Steady State Phytoplankton Assemblages Research Articles

The effects of Microcystis aeruginosa (cyanobacterium) on Cryptomonas ovata (Cryptophyta) in laboratory cultures: why these organisms do not coexist in steady-state assemblages?

The inhibitory effects of cyanobacterial compounds as possible explanation of the lack of stable Cyanobacteria–Cryptophyta coexistence in steady-state phytoplankton assemblages were studied. The possible interactions between two phytoplankton species, a toxic Microcystis aeruginosa (cyanobacteria) and a non-toxic Cryptomonas ovata (Cryptophyta) were investigated (i) in mixed cultures (containing C. ovata and M. aeruginosa cells); (ii) in M. aeruginosa crude extract-treated C. ovata cultures and (iii) in purified microcystin-LR (MC-LR) treated C. ovata cultures. The results of experiments proved that the presence of living M. aeruginosa cells have more inhibitory effects on C. ovata cultures than the crude extract of the M. aeruginosa cells; or the presence of the purified MC-LR. These results suggest that MCs does not play as important role in cyanobacteria–Cryptophyta interaction as it was presumed; hence more complex effects (allelopathy among them) can be significant in shallow lakes ecosystems.

Spatial and temporal dynamics of the steady-state phytoplankton assemblages in a temperate shallow hypertrophic lake (Lake Manyas, Turkey)

Spatial and temporal dynamics of phytoplankton biomass and species composition in the shallow hypertrophic Lake Manyas, Turkey, were studied biweekly from January 2003 to December 2004 to determine steady-state phases in phytoplankton assemblages. Steady-state phases were defined when one, two or three coexisting species contributed to at least 80% of the standing biomass for at least 2 weeks and during that time the total biomass did not change significantly. Ten steady-state phases were identified throughout the study peiod. During those periods, Achnanthes microcephala (Kutzing) Cleve twice dominated the phytoplankton biomass alone and contributed to more than 50% of the total biomass in seven phases. Microcystis aeruginosa (Kutzing) Kutzing, Anabaena spiroides Klebahn, Cyclotella stylorum Brightwell, Pediastrum boryanum (Turpin) Meneghini and Phacus pusillus Lemmermann were also represented once in steady-state phytoplankton assemblages. A. microcephala was dominant usually during cold periods of the year, while M. aeruginosa and A. spiroides were usually dominant in warm seasons. The total number of species showed a clear decrease during steady-state phases at all stations. All stations were significantly different in terms of the measured physical and chemical parameters (P < 0.05) and phytoplankton biomass (F = 117, P < 0.05).

Phytoplankton equilibrium phases during thermal stratification in a deep subtropical reservoir

Summary1. Equilibrium and non‐equilibrium hypotheses have often been used to explain observations in community ecology. Published case studies have demonstrated that steady state phytoplankton assemblages are more likely to occur in deep lakes than in shallow mixed ones.2. Phytoplankton seasonal succession was studied by weekly sampling in Faxinal Reservoir (S Brazil), a subtropical deep, clear, warm monomictic and slightly eutrophic reservoir. This study demonstrated an alternation of steady and non‐steady state phases of phytoplankton assemblages with different dominant species during the steady states.3. During the studied period, three steady states were identified with different dominant algal species: Anabaena crassa (Cyanobacteria), Nephrocytium sp. (green algae) and Asterionella (diatoms).4. Each steady state in Faxinal Reservoir developed under stratified conditions of the water column according to the predictions of the disturbance concepts. Apparently, the major forces driving the development and persistence of these steady‐state phases were closely related to thermal stratification and its consequences.5. This study is the first report on development of more than one steady state within a year in a stratified water body. The development of three steady states might be the result of the relatively long stratification period in the Faxinal Reservoir and to its unique geochemical features.

Steady state phytoplankton assemblages during thermal stratification in deep alpine lakes. Do they occur?

Steady state phytoplankton assemblages during thermal stratification in deep alpine lakes. Do they occur?

Steady-state phytoplankton assemblages in shallow Bulgarian wetlands

Steady-state phytoplankton assemblages in shallow Bulgarian wetlands

Are there steady-state phytoplankton assemblages in the field?

Are there steady-state phytoplankton assemblages in the field?