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The effect of temperature on photosynthetic and respiratory electron transport system activity in the shallow and deep‐living phytoplankton of a subalpine lake
Author(s) -
PRISCU JOHN C.,
GOLDMAN CHARLES R.
Publication year - 1984
Publication title -
freshwater biology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.297
H-Index - 156
eISSN - 1365-2427
pISSN - 0046-5070
DOI - 10.1111/j.1365-2427.1984.tb00028.x
Subject(s) - photosynthesis , phytoplankton , respiration , hypolimnion , botany , electron transport chain , environmental chemistry , biology , nitrogen , chemistry , zoology , ecology , eutrophication , nutrient , organic chemistry
SUMMARY. 1. The influence of temperature on in vivo photosynthetic and in vitro respiratory electron transport system (ETS) activity was determined over the season for the 3 m (warm‐water) and a 20m (cold‐water) phytoplankton communities in Castle Lake. The optimum temperature of photosynthesis at 3 m ( X̄ =20.8°C) was significantly higher than the average optimum at 20 m ( X̄ =14.8°C). 2. Seasonally, the photosynthetic temperature optimum increased when the blue‐green alga Chroococcus limneticus Lemm. was present. The temperature characteristics of this organism were maintained even after it had settled into the cold water of the hypolimnion. 3. Temperature optima were not significantly different in experiments conducted under limiting or saturating photosynthetic photon flux densities (PPFD). 4. Short‐term (1 h) preincubations with dissolved inorganic nitrogen (DIN) (≃80 μg NH 4 NO 3 ‐N l −1 ) had little effect on the temperature characteristics of photosynthesis while the longer (>24 h) incubations provided by a whole‐lake epilimnetic DIN addition (≃75 μg NH 4 NO 3 ‐ N l −1 ) significantly lowered the photosynthetic temperature optimum to 12.5°C. Once this epilimnetic DIN was depleted the optimum roseto25°C, a value higher than that present before the enrichment, which coincided with the growth of C limneticus. 5. Respiratory ETS activity usually began to inactivate between 19 and 20°C. However, when C. limneticus was abundant the inactivation temperature was often greater ihan 25°C. 6. The average energy of activation (E) and Q 10 value for the 3 m community (15.9 kcal mol −1 and 2.6 respectively) were significantly higher than those at 20 m (14.2 kcal mol −1 and 2.4 respectively). Seasonally, the highest E and Q 10 values of ETS activity occurred during the late‐summer bloom of C. limneticus. 7. These results demonstrate that the epilimnetic and hypolimnetic phytoplankton communities in Castle Lake are physiologically distinct with regards to their temperature characteristics.