Table 1. Locations of sediment collection sites in Pool 15 given in Mississippi River Miles upstream from the Ohio 

 River. Sample site locations in this table correspond to sample site locations in Figure 1 . Sediment samples were 

 collected at these locations using a Ponar grab. 



