TY - JOUR

T1 - Effects of lowered pH on marine phytoplankton growth rates.

AU - Berge, Terje

AU - Daugbjerg, Niels

AU - Andersen, Betinna Balling

AU - Hansen, Per Juel

PY - 2010

Y1 - 2010

N2 - Continued anthropogenic carbon emissions are expected to result in an increase in atmosphericCO2 concentration to 700 ppm by the end of this century. This will cause a corresponding dropin the global average surface water pH of the oceans by ~0.4 units to ~7.8 and an increase in the CO2 concentrationof seawater. Ocean acidification may potentially both stimulate and reduce primary productionby marine phytoplankton. Data are scarce on the response of marine phytoplankton growth ratesto lowered pH/increased CO2. Using the acid addition method to lower the seawater pH and manipulatethe carbonate system, we determined in detail the lower pH limit for growth rates of 2 model speciesof common marine phytoplankton. We also tested whether growth and production rates of 6 othercommon species of phytoplankton were affected by ocean acidification (lowered to pH 7.0). The lowerpH limits for growth of the dinoflagellate Heterocapsa triquetra and the cryptophyte Teleaulax amphioxeiawere pH ~6.0 and 6.3, respectively. The growth rates of these 2 species were significantly reducedin the range of pH 6.4 to 6.5. Cell volume, growth, and production rates of the 6 other phytoplankton specieswere statistically similar in the pH range of ~7.0 to 8.5. Our results and literature reports on growthat lowered pH indicate that marine phytoplankton in general are resistant to climate change in terms ofocean acidification, and do not increase or decrease their growth rates according to ecological relevantranges of pH and free CO2. We speculate about whether common natural pH fluctuations in time andspace from 7.0 to 9.0 make phytoplankton capable of tolerating near-future ocean acidification. However,due to the less fluctuating pH environment of oceanic regions compared to coastal regions, trulyoceanic species may be more sensitive to lowered pH than coastal species.

AB - Continued anthropogenic carbon emissions are expected to result in an increase in atmosphericCO2 concentration to 700 ppm by the end of this century. This will cause a corresponding dropin the global average surface water pH of the oceans by ~0.4 units to ~7.8 and an increase in the CO2 concentrationof seawater. Ocean acidification may potentially both stimulate and reduce primary productionby marine phytoplankton. Data are scarce on the response of marine phytoplankton growth ratesto lowered pH/increased CO2. Using the acid addition method to lower the seawater pH and manipulatethe carbonate system, we determined in detail the lower pH limit for growth rates of 2 model speciesof common marine phytoplankton. We also tested whether growth and production rates of 6 othercommon species of phytoplankton were affected by ocean acidification (lowered to pH 7.0). The lowerpH limits for growth of the dinoflagellate Heterocapsa triquetra and the cryptophyte Teleaulax amphioxeiawere pH ~6.0 and 6.3, respectively. The growth rates of these 2 species were significantly reducedin the range of pH 6.4 to 6.5. Cell volume, growth, and production rates of the 6 other phytoplankton specieswere statistically similar in the pH range of ~7.0 to 8.5. Our results and literature reports on growthat lowered pH indicate that marine phytoplankton in general are resistant to climate change in terms ofocean acidification, and do not increase or decrease their growth rates according to ecological relevantranges of pH and free CO2. We speculate about whether common natural pH fluctuations in time andspace from 7.0 to 9.0 make phytoplankton capable of tolerating near-future ocean acidification. However,due to the less fluctuating pH environment of oceanic regions compared to coastal regions, trulyoceanic species may be more sensitive to lowered pH than coastal species.

U2 - 10.3354/meps08780

DO - 10.3354/meps08780

M3 - Journal article

VL - 416

SP - 79

EP - 91

JO - Marine Ecology - Progress Series

JF - Marine Ecology - Progress Series

SN - 0171-8630

ER -