Microbial communities of salmon resource subsidies and associated necrophagous consumers during decomposition: Potential of cross-ecosystem microbial dispersal

Authors: PECHAL, JENNIFER - Michigan State University; Crippen, Tawni - Tc; CAMMACK, JONATHAN - Texas A&M University; TOMBERLIN, JEFFERY - Texas A&M University; BENBOW, MARK - Michigan State University

Submitted to: FOOD WEBS
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/26/2019
Publication Date: 6/1/2019
Publication URL: http://handle.nal.usda.gov/10113/6443626
Citation: Pechal, J.L., Crippen, T.L., Cammack, J.A., Tomberlin, J.K., Benbow, M.E. 2019. Microbial communities of salmon resource subsidies and associated necrophagous consumers during decomposition: Potential of cross-ecosystem microbial dispersal. FOOD WEBS. 19:1-7. https://doi.org/10.1016/j.fooweb.2019.e00114.
DOI: https://doi.org/10.1016/j.fooweb.2019.e00114

Interpretive Summary: The ecosystem is affected by resources that contribute both long-term and short-term additions of nutrients. Salmon of the Pacific Northwest are one predictable short-lived carrion resource. During their life cycle, immature salmon feed and develop in the ocean and return as adults to freshwater streams for spawning, after which they die and leave large numbers of carcasses to decompose. Nutrients from these carcasses act as subsidies for both water and land communities. But the microbial populations that accompany salmon from freshwater to the ocean and back to freshwater for decomposition is less understood. Therefore, this study evaluated the microbiomes of salmon carcasses and how they changed in conjunction with the larval blow fly (Diptera: Calliphoridae) which utilize these carcasses. The system offered a predictable model. It turns out that several microbial taxa were shared between the carcasses and the blow fly larvae. Interestingly, some microbial taxa were eliminated by the larval feeding, but the taxa remaining have the potential to be dispersed into the surrounding ecosystem by adult flies. Therefore, this study links the contribution of these transient microbial communities to the insects interacting with the carrion in the environment. Understanding these interactions will lead to a better understanding and the development of control and capture methods for carrion-feeding insects that could be transporting harmful pathogenic and foodborne bacteria.

Technical Abstract: Ephemeral resource subsidies are known to affect ecosystems at both short- and long-term temporal scales. One such resource is carrion, which varies in size and nutrient composition. Salmon of the Pacific Northwest have an anadromous life cycle resulting in immatures feeding and developing in vast oceanic expanses and adults returning to freshwater streams for spawning and eventual death, leaving large numbers of carcasses to decompose. Previous studies demonstrated how nutrients from these carcasses act as subsidies for both aquatic and terrestrial communities. However, what is less understood is the fate of microbial communities of the once living, oceanic salmon upon death and then decomposition in watershed ecosystems. Therefore, this study evaluated the microbiomes of salmon carcasses and how they changed in conjunction with associated necrophagous larval blow fly consumers (Diptera: Calliphoridae). It was determined that several microbial taxa were shared among the carcass resource, the internal communities of blow fly larvae, and the excretions and secretions from aggregations of larvae. Larvae also fed in a way that eliminated some microbial taxa from the collective community. These results suggest much of the microbial community of the carcass resource is eliminated trophically by primary insect consumers during feeding, assimilation, and egestion. Ultimately, the taxa remaining with larvae can potentially be dispersed into an ecosystem by adult flies. Our microbiome findings suggest a high probability of microbial transfer among ecosystems via salmon necrobiome food webs. Additional controlled field studies are needed to test and identify the persistence and mechanism of these potential bottom-up trophic dynamics.