The effect of top‐predator presence and phenotype on aquatic microbial communities

Abstract

The presence of predators can impact a variety of organisms within the ecosystem, including microorganisms. Because the effects of fish predators and their phenotypic differences on microbial communities have not received much attention, we tested how the presence/absence, genotype, and plasticity of the predatory three‐spine stickleback (Gasterosteus aculeatus) influence aquatic microbes in outdoor mesocosms. We reared lake and stream stickleback genotypes on contrasting food resources to adulthood, and then added them to aquatic mesocosm ecosystems to assess their impact on the planktonic bacterial community. We also investigated whether the effects of fish persisted following the removal of adults, and the subsequent addition of a homogenous juvenile fish population. The presence of adult stickleback increased the number of bacterial OTUs and altered the size structure of the microbial community, whereas their phenotype affected bacterial community composition. Some of these effects were detectable after adult fish were removed from the mesocosms, and after juvenile fish were placed in the tanks, most of these effects disappeared. Our results suggest that fish can have strong short‐term effects on microbial communities that are partially mediated by phenotypic variation of fish.

Predator‐induced changes in dissolved organic carbon dynamics

“…food chain length, community composition, seasonality), our experiment provides some of the first experimental evidence that food web structure can influence the composition of the DOC pool. If effects of predators on both primary producers and bacteria are positive, as was the case in our experiment and those of others (Shurin et al 2012, Atwood et al 2013, Saarenheimo et al 2016, Sullam et al 2017, predators could stimulate both the biological pump by increasing sedimentation (Flanagan et al 2006) and the microbial carbon pump by increasing the production and degradation of DOC. In light of anthropogenic changes to aquatic ecosystems in general, and to the abundance of predators in particular (Duffy 2003, Estes et al 2011, it seems prudent to improve our understanding about the effects of food web structure on carbon sequestration pathways.…”

“…Previous studies showed that fish can stimulate the biological carbon pump by increasing primary production (Schindler et al 1997, Atwood et al 2013 and sedimentation rates (Flanagan et al 2006), resulting in reduced emission of CO 2 from freshwater ecosystems (Schindler et al 1997, Flanagan et al 2006, Atwood et al 2013. Fish can also influence the key components of the microbial carbon pump: they can have cascading effects on the abundance and composition of bacterial communities (Shurin et al 2012, Saarenheimo et al 2016, Sullam et al 2017, and on the algal contribution to DOC (Harmon et al 2009). If effects of fish on both algal and bacterial abundance are positive, as has previously been observed in experiments in freshwater ecosystems (Shurin et al 2012, Atwood et al 2013, Saarenheimo et al 2016, Sullam et al 2017, fish could stimulate both the biological pump and the microbial carbon pump, resulting in increased carbon sequestration.…”

“…Fish can also influence the key components of the microbial carbon pump: they can have cascading effects on the abundance and composition of bacterial communities (Shurin et al 2012, Saarenheimo et al 2016, Sullam et al 2017, and on the algal contribution to DOC (Harmon et al 2009). If effects of fish on both algal and bacterial abundance are positive, as has previously been observed in experiments in freshwater ecosystems (Shurin et al 2012, Atwood et al 2013, Saarenheimo et al 2016, Sullam et al 2017, fish could stimulate both the biological pump and the microbial carbon pump, resulting in increased carbon sequestration. Collectively, these previous studies suggest that trophic effects of fish can extend beyond their impacts on biomass and biodiversity, so as to influence carbon cycling (Schmitz et al 2014).…”

Depth and location influence prokaryotic and eukaryotic microbial community structure in New Zealand fjords

“…Microorganisms play a major role in the cycling of both organic and inorganic nutrients in all major ecosystems (Falkowski et al, 2008; Junge et al, 2006; Sullam et al, 2017; Zahran, 1999). In particular, marine microbes have been linked to global nutrient cycling with community changes affecting global balances of carbon and nitrogen (Arrigo, 2005).…”

Diversity patterns of planktonic microeukaryote communities in tropical floodplain lakes based on 18S rDNA gene sequences

“…Thus, we believe that other variables that are not strictly limnological or morphometric, such as biotic interactions, can also be considered in future studies involving microbiota (e.g. Charvet et al, 2014;Sullam et al, 2017) or human degradation gradients (e.g. Tolkkinen et al, 2015;Volant et al, 2016).…”