北极黄河站夏季冰川消融对近岸海域微型浮游植物群落的调控作用研究

Glaciers melt rapidly during summer induced by increasing temperature in the arctic. Meltwater carries great amount of continental substances into sea and brings significant effects on coastal pelagic community. The effect would be more serious along with the enhanced increase of arctic temperature. However, there is little study focus on such effects. The glaciers covers 60% of the Svalbard islands， where the Chinese Yellow River Station locates. Nano- and Pico-fractions are the main components of phytoplankton communities in the arctic coastal waters near the Yellow Revier Station in summer. The two fractions account for about 80% of the biomass of the phytoplankton community. Consequently, the Yellow River Station is an appropriate location to study effects of glacial meltwater on coastal pelagic ecosystems. This study plans to research the nano- and pico-fractions of microalgae in cryoconite holes, glacial meltwater, and coastal water near the Yellow River Station. Analytical techniques including molecular biological methods, microscopic observation, flow cytometry, high performance liquid chromatography for photosynthetic pigment analysis will be used in this study; both investigations and experiments in situ and simulation experiments in laboratory would be carried out; and the data would be analyzed by statistics. By this way, we would like to know the distribution and structure of microalgae community in cryoconite, glacial meltwater, and seawater of high arctic; and explore the feasibility of the continental and glacial pico- and nano-phytoplanton in denoting mixing process of meltwater into seawater. We also try to clarify the impact of glacial meltwater, and accordingly, to evaluate the potential effects of glacial ablation on pelagic communities in the arctic coastal water.

北极地区升温导致冰川在夏季快速消融，融水携带大量冰（陆）源物质入海，会对近岸海域浮游生物群落产生显著影响。随着北极升温加剧，该影响将更为深远，但目前国际上尚未对此进行深入研究。我国北极黄河站所在的斯瓦尔巴群岛冰川覆盖率为60%，而微型浮游植物（粒径<20 μm）作为北极高纬海域夏季优势类群，约占北极黄河站近岸海域浮游植物生物量的80%。依托北极黄河站开展冰川消融对海洋微型浮游植物群落影响研究，对了解冰川融化对近岸海洋生态系统的影响具有重要意义。本研究拟以黄河站附近的冰川-冰川融水-近岸海域为研究介质、以微型浮游植物为主要研究对象，通过现场调查及模拟实验，了解不同生境微型浮游植物的群落结构及分布特征，阐明冰川融水对北极高纬近岸海域浮游生物群落的调控作用，探索利用陆源生物指示冰川融水在海中的输送途径，评估在可预见的北极持续升温的背景下，冰川消融对北极近岸海域浮游生物群落的潜在影响。

北极王湾是一个很适合研究气候变化的海域，受冰川融水的影响很重，作为最重要的初级生产力，人们对微型浮游植物的群落分布及受冰川融水的影响方式及程度知之不多。本项目的执行较好地解决了这个问题。我们对北极黄河站微型浮游生物群落在冰川-冰川融水-海水中的结构及空间分布进行了对比分析；并对冰川（陆源）微型浮游植物的融水输送途径指示作用进行了探讨，同时探索了冰川融水对海洋微型浮游植物群落的影响。结果显示：（1）绿藻中的微胞藻（Micromonas）、塔胞藻（Pyramimonas）、葡萄球藻（Bathycoccus）、Prasinoderma及金藻中的Poterioochromonas与Paraphysomonas是冰川融水至入海口的主要微型浮游植物。在冰川融水中Poterioochromonas是第一优势类群；在入海口处，绿藻成了第一优势类群，其中Micromonas在盐度较高的水体中含量较高，而Pyramimonas在盐度较低的水体中含量较高。（2）未发生藻华时，Micromonas是绝对优势类群，Bathycoccus，Skeletonema，Amoebophrya，Karlodinium，Bolidomonas及Paraphysomonas均能占到整个微微型浮游生物群落的0.5%以上；而发生夏季藻华时，淡水种Poterioochromonas malhamensis更能适应王湾的环境，成为引发种，且群落优势类群变为Poterioochromonas，Micromonas，Prasinoderma，Spumella，Thalassiosira，Chaetoceros，Ebria及Bathycoccus。相对于适应于海水的Micromonas pusilla，Poterioochromonas malhamensis更能适应半咸水状态的王湾。（3）未发生藻华时，王湾中的微型浮游植物表现出明显的水团分布特性；而发生藻华时，这一特性基本消失。（4）蓝藻是海源的，可作为大西洋入流的指示生物；Paraphysomonas 及 Cryothecomonas 可以作为海冰融化的指示生物，Corallochytrium 可以成为冰川融水入海的指示生物。（5）比例1:9的融水输入对浮游植物的生长有微弱地促进作用。