Does size matter? Assessing the role of lentic system area on diatom diversity in subarctic Finland

Lentic systems are often small, experiencing a wide range of consequences of climate change through shifts in chemistry and community assembly processes. Such vulnerable systems support most of the regional freshwater biodiversity in the Finnish subarctic, highlighting their conservation value. Despite increasing research of subarctic freshwater diatoms focusing on the relationship between biodiversity and various factors, the effect of habitat size on benthic diatoms remains understudied. This study compared diatom diversity and water chemistry between and within subarctic lentic systems. Significant differences in species richness, water pH, conductivity, Ca, Cl, and Na were found between lakes and ponds, but the variation within systems was insignificant. Our results suggest that there were size-dependent differences in community composition, assembly processes, and local contributions towards beta diversity, and that differences in water chemistry between ponds and lakes help shape the benthic diatom communities. Thus, surface area may be used as a proxy for water chemistry. Microhabitat abundance and environmental harshness likely cause such area effects, but further investigation is required on isolation, dispersal limitations, and water depth. Studying the benthic communities of these vulnerable systems will provide insight into the effects of climate change.

静水生态系统（lentic systems）通常体量较小，会因化学性质改变与群落组装过程的变化，承受气候变化带来的一系列连锁影响。这类脆弱的生态系统维系着芬兰亚北极区域绝大多数的淡水生物多样性，凸显了其极高的保护价值。尽管当前针对亚北极淡水硅藻（diatoms）的研究与日俱增，且多聚焦于生物多样性与各类影响因子之间的关联，但生境面积对底栖硅藻（benthic diatoms）的影响仍未得到充分探究。本研究对比了亚北极静水生态系统之间以及系统内部的硅藻多样性与水体化学特征。研究发现，湖泊与池塘在物种丰富度、水体pH值、电导率、钙（Ca）、氯（Cl）与钠（Na）含量上存在显著差异，但系统内部的差异并不显著。研究结果表明，群落组成、组装过程以及局地对β多样性（beta diversity）的贡献均存在面积依赖性差异，且池塘与湖泊间的水体化学性质差异有助于塑造底栖硅藻群落。因此，表面积可作为水体化学性质的替代指标。微生境丰度与环境严酷性或为这类面积效应的成因，但仍需进一步开展关于隔离程度、扩散限制以及水深的相关研究。对这类脆弱生态系统的底栖群落展开研究，将有助于深入理解气候变化所带来的效应。