Alkenones in the Mediterranean Sea@en

Time-series of downward alkenone fluxes have been investigated at 200 m depth over a one year sediment trap experiment, in the Northwestern Mediterranean Sea. Alkenone flux maxima occurred in autumn and to a lesser extent in May, during the spring bloom. Temperature estimates calculated from the UK'37 index revealed that alkenone producers preferentially develop in subsurface waters (at about 50 m) in spring, whereas the autumn alkenone production occurred upper in the water column (around 30 m). Examination of the core-top UK'37 index values at various sites of the Northwestern Mediterranean basin, suggested that the spring bloom period do not significantly imprint the temperatures recorded in the sediments. The sedimentary temperature estimates would rather reflect annually integrated SST, with a major influence of the autumnal post-bloom development of the coccolithophores in the euphotic zone.本研究依托地中海西北部海域为期一年的沉积物捕集器实验，对200米水深处的下沉烯酮（alkenone）通量时间序列开展了调查分析。研究发现，烯酮通量峰值主要出现在秋季，春季水华期间的5月也存在强度较弱的次级峰值。基于UK'37指数计算得到的温度估算结果显示：春季时，烯酮生产者优先在约50米深的次表层水体中繁衍；而秋季的烯酮生产活动则发生在水柱更上层（约30米处）。对地中海西北部盆地多个站位的表层沉积物岩心UK'37指数值进行分析后发现，春季水华期并未对沉积物记录的温度产生显著印记。相较而言，沉积物的温度估算结果更能反映全年平均海表温度（Sea Surface Temperature, SST），其主要受秋季水华后真光层内颗石藻（coccolithophore）繁衍过程的主导影响。