25 



sample, although it had obviously been fully immersed in mud. In these 

 situations, we were forced to move the station slightly to find a more 

 cohesive bottom. Even here, however, the sediments visually resembled a 

 loose gel. In these cases, the bucket screens offered little impediment 

 to the grab's penetration into the bottom, and many organisms were 

 caught on the screens. In essence, the sediments were so low in bearing 

 strength that the grab sank to an unknown depth with the surface layers 

 being sieved by the bucket screens in the process. 



Timson (personal communication) observed a similar sedimentary 

 phenomenon in Muscongus Bay, Maine, while working with sidescan sonar. 

 He describes it as a nepheloid or gel layer which is intermediate 

 between the water column and bottom. We call it fluid mud and believe 

 it is caused by tidal currents which are strong enough to prevent 

 complete deposition of silt and clay-sized particles, but which do not 

 have a sufficient excursion to disperse them from the system. If this 

 is true, we would expect variations in the depth and extent of the layer 

 over a spring-neap tidal cycle. In any event, the phenomenon must have 

 a profound effect on the nature of the benthic community and is worthy 

 of additional study. 

 Sediment Carbon and Nitrogen 



Sediment organic carbon values as determined by chromic acid 

 digestion are presented in Table 2 and Fig. 10. Values range from 1.5 

 to 44.5 mg/g dry weight with an overall mean of 25.2 mg/g. Station 36, 

 which exhibited 233.0 mg/g organic carbon due to a high proportion of 

 wood chips, is an extreme outlier and is excluded from organic carbon 

 numerical analyses. The station is located at the mouth of the 

 Presumpscot River on a deposit of wood chips resulting from past 



