On giant shoulders: How a seamount affects the microbial community composition of seawater and sponges

• Published in: Biogeosciences
• Main Authors: Busch, Kathrin, Hanz, Ulrike, Mienis, Furu, Müller, Benjamin, Franke, Andre, Roberts, Emyr Martyn, Rapp, Hans Tore, Hentschel, Ute
• Format: Article in Journal/Newspaper
• Language: English
• Published: Copernicus Publications (EGU) 2020
• Subjects: Arctic; Schulz Bank
• Online Access: https://oceanrep.geomar.de/id/eprint/48865/; https://oceanrep.geomar.de/id/eprint/48865/1/bg-17-3471-2020.pdf; https://oceanrep.geomar.de/id/eprint/48865/2/bg-17-3471-2020-supplement.pdf; https://www.biogeosciences.net/17/3471/2020/; https://doi.org/10.5194/bg-17-3471-2020

Seamounts represent ideal systems to study the influence and interdependency of environmental gradients at a single geographic location. These topographic features represent a prominent habitat for various forms of life, including microbiota and macrobiota, spanning benthic as well as pelagic organisms. While it is known that seamounts are globally abundant structures, it still remains unclear how and to which extent the complexity of the sea floor is intertwined with the local oceanographic mosaic, biogeochemistry, and microbiology of a seamount ecosystem. Along these lines, the present study aimed to explore whether and to what extent seamounts can have an imprint on the microbial community composition of seawater and of sessile benthic invertebrates, sponges. For our high-resolution sampling approach of microbial diversity (16S rRNA gene amplicon sequencing) along with measurements of inorganic nutrients and other biogeochemical parameters, we focused on the Schulz Bank seamount ecosystem, a sponge ground ecosystem which is located on the Arctic Mid-Ocean Ridge. Seawater samples were collected at two sampling depths (mid-water, MW, and near-bed water, BW) from a total of 19 sampling sites. With a clustering approach we defined microbial microhabitats within the pelagic realm at Schulz Bank, which were mapped onto the seamount's topography and related to various environmental parameters (such as suspended particulate matter, SPM; dissolved inorganic carbon, DIC; silicate, SiO−4; phosphate, PO3−4; ammonia, NH+4; nitrate, NO2−3; nitrite, NO−2; depth; and dissolved oxygen, O2). The results of our study reveal a “seamount effect” (sensu stricto) on the microbial mid-water pelagic community at least 200 m above the sea floor. Further, we observed a strong spatial heterogeneity in the pelagic microbial landscape across the seamount, with planktonic microbial communities reflecting oscillatory and circulatory water movements, as well as processes of bentho-pelagic coupling. Depth, NO2−3, SiO−4, and O2 concentrations ...