General Allometric Equations for Rates of Nutrient Uptake, Ingestion, and Respiration in Plankton Organisms

General allometric equations are derived for rates of nutrient uptake, ingestion, and respiration by planktonic organisms. Previous studies commonly calculated parameters a and b in the allometric equation $R = aM^b$ by linear regressions on log-transformed data. This practice results in variability between data sets in estimates of both a and b, making meanigful comparisons difficult. This problem is overcome by assuming the mass-specific from of b to be -0.25, based on accumulated empirical evidence. Values of a are then recalculated from published data, with log transformations and an assumed regression slope of -0.25. Resulting regressions predict valus of a $(in pg C^0.25 d^-1)$ at $20\circ C$ as follows: 3.6 for nutrient uptake by phytoplankton and bacteria; 63 and 13 for ingestion and respiration by particle-feeding heterotrophs. It is hypothesized that organisms that take up dissolved nutrients from solution (autotrophs and osmotrophs, e.g. phytoplankton and bacteria) have lower specific respiration rates (i.e. smaller a) when compared with organisms (either unicellular or multicellular) that ingest particulate material.