EFFECTS OF VARIATION IN TEMPERATURE .2. ON THE FATTY-ACID COMPOSITION OF 8 SPECIES OF MARINE-PHYTOPLANKTON

Eight species of marine phytoplankton showed significant variation in the relative amount of some fatty acids (FAs) in response to variation in temperature. Large changes in relative amounts of certain FAs occurred as a result of a 15-degrees-C change in growth temperature. For example, 14:0 increased from congruent-to 4% of total FAs at 10-degrees-C to >20% at 25-degrees-C for Chaetoceros simplex and Isochrysis aff. galbana but decreased for Phaeodactylum tricornutum. The percentage of the polyunsaturated fatty acid (PUFA) 16:4-omega-1 was consistently greater at 10-degrees-C than at 25-degrees-C, and the converse was usually true for 16: 4-omega-3. Calculated over all eight species, there was a modest but significant inverse relationship between the percentage of PUFAs and temperature. Only for Thalassiosira pseudonana was the percentage of either of the PUFAs and nutritionally essential fatty acids (EFAs) also an inverse function of temperature. For T. pseudonana, the percentage of the EFA 22.6-omega-3 decreased linearly with increasing temperature over the range from 10 to 25-degrees-C. For three species, the ratio of unsaturated/saturated FAs was correlated with growth rate when growth rate was controlled by variation in irradiance and temperature. Only for Thalassiosira pseudonana was the ratio Of unsaturated/saturated FAs also an inverse function of temperature alone.