Abstract
Establishment of adequate conservation areas represents a challenging but crucial task in the conservation of genetic diversity and biological variability. Anthropogenic pressures on marine ecosystems and organisms are steadily increasing. Whether and to what extent these pressures influence marine genetic biodiversity is only starting to be revealed. Using 16S rRNA gene amplicon sequencing, we analysed the microbial community structure of 33 individuals of the habitat-forming glass sponge Vazella pourtalesii, as well as reference seawater, sediment, and biofilm samples. We assessed how two anthropogenic impacts, i.e. habitat destruction by trawling and artificial substrate provision (moorings made of composite plastic), correspond with in situ V. pourtalesii microbiome variability. In addition, we evaluated the role of two bottom fishery closures in preserving sponge-associated microbial diversity on the Scotian Shelf, Canada. Our results illustrate that V. pourtalesii sponges collected from protected sites within fishery closures contained distinct and taxonomically largely novel microbial communities. At the trawled site we recorded significant quantitative differences in distinct microbial phyla, such as a reduction in Nitrospinae in the four sponges from this site and the environmental references. Individuals of V. pourtalesii growing on the mooring were significantly enriched in Bacteroidetes, Verrucomicrobia and Cyanobacteria in comparison to sponge individuals growing on the natural seabed. Due to a concomitant enrichment of these taxa in the mooring biofilm, we propose that biofilms on artificial substrates may ‘prime’ sponge-associated microbial communities when small sponges settle on such substrates. These observations likely have relevant management implications when considering the increase of artificial substrates in the marine environment, e.g., marine litter, off-shore wind parks, and petroleum platforms.
Highlights
Glass sponges (Hexactinellida) are extraordinary animals with a skeleton made of silicon dioxide and a unique histology which is distinct from all other known sponge classes (Leys et al 2007)
The V. pourtalesii microbiomes showed a higher variability of their α-diversity than the environmental reference microbiomes
Rarefaction curves (α-diversity) revealed further that microbial richness was highest in the biofilm samples collected from the Ocean tracking network (OTN) mooring, second highest in seawater, and lowest in V. pourtalesii samples (Online Resource 1: S1)
Summary
Glass sponges (Hexactinellida) are extraordinary animals with a skeleton made of silicon dioxide and a unique histology which is distinct from all other known sponge classes (Leys et al 2007). The greatest taxonomic diversity of glass sponges is found between 300 and 600 m depth, with only a few populations occurring in shallow (euphotic) waters (Leys et al 2007). The microbial communities associated with sponges can be very diverse, with more than 63 phyla reported previously. In order to gain a holistic understanding of multicellular organisms, their internal symbiotic associations should be considered (McFall-Ngai et al 2013). ‘metaorganism’ (Bosch and McFall-Ngai 2011)) has been defined to cover the host plus its associated microbiota (Bordenstein and Theis 2015; Rohwer et al 2002). While the histology and trophic ecology of glass sponges has been a matter of several previous studies (Kahn and Leys 2017; Kahn et al 2018), the microbiology of glass sponges still remains largely unexplored (but see Steinert et al 2020; Tian et al 2016; Savoca et al 2019)
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