The Effects of Ocean Acidification and Warming on Growth of a Natural Community of Coastal Phytoplankton

Bonggil Hyun,Keun-Hyung Choi,Kitack Lee,Ja-Myung Kim,Eun Jin Yang,Pung-Guk Jang,Jae Hoon Noh,Kyoungsoon Shin,Min-Chul Jang

doi:10.3390/jmse8100821

Abstract

An in situ mesocosm experiment was performed to investigate the combined effects of ocean acidification and warming on the coastal phytoplankton standing stock and species composition of a eutrophic coastal area in the temperate-subtropical region. Experimental treatments of natural seawater included three CO2 and two temperature conditions (present control: ~400 μatm CO2 and ambient temperature, acidification conditions: ~900 μatm CO2 and ambient temperature, and greenhouse conditions: ~900 μatm CO2 and ambient temperature +3 °C). We found that increased CO2 concentration benefited the growth of small autotrophic phytoplankton groups: picophytoplankton (PP), autotrophic nanoflagellates (ANF), and small chain-forming diatoms (DT). However, in the greenhouse conditions, ANF and DT abundances were lower compared with those in the acidification conditions. The proliferation of small autotrophic phytoplankton in future oceanic conditions (acidification and greenhouse) also increased the abundance of heterotrophic dinoflagellates (HDF). These responses suggest that a combination of acidification and warming will not only increase the small autotrophic phytoplankton standing stock but, also, lead to a shift in the diatom and dinoflagellate species composition, with potential biogeochemical element cycling feedback and an increased frequency and intensity of harmful algal blooms.

Highlights

Over the past few centuries, anthropogenic emissions of carbon dioxide (CO2) have resulted in an increase in the atmospheric CO2 concentration from average preindustrial levels of ~280 parts per million volume to more than 400 ppmv in 2014 [1]
The increase in atmospheric CO2 leads to ocean warming, via the greenhouse effect, but, ocean acidification through an increase in CO2 dissolved in the sea surface, a decrease in sea surface pH, and a decrease in the saturation state of calcium carbonates in the ocean [3]
The major finding of the present study is that the growth of autotrophic phytoplankton populations (ANF, PP, and small chain-forming DT species) may benefit under future oceanic conditions

Summary

Introduction

Over the past few centuries, anthropogenic emissions of carbon dioxide (CO2) have resulted in an increase in the atmospheric CO2 concentration from average preindustrial levels of ~280 parts per million volume (ppmv) to more than 400 ppmv in 2014 [1]. The current pace of climate change is unprecedented throughout geological history, and some coastal waters will be subjected to temperature increases exceeding 2 ◦C [5]. These altered oceanographic conditions may impact marine phytoplankton [6,7]. Since CCM efficiencies differ between phytoplankton species, subtle changes in or neutral effects on the phytoplankton standing stock and primary production have been reported [14,15,16]

Methods

Results

Conclusion