INTRODUCTION 



In general, the amount of particulate matter in the oceans 

 decreases exponentially below the productive photic zone 

 (Hargrave, 1984). The relatively rapid (1-1000 m • d -1 ) sinking 

 of heavy particles like zooplankton fecal pellets can contribute 

 substantially to the vertical export of organic compounds and 

 various elements (Fowler and Knauer, 1986). However, the amount 

 of fecal matter produced and the rate at which this matter 

 settles vary considerably in relation to a host of physical and 

 biological factors, e.g., advection, viscosity, diet, and 

 decomposition. Consequently, mathematical models developed to 

 predict regional and global flux rates of biogenic material 

 require detailed information about the production and 

 distribution of these important particles (Hargrave, 1985). Most 

 of the existing data about particle flux has been based on in 

 situ sampling with sediment traps, pump-supported equipment, 

 optical techniques or scuba (Alldredge and Gotschalk, in press,; 

 Bishop et al., 1985; Lampitt, 1985; Urrere and Knauer, 1981). 

 Data obtained from sediment traps and optical-based devices can 

 be misleading in that the amount of material measured may be a 

 mixture of particles from vertical sinking, lateral advection and 

 resuspension. Similarly, information derived from filtration 

 systems may include both suspended and fast-sinking particles. 

 Scuba assessments of the sizes, sources and sinking of 

 particulate material are depth limited. 



We report here another approach, the use of a technically 

 advanced, manned submersible. Our water column research showed 

 where and when fecal pellets were produced by the euphausiid 

 Meganyctiphanes norveqica and quantified the chemical composition 

 and flux of these biogenic particles. The persistence of feeding 

 activity in both mixed layer and epibenthic regimes by large 

 populations of euphausiids was unexpected and introduces, via 

 egested feces, a substantive supply of utilizable food for 

 demersal suspension- and deposit-feeding invertebrates. 



METHODS 



Fecal pellets and euphausiids were observed in situ with 

 the Johnson Sea-Link submersibles within the Gulf of Maine and 

 along the southern edge of Georges Bank during July-August in 

 1983, 1984 and 1985 (Fig. 1). Devices designed to collect fecal 

 pellets for chemical and other measurements were available only 

 in 1985. Vertical depth profiles of temperature, conductivity 

 and transmittance were recorded simultaneously at 1-s intervals 

 with a data logging system attached to the submersible 

 (Youngbluth, 1984). 



One or more of four techniques, two photographic, one visual 

 and one collection, were used to quantify the abundance of fecal 

 pellets and euphausiids in the water column. The first method 

 employed a 70 mm Hasselblad camera/strobe configuration to take 

 color images of approximately 0.004 m^ of seawater directly 



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