The effect of seawater CO₂ concentration on growth of a natural phytoplankton assemblage in a controlled mesocosm experiment

Abstract

We examine the effects of seawater p CO 2 concentration of 25, 41, and 76 kPa (250, 400, and 750 matm) on the growth rate of a natural assemblage of mixed phytoplankton obtained from a carefully controlled, 14‐d mesocosm experiment. Throughout the experiment period, in all enclosures, two phytoplankton taxa (microflagellates and cryptomonads) and two diatom species ( Skeletonema costatum and Nitzschia spp.) account for approximately 90% of the phytoplankton community. During the nutrient‐replete period from day 9 to day 14 populations of Skeletonema costatum and Nitzschia spp. increased substantially; however, only Skeletonema costatum showed an increase in growth rate with increasing seawater p CO 2 . Not all diatom species in Korean coastal waters are sensitive to seawater p CO 2 under nutrient‐replete conditions.