Seasonal co-occurrence patterns of bacterial and eukaryotic
phytoplankton communities and ecological effects of keystone taxa in an
urban river
Abstract
Microorganisms play a key role in aquatic ecosystems. Recent studies
have showed that some keystone taxa in microbial communities can drive
the changes in community composition and function. However, most studies
have focused on abundant taxa, whereas rare taxa are neglected because
of their low abundance. Therefore, it is important to clarify the
seasonal variation of bacterial and microalgal communities and
understand the synergistic adaptation of these organisms to different
environmental factors. We investigated the bacterial and eukaryotic
phytoplankton communities and their seasonal co-occurrence patterns
using16S and 18S rDNA sequencing approach. Our results indicated that in
eukaryotic phytoplankton networks, spring and autumn networks had higher
connectivity and complexity, forming the highly stable community
structure. The positive interactions of bacterial network were
significantly higher than the negative interactions, indicating that
more mutual cooperation can make the microbial communities better resist
changes in the external environment, thereby maintaining the stability
of microbial network. The main genera identified as keystone taxa in
bacterial networks were Pseudomonas, Stenotrophobacter,
Bosea, and Hyphomicrobium, which were significantly
related to many predicted functions. The main genera identified as
keystone taxa in eukaryotic phytoplankton networks were Monodus,
Tetradesmus, Scenedesmus, Monoraphidium, and
Amphora, which were affected by dissolved organic carbon,
nitrate, nitrite, and phosphate, changes in these environmental factors
can affect the stability of network. Through the co-occurrence patterns,
we analyzed the internal mechanism of interaction between bacteria and
eukaryotic phytoplankton and understood the potential importance of
keystone taxa in ecological processes such as carbon, nitrogen, and
phosphorus dynamics.