The vertical distribution of rotifers in a coastal meromictic lake of Papua New Guinea (Lake Nagada, Madang province)
De Meester, L.; Vyverman, W. (1993). The vertical distribution of rotifers in a coastal meromictic lake of Papua New Guinea (Lake Nagada, Madang province), in: Chardon, M. et al. Third Belgian Congress of Zoology, 5-6 November 1993. Belgian Journal of Zoology, 123(Suppl. 1): pp. 20
In: Chardon, M.; Goffinet, G. (Ed.) (1993). Third Belgian Congress of Zoology, 5-6 November 1993. Belgian Journal of Zoology, 123(Suppl. 1). University of Liège: Liège. 109 pp., meer
In: Belgian Journal of Zoology. Koninklijke Belgische Vereniging voor Dierkunde = Société royale zoologique de Belgique: Gent. ISSN 0777-6276; e-ISSN 2295-0451, meer
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Documenttype: Samenvatting
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| Abstract |
Lake Nagada is a coastal meromictic lake in NE Papua New Guinea (1). As part of a field study on the limnology of this lake, we studied the day- and nighttime vertical distribution of the rotifer Brachionus cf. plicatilis (“S-type”) (2) in relation to the stratification of abiotic factors (temperature, conductivity, redox potential, pH, dissolved oxygen, total sulfides, and light transmission) as well as of phytoplankton and photosynthetic bacteria. At the end of May 1992, the thermocline was situated at 2.00 m depth, whereas the chemocline was at 4.75 m depth. A phytoplankton peak concentration was observed at the thermocline (1.5- 2 m), whereas a dense bacterial plate occurred at the chemocline. Light intensity dropped sharply to less than 0.1 % at the depth of the bacterial plate. The day- and nighttime vertical distribution of Brachionus cf. plicatilis was sampled at 0.5 m intervals. During the day, a bimodal distribution was observed, with a peak of more than 900 ind. 1-1 at 1-1.5 m depth, and a smaller peak of about 400 ind. 1-1 at 4.5 m. A small number of individuals was found below the chemocline (up to 6.5 m depth). At night, there was a clearcut unimodal distribution, with a peak concentration of 1040 ind. 1-1 at 1.5 m. Our results indicate two subpopulations of B. cf. plicatilis in Lake Nagada, with the animals residing near the chemocline during the day migrating to the phytoplankton maximum during the night.(1) W. VYVERMAN (1991). Biol. Jb. Dodonaea 59:100-108.(2) Y. FU, K. HIRA Y AMA and Y. NATSUKARI (1991). J. exp. mar. biol. Ecol. 151:29-41. |
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