Phytoplankton productivity and community structure changes in the middle Okinawa Trough since the last deglaciation
Phytoplankton productivity and community structure changes in the middle Okinawa Trough since the last deglaciation
复制标题
上次冰消期以来冲绳海槽中部浮游植物生产力和群落结构的变化
DOI：
10.1016/j.palaeo.2022.111349
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发表时间：
2022
期刊：
影响因子：
--
通讯作者：
Zhao Meixun
中科院分区：
文献类型：
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作者：
Chen Mengna;Li Da-Wei;Li Li;Jin Gui'e;Li Guangxue;Xu Jishang;Zhao Meixun
海洋浮游植物在海洋生物泵中起着重要的作用，然而，我们对浮游植物生长对全球气候和环境变化的响应的认识仍然存在争议。由于东亚和印度洋-太平洋暖池之间强烈的陆-海相互作用，冲绳海槽具有高浮游植物生产力和快速沉积的特征，因此它为研究千年至轨道时间尺度上的海洋生产力变化提供了理想的档案。在这项研究中，对从冲绳海槽中部取回的沉积物柱芯M063-05中的C37烯酮、甲藻甾醇和油菜甾醇的脂质生物标志物进行了分析，以重建过去15.8 kyr浮游植物生产力和群落结构的变化。结果表明，这些脂类生物标志物含量的时间变化与长江流域末次冰消期降水变化相一致，在降水增加期（14.5- 12.7ka）含量较高，降水减少期（15.8- 15.0ka和12.7- 11.5ka）含量较低。我们认为，在末次冰消期，降水引起的陆地营养盐供应控制了冲绳海槽中部浮游植物的生长。脂质生物标志物的比例显示高（低）的硅藻和甲藻的总浮游植物生产力的贡献增加（减少）降水间隔。浮游植物群落结构记录也是一致的降水引起的陆地营养强迫在冰消期阶段，较高的营养条件有利于硅藻和甲藻的生长。长江流域的降水主要受东亚夏季风变化和热带辐合带迁移的控制，但冰消期海平面上升也通过影响陆源营养盐向长江流域的输送距离来调节降水对浮游植物生长的强迫作用。从末次冰消期到全新世，生物标志物含量减少，颗石藻对浮游植物总生产力的贡献增加，而甲藻和硅藻则减少。最有可能的解释是制度转变的主要营养源支持浮游植物的生长，从陆地河流营养在冰消期黑潮次表层水营养在全新世。我们的研究结果提供了过去的浮游植物对气候和环境变化的反应的新见解。
Marine phytoplankton plays an important role in the ocean biological pump, whereas our understandings of phytoplankton growth in response to global climate and enviromment changes are still debated. Due to the forcing from the strong land-ocean interaction between the East Asia and the Indo-Pacific Warm Pool, the Okinawa Trough is characterized by high phytoplankton productivity and fast sediment accumulation, therefore it provides ideal archives to study marine productivity changes on millennial-to-orbital timescales. In this study, lipid biomarkers of C37alkenones, dinosterol and brassicasterol, were analyzed in a sediment core M063–05 retrieved from the middle Okinawa Trough to reconstruct phytoplankton productivity and community structure changes over the last 15.8 kyr. We find that temporal variations of these lipid biomarker contents are parallel with precipitation changes in the Changjiang drainage basin during the last deglaciation, with high values during increased precipitation interval (14.5–12.7 ka) and low values during decreased precipitation intervals (15.8–15.0 ka and 12.7–11.5 ka). We propose that precipitation-induced terrestrial nutrient supply controlled phytoplankton growth in the middle Okinawa Trough during the last deglaciation. Lipid biomarker ratios reveal high (low) contributions of diatoms and dinoflagellates to total phytoplankton productivity during increased (decreased) precipitation intervals. The phytoplankton community structure record is also consistent with precipitation-induced terrestrial nutrient forcing during the deglacial stage, with higher nutrient condition favored diatom and dinoflagellate growth. Precipitation in the Changjiang drainage basin was mainly controlled by the East Asian summer monsoon change and the Intertropical Convergence Zone migration, however the deglacial sea level rise also modulated the forcing of precipitation on phytoplankton growth by affecting the delivery distance of terrestrial nutrients to our site. From the last deglaciation to the Holocene, the biomarker content decreased and the contribution of coccolithophorids to total phytoplankton productivity increased at the expense of dinoflagellates and diatoms. The most likely explanation is the regime shift of major nutrient sources supporting phytoplankton growth, from terrestrial riverine nutrients during the deglaciation to the Kuroshio subsurface water nutrients during the Holocene. Our results provide new insight of past phytoplankton responses to climate and environment changes.