Offshore–inshore and vertical distributional patterns of heteropod mollusks off leeward Oahu, Hawaii
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Replicated zooplankton tows were taken during day and night periods at neritic (1 nmi offshore) and oceanic (5 and 15 nmi offshore) stations off the leeward side of Oahu, Hawaii during fall (September) and spring (April). Plankton samples were obtained with a 1-m2 MOCNESS net system towed obliquely through seven depth strata to 80 m (neritic station) and eight depth strata to 200 m (oceanic stations). Five more species were collected in April (17) than in September (12). During both months the number of species decreased from the 15 to the 1 nmi stations; from 11 to 9 in September and 15 to 11 in April. Species diversity, as measured by species accumulation (rarefaction) curves, was higher at the 15 than the 1 nmi stations during both months. Total nighttime water column density in April was about double that in September. In September, the density decreased sevenfold from the 15 to 1 nmi stations, but in April densities were comparable among the three stations; mainly as a result of the shoreward increase in density of Atlanta plana. The most abundant species in both months were A. plana, A. lesueuri, A. inflata, A. peroni, and Protatlanta souleyeti, which in combination accounted for 93% (September) and 91% (April) of the total nighttime water column densities. The vertical ranges of six species were limited to the upper 100 m, and nocturnal migration was suggested for two (A. helicinoides during both months and A. turriculata in April). The ranges of the remaining 11 species extended to 160 or 200 m, and among them nocturnal migration was suggested for five (A. plana, A. meteori and Pterotrachea hippocampus during both months, and A. peroni and Protatlanta soueleyti in April).
KeywordsDepth Interval Shelf Water Vertical Range Night Period Offshore Station
I am most grateful to George Boehlert, former director of the Honolulu NMFS Laboratory, for enabling and facilitating my examination of MOCNESS and Manta net samples. He graciously provided laboratory space and use of a dissection microscope during my series of visits to the NMFS facility. The assistance of Bruce Mundy, the field and laboratory project coordinator, is most gratefully acknowledged. He assembled the zooplankton samples for my examination during each visit, set aside sufficient space in his lab for my needs, and provided photocopies of relevant data sheets and plots of water column physical properties. Lastly, I thank Sean Walker for his insights on assessment of species diversity and for assistance in carrying out the rarefaction analyses.
- Boehlert GW, Mundy BC (1996) Ichthyoplankton vertical distributions near Oahu, Hawai’i, 1985–1986: data report. NOAA-NMFS Tech Memo, NOAA-TM- NMFS- SWFSC-235Google Scholar
- Frontier S (1966) Zooplancton de la région de Nosy-Bé. I. Programme des Récoltes et techniques d’études. II. Plancton de surface aux stations 5 et 10. Cah ORSTOM, sér Océanogr 4:3–36Google Scholar
- Frontier S (1973a) Zooplancton de la région de Nosy-Bé. VI. Ptéropodes, Hétéropodes—Première partie: espèces holonéritiques et néritiques-internes. Cah ORSTOM, sér Océanogr 11:273–289Google Scholar
- Frontier S (1973b) Zooplancton de la région de Nosy-Bé. VII. Ptéropodes, Hétéropodes—Deuxiéme partie: espèces néritiques-externes et océaniques tolérantes. Cah ORSTOM, sér Océanogr 11:291–302Google Scholar
- Gotelli NJ, Entsminger GL (2001) EcoSim: Null models software for ecology. Version 7.0. Acquired Intelligence Inc. & Kesey-Bear. http://homepages.together.net/~gentsmin/ecosim.htm
- Michel HB, Michel JF (1991) Heteropod and thecosome (Mollusca: Gastropoda) macroplankton in the Florida Straits. Bull Mar Sci 49:562–574Google Scholar
- Pafort-van Iersel T (1983) Distribution and variation of Carinariidae and Pterotracheidae (Heteropoda, Gastropoda) of the Amsterdam Mid North Atlantic Plankton Expedition 1980. Beaufortia 33:73–96Google Scholar
- Richter G (1982) Mageninhaltsuntersuchungen an Oxygyrus keraudreni (Lesueur) (Atlantidae, Heteropoda). Beispiel einer Nahrungskette im tropischen Pelagial. Senckenbergiana marit 14:47–77Google Scholar
- Richter G, Seapy RR (1999) Heteropoda. In: Boltovskoy D (ed) South Atlantic Zooplankton. Backhuys, Leiden, pp 621–647Google Scholar
- Seapy RR (1990b) The pelagic family Atlantidae (Gastropoda: Heteropoda) from Hawaiian waters: a faunisitic survey. Malacologia 32:107–130Google Scholar
- Tesch JJ (1949) Heteropoda. Dana Rep 34:1–53Google Scholar