THE ALLOMETRY OF ALGAL RESPIRATION

For 30 years, study after study has shown that respiration rates incre ase as similar to 0.75 of body size for organisms ranging from protozo ans to mammals. However, a number of studies suggested that the respir ation-size relationship for algae may be a rare exception to this gene ral rule. Algal respiration may be almost proportional to cell size, s uch that the slope of the respiration-size relationship is closer to u nity. The present study examined the effect of cell size and taxon on phytoplankton respiration, using data collected from the literature. T o this end, we collected a data set of 178 observations of algal respi ration and cell size representing six divisions-chlorophytes, chrysoph ytes, cyanophytes, euglenophytes, pyrrophytes and rhodophytes. The rel ationship between respiration (R, in pl O-2 cell(-1) h(-1)) and cell c arbon content (C, in pg C cell(-1)) is described as R = 0.030C(0.93) a nd the exponent is significantly >3/4. When we expressed cell size in terms of volume, the exponent decreased to 0.88 but this is still sign ificantly >3/4. Among the six divisions studied, chlorophytes, eugleno phytes and rhodophytes seemed to differ significantly in their respira tion-size relationship from other taxa. However, euglenophytes and rho dophytes have such small size ranges that no meaningful relationships can be developed for those groups alone. The chlorophyte respiration-s ize relationship has obvious patterns in its residuals which may indic ate that significant sources of error were not controlled in these het erogeneous data. Thus, for the present, the general model seems most a ppropriate for the prediction of respiration rates of phytoplankton.