STUDIES OF MARINE PLANKTONIC DIATOMS: III. SOME EFFECTS OF TEMPERATURE ON RESPIRATION OF FIVE SPECIES

The respiratory coefficient, expressed here as respiration per unit of chlorophyll, of six clones (five species) of diatoms was measured at temperatures of 5°, 10°, 15°, 20°, and 25 °C. The acclimatized cultures used were grown at each of these temperatures that supported sufficient growth. Considering any one of the five temperatures of measurement, the respiratory coefficient varied with temperature of acclimatization, but not consistently in the different clones. Moreover, for any of the given temperatures of acclimatization, there was no trend common to all clones in the relationship between respiratory coefficient and temperature at which respiration was measured. In any respiration experiment, greater differences were observed between two clones of the same species than between species differing in size by as much as two orders of magnitude. The highest respiratory coefficients were observed in the two eurythermal clones, and the increase in respiration with temperature was more regular, with Q 10 = ca. 2.0. Respiration of the four stenothermal clones was more variable in relation to temperature, and both respiratory coefficients and Q 10 were lower.