When snows bloom: snow algae associated microbial communities are
underpinned by trophic partitioning
Abstract
Snow microbial communities (algae, bacteria, and fungi) play major roles
in snow ecosystem processes and are linked to snowmelt dynamics, but
patterns and mechanisms underpinning their spatial distributions,
community assembly, and maintenance dynamics are poorly understood. Here
we examine nival microbial communities and physicochemical measures
across a semi-continental scale and across categorical snow algae bloom
zones to elucidate interrelation between communities and their
environment. Evidence suggests that trophic partitioning may be a major
driver of snow community sub-networks. Samples from snows from the
Cascade Mountains (USA) and the Rocky Mountains (USA) were collected
from active red snow algae blooms from the center of the bloom (medial),
from the edge of the bloom (peripheral), and in adjacent ‘white’ snow.
Medial sections of snow algae blooms show increased levels of
anemophilous bisaccate pollen, lower oxidation-reduction potential,
decreased algal and increased bacterial richness, and increased levels
of potassium. Fungal communities between the Cascade and Rocky Mountains
are distinct but bacterial and algal communities show little
intracontinental differentiation. Ecological modules were identified
using a weighted gene co-expression analysis (WGCNA), which shows that
dominant microbial consortia correlate differentially to environmental
parameters, suggesting complex subcommunities drive observed ecological
patterns. Individual OTU networks (fungi and bacteria) show high levels
of network connectivity compared to networks based on the snow algae
Sanguina nivaloides, which underscores associative differences between
algal dominated networks and other OTU networks, indicative of trophic
partitioning.