Allometric scaling and taxonomic variation in nutrient utilization traits and maximum growth rate of phytoplankton

TLDR

Nutrient utilization traits link phytoplankton ecophysiology to population dynamics and community structure across environmental gradients. The study compiles and analyzes literature on four key traits—maximum nutrient uptake rate, half‑saturation constant, minimum subsistence quota for nitrate and phosphate, and maximum growth rate—to investigate their relationships. Using the compiled data, the authors examine these traits and two composite metrics, uptake affinity and scaled uptake affinity, across phytoplankton species. Traits generally increase with cell volume, except scaled uptake affinity and maximum growth rate decline; scaling relationships are largely similar between freshwater and marine species, taxonomic differences are largely driven by size, and trait correlations hint at evolutionary constraints but are confounded by volume, offering improved parameterization for size‑ or taxon‑based phytoplankton models.

Abstract

Nutrient utilization traits can be used to link the ecophysiology of phytoplankton to population dynamic models and the structure of communities across environmental gradients. Here we analyze a comprehensive literature compilation of four traits: maximum nutrient uptake rate; the half‐saturation constant for nutrient uptake; the minimum subsistence quota, measured for nitrate and phosphate; and maximum growth rate. We also use these traits to analyze two composite traits, uptake affinity and scaled uptake affinity. All traits tend to increase with cell volume, except for scaled uptake affinity and maximum growth rate, which tend to decline with cell volume. Most scaling relationships are the same for freshwater and marine species, although important differences exist. Most traits differ on average between major taxa, but between‐taxon variation is nearly always due to between‐taxon variation in volume. There is some evidence for between‐trait correlations that could constrain trait evolution, but these correlations are difficult to disentangle from correlation driven by cell volume. These results should enhance the parameterization of models that use size or taxonomic group to structure physiological variation in phytoplankton communities.