The past, present and future of snow algae in Antarctica: a threatened terrestrial ecosystem?

南极洲雪藻的过去、现在和未来：陆地生态系统受到威胁吗？

• 批准号: NE/V000896/1
• 负责人: Peter Convey
• 金额: $ 10.97万
• 依托单位: British Antarctic Survey
• 依托单位国家: 英国
• 项目类别: Research Grant
• 财政年份: 2021
• 资助国家: 英国
• 起止时间: 2021 至 无数据
• 项目状态: 未结题
• 来源: https://gtr.ukri.org/projects?ref=NE%2FV000896%2F1
• 关键词: past; present; future; snow; algae

In Antarctica, less than 0.2% of the land is ice-free for at least part of the year and so is able to support terrestrial life. As in all habitats, these ecosystems have as their basis the primary producers - that is organisms that photosynthesise by using the sun's energy to capture CO2 from the atmosphere and make sugars. Even so, in the Antarctic Peninsula, only 1.34% of this exposed ground is estimated to be vegetated.Satellite images can be used to determine vegetated areas on the ground because photosynthetic organisms have distinct colours that can be detected. Perhaps surprisingly, when some of these areas have been inspected directly - in a process called ground-validation - a major group of photosynthetic organisms are snow-algae living on the surface of (or just below) the snow fields. Many species have dormant stages where they make red pigments - this has led to them being mistaken for drops of blood in the snow. As well as the fact that snow algae may be one of the major primary producers, they are also important for cycling nutrients in the habitable terrestrial regions of Antarctica. As the snow melts they are washed off into the surrounding environments providing nutrients to the adjacent land and into the sea. The contribution of snow algae to these ecosystems, both in absolute terms and relative to the area of 'true' terrestrial habitat in the Antarctic, is therefore likely to be considerable. Recently, we have carried out studies to make the first-ever large-scale area and biomass distribution map of snow algae across the whole of the Antarctic Peninsula. Essentially we have been able to record for the first time the third largest terrestrial photosynthetic ecosystem on the Antarctic Peninsula after mosses and lichens. We detected 1679 green snow algae blooms covering approximately 1.9km2, which overall was estimated to weigh 1327 tonnes and taking up 1757 tonnes of CO2 per year. We found that these blooms were influenced by both temperature and nutrients with 60% of blooms being within 5km of a penguin colony. We also found that 62% of blooms were on small, low-lying islands that, should the Peninsula continue to warm, will lose their summer snow cover along with their snow algae. However, the other larger blooms were found further north on the Peninsula, on sites that would allow the blooms to expand onto higher ground.Now we have the initial estimates of where and how much snow algae there is in one part of Antarctica it is important that we work out 1: where snow algae are in the rest of Antarctica 2, increase the detection sensitivity of our methods by using drones to detect the red as well as green blooms 3, the range of temperatures, nutrients and light required for the snow algae to bloom 4, how the snow algae compare to other major plants in the region such as lichens and mosses and 5, whether the snow algae species across Antarctica are all the same and what are they made of. We will also look at historical satellite images of Antarctica to see if the blooms are spreading, decreasing or have remained in the same places. To do this we need to carry out a comprehensive survey of snow algae blooms from detected sites all the way along the Antarctic Peninsula in 2021 and then studying one very large bloom for a whole growth season in 2022. There we will ground-truth the blooms and other vegetation and to carry out a detailed analysis of the nutrients in the snow and the photosynthetic activity of the snow algae and other plants in the area. This will allow us to estimate their overall contribution to the polar carbon budget. Once we have all this information we can make detailed models to predict how the snow algae blooms will change in location, size, biomass and species in the coming years. Overall, this will be a significant advance in our understanding of the Antarctic terrestrial ecosystem.

在南极洲，不到0.2%的土地至少在一年中有部分时间是无冰的，因此能够支持陆地生命。与所有栖息地一样，这些生态系统以初级生产者为基础，即利用太阳能从大气中捕获二氧化碳并产生糖的生物体。即便如此，在南极半岛，估计只有1.34%的裸露地面被植被覆盖。卫星图像可以用来确定地面上的植被区域，因为光合生物具有明显的颜色，可以被检测到。也许令人惊讶的是，当在一个被称为地面验证的过程中对其中一些地区进行直接检查时，一群主要的光合生物是生活在雪地表面（或下面）的雪藻。许多物种都有休眠阶段，在这个阶段它们会分泌红色色素——这导致它们被误认为是雪中的血滴。事实上，雪藻可能是主要的初级生产者之一，它们对于在南极洲可居住的陆地区域循环养分也很重要。当雪融化时，它们被冲刷到周围的环境中，为邻近的土地和海洋提供营养。因此，雪藻对这些生态系统的贡献，无论是在绝对意义上还是相对于南极“真正”陆地栖息地的面积而言，都可能是相当可观的。最近，我们开展了研究，绘制了有史以来第一张整个南极半岛大尺度的雪藻面积和生物量分布图。从本质上说，我们已经能够第一次记录南极半岛上第三大陆地光合生态系统，仅次于苔藓和地衣。我们发现了1679个绿雪藻华，覆盖面积约1.9平方公里，总体估计重1327吨，每年吸收1757吨二氧化碳。我们发现这些水华受到温度和营养物质的影响，60%的水华发生在企鹅聚居区5公里范围内。我们还发现，62%的水华发生在地势低洼的小岛上，如果半岛继续变暖，这些岛屿将失去夏季积雪和雪藻。然而，在半岛更北的地方发现了其他更大的花朵，这些地方可以让花朵扩展到更高的地方。现在，我们已经初步估计了南极洲某一地区的雪藻分布地点和数量，重要的是我们要弄清楚：南极雪藻类在剩下的2,增加检测灵敏度的方法通过使用无人驾驶飞机来检测红色以及绿色花朵3,温度的范围,所需营养和轻雪藻类开花4,如何比较雪藻类和其他地区的主要植物如地衣和苔藓,藻类物种在南极雪是否都是一样的,它们是由什么组成的。我们还将查看南极洲的历史卫星图像，看看藻华是在扩散、减少还是在同一地方保持不变。要做到这一点，我们需要在2021年对南极半岛沿线检测到的雪藻华进行全面调查，然后在2022年研究整个生长季节的一次非常大的华。在那里，我们将实地考察水华和其他植被，并对雪中的营养物质以及雪藻和该地区其他植物的光合作用进行详细分析。这将使我们能够估计它们对极地碳收支的总体贡献。一旦我们掌握了所有这些信息，我们就可以建立详细的模型来预测未来几年雪藻爆发在位置、大小、生物量和物种上的变化。总的来说，这将是我们对南极陆地生态系统理解的重大进步。

项目成果

Remote Sensing Phenology of Antarctic Green and Red Snow Algae Using WorldView Satellites.

• DOI: 10.3389/fpls.2021.671981
• 发表时间: 2021
• 期刊: Frontiers in plant science
• 影响因子: 5.6
• 作者: Gray A;Krolikowski M;Fretwell P;Convey P;Peck LS;Mendelova M;Smith AG;Davey MP
• 通讯作者: Davey MP