forward of the submersible ' s acrylic pressure hull. The second 

 system consisted of a 35 mm Benthos camera/f resnel lens package 

 (Honjo et al., 1984) to take black-and-white photographs of a 

 light-defined volume (0.28 m^ ) at 12-s intervals while the 

 submersible moved horizontally at 0.7 kt for 5-min transects. 

 Abundances were also estimated in situ by visual observations 

 using nearest neighbor distances (Mackie and Mills, 1983). Care 

 was taken to limit the use of submersible lights when estimating 

 krill abundance. 



Fecal pellets were collected using eight specially-designed 

 cylindrical 7.5 1 acrylic samplers (17.6 cm ID x 35.4 cm long). 

 These samplers were mounted vertically along a linear framework 

 just forward of the submersible ' s pressure hull. The ends of 

 each cylinder were sealed by a pair of lids that moved 

 horizontally over the openings. Sieves consisting of 209 urn 

 plankton netting glued to 8 cm tall, acrylic frames (17 cm ID) 

 were inserted into the bottom of each sampler. In use, the 

 samplers' lids were partially opened during launching of the 

 submersible. After launch, as soon as the samplers filled with 

 water forcing out all residual air, the lids were closed. The 

 submersible then descended to a depth just below the layer of 

 fecal pellets, the lids were opened and the submersible was made 

 just slightly positively buoyant. After traversing upwards 

 through the fecal pellet layer, the lids were closed, and the 

 submersible descended again to just below the layer where the 

 sampling process was repeated five to six times. The total 

 volume filtered by each sampler ranged from 1-1.5 m^. 



Sinking rates ( Komar et al . , 1981) of fresh, individual 

 pellets were measured at several in situ temperatures onboard 

 ship using a gimballed, cylindrical glass container (46 cm tall x 

 6 cm ID) filled with filtered (0.4 urn) seawater. 



Microbial enumerations followed established procedures 

 (Davoll and Silver, 1986). Fixation techniques for scanning 

 electron microscopy were standard (Blades and Youngbluth, 1979). 

 Proximate chemical analyses employed proven methods (Bailey and 

 Robison, 1986). 



RESULTS 



At most locations, pellets occurred in a discrete layer (ca. 

 5-17 m in vertical extent) between midnight and sunrise. The 

 bulk of these layers coincided with the pycnocline (Fig. 2). By 

 mid-morning such concentrations were absent at the density 

 interface, but pellets were still conspicuous, although quite 

 dispersed, throughout the deeper Maine Intermediate Water. 



Fecal pellet abundance within the layers averaged 325 

 pellets • m~3 + 29 SE. The pellets were relatively large, 

 cylindrical rods (0.2 mm OD x 3-10 mm long) and golden-brown in 

 color. Both the vertical distribution and relative abundance of 

 fecal pellets coincided with the presence of the euphausiid 



208 



