The Effect of Temperature on Rates of Photosynthesis by Phytoplankton in Lake Itasca, Minnesota
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The effect of temperature on maximum specific photosynthetic rates,(Pmax), of a natural algal population in Lake Itasca, Minnesota was studied for a ten week period in autumn,197S. Evaluations were also made of solar radiation, phosphorus nutrition, and the generic composition of the phytoplankton population for this period. The temperature decreased rather constantly from 14.1 to 3.8°c and maximum specific photosynthetic rates ranged from 3.80 to 1.87mgC/mg chlorophyll/hr. Alkaline phosphatase activity, used to measure phosphorus nutrition, and solar radiation remained relatively constant except for a slight increase in the former and a slight decrease in the latter during the last three experiments. The algal population also remained constant, dominant forms being genera of the Bacillariophyoeae. The variation of maximum speoific photosynthetic rates was well explained by the Arrhenius relationship, the natural log of the rate being expressed as a linear function of reciprocal temperature Kelvin. A significant correlation was also found between Pmax and solar radiation. A multiple linear regression of Pmax with temperature and solar radiation as independent variables was of the same predictive value as a regression by temperature alone.