Abstract
Marine snow is an important habitat for microbes, characterized by chemical and physical properties contrasting those of the ambient water. The higher nutrient concentrations in marine snow lead to compositional differences between the ambient water and the marine snow-associated prokaryotic community. Whether these compositional differences vary due to seasonal environmental changes, however, remains unclear. Thus, we investigated the seasonal patterns of the free-living and marine snow-associated microbial community composition and their functional potential in the northern Adriatic Sea. Our data revealed seasonal patterns in both, the free-living and marine snow-associated prokaryotes. The two assemblages were more similar to each other in spring and fall than in winter and summer. The taxonomic distinctness resulted in a contrasting functional potential. Motility and adaptations to low temperature in winter and partly anaerobic metabolism in summer characterized the marine snow-associated prokaryotes. Free-living prokaryotes were enriched in genes indicative for functions related to phosphorus limitation in winter and in genes tentatively supplementing heterotrophic growth with proteorhodopsins and CO-oxidation in summer. Taken together, the results suggest a strong influence of environmental parameters on both free-living and marine snow-associated prokaryotic communities in spring and fall leading to higher similarity between the communities, while the marine snow habitat in winter and summer leads to a specific prokaryotic community in marine snow in these two seasons.
Highlights
Marine snow, described as detrital particles larger than 500 μm, plays an important role in the export of organic carbon to the deep sea and the sequestration via the biological carbon pump (Cho and Azam, 1988; Ducklow et al, 2001; Herndl and Reinthaler, 2013)
Adaptations to a free-living life-style in winter included coping with phosphorus limitation and energy acquisition from labile organic matter
prokaryotes supplement heterotrophic growth with solar radiation energy harvested with proteorhodopsins
Summary
Marine snow, described as detrital particles larger than 500 μm, plays an important role in the export of organic carbon to the deep sea and the sequestration via the biological carbon pump (Cho and Azam, 1988; Ducklow et al, 2001; Herndl and Reinthaler, 2013). Microbial community composition, and activity of marine snow in a large variety of oceanic regions. A few studies investigated the dynamics of marine snow and its associated microbial community over a few weeks (Kaltenböck and Herndl, 1992; Müller-Niklas et al, 1994). The importance of increasing the spatial and temporal resolution of research studies to understand the dynamics in the community composition and functioning of ecosystems has been emphasized (Chow et al, 2013; Fuhrman et al, 2015; Ward et al, 2017). Marine snow-associated microbial communities are considered to be relatively insensitive to changes in environmental parameters of the bulk seawater. With increasing size and volume of the individual marine snow, the physico-chemical conditions determine the composition and activity of the marine snow associated microbiome (Vojvoda et al, 2014; Yung et al, 2016)
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