Benthic diatom community assembly and factors driving its structure

Background/Question/Methods

Testing assembly rules within ecological communities has been pervasive in the scientific literature, but studies testing for assembly mechanisms in microbial communities are limited.  The organization of these communities may primarily be driven by both biotic and abiotic processes such as (1) environmental filtering (2) species interactions (e.g. competition, mutualism).  Alternatively, communities may not be organized and form through stochastic processes (i.e., random compositions).  We sampled 18 streams with varying land use for benthic diatom assemblages to test if diatom communities are structured by deterministic processes and what processes are influencing community structure.  At each stream, rocks were collected and environmental variables (e.g., water velocity, depth, canopy cover, nutrients) were collected to account for environmental factors which may explain similarities across diatom communities. 

Results/Conclusions

Using species co-occurrence null model analyses, preliminary results indicate that benthic diatom communities within streams are structured by deterministic processes (i.e., structure is non-random) which are influenced by both species interactions and environmental constraints.  Although diatoms are known water quality indicators, thus implying that they are structured by environmental conditions such as high nutrient concentrations, other biotic processes can structure diatom communities.