Biological evolution of Antarctic lakes

Beaver Lake, a large epishelf lake in Eastern Antarctica was sampled on two occasions during the austral summer of 2000. Two sites, one 1km offshore and another 6km offshore were sampled at intervals to depths of 40m and 110m respectively. The lake is an end member of ultra-oligotrophic lake systems with a very low carbon pool. Dissolved organic carbon concentrations ranged between 95-652 micro grams per litre. Nutrient levels were generally low with soluble reactive phosphorus ranging from undetectable to 8.4 micro grams per litre, ammonium ranged between 1.8-5.0 micro grams per litre, nitrate from undetectable to 161 micro grams per litre and nitrite 1.1-5.3 micro grams per litre. Chlorophyll a concentrations ( 0.39 - 4.38 micro grams per litre) showed an unusual distribution with the highest levels close to the lake bottom at the offshore site (110m) where the phototrophic nanoflagellates displayed strong autofluorescence. Bacterial concentrations were low, with a maximum of 7.60 x 107 per litre, as were the concentrations of heterotrophic nanoflagellates that exploit them. Primary production ranged between 19.7 - 25.49 micro grams C per litre day-1 and bacterial production from 0.32 - 1.15 micro grams C per litre day-1. In common with other continental Antarctic lakes, the system was dominated by a microbial plankton. However, a dwarf variety of the calanoid copepod, Boeckella poppei, occurred below 25m at concentrations of 3-5 per litre. The data suggest that primary production and bacterial production were not limited by nutrient availability, but by other factors e.g. in the case of bacterial production by organic carbon concentrations and primary production by low temperatures.The fields in this dataset are:EvolutionBiologicallakesalinitydepth mciliates per litrecystsboeckellabacteriaglucoseglycineparticulate organic carbon (POC)total organic carbon (TOC)DiAskenasia 15/2/00sloved organic carbon (DOC)MonodiniumAskenasiaStrombidiumHeliozoascuticociliatesHolophyraPNAN = Phototrophic nanoflagellates HNAN= heterotrophic nanoflagellates

2000年南极夏季，研究人员对南极东部的大型冰架湖（epishelf lake）比弗湖（Beaver Lake）开展了两次采样。共设置两个采样点位：一处距岸1公里，分层采样深度达40米；另一处距岸6公里，分层采样深度达110米。该湖属于超贫营养湖系统的端元组分，碳库储量极低。溶解有机碳（dissolved organic carbon, DOC）浓度介于95~652微克每升之间。营养盐水平普遍偏低：可溶性反应磷浓度介于未检出至8.4微克每升之间；铵态氮浓度介于1.8~5.0微克每升之间；硝态氮浓度介于未检出至161微克每升之间；亚硝态氮浓度介于1.1~5.3微克每升之间。叶绿素a浓度介于0.39~4.38微克每升之间，其分布特征较为特殊：距岸6公里的点位（采样深度110米）的湖底附近叶绿素a浓度最高，该处的光合营养型纳米鞭毛虫（phototrophic nanoflagellates）呈现出强烈的自发荧光。细菌浓度较低，最高值为7.60×10^7个每升；以细菌为营养来源的异养型纳米鞭毛虫（heterotrophic nanoflagellates）浓度同样偏低。初级生产力介于19.7~25.49微克碳每升·天，细菌生产力介于0.32~1.15微克碳每升·天。与其他南极内陆湖泊一致，该湖生态系统以微型浮游生物为优势类群。不过，在25米以下水域出现了一种小型化的哲水蚤目桡足类——鲍氏拟镖剑水蚤（Boeckella poppei），其浓度为3~5个每升。数据表明，初级生产力与细菌生产力并非受营养盐可获得性限制，而是受其他因素制约：例如细菌生产力受有机碳浓度限制，初级生产力则受低温限制。本数据集包含以下字段：演化（Evolution）、生物学（Biological）、湖泊（lakes）、盐度（salinity）、采样深度（米，depth m）、纤毛虫（个/升，ciliates per litre）、包囊（cysts）、鲍氏拟镖剑水蚤属（boeckella）、细菌（bacteria）、葡萄糖（glucose）、甘氨酸（glycine）、颗粒有机碳（POC，particulate organic carbon (POC)）、总有机碳（TOC，total organic carbon (TOC)）、DiAskenasia 15/2/00、溶解有机碳（DOC，dissolved organic carbon (DOC)）、单甲藻属（Monodinium）、Askenasia属（Askenasia）、急游虫属（Strombidium）、太阳虫目（Heliozoa）、被纤毛虫（cuticociliates）、全毛目（Holophyra）、PNAN=光合营养型纳米鞭毛虫（Phototrophic nanoflagellates）、HNAN=异养型纳米鞭毛虫（heterotrophic nanoflagellates）