LB 10-118 - Whole-microbial community (Bacteria and Eukarya) assembly across the river continuum

Background/Question/Methods:

The Microbiomes of Aquatic, Plant, and Soil Systems across Kansas (MAPS) project is a multidisciplinary project that examines how microbes affect ecosystem productivity, mediate the effects of agricultural impacts on ecosystems, and contribute to ecosystem functions across the state of Kansas. MAPS looks at connections between the plant, aquatic, and soil systems in these ecosystems. Data was sampled from over 70 sampling events that occurred in the spring and summer of 2018. This dataset was co-collected with biogeochemical and stream network data, and will provide an opportunity for synthetic analysis. This data represents a whole microbiome dataset including prokaryotic 16s rRNA and eukaryote 18S rRNA genes with both phototrophs and heterotrophs identified. This presents an opportunity to study the effect of trophic level relationships in the microbiome. We contrast expectations from the river continuum concept (RCC) and residence time hypothesis. We expect phototrophs to be consistent with the predictions of RCC and there diversity to increase with stream order as they will directly benefit from increase light availability in higher order streams. We expect diversity to decrease for heterotrophs consistent with the residence time hypothesis as terrestrial species are progressively lost from the system as stream order increases.

Results/Conclusions:

Illumina sequencing was conducted on all samples for both 18S and 16S rRNA gene regions. As part of our initial analysis we examined community composition changes using PERMANOVA analysis. Prokaryotic composition was significantly different according to stream order for both cyanobacteria (p< 0.001) and non phototrophic prokaryotes (p< 0.001). Eukaryotic composition was also varied significantly according to stream order (p< 0.001). Using an ANOVA approach we found Shannon’s Diversity was only significantly correlated with stream order for cyanobacteria (p< 0.001) increasing with higher stream orders. Though overall diversity did not decrease for our non-cyanobacteria, there is still evidence for the residence time hypothesis with different community assemblages in higher order streams. Further analysis is needed to determine if a decrease in terrestrially sourced species occurs in higher order streams as the residence time hypothesis would predict. The increase in diversity for cyanobacteria is evidence that these phototrophic organisms following the predictions of the river continuum concept. Higher order streams have greater light availability on average and can support a greater number of phototrophic organisms.