近年來有關(guān)氣候變化與生態(tài)系統(tǒng)響應(yīng)的研究發(fā)現(xiàn),,全球或區(qū)域氣候變化對(duì)藍(lán)藻水華的發(fā)生具有促進(jìn)作用,,并與湖泊水體富營養(yǎng)化疊加,,共同促進(jìn)了藍(lán)藻水華強(qiáng)度的增加。已有研究主要基于藍(lán)藻的生理特性分析,,認(rèn)為全球變化導(dǎo)致的溫度升高有利于藍(lán)藻的生長,,而野外觀測往往不能充分支持溫度升高促進(jìn)藍(lán)藻水華發(fā)生的觀點(diǎn),因此亟需深入揭示氣候變暖導(dǎo)致藍(lán)藻水華強(qiáng)度擴(kuò)張的機(jī)制以解釋這種現(xiàn)象,。最近,,中國科學(xué)院南京地理與湖泊研究所孔繁翔研究員的團(tuán)隊(duì)在藍(lán)藻水華強(qiáng)度擴(kuò)張與氣候變化定量關(guān)系研究中獲得新進(jìn)展。
該團(tuán)隊(duì)研究人員張民在Water Research上發(fā)表的論文(Min Zhang et.al.,,2012,,46:442-452)認(rèn)為,平均溫度的升高不能有效解釋藍(lán)藻水華強(qiáng)度擴(kuò)張主要緣于溫度升高效應(yīng)的復(fù)雜性,,野外研究中經(jīng)常把溫度升高看成一個(gè)整體事件,,沒有把溫度的直接影響從溫度誘導(dǎo)的如水體穩(wěn)定性增加、風(fēng)速降低等間接影響中剝離出來,,而這些因素都直接或間接地影響藻類的生長與水華的形成,。
該研究利用遙感影像數(shù)據(jù)獲取了近20年來太湖水華藍(lán)藻的物候?qū)W信息,篩選了近20年來太湖藍(lán)藻水華強(qiáng)度擴(kuò)張(藍(lán)藻水華發(fā)生初始時(shí)間和年內(nèi)持續(xù)時(shí)間)的主要驅(qū)動(dòng)因子,,并對(duì)不同因子的貢獻(xiàn)進(jìn)行了定量研究,。研究發(fā)現(xiàn),在太湖高營養(yǎng)鹽濃度的背景下,,近20年來藍(lán)藻水華強(qiáng)度的擴(kuò)張主要受氣候變化因子的影響,,而風(fēng)速和日照時(shí)間是解釋藍(lán)藻水華擴(kuò)張的主要因子,這兩個(gè)因子解釋了84.6%的藍(lán)藻水華初始發(fā)生時(shí)間提前,,58.9%的藍(lán)藻水華年內(nèi)持續(xù)時(shí)間延長的變化,。
全球變暖不僅僅意味著平均溫度的升高,,其同時(shí)也使得短期的溫度波動(dòng)更加劇烈和頻繁。浮游藻類由于細(xì)胞體積小,,生命周期短,,其對(duì)溫度波動(dòng)極為敏感。這種短期溫度波動(dòng)會(huì)給氣候變暖對(duì)浮游藻類影響的研究帶來更大的不確定性,。因此,,評(píng)估全球變暖對(duì)水華藍(lán)藻種群優(yōu)勢形成的影響不僅要考慮平均溫度的升高,而且要考慮短期溫度波動(dòng)的影響,。張民利用室內(nèi)模擬試驗(yàn)和野外觀測數(shù)據(jù)研究發(fā)現(xiàn),,春季溫度的快速波動(dòng)增加有利于藍(lán)藻的光合作用和生長,而不利于其它藻類,。
這一結(jié)果表明在春季藻類群落演替期間,,溫度波動(dòng)很可能會(huì)促進(jìn)水華藍(lán)藻種群優(yōu)勢的更早確立。該研究成果已經(jīng)發(fā)表在Phycological Research上(Min Zhang et.al.,,2012,,60:199-207)。
該研究充分認(rèn)識(shí)到了水體營養(yǎng)鹽濃度與氣候變化對(duì)藍(lán)藻水華形成的疊加效應(yīng),,并認(rèn)為在氣候變化的大背景下控制藍(lán)藻水華,,對(duì)降低水體營養(yǎng)鹽濃度提出了更高的要求。研究成果對(duì)于湖泊治理和管理決策具有重要的指導(dǎo)意義,。
上述研究得到國家“973”項(xiàng)目,、國家自然科學(xué)基金項(xiàng)目、江蘇省自然科學(xué)基金的資助,。(生物谷Bioon.com)
DOI: 10.1111/j.1440-1835.2012.00654.x
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Photochemical responses of phytoplankton to rapid increasing-temperature process
Min Zhang, Yang Yu, Zhen Yang, Fanxiang Kong
Phytoplankton is sensitive to rapidly increasing temperature in spring. However, studies on the effect of temperature on phytoplankton have mainly focused on constant temperatures. It is necessary to clarify the determining parameters of phytoplankton shifts during temperature increases, as temperatures are predicted to fluctuate more intensively and frequently in the future. In the study, we analyzed the responses of photosynthetic properties and growth in a cyanobacterium (Microcystis aeruginosa) and a green alga (Chlorella pyrenoidosa), the dominant species in Taihu, to rapid increasing-temperature process in the laboratory and in the field. The results show that gradually increasing temperature inhibited photosynthesis and the growth of C. pyrenoidosa and had almost no effect onM. aeruginosa. Elevated increasing temperature range also had more significant effects on the photosynthetic properties and growth rates of C. pyrenoidosa than those of M. aeruginosa in the laboratory and in the field. All of these results suggest that the photosynthetic performance of M. aeruginosa is more suitable to gradually increasing temperature and relatively strong temperature variations than that of C. pyrenoidosa, which might partially contribute to Microcystis excluding Chlorellacompetitively in aquatic ecosystem. Our findings point out the possible importance of the rapid and dramatic increasing-temperature process to the formation of cyanobacterial blooms.