Impact of salinity and growth phase on alkenone distributions in coastal haptophytes

Batch cultures of Isochrysis galbana (strain CCMP 1323) and Chrysotila lamellosa (strain CCMP 1307) were grown at salinity values of ca. 10 to ca. 35 and the alkenone distributions determined for different growth phases. U 37 K ′ values decreased slightly with salinity for C. lamellosa but were largely unaffected for I. galbana, except during the decline phase. The values decreased with incubation time in both species. The proportion of C37:4, used as a proxy for salinity, increased in both species at 0.16–0.20% per salinity unit, except during the stationary phase for I. galbana. C37:4 was much more abundant in C. lamellosa (30–44%) than in I. galbana (4–12%). Although our results suggest that salinity has a direct effect on alkenone distribution, growth phase and species composition should also have a marked impact, complicating the use of the distributions as a proxy for salinity in the marine environment.