MEPS 509:103-112 (2014)  -  DOI: https://doi.org/10.3354/meps10883

ABSTRACT: Geometry, size and shape are fundamentally important features of living organisms. It was hypothesised that in aquatic primary producers differences in geometry, shape and density would affect the relationship between dry mass, surface area and volume and that scaling relationships between rates of nutrient uptake and dry mass would vary depending on transport kinetics and nutrient concentration. Allometric relationships between dry mass (M) and volume (V), surface area (SA), growth rate and rates of nitrate uptake were determined using reduced major axis regressions. Volume scaled as M^1.03 and surface area as M^0.79 (and V^0.76) for aquatic primary producers. However, maximum growth rate, when expressed as g dry weight ind.^-1 d^-1, scaled as M^0.88. Maximum rates of nitrate uptake (expressed as µmol ind.^-1 h^-1) scaled similarly to growth (M^0.86). However, the scaling exponents (M^0.79) for rates of nitrate uptake at low concentrations and affinity (maximum uptake rate/the concentration of nutrient that gives half the maximum rate of uptake, V_max/K_m) were the same as the scaling exponent for surface area. Transport systems provide a useful approach to allometric relationships and illustrate that (1) scaling exponents for a given process can vary and (2) observed scaling exponents for transport are explicable through differences in the kinetics of transport systems. The maximum total surface area of the picoplankter Prochlorococcus and the kelp Postelsia per m² ocean surface are very similar, and the potential of marine ‘leaf area indices’ as a unifying concept is discussed.

KEY WORDS: Algae · Allometry · Macroalgae · Microalgae · Nitrate uptake