24 m on new moon nights (Mann Whitney U Test, p > 0.05) but did have greater 

 numbers than samples from 15 m or 24 m on new moon nights. This holds for 

 counts both with and without 0^ colcarva , except that samples from 6 m have 

 more individuals than those from 24 m on full moon nights when 0. colcarva is 

 i ncluded. 



Composition of Zooplankton 



The mean, standard deviation, and percent occurrence for 29 categories of 

 organisms are presented in table 1. No statistically significant differences 

 between sites in occurrence of taxa were noted across all nights, with the 

 exception of the absence of several organisms and the exceptional abundance of 

 a holoplanktonic decapod, Lucifer sp., at 6 m. The relative abundance of 

 copepod groups was similar (Spearman Rank Correlation, p < 0.01) at all sites, 

 but the ranking of noncopepod groups differed between 6 m and both 15 m and 24 m 

 (Spearman Rank Correlations, p > 0.05). The 24 m site possessed a significantly 

 greater number of organism categories [17.9 +_ 6.2 (S.D.)] than did the sites at 

 either 6 m (10 + 3.2) or 15 m (12.5 + 5.9). Evenness and species diversity 

 were consistentTy higher at 15 m and 24 m than at 6 m (X H' at 6 m = 1.35, 

 15 m = 2.11, 24 m = 2.46). 



Bomb Calorimetry and Biomass Determination 



The results of caloric and biomass determinations are presented in table 

 2. Bomb calorimetry produced caloric values of 5.6 [+ 0.05(S.D.)] calories/mg 

 dry weight, a figure which agrees well with published values (Cummins and 

 Wuycheck, 1971). Only 6% of the freeze dried weight was inorganic ash material. 

 The weighing of a known number of Oithona colcarva individuals (the dominant 

 organism; Ohlhorst, 1980, 1982) produced weights averaging 2.5 y g/i ndi vidual , 

 while the weighing of a known volume with a calculated number of individuals 

 produced weights averaging 1.6 u g/indi vidual . 



DISCUSSION 



The highly three-dimensional nature of the reefs in this study made it 

 impossible to place traps completely flush with the reef floor, and thus some 

 zooplankton movement undoubtedly occurred both into and out of the traps. A 

 number of workers have addressed the problems related to demersal trap design 

 (Robichaux, et al . , 1981; Youngbluth, 1982), and their results should be taken 

 into account when evaluating the results of work based on demersal emergence 

 traps. Caution is necessary in interpreting the origin of the zooplankton 

 ["demersal traps" catch more than demersal plankton (Robichaux, et al . , 1981)] 

 and their relative abundances due to differing plankton behavior - ("Robi chaux, et 

 al . , 1981; Youngbluth, 1982). Nonetheless, studies such as this, with one 

 method used throughout, provide data by which different sites can be compared. 

 The volumes of zooplankton obtained in this study give an indication of the 

 amount and types of zooplankton available for capture by the sessile inhabitants 

 of the reef, and serve as a useful basis for comparison of different reef sites. 



108 



