In situ microbial successional dynamics of natural and model freshwater particles

Anthropogenic disturbances and climate change are increasing the density and modifying the nature of aquatic particles, which serve as important microbial habitats. Here, we conducted a short in situ time-series experiment over 6 days and 13 time points at the Cornell Experimental ponds. We evaluated the impact of increased particulate organic matter on microbial communities by adding model chitin particles to dialysis bag mesocosms in triplicate. We measured both free-living and particle-associated microbial communities through 16S rRNA gene sequencing, performed images analysis for particle aggregation and qPCR for absolute quantification of the 16S rRNA gene in each fraction. While particle richness and eveness did not differ between experimental groups, the evenness of the free-living communities increased with the chitin particle addition. Particle aggregation occurred in both control and experimental mesocosms, with a more prnounced effect in the chitin addition. At peak aggregation, the chitin addition exhibited a simultaneously low evenness in the particle communities. The experimental group was significant and accounted for a greater proportion of variation in the composition of particle communities compared to the free-living communities. Finally, control mesocosms had Cyanobacterial dominated particles composed of filamentous and colonial genera whereas experimental chitin particles had more Bacteroidota and Gammaproteobacterial genera. This experimental approach aids in precise measurement and prediction of microbial community responses to environmental changes using specific particle substrates.

Primary Presenter: Marian Schmidt, Cornell University (marschmi@cornell.edu)

Authors:

Joseph Nocua-Tole, Cornell University  (jsn74@cornell.edu)