Abstract
Microorganisms play a critical role in the decomposition of organic matter, which contributes to energy and nutrient transformation in every ecosystem. Yet, little is known about the functional activity of epinecrotic microbial communities associated with carrion. The objective of this study was to provide a description of the carrion associated microbial community functional activity using differential carbon source use throughout decomposition over seasons, between years and when microbial communities were isolated from eukaryotic colonizers (e.g., necrophagous insects). Additionally, microbial communities were identified at the phyletic level using high throughput sequencing during a single study. We hypothesized that carrion microbial community functional profiles would change over the duration of decomposition, and that this change would depend on season, year and presence of necrophagous insect colonization. Biolog EcoPlates™ were used to measure the variation in epinecrotic microbial community function by the differential use of 29 carbon sources throughout vertebrate carrion decomposition. Pyrosequencing was used to describe the bacterial community composition in one experiment to identify key phyla associated with community functional changes. Overall, microbial functional activity increased throughout decomposition in spring, summer and winter while it decreased in autumn. Additionally, microbial functional activity was higher in 2011 when necrophagous arthropod colonizer effects were tested. There were inconsistent trends in the microbial function of communities isolated from remains colonized by necrophagous insects between 2010 and 2011, suggesting a greater need for a mechanistic understanding of the process. These data indicate that functional analyses can be implemented in carrion studies and will be important in understanding the influence of microbial communities on an essential ecosystem process, carrion decomposition.
Highlights
Decomposition is an important component of nutrient and organic matter cycling in ecosystems [1,2,3] and forms the base of many food webs [4]
Seasonal Variation Spring overall microbial functional use of the carbon resources was highest of all seasons (Fig. 1) and increased by 6.0% from the first (121 accumulated degree hours (ADH)) to the last sampling day (4,426 ADH); the greatest functional activity change occurred during the summer with an increase of 27.1% from the first (345 ADH) to last (3,066 ADH) sampling day; autumn activity decreased by 20.9% over decomposition from 671 to 11,075 ADH; and winter microbial activity increased by 26.2% from 0 to 12,504 ADH
Using PERMANOVA we found no significant differences in normalized microbial metabolic community profiles (MMCPs) among the sample locations of each carcass; data were pooled for the remainder of analyses
Summary
Decomposition is an important component of nutrient and organic matter cycling in ecosystems [1,2,3] and forms the base of many food webs [4]. Microbes are a major component of large carrion resource pulses such as salmon runs [13,14] and cicada emergences [15], which are important in mediating ecosystem structure and function [16,17]. Often in such studies, decay rates or nutrient fluxes provide a measure of the overall decomposition process [10], with little attention given to the discrete function, the carbon source use, of the associated microbial communities and their influence on decomposition rates [18,19,20]
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