and Porter (1977)." Their samples, taken above 

 coral and sand substrata, included far fewer 

 copepods than the Alldredge and Porter collec- 

 tions I but many more than ours»; nevertheless, 

 they recognized the presence of holoplanktonic 

 forms (e.g., siphonophores, crustacean and fish 

 eggs, and fish larvae), which they assumed ". . . 

 either swam ( or were carried ) under the base of the 

 trap from the open water . . .." 



So we believe that the studies by the Alldredge 

 and Porter groups are flawed by the unrecognized 

 occurrence in their samples of organisms from the 

 surrounding water column. At Enewetak .Atoll 

 (Hobson and Chess 1978), we concluded that many 

 of the zooplankters above lagoon reefs at night are 

 visitors from the deeper water. If this cir- 

 cumstance existed where Alldredge and Porter set 

 their traps, then their collections probably in- 

 cluded deep-water forms. If so, the figures pre- 

 sented as measures of zooplankters that emerge 

 from defined areas of particular nearshore sub- 

 strata probably include not only holoplankters as- 

 sociated by day with other nearshore substrata 

 but also holoplankters from outside the nearshore 

 realm. 



We consider our collectons conservative esti- 

 mates of the numbers of organisms that emerge 

 from the sampled substrata. It may be that some 

 forms which ordinarily rise into the water column 

 were inhibited by our trap, and undoubtedly some 

 that rose into the trap found their way back to the 

 sea floor. But we feel our trap should have been as 

 effective in capturing emerging zooplankters as 

 those used by the Alldredge and Porter groups. 

 Possibly some strictly benthic forms entered our 

 samples by climbing up the inside of the trap. The 

 few prosobranch gastropods that were taken may 

 have been trapped this way, although they were 

 small enough to have been swept up into the water 

 column by surge, or perhaps to possess some flota- 

 tion device that periodically permits a planktonic 

 mode, as is the case with certain foraminiferans 

 (e.g., Tretomphalus and perhaps Atnphistigina). 

 Significantly, most of the organisms collected be- 

 long to groups that include forms we have col- 

 lected in the water column at night elsewhere: 

 e.g., the foraminiferan genus Tretomphalus (at 

 Majuro and Enewetak Atolls: Hobson and Chess 

 1973, 1976): the polychaete genus Polyophthal- 

 miis (at Enewetak Atoll: Hobson and Chess 1978); 

 and the ostracod subfamily Cylindroleberdinae, 

 the tanaid genus Leptochelia. the isopod genera 

 Cirolana and Munna. and family Anthuridae, the 



gammarid genus Aoroides. and families 

 Eusiridae, Oedicerotidae, and Phoxocephalidae 

 I at Santa Catalina. southern California: Hobson 

 and Chess 1976. in prepi. The forms that predomi- 

 nated in our collections belong to groups that were 

 only relatively minor elements in the Alldredge 

 and Porter collections. Most, in fact, w^ere lumped 

 by Porter et al. ( 1977) in their summarizing Fig- 

 ure 2 as "miscellaneous." This is not because they 

 took fewer of these forms than we did, but rather 

 because copepods and larvaceans so dominated 

 their collections. 



We believe that the major difference between 

 our collections and those of the Alldredge and Por- 

 ter groups is that we excluded organisms from the 

 surrounding water column. Alldredge and King 

 (19771 were aware that outside organisms could 

 enter through the gaps around the base of their 

 traps, but seemed more concerned about or- 

 ganisms inside that might have escaped. They 

 dismissed both possibilities as significant sources 

 of error with the statement (p. 318 1 ". . . as many 

 plankters may also enter the trap through these 

 gaps as escape through them." But because these 

 devices were, after all, traps, probably many more 

 zooplankters came in than went out. And if in fact 

 zooplankters entered the traps through these 

 gaps, it seems certain that forms from the sur- 

 rounding water, including holoplankters, were 

 continuously captured. Porter et al. (1977) re- 

 ported about 1.5 to 2 times as man\' zooplankters 

 as did Alldredge and King. They attributed this 

 difference to more effective methods and equip- 

 ment, but their traps, tethered above the reef, may 

 simply have been more readily entered by holo- 

 plankters. This would also account for the rela- 

 tively large numbers of zooplankters they trapped 

 by day. Both studies may have suffered from a 

 misconception about the movements of these or- 

 ganisms. Alldredge and King doubted that many 

 escaped through the gaps around the bases of their 

 traps because they assumed (p. 3181". . . emerging 

 plankton swim primarily upward . . .."The Porter 

 group would seem to have based their trap design 

 — inverted cones tethered above the bottom — on 

 the same assumption. But while these animals 

 certainly rise progressively higher in the water 

 column after emerging from the sea floor, gener- 

 ally they swim — some flit — in short, irregular 

 tangents more horizontal than vertical (based on 

 our direct observations of a wide variety of forms 

 in many locations). In any event if holoplankton 

 did enter these traps in significant numbers, then 



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