Planktic cyanophytes and their ecology in the shallow Lake Mikri Prespa, Greece |
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Authors: | E Tryfon M Moustaka-Gouni G Nikolaidis |
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Institution: | Institute of Botany, School of Biology, Aristotle University of Thessaloniki, 540 06 Thessaloniki, Greece |
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Abstract: | Cyanophytes dominated the phytoplankton of shallow Lake Mikri Prespa during the period May 1990 to September 1992 (76.5 and 52.0% of the total phytoplankton biomass in 1990–1991 and 1991–1992, respectively). Biomass peaks were observed in autumn (from 5.2 to 34.5 g m-3) when low dissolved inorganic nitrogen, high phosphate phosphorus and low Zcu to Zmix ratio prevailed. The dominant species were Microcystis aeruginosa and M. wesenbergii. These represented 64 and 86% of the cyanophyte biomass in 1990–1991 and 1991–1992, respectively and revealed similar patterns of seasonality forming biomass peaks in late summer - autumn. Small chroococcalean cyanophytes (< 2 μm) showed also similar temporal distributions. Of the filamentous cyanophytes, the most important species was Anabaena lemmermannii var. minor which formed peaks in late summer and autumn (2.6 and 1.1 g m-3 in 1990 and 1992, respectively). Rainfall and the N:P ratio were probably the main factors influencing the seasonality of all of the filamentous cyanophytes in the lake. Cyanophytes, tended to increase at temperatures higher than 16 °C and at inorganic nitrogen concentrations lower than 100 μg 1--1. The frequent mixing of the water column did not seem to prohibit the substantial increase of the group. |
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