Field Methods 



Since metals were chosen as the initial pollutants of interest, a completely 

 metal-free apparatus was desired for deploying mussels in the field. In view of 

 potential use by other investigators, a simple, relatively inexpensive apparatus 

 which was easy to deploy and service was a secondary goal of the design 

 process. The present apparatus is shown in Figure 3-3. 



A plastic float is attached to a concrete weight by approximately two meters 

 of polypropylene line. The mussel holding baskets, 15 x 15 x 15 cm 

 polypropylene test tube baskets with snap-on lids, are suspended from the line 

 approximately 1 meter above the sediment surface. 



A M. edulis monitoring station is deployed in a two-step operation. The 

 apparatus, minus the mussel baskets, is lowered to the bottom in 5 to 8 m of 

 water, after which typically eight mussel baskets are taken down and 

 suspended in groups of four from the line by scuba divers. The 

 deployment operation requires 10 to 15 minutes on-station and subsequent 

 sampling only about five minutes. Each basket of 20 mussels serves as a 

 subsample, thereby allowing removal of the desired sample without disturbing 

 the remaining mussels. Samples for metals analyses are immediately transferred 

 to "ziploc" polypropylene bags and frozen until analyzed. 



plastic 

 float 



polypropylene 

 line 



mussel 

 baskets 



anchor 



ru^ 



Approx. I m 



Figure 3-3. Schematic of subsurface mussel station. 



30 



