Are Carotenol-Chlorin Esters Diatom Biomarkers?

研究人员最近在阿曼和秘鲁边缘、南加州湾和蒙特雷湾的沉积物中发现了胡萝卜素和二氢卟酚的新酯（Carotenol-Chlorin-Esters，CCEs）。 与CCEs相关的二氢卟酚是脱镁叶绿酸a和焦脱镁叶绿酸a，叶绿素a（Chl a）的降解产物。 异岩藻黄质-β-胡萝卜素和异岩藻黄质醇-β-胡萝卜素是岩藻黄质的降解产物和硅藻的生物标志物，是与CCE相关的唯一胡萝卜素醇。 PI还在硅藻占主导地位的区域的水柱样品中发现了CCE，并且在实验室中在摄食硅藻的桡足类动物的粪便颗粒中发现了CCE。 这表明，CCEs产生的酶介导的transferfications在桡足类放牧硅藻。 因此，沉积物中的CCEs可能是硅藻产生的新产物的标志，有机碳和氮同位素特征将反映硅藻对碳向沉积物的通量的贡献。 一组实验室实验将进一步证实这一假设。 最初的实验将与桡足类，哲水蚤太平洋，这是目前全年关闭加州进行。匹配的水柱和沉积物收集器样本从圣巴巴拉盆地和蒙特雷湾，涵盖所有季节，将被用来与生产的CCE浮游植物群落结构和其他环境因素。

Novel esters of carotenols and chlorins (Carotenol-Chlorin-Esters, CCEs) were recently discovered by the investigator in sediments from the Oman and Peru margin, the Southern California Bight, and Monterey Bay. The chlorins associated with CCEs were pheophorbide a and pyropheophorbide a, degradation products of chlorophyll a (Chl a). Isofucoxanthin-dehydrate and isofucoxanthinol-dehydrate, degradation products of fucoxanthin and a biomarker for diatoms, were the only carotenols associated with CCEs. The PI also found CCEs in water column samples in regions dominated by diatoms and CCEs were found in the fecal pellets of a copepod fed diatoms in the laboratory. It is suggested that CCEs are produced by enzymatically mediated transesterifications in copepods grazing on diatoms. Thus, sedimentary CCEs could be markers for new production derived from diatoms and the organic carbon and nitrogen isotopic signature would reflect that of the diatoms that contributed to the flux of carbon to the sediments. A set of laboratory experiments will further corroborate this hypothesis. Initially experiments will be performed with the copepod, Calanus pacificus, that is present year-round off California. Matched water column and sediment trap samples from the Santa Barbara Basin and Monterey Bay, covering all seasons, will be used to relate the production of CCEs to phytoplankton community structure and other environmental factors.