The C37 alkenone record of sea water of time series station DYNAPROC@en

The concentrations of suspended particulate pigments, C37-C38 alkenones, total organic carbon and nitrogen in the Ligurian Sea (northwestern Mediterranean) have been studied at 5 and 30 m depth during well defined thermocline conditions. An accurate description of the short term changes of these compounds has been achieved by means of four 36-h sampling cycles each encompassing consecutive filtration periods of 4 h. During sampling the thermocline changes were followed closely by simultaneous measurements of water column temperature, salinity and other physical parameters. The analysis of the collected samples indicates that the Haptophyte pigments and alkenones are essentially synthesized at the levels of highest primary production and therefore the C37 alkenone record reflects the seawater temperature at this depth level. The study also shows that part of these alkenones are distributed throughout the water column in association to the suspended particles. This process results in C37 alkenone distributions that, due to their high resistance to chemical and microbial degradation, record the temperature of the highest primary productivity layers even at shallow (e.g., 5 m depth) or deep (e.g., 1100 m depth) waters.本研究针对地中海西北部的利古里亚海，在明确界定的温跃层条件下，于5米与30米水深站位，测定了悬浮颗粒色素、C37-C38烯酮、总有机碳与总氮的浓度。为精准刻画上述化合物的短期变化特征，本研究设置了4个时长36小时的采样周期，每个周期包含连续4小时的过滤时段。采样期间，通过同步测定水柱温度、盐度及其他物理参数，实时追踪了温跃层的变化过程。对采集样品的分析结果表明，定鞭金藻（Haptophyte）色素与烯酮主要在初级生产力最高的水层中合成，因此C37烯酮的记录可反映该水层的海水温度。本研究同时发现，部分此类烯酮会与悬浮颗粒结合并在整个水柱中分布。由于C37烯酮对化学降解与微生物降解具有较高抗性，该过程使得其分布记录即便在浅层（如5米水深）或深层（如1100米水深）水体中，仍能反映初级生产力最高水层的温度。