Diatom diversity and ecological variables in the Arctic lakes of the Kostyanoi Nos Cape (Nenetsky Natural Reserve, Russian North)

We identified 185 diatom species in 87 samples collected from 17 Arctic lakes of the Kostyanoi Nos Cape in July 2003. Species richness varies from 9 to 97 per lake with <i>Aulacoseira islandica</i> (O.F. Müller) Simonsen, <i>Fragilaria</i><i>mesolepta</i> Rabenhorst, <i>Psammothidium subatomoides</i> (Hustedt) L. Bukhtiyarova and Round as dominant species. Bioindication attests to preponderance of temperate, moderately oxygenated, low-to-moderate organic-enriched alkaline, and circumneutral low saline water. Oligotrophic to mesotrophic state correlates with the type of sediments and low organic pollution (saprobity index 0.81–1.73 and Classes 2–3 of water quality). The diatom assemblages contain cosmopolitan species accompanied by the large group of 45 boreal species including 28 Arctic–alpine taxa. Canonical correspondence analysis shows conductivity and the type of sediments being the most important variables. Multivariate regression testifies to importance of depth and area of the lake. The community level analysis reveals four groups correlated with species richness, type of sediments, pH, and salinity. Potential species richness is estimated as 800 species square kilometer based on species–area relationships. Since the diatom assemblages of Arctic lakes are sensitive to climate warming and associated changes of salinity and trophic conditions, they are under high risk of extinction, the diversity losses being scarcely compensated by the rise of tolerant species.

本研究于2003年7月在科斯特亚诺伊诺斯角（Kostyanoi Nos Cape）的17个北极湖泊中采集了87份样本，从中鉴定出185种硅藻（diatom）。各湖泊的硅藻物种丰富度介于9至97种之间，优势种包括冰岛直链藻（*Aulacoseira islandica*）(O.F. Müller) Simonsen、中缝脆杆藻（*Fragilaria mesolepta*）Rabenhorst以及亚拟形砂皮藻（*Psammothidium subatomoides*）(Hustedt) L. Bukhtiyarova & Round。生物指示（bioindication）分析结果表明，该区域水体以温带、中度含氧、低至中度富有机质的碱性及近中性低盐水环境为主。水体的贫营养至中营养状态与沉积物类型及低有机污染程度相匹配，对应的污生指数（saprobity index）为0.81~1.73，水质等级为2~3级。该硅藻群落（diatom assemblages）中既有广布种，还包含45种北方特有类群，其中28种为北极-高山类群（Arctic–alpine taxa）。典范对应分析（Canonical correspondence analysis）结果显示，水体电导率与沉积物类型是影响硅藻群落分布的最关键环境变量。多元回归分析证实，湖泊水深与湖泊面积同样为重要的影响因子。群落水平分析将该硅藻群落划分为4个类群，各类群分别与物种丰富度、沉积物类型、pH值及盐度显著相关。基于物种-面积关系（species–area relationships），本研究估算该区域的潜在硅藻物种丰富度可达每平方千米800种。由于北极湖泊的硅藻群对气候变暖及其引发的盐度与营养状态变化极为敏感，因此面临极高的灭绝风险，且耐受物种的增殖难以弥补该区域的多样性损失。