Table l. — Organisms trapped by day and night at Kure and 

 Midway Atolls. 



'All foraniinifefans were eittier Tretomphalus sp. {72*'-o) or Amphistigina sp. 

 (28%) 



^The rnapr polychaete was Polyophthalmus sp. 



^Included one 8-mm dond opisttiobranch: the rest were prosobranchs ' 3 

 mm long 



'The major ostracod was a species of Cytindroleberdinae 



-All identifiat>le calanotds were Paramisophna sp . probably undescnbed 

 (Abraham Remingef, SCTipps Institution of Oceanography. LaJolla, CA 92038. 

 pers commun Apnl 1978) 



'All identified harpacticoids were of a species of the family Peltidndae 



'All the tanaids appeared to be of a species of Leptochefia. dose to L dubia 

 (see Hobson and Chess 1976). 



'Major isopods were Ciroiana sp., laniropsis sp.. Muma sp.. anthunds. 

 and cryptoniscid larvae 



'Gammands included Aoroides sp . Dexaminoides ohentahs, UIgeborgia 

 sp.. a eusind, an oedicefotid, and a phoxocephalid. 



'"All chaetognaths were Spadella gaetanoi (A. Alvanno. Fishery Biologist, 

 Southwest Fishenes Center. NMFS. NOAA. La Jolla. CA 92038. pers com- 

 mun Sept 1978) 



Discussion 



Our collections and collecting sites were too few 

 to comprehensively quantify the zooplankters 

 that emerge from the lagoon substrata at Kure 

 anti Midway Atolls. Despite its limitations, how- 

 ever, this study increases our understanding of the 

 kinds of organisms that have this habit. Further- 

 more, it indicates there may be serious problems 

 with the more extensive studies of Alldredge and 

 King (1977). Porter et al. il977), and Porter and 

 Porter (1977). 



Certainly some of the differences between their 

 samples and ours are unrelated to sampling prob- 

 lems. We assume, e.g., that the zooplankton fauna 

 at Kure and Midway Atolls is distinguishable 

 from the zooplankton fauna in the more tropical 

 latitudes of the western Pacific Ocean where the 

 Alldredge and Porter groups studied. It is un- 

 likely, however, that zoogeographic variations can 

 account for certain of the more striking differences 



between their samples and ours. The predominant 

 forms in their collections were calanoid and cy- 

 dopoid copepods. Alldredge and King (19771 cal- 

 culated that during the night a mean of 6.679 

 calanoids emerged from each square meter of the 

 reef face, and Porter et al. (1977) reported that 

 over 10.000 calanoids emerged during the night 

 from each square meter of branching coral in their 

 study area. In comparison, our night-long collec- 

 tions from a variety of substrata, including coral, 

 yielded a mean of only 17.7 calanoids/m^. Of 

 course, we did not sample a well-developed reef 

 Only two of our sites included living coral, and 

 these were isolated heads tour traps required a bed 

 of sand). So habitat features could have contrib- 

 uted differences between the collections. 

 Nevertheless, if one considers the species of 

 calanoids and cyclopoids collected by Alldredge 

 and King, there are strong indications that the 

 large numbers reported were inflated by holo- 

 planktonic forms. The only calanoids and cy- 

 clopoids they identified were Acartia spp. and On- 

 caea spp. Species of these two genera are exceed- 

 ingly numerous in the water column during both 

 day and night (see Emery 1968: Hobson and Chess 

 1976). and we question whether they could in fact 

 assume a benthonic mode. As stated i Hobson and 

 Chess 1 978:149 ) "We would expect organisms that 

 live in the substrate by day to have morphological 

 features reflecting this habit that distinguish 

 them from holoplanktonic relatives at the generic 

 level or higher." .Although the Porter group did not 

 identify their calanoids and cyclopoids to lower 

 taxa, they too sampled western Pacific reefs and so 

 the copepods that similarly dominated their col- 

 lections may well have been the same, or very 

 similar, to those taken by Alldredge and King. All 

 our calanoids, on the other hand, appeared to be 

 referable to the little known genus Paramisophna 

 (Abraham Fleminger, Associate Research 

 Biologist, Scripps Institution of Oceanography, La 

 Jolla, CA 92038, pers. commun. April 1978). This 

 fact agrees with our contention that zooplankters 

 which periodically enter the substrate should be 

 morphologically distinctive. If the diurnal benthic 

 mode of this species is a generic characteristic, 

 which seems probable, then its poorly known 

 status likely stems from failure to be sampled by 

 standard plankton-collecting techniques. 



During a marine survey of the Palau Islands, 

 Randall et al. (1978) attempted to measure the 

 zooplankters that emerged from the sea floor using 

 traps ". . . built according to the design of Porter 



278 



