Physiological controls on the distribution of the macroalga Spyridea hypnoides: patterns along a eutrophication gradient in Bermuda

Abstract

Filamentous mat-forming macroalgae, primarily Spyridea hypnoides, dominated the eutrophic inner bay but were absent from the low-nutrient outer bay. The author tests the hypothesis that S. hypnoides was absent from the low-nutrient outer bay because its metabolic nitrogen demands exceeded its nitrogen storage capacity and its ability to acquire nitrogen at low ambient concentrations to replenish depleted internal pools. S. hypnoides was transplanted from the high-nutrient inner bay to the low-nutrient outer bay, and these transplants were compared to macroalgae handled and transplanted in situ and to unmanipulated controls. This study suggests that the physiological cost of high metabolic nitrogen demands is a low nutrient storage capacity and a greater vulnerability to nutrient stress when ambient nutrient concentrations are chronically low. -from Author