Allometric settling of maximal photosynthetic growth rate to surface/volume ratio

Values for maximum growth rates (µmax) (d−1) at 15°–20°C and surface area/volume ratios (SA/V) (m2 m−3) for aquatic angiosperms (n = 14), macroalgae (n = 34), and microalgae (n = 44) were derived from our own experimental work and from the literature. A significant linear relationship (R2 = 0.86) was found between log µmax and log SA/V with the slope 0.66 (95% C.I.: 0.61–0.72) and the intercept −3.80[95% C.I.: (−3.59)−(−4.00)]. One general allometric expression can therefore describe the scaling of maximal growth rate as a function of organism size over a 1,700-fold range of SA/V ratios spanning small unicellular algae as well as multicellular aquatic angiosperms. The size dependence of maximal growth rate for aquatic photosynthetic organisms is close to that expected from the well-known “¾ law,” governing the size dependence of metabolic rates in animals.