and gastropods dominated the samples. Samples collected in the hour following 

 sunset were dominated by harpacticoids, with a variety of other organisms 

 (including 0. colcarva and gastropods) occurring abundantly. Samples taken 

 during the second hour after sunset again were dominated by harpacticoids, 

 although the relative abundance of the different harpacticoid species switched 

 (table 3). Oithona colcarva and a species of cumacean were the other most 

 abundant taxa during this second hour. Oithona colcarva dominated the other 

 night time intervals from 2030-0500. 



The relative abundance of nine common taxa ( 0. colcarva , calanoid copepods, 

 harpacticoid copepods, copepod nauplii, amphipods, cumaceans, pagurid larvae, 

 polychaetes and gastropods; table 3) were compared using Spearman Rank Corre- 

 lations (SRC). Although the abundances were greater at night, the relative 

 abundances (% total sample) of these taxa were correlated (p _< 0.05) between 

 pooled day samples and pooled night samples. When samples from consecutive 

 time intervals were compared, the relative abundances of taxa in all such pairs 

 were correlated (p _< 0.05) except those from 1800/1830 vs. 1930, and 1930 vs. 

 2030. For example, harpacticoids, pagurid larvae, calanoids, and polychaetes 

 were relatively more important, while copepod nauplii, amphipods, and gastropods 

 were relatively less abundant, at 1930 than at 1800/1830. Cumaceans and 

 amphipods increased in relative abundance between 1930 and 2030, while gastropods 

 and pagurid larvae decreased in relative numbers over this interval. Therefore, 

 the hours around dusk were the only ones where the relative abundance of captured 

 organisms differed. 



Differences in the relative abundances of certain taxa reflect their 

 different temporal behavior patterns. Sixty-two percent of the 29 common taxa 

 (table 3) were captured in greatest numbers during the first hour after sunset 

 (1830-1930), while 17% were captured in greatest abundance during the second 

 hour after sunset. The only taxon showing peak abundance during the day was 

 foraminifera. Many of the taxa exhibit sustained vertical migration throughout 

 the night following the post-sunset pulse (e.g., calanoid "A," amphipod "A," 

 cumacean "A," pagurid larvae in table 3). A few taxa (calanoid "B," decapod 

 zoea) were captured most frequently during the last interval of night (0230-0500), 

 and many (28%) exhibited a pulse of migration at this time. Only the cyclopoid 

 Corycaeus spp. peaked in abundance during the hour prior to sunrise (0500-0600); 

 the harpacticoid Microsetel la spp. also exhibited a pulse of vertical migration 

 at this time. The behavior of 0. colcarva was variable throughout the various 

 time intervals (fig. 1). The mean number of this species captured for both 

 nights combined was greatest at 0230; however, that peak reflects an especially 

 high number captured on July 17 (X = 638) and a similar pattern was not observed 

 on July 16 (fig. 1). Migration rates for this species were high during all 

 night hours. 



DISCUSSION 



The zooplankton captured by emergence traps in this study do not solely 

 represent, either in numbers or composition, the demersal zooplankton (Hobson 

 and Chess, 1979; Robichaux, et al . , 1981) living within the reef substrata over 

 which the traps are placed. These data do, however, provide information on the 

 temporal patterns of migration by the total reef zooplankton which is of value 

 to studies of reef energetics and the behavior of reef plankti vores. 



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