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 delta¹³C 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. delta¹³C values of P. tricornutum showed little response to changes in growth photon flux density (except at low PFD <10 umol m^-2 s^-1) and growth pH. delta¹³C 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 delta¹³C values of 2 contrasting algal species suggest that species-specific responses to environmental change may be important in understanding the variability of delta¹³C values found in particulate organic carbon obtained from oceanic and coastal waters. The role of environmental variables in hindcasting dissolved [CO₂] is discussed.

KEY WORDS: ¹³C discrimination . Emiliania huxleyi . Phaeodactylum tricornutum . Temperature . pH . Photon flux density

Published in MEPS Vol. 132 (1996) on February 29
ISSN: 0171-8630. Copyright © Inter-Research, Oldendorf/Luhe, 1996