Environmental and stochastic processes drive diatom taxonomic and functional temporal beta diversity

ABSTRACT: Studying patterns of biodiversity is central to ecological research. Temporal beta diversity, i.e. the change in community composition over time, has emerged as a promising study field during the last decades. Following global climatic change, understanding the consequences of environmental alterations on temporal community composition has become increasingly important. We examined patterns and drivers of temporal beta diversity and whether the temporal variation in community composition is related to temporal environmental variation among 9 coastal diatom communities sampled 12 times at a ca. 10 d interval. We applied a temporal beta diversity index (TBI) decomposed into gains and losses to quantify changes in taxonomic and functional community similarity through time, and for environmental variables to determine temporal change in local abiotic conditions. We assessed environmental and spatial drivers of temporal community change by regression models and partitioned variation in the community composition according to sampling day by distance-based redundancy analyses. Taxonomic TBI was higher than functional TBI, characterized by sharper changes in species gains and losses. Taxonomic TBI was explained by site location, whereas functional TBI had a linkage with both spatial and environmental variables. Environmental TBI was significantly related to taxonomic TBI only. The sites significantly differing in taxonomic or functional TBI did not coincide with those with a significantly different environmental TBI between the sites. The communities were probably structured by both environmental variation and random stochastic processes, creating unpredictability in the TBI. Our results highlight the importance of rapid environmental alterations in shaping temporal beta diversity within dynamic coastal communities.