Documentation of how interactions among members of different stream community trophic levels including microbial communities and aquatic insect functional feeding groups (FFGs) influence the growth, survival, and recruitment of stream fishes is limited. Lake Sturgeon spawning habitats and substrates occupied by benthic insects overlap, suggesting species interactions across trophic levels are common. Lake Sturgeon eggs were incubated in five FFG experimental treatments including: predators (Perlidae), facultative-scrapers (Heptageniidae), obligate-scrapers (Helicopsychidae), filterers (Isonychiidae), and no invertebrates controls. We quantified and compared the effects of different FFGs on the taxonomic composition and relative abundance of egg surface bacterial and lower eukaryotic communities, egg size, incubation time to hatch, free embryo body size (total length) at hatch, yolk-sac area, (a measure of resource utilization) , and percent survival to hatch.
Results/Conclusions
Eggs exposed to predators were of smaller size, had shorter incubation periods, and lower survival relative to controls. Larvae from eggs exposed to predators had smaller yolk sacs and body lengths relative to controls. 16S quantitative (q)PCR estimates of bacterial copy number on egg surfaces varied significantly among treatments. Metabarcoding interrogation of egg surface bacterial (16S) and lower eukaryotic (18S) communities indicated egg surface bacterial and lower eukaryotic taxonomic diversity differed significantly among eggs exposed to different FFGs. Egg surface microbial community composition varied significantly among FFG treatments and between time periods. Results indicate that interactions between lake sturgeon eggs and free embryos and aquatic insects (particularly predatory Perlidae) contribute to trait variability. The mechanisms underlying indirect affects of different insect FFGs on behavioral and physiological plasticity during incubation and alteration of egg surface microbial community abundance and composition may differ spatially and temporally; however, results under conditions evaluated here are of sufficient magnitude to affect recruitment and population viability.