Temporal changes in the periphytic algal communities in a drowned tropical forest reservoir in Malaysia: Lake Kenyir

Abstract

AbstractPeriphytic algal assemblages, comprising bacillariophytes, cyanophytes and chlorophytes of standing dead trees in Lake Kenyir, a tropical drowned forest reservoir, were studied during 1995. A total of 317 algal taxa were identified in this study. The monthly floral mean species richness and cell count data demonstrated significant temporal differences between the months, in one‐way anova (P < 0.05). Both redundancy analysis and cluster analysis on monthly blue‐green abundance and diatom assemblages exhibited conspicuous groupings among the months, with underpinning seasonal differences. The responses were not similar, however, between the upstream and downstream ends of the lake. The grouping or clustering of months can be generalized as: (i) November, December and January as the monsoonal months; (ii) February, March, April and May as the transitional months; and (iii) June to October as the dry months. Based on stepwise multiple regression with forward selection, alkalinity and dissolved oxygen concentration were significant environmental predictors at the downstream dam sampling site, and reactive silica, electrical conductivity, Secchi depth transparency and sunshine hours were significant predicators at the upstream riverine sampling site, based on Monte Carlo tests. Being a ploymictic, mesotrophic lake, the limnology and temporal changes for Lake Kenyir appears to be complex and driven by monsoons, as evidenced from the temporal changes in its periphytic algae communities, particularly the diatom assemblages. The downstream sampling site (site 1) at the dam, in the main basin and deeper zone of the lake, the seasonal amplitude was likely complex because of thermocline formation and stratification processes. In contrast, the upstream sampling site in the Petang River (site 2) exhibited a clearer distinction between the dry and monsoon months, based on its cyanophyte and diatom floral assemblages. These study results are pertinent for lake management, especially for developing biomonitoring programmes or lake productivity studies, as well as for climate change studies, within the context of tropical lake ecology.