PLANKTON COMMUNITY RESPIRATION - RELATIONSHIPS WITH SIZE DISTRIBUTION AND LAKE TROPHY

Allometric interpretations of community size structure often assume that laboratory relations between physiological rates and body size apply in the field, but this assumption is rarely examined critically. We therefore tested the hypothesis that limnoplankton community respiration rates are predictable functions of mean body size, and compared these functions to laboratory relations. Over a broad range of trophic conditions (6.5 less-than-or-equal-to [TP] less-than-or-equal-to 130-mu-g l-1; 1.2 less-than-or-equal-to [chl-a] less-than-or-equal-to 29-mu-g l-1), the mean respiration rate per organism for picoplankton, nannoplankton, and net plankton assemblages was a power function of mean organism size, with an exponent of 0.73. When respiration (R) and biovolume (B) are standardized to equivalent carbon units, the R/B ratio was a power function of mean organism size, with an exponent of -0.30. These results provide empirical support for the contention that size distributions may be used to construct comprehensive models of community physiology. The total epilimnetic phosphorus concentration was correlated with both the biovolume and respiration rate of the plankton community, as well as with the respiration rates of the three plankton size classes; so these aspects of community function may also be predictable functions of lake trophic state.