基于硅藻功能群特征揭示海西海近现代生态环境变化

依据硅藻的形态、生理与生态特点而定义的功能群分类,可以更好地描述对湖泊环境胁迫的响应特征.本研究识别了海西海表层沉积物硅藻群的空间分布模式,并通过多指标分析探讨其与环境因子的关系.结果表明: 主成分分析和冗余分析,水深和沉积物总氮含量是硅藻功能群空间分布异质性的主要驱动因子;水深8 m左右可能是海西海硅藻出现功能群分异的阈值,与热力分层深度等湖泊水文特征相对应.上述表层沉积物硅藻功能群空间分布结果为沉积物化石记录的解释提供了依据.沉积物钻孔分析显示,近百年来海西海硅藻功能群呈现明显的阶段性波动,与年均气温、沉积物总氮含量、中值粒径等指标变化相对应.气候变暖、富营养化和水位上升是驱动海西海硅藻功能群长期变化的主要环境因子,协同促进了功能群D、P、MP占优势.硅藻功能群多样性变化的长期特征表明气候变暖和营养盐富集促进了硅藻功能群多样性的增加,而海西海1957年筑坝和1990年水库扩容两次典型水文调控显著增加了湖泊水深,导致硅藻功能群多样性降低.

Spatial distributions and environmental control of diatom functional groups in sediments of Haixi Lake,Southwest China.

Functional group classification based on the morphological, physiological and ecological characteristics of diatoms is advanced in describing the tolerance and sensibility of diatoms to environmental stressors. In this study, we examined the spatial distribution of diatom functional groups in surface sediments of Haixi Lake and explored the relationships between diatom distributions and environmental variables using multivariate analyses. Principal components analysis (PCA) and redundancy analysis (RDA) results showed that water depth and total nitrogen (TN) were the key drivers for the heterogeneous distribution of diatom functional groups. Water depth of ca. 8 m was the threshold depth in influencing diatom functional group structures linking with thermal stratification. These results provided a basis for fossil record interpretation of the short core. Diatom functional groups fluctuated over the last century, in keeping with mean annual temperature, sediment TN, and median grain size. Climate warming, accelerated nutrient enrichment and intensified hydrological changes led to the dominance of functional group D, MP and P. Additionally, climate warming and nutrient enrichment led to increased diatom functional group diversity, while increased water depth (led by damming and reservoir reinforcement) contributed to diversity loss around 1957 and 1990 AD, respectively.