Abstract
Lake Elphinstone is a tropical inland water body in the far north of the Fitzroy Catchment in Central Queensland, Australia, and has experienced recurrent toxic cyanoprokaryote blooms since 1997. This article reports on an examination of the environmental conditions of the lake and the concurrent cyanoprokaryote species together with their toxicity. The lake was sampled three times during periods of high cyanoprokaryote cell concentrations. Successive changes in the dominant Microcystis species were accompanied by variation in the concentration of the hepatotoxin microcystin. Environmental parameters recorded during dominance by both the highly toxic species Microcystis panniformis and the nontoxic M. botrys are provided. Nutrient status, temperature, and light conditions were associated with species change within the blooms. Variation of microcystin concentrations coincided with speciation change (i.e., morphological variation) within the blooms. Also discussed is the environmental impact of toxin production by M. panniformis with respect to influence on cell division, energy states, and toxin photodegradation. Lake Elphinstone is the first Australian location reported to have M. panniformis.
Highlights
The combination or synergy of environmental factors required to trigger speciation change in toxic algal blooms varies depending on the water body and species
Specimens taken from Lake Elphinstone were in agreement with the descriptions of Komarek et al (2001), with evenly and densely arranged cells occurring on surface layers of colonies (Plates 1 and 2)
Phytoplankton Species Composition A strong similarity was found between the composition of the phytoplankton assemblages at Lake Elphinstone and that recorded from the Tabocas Reservoir (Brazil), the source of the Caruaru tragedy (Komarek et al, 2001)
Summary
The combination or synergy of environmental factors required to trigger speciation change in toxic algal blooms varies depending on the water body and species. Contract grant sponsor: Nebo Shire Council (Lake Elphinstone Alliance). Functioning of these factors in tropical lakes remains poorly understood (Dokulil & Teubner, 2000). Temperate studies regarding blooms have limited applicability in tropical environments (Huszar et al, 1998), and the understanding of phytoplankton dynamics in southern hemisphere lakes remains inadequate (Harding, 1997). Cyanoprokaryote toxicity is variable both within and between blooms (Falconer, 2001; Ressom et al, 1994). Algal cell concentrations are not necessarily correlated with the toxicity of blooms, as both toxic and nontoxic cyanoprokaryotes can coexist (DeMott & Moxter, 1991). Toxin content may be influenced by physicochemical parameters such as light penetration, nutrient availability, pH, and temperature (Orr & Jones, 1998); 404 WHITE, FABBRO, AND DUIVENVOORDEN phosphorus concentrations above 200 g LϪ1 were recorded during 2002
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