多参数指示南极普里兹湾浮游植物的时空变化

以南极普里兹湾沉积物为研究对象,运用气相色谱技术,研究了生物标志物菜子甾醇、甲藻甾醇、长链烯酮对应指示的硅藻、甲藻、颗石藻等浮游植物的生产量和种群结构的历史变化,结合2001—2011年实测和遥感水体ρ(Chla)(Chla为叶绿素a)及SST(海水表层温度)数据,探讨了该湾浮游植物生产量时空变化特征及其影响因素. 结果表明:过去100多年间南极普里兹湾浮游植物总生产量(212.04~759.10 ng/g)〔以w(菜子甾醇)+w(甲藻甾醇)+w(长链烯酮)计〕和w(硅藻)所占比例(62.28%~87.13%)〔以w(菜子甾醇)所占比例计〕均呈上升趋势,而w(甲藻)所占比例(10.09%~27.98%)〔以w(甲藻甾醇)所占比例计〕和w(颗石藻)所占比例(1.97%~9.74%)〔以w(长链烯酮)所占比例计〕则呈下降趋势. 全球变暖背景下浮游植物种群变动通过改变南大洋对CO₂的吸收进而影响全球碳循环. 水体ρ(Chla)与沉积生物标志物指示的浮游植物总生产量均具有湾内高、湾外低的空间分布特征. 湾内ρ(Chla)与SST的年际变化趋势相似,二者以2002—2003年和2009—2010年相对较高,SST分别为-0.30和0.01 ℃,ρ(Chla)分别为1.69和2.31 mg/m3；以2001—2002年和2010—2011年相对较低,SST分别为-1.19和-0.95 ℃,ρ(Chla)分别为1.08和0.79 mg/m3,表明该湾SST变化可较明显地影响浮游植物的生长. 

Spatial and Temporal Variation of Phytoplankton Indicated by Multi-Proxies in Prydz Bay, Antarctica

The impacts of climate change are particularly striking on Antarctic marine ecosystems, due to the sensitivity of phytoplankton to sea-ice retreat and to minor temperature increases. The sensitivity of Antarctic marine ecosystems to climate change can be exposed by the significant variation in the marine phytoplankton biomass and community structure. In the Antarctic Prydz Bay, the marine phytoplankton biomass and community structure changes significantly impact the marine biological pump and CO₂ absorption in the Southern Ocean. The sedimentary biomarkers (brassicasterol, dinosterol and alkenones), which indicate individual algae (diatoms, dinoflagellates and coccolithophores), were determined by GC (gas chromatography), and were used to reconstruct the historical changes in the phytoplankton biomass and community structure. The data, combined with field and remote sensing Chla(chlorophyll a) and SST (sea surface temperature) data collected in 2001-2011, were employed to reveal the spatial and temporal variations of the phytoplankton biomass and the impact factors in the bay. The results showed that, over the past century, the phytoplankton biomass indicated by three biomakers (from 212.04 to 759.10 ng/g) and w (diatoms) ratio indicated by brassicasterol (from 62.28% to 87.13%) increased, while w(dinoflagellates) ratio indicated by dinosterol and w(coccolithophores) ratio indicated by alkenones (from 10.09% to 27.98% and from 1.97% to 9.74%, respectively) decreased. Therefore, the phytoplankton community structure variation could impact the global carbon cycle by changing the CO₂ absorption in the Southern Ocean and affecting global warming. The phytoplankton biomass indicated by the sea water ρ(Chla) and the sedimentary biomarker records showed significant spatial and temporal patterns in the Prydz Bay and adjacent areas. The indices decreased from the continental shelf of the bay to the continental slope and to the deep sea off the bay. The annual variation in ρ(Chla) was similar to SST:the ρ(Chla) (1.69 and 2.31 mg/m3) and SST (-0.30 and 0.01 ℃) were significantly high in 2002-2003 and 2009-2010, while they were significantly low in 2001-2002 and 2010-2011 (1.08 and 0.79 mg/m3, -1.19 and -0.95 ℃, respectively). The results indicate that the growth of phytoplankton was significantly impacted by the SST variation in the bay. Further work is necessary to explore the mechanism of variation in the marine phytoplankton biomass and the community structure to climate-driven SST and ocean CO₂ absorption change in the Antarctic area.