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 ca. 10 to ca. 35 and the alkenone distributions determined for different growth phases. UK'37 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 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 distributions, growth phase and species composition will also have a marked impact, complicating the use of alkenone distributions as a proxy for salinity in the marine environment.以盐度约10至约35的条件培养等鞭金藻（Isochrysis galbana，菌株CCMP 1323）与片形金藻（Chrysotila lamellosa，菌株CCMP 1307）的批量培养物，并测定不同生长阶段的烯酮（alkenone）分布特征。对于片形金藻，UK'37值随盐度升高略有下降；而等鞭金藻的UK'37值基本不受盐度影响，仅在衰亡期出现变化。两种藻类的UK'37值均随培养时长增加而降低。作为盐度替代指标（proxy）的C37:4占比，在两种藻类中均以每盐度单位0.16%~0.20%的幅度升高，仅等鞭金藻的稳定生长期例外。片形金藻中C37:4的相对丰度（30%~44%）远高于等鞭金藻（4%~12%）。尽管本研究结果表明盐度对烯酮分布具有直接调控作用，但生长阶段与物种组成同样会产生显著影响，这使得利用烯酮分布作为海洋环境盐度替代指标的应用场景复杂化。