外源溶解性有机质对铁、磷生物可利用性和浮游植物生长的影响研究

Due to the climate change, allochthonous dissolved organic matter (DOM) has increased in many lakes and thus may affect the growth of phytoplankton. Humic and fulvic acid, which make up the majority of allochthonous DOM, have highly reactive carboxyl groups that complex with iron (Fe). The complexation of DOM-Fe-P may affect the bioavailability of iron and phosphorus (P) to phytoplankton. Whether the binding of Fe and P by DOM enhances or inhabits the growth of phytoplankton is in argument. In our previous investigation into the high-altitude lakes (3800-4200 m asl) in Yunnan province, we found that there is a positive relationship between allochthonous DOM concentration and growth of phytoplankton biomass. We hypothesize that the enhancement is due to the high solar radiation (especially UVR) inducing a fast release of Fe and P from DOM-Fe-P complex in the high-altitude areas. Therefore, in this project, a high-altitude, humic-rich lake, Tiancai Lake in Yunnan province, is selected as the study site. The effect of allochthonous DOM on the growth of phytoplankton in the presence and absence of UV irradiation will be studied with in situ experiments in Tiancai Lake. Then, the complexation process of DOM with Fe and P and the photoreduction of DOM-Fe-P to release bioavailable Fe and P will be investigated by controlled experiments in lab. Finally, the role of allochthonous DOM on the bioavailability of Fe and P to phytoplankton will be evaluated. The results of this project will reveal how allochthonous DOM affects the growth of phytoplankton. The results will shed light on the understanding the response of lake ecosystems to the climate change, also provide a scientific support for to protect the high-altitude lake ecosytems.

气候变化导致许多湖泊中外源溶解性有机质（DOM）增加，可能影响浮游植物的生长。外源DOM容易和铁（Fe）、磷（P）形成络合物（DOM-Fe-P），改变了Fe、P的生物可利用性。DOM-Fe-P形成后，是促进还是抑制浮游植物的生长，目前并没有定论。申请者发现在云南高海拔地区的湖泊，外源DOM浓度与浮游植物生物量呈正相关，认为这和该地区太阳辐射（尤其是紫外辐射）强，DOM-Fe-P易光还原释放Fe和P有关。因此，本研究选择云南天才湖（高海拔、外源DOM浓度较高）为研究对象，通过原位实验研究在有、无（滤除）紫外辐射时，外源DOM对浮游植物生长的影响；再通过室内受控实验研究外源DOM对Fe、P的络合和光还原释放Fe、P的过程，阐明外源DOM对Fe、P生物可利用性的影响。结果将揭示外源DOM对浮游植物生长的影响；有助于了解气候变化背景下不同湖泊生态系统的响应，为保护高原湖泊生态系统提供理论依据。

气候变化导致许多湖泊中外源溶解性有机质（DOM）增加，可能影响浮游植物的生长。本项目通过对太阳辐射强、外源DOM较高的云南老君山和哈巴黑海地区湖泊的调查显示，发现湖泊中腐殖质的浓度和可生物利用的Fe、P浓度以及叶绿素的浓度正相关。在天才湖——高山湖泊（海拔3800m）的原位实验显示，紫外光能促进DOM的降解，促进Fe的光还原；存在紫外光的实验组中浮游植物的生长更快。避光室内实验结果表明有机质的存在能提高Fe和P的溶解度，溶液中Fe主要存在形式是络合态。综合这些研究结果，认为在太阳辐射强的地区湖泊，外源有机质的输入可能通过两种原因促进浮游植物的生长，一是有机质自身光降解产生更多的可利用的营养盐，二是DOM-Fe-P的光还原可能释放营养物质Fe和P。该项目的研究预示在全球变暖、外源DOM增加的背景下，在太阳辐射强烈地区的湖泊，初级生产力可能会增强。