5:15 PM - 6:45 PM
[BBG01-P03] The characteristics and advantages of microorganisms attached to diatom fossils in the submarine environment
Keywords:Subseafloor, microorganisms, diatom, guaymas, Southern Ocean, IODP
Diatoms are unicellular algae surrounded by siliceous capsules and are found in diverse hydrosphere, including marine ecosystems. They are estimated to constitute 444-582 Tg - C in global biomass and be a major primary producer accounting for about 1/3 of primary production. The role of diatoms in the ocean includes CO2 assimilation, carbon cycling, and biological pumps. A recent report documented the potential role of specific microorganisms attaching to diatoms in water column to increase the formation of marine snow and increase the efficiency of biological pumps. Numerous studies have been conducted on the microorganisms attached to these living diatoms, including their community composition and interactions.
Although the fossil of diatoms is also the global research target for paleoclimates, especially in deeper marine environments below CCD, not many things are known about the relationship between diatom fossils and microorganisms. In the sediment samples collected by the 2019 International Ocean Discovery Program Expedition 385 (Guaymas Basin) we have observed many microbes attaching to the surface of diatoms in higher abundance than surrounding sediments. The high-density attachment of microbes to diatom fossils in the nutrient-poor seafloor is considered advantageous for survival in the subseafloor environment. Based on the above hypothesis, we characterized the abundance and microbial community structure of diatom-attached microorganisms in comparison with sediments.
Samples were sediment cores containing diatoms from the drilled cores of the Guaymas Basin, and from the Atlantic sector of the Southern Ocean (Weddell Sea) of the Hakuho Maru KH-19-6 voyage and the Indian Ocean sector of the Southern Ocean of the Hakuho Maru KH-20-1 voyage. The sediment samples collected from the surface of seafloor were observed with fluorescence microscopy and scanning electron microscopy. Additionally, microbial community structure was analyzed by sequencing 16S rRNA gene amplicon sequencing. With the fluorescence microscopy observations, we discovered that roughly 10% of the microbial cells present in the surface sediments were attached to diatom fossils. Scanning electron microscopy observations revealed that the microorganisms attached to the diatoms by producing thread-like fibers. The microbial community analysis revealed that, besides Alphaproteobacteria, which were found to be attached to the water column, many Planctomycetes and Acidimicrobiia were also attached to the diatom fossil. Differences in the major microbial communities were observed when compared to the sediment as a whole. These results indicate that the surface of diatom fossils acts as niche hosting certain microbial species.
This presentation will discuss considerations and perspectives on the differences and attachment advantages between microbial communities in sediments and those attached to diatom fossils, both from oceanographic and microbiological perspectives at the collection sites.
Although the fossil of diatoms is also the global research target for paleoclimates, especially in deeper marine environments below CCD, not many things are known about the relationship between diatom fossils and microorganisms. In the sediment samples collected by the 2019 International Ocean Discovery Program Expedition 385 (Guaymas Basin) we have observed many microbes attaching to the surface of diatoms in higher abundance than surrounding sediments. The high-density attachment of microbes to diatom fossils in the nutrient-poor seafloor is considered advantageous for survival in the subseafloor environment. Based on the above hypothesis, we characterized the abundance and microbial community structure of diatom-attached microorganisms in comparison with sediments.
Samples were sediment cores containing diatoms from the drilled cores of the Guaymas Basin, and from the Atlantic sector of the Southern Ocean (Weddell Sea) of the Hakuho Maru KH-19-6 voyage and the Indian Ocean sector of the Southern Ocean of the Hakuho Maru KH-20-1 voyage. The sediment samples collected from the surface of seafloor were observed with fluorescence microscopy and scanning electron microscopy. Additionally, microbial community structure was analyzed by sequencing 16S rRNA gene amplicon sequencing. With the fluorescence microscopy observations, we discovered that roughly 10% of the microbial cells present in the surface sediments were attached to diatom fossils. Scanning electron microscopy observations revealed that the microorganisms attached to the diatoms by producing thread-like fibers. The microbial community analysis revealed that, besides Alphaproteobacteria, which were found to be attached to the water column, many Planctomycetes and Acidimicrobiia were also attached to the diatom fossil. Differences in the major microbial communities were observed when compared to the sediment as a whole. These results indicate that the surface of diatom fossils acts as niche hosting certain microbial species.
This presentation will discuss considerations and perspectives on the differences and attachment advantages between microbial communities in sediments and those attached to diatom fossils, both from oceanographic and microbiological perspectives at the collection sites.