The effect of environmental variables on 13C discrimination by two marine phytoplankton

Abstract

The effects that environmental variables, other than dissolved CO2, have on 13C discrimination by marine phytoplankton were studied. Two selected species showed different responses. The δ13C values of the marine diatiom Phaeodactylum tricornutum grown in a range of temperatures with a constant dissolved [CO2] were more negative as the growth temperature decreased. δ13C values of P. tricornutum showed little response to changes in growth photon flux density (except at low PFD <10 μmol m-2 s-1) and growth δ13C values of the prymnesiophyte Emiliania huxleyi were more negative with decreased growth temperature, more negative with decreased growth PFD and less negative with decreased growth pH. The distinct effects which environmental variables have on the δ13C values of 2 contrasting algal species suggest that species-specific responses to environmental change may be important in understanding the variability of δ13C values found in particulate organic carbon obtained from oceanic and coastal waters. The role of environmental variables in hindcasting dissolved [CO2] is discussed.