THE EFFECT OF TEMPERATURE ON SPECIFIC GROWTH RATE AND ACTIVATION ENERGY OF MICROCYSTIS AND SYNECHOCOCCUS ISOLATES RELEVANT TO THE ONSET OF NATURAL BLOOMS

SUMMARY

To investigate the correlation between temperature and the appearance of Microcystis blooms in nature, the effect of temperature on the growth of four Microcystis izolates (two toxic and two non-toxic) was investigated. The lower temperature limit for Microcystis varied between 10,5 and 13,5°C, the thermal growth optimum between 28,8 and 30,5°C and the upper temperature limit between 35,0 and 40,0°C. The corresponding values for Synechococcus were 10,3, 34,5 and 44,3° C. Due to the construction of the apparatus, saturating light intensities could not be used. Increasing the light intensity influenced the lower temperature limit (13,2 to 12,0° C) the thermal growth optimum (30,5 to 28,8° C) and the upper temperature limit (36,4 to 35,0° C) of Microcystis. Activation energies were calculated for the different isolates from the respective Arrhenius plots. Arrhenius equations and Q₁₀ values were also calculated. An inflection in the gradient of the Arrhenius plot indicating a sudden decrease in activation energy and an increase in Q₁₀ above 17,5°C coincided with the temperature value for the onset of natural blooms of Microcystis. These data may be useful in the construction of a model to predict bloom formation of Microcystis in nature. The results did not have any taxonomic value at the species level.

KEY WORDS:

• Microcystis
• Temperature
• Activation energy
• Arrhenius equations
• Natural blooms
• Growth