Physical Factors Correlate to Microbial Community Structure and Nitrogen Cycling Gene Abundance in a Nitrate Fed Eutrophic Lagoon.
Nitrogenous run-off from farmed pastures contributes to the eutrophication of Lake Ellesmere, a large shallow lagoon/lake on the east coast of New Zealand. Tributaries periodically deliver high loads of nitrate to the lake which likely affect microbial communities therein. We hypothesized that a nutrient gradient would form from the potential sources (tributaries) creating a disturbance resulting in changes in microbial community structure. To test this we first determined the existence of such a gradient but found only a weak nitrogen (TN) and phosphorous gradient (DRP). Changes in microbial communities were determined by measuring functional potential (quantification of nitrogen cycling genes vianifH,nirS,nosZI, andnosZIIusing qPCR), potential activity (via denitrification enzyme activity), as well as using changes in total community (via 16S rRNA gene amplicon sequencing). Our results demonstrated that changes in microbial communities at a phylogenetic (relative abundance) and functional level (proportion of the microbial community carryingnifHandnosZIgenes) were most strongly associated with physical gradients (e.g., lake depth, sediment grain size, sediment porosity) and not nutrient concentrations. Low nitrate influx at the time of sampling is proposed as a factor contributing to the observed patterns.
Department of Microbiology and Immunology, Otago School of Medical Sciences, University of Otago Dunedin, New Zealand.
Matthew P
MP
Highton
Department of Microbiology and Immunology, Otago School of Medical Sciences, University of Otago Dunedin, New Zealand.
Stéphanie
S
Roosa
Department of Marine Science, University of Otago Dunedin, New Zealand.
Josie
J
Crawshaw
Department of Zoology, University of Otago Dunedin, New Zealand.
Marc
M
Schallenberg
Department of Microbiology and Immunology, Otago School of Medical Sciences, University of Otago Dunedin, New Zealand.
Sergio E
SE
Morales
16S rRNA; DEA; ICOLL; denitrification; nutrient; qPCR; sediment grain size