New Zealand Journal of Marine and Freshwater Research abstracts

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The role of buoyancy in the distribution of Anabaena sp. in Lake Rotongaio

ANTHONY E. WALSBY¹

COLIN S. REYNOLDS²

ROD L. OLIVER³

JACCO KROMKAMP⁴

MAX M. GIBBS⁵

¹Department of Botany University of Bristol United Kingdom BS8 1UG

²Freshwater Biological Association Windermere Laboratory Ambleside, United Kingdom LA22 OLP

³Murray-Darling Freshwater Research Centre Albury, New South Wales Australia 2640

⁴University of Amsterdam Nieuwe Achtergracht 127 1018 WS Amsterdam, The Netherlands

⁵Taupo Research Laboratory Department of Scientific and Industrial Research P.O. Box 415, Taupo, New Zealand

Abstract The species of Anabaena that dominated the phy-toplankton community of Lake Rotongaio during February and March 1987 was a non-colonial, filamentous organism made buoyant with gas vacu-oles. Light microscopy indicated that gas vacuoles were abundant in almost all of the cells, except for the heterocysts. Pressure nephelometry (see Walsby & McAllister: p. 521 this issue) was used to determine the critical collapse pressure of the gas vesicles: in filaments suspended in 0.5 M sucrose solution the mean critical pressure (P_c) was slightly over 0.62 MPa (6.2 bar); in filaments suspended in lake water the mean apparent critical pressure (P_a) varied between 0.19 and 0.29 MPa. The cell turgor pressure, given by the difference in these pressures, P_t = P_c- P_a (Walsby 1980), therefore varied between 0.43 and 0.33 MPa in this organism. The higher turgor pressures were usually found in cells collected near the lake surface and in samples incubated in plastic containers tethered at the surface.

New Zealand Journal of Marine and Freshwater Research, 1987, Vol. 21: 525-526 0028-8330/87/2103-0525$2.50/0 © Crown copyright 1987 Received 13 March 1987; accepted 29 May 1987

PDF file of entire paper: medium quality (165K); (scanned from paper original: notes about this process)

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