Since their first discovery in 1977, chemosynthetic ecosystems such as hydrothermal vents, cold seeps, and organic falls have become one of the hottest topics in marine science. With the advancement in technology, we are now able to carry out more deep-sea explorations and investigations, revealing the greater habitat complexity and biodiversity of chemosynthetic ecosystems. It is also recognized that previous studies may have underestimated the roles of the “dark energy” fueled by chemosynthetic production in the global carbon cycle. Deep-sea chemosynthetic ecosystems, therefore, are now considered as an ideal experiment model in studying the interactions among geosphere, hydrosphere and biosphere. With the help of state-of-the-art geochemical and molecular technologies, we have entered a rapidly developing era of understanding the deep-sea chemosynthetic ecosystem and its role in global biosphere functioning.
The cold seep and hydrothermal vent systems are the energy hotspots on the deep-sea seafloor. Though occurring in different geological settings, the environments of these systems are much similar, having a high concentration of reduced compounds including methane, HS-, H2 and iron II in the fluids through the sedimentary column and supporting the thrive of local organisms. A series of studies are conducted on the biogeochemistry of the seeps and vents to characterize the reservoir and flux of key elements and figure out how the systems originate, evolve and support the biota community and global cycling of these elements. To date, studies on the biota community of deep-sea chemosynthetic ecosystems have mainly focused on the diversity, biochemistry and ecological significance of chemoautotrophs. Using cultivation dependent and independent methods, it has been found that a majority of the chemoautotrophs could obtain energy from diverse reduced compounds and fix inorganic carbon via multiple pathways. Moreover, it has been suggested that the chemosynthetic production by these microbes could be an important food source for deep-sea benthic consumers. However, it is also noticeable that only few studies have been conducted either in situ in the deep-sea or using genome-wide or transcriptome-wide approaches. Meanwhile, information about temporal and spatial changes of the free-living chemosynthetic microbial community is still rare, let alone the symbiotic population changes in deep-sea invertebrates. Besides studies focusing on the microbes, attention has also been paid to the megafauna inhabiting the chemosynthetic ecosystem. With more investigations into the biodiversity of deep-sea megafauna, it has been well known that the majority of megafauna could obtain the nutrients from not only endosymbiotic bacteria, but also episymbiotic bacteria. Besides the nutritional interactions, the tight symbiosis between host and symbionts could also shelter them from harsh environments such as heavy metals and high temperature. However, how these megafauna disperse, evolve and establish the symbiosis still needs to be elucidated. What’s more, the biogeography, succession and ecological function of these chemosynthetic holobionts are also less characterized. Finally, though deep-sea mining is still in its infancy, growing efforts have been made to clarify the influence of environment changes and human activities on deep-sea chemosynthetic ecosystems.
This Research Topic intends to present original research articles, mini-reviews and reviews providing a comprehensive perspective on the following aspects:
1. Biogeochemical processes of deep-sea chemosynthetic ecosystem;
2. Diversity, biochemistry and ecological significance of microbes (especially the chemoautotrophs) and virus in deep-sea chemosynthetic ecosystem;
3. Diversity, phylogeny, evolution and connectivity of deep-sea megafauna;
4. Nutritional and reproductive strategies of deep-sea organisms;
5. The physiological diversity of chemosynthetic symbiosis and the interaction between of invertebrate host and chemosynthetic symbionts (especially the mechanisms beneath the acquisition of symbionts of host);
6. The metabolic versatility of chemosynthetic symbionts to gain energy and build biomass and the ecological function of holobionts in the deep-sea ecosystems;
7. How deep-sea organisms evolve and adapt to the extreme environments and the biological responses of deep-sea organisms to stresses;
8. Impacts of global or regional environment changes and human activities on deep-sea chemosynthetic ecosystems.
9. The application of state-of-the art methods (such as single-cell sequencing, spatial transcriptomics, mass spectrometry imaging, in situ experiments and in situ detection) in revealing the phylogenetic or physiological diversity of deep-sea organisms.
Since their first discovery in 1977, chemosynthetic ecosystems such as hydrothermal vents, cold seeps, and organic falls have become one of the hottest topics in marine science. With the advancement in technology, we are now able to carry out more deep-sea explorations and investigations, revealing the greater habitat complexity and biodiversity of chemosynthetic ecosystems. It is also recognized that previous studies may have underestimated the roles of the “dark energy” fueled by chemosynthetic production in the global carbon cycle. Deep-sea chemosynthetic ecosystems, therefore, are now considered as an ideal experiment model in studying the interactions among geosphere, hydrosphere and biosphere. With the help of state-of-the-art geochemical and molecular technologies, we have entered a rapidly developing era of understanding the deep-sea chemosynthetic ecosystem and its role in global biosphere functioning.
The cold seep and hydrothermal vent systems are the energy hotspots on the deep-sea seafloor. Though occurring in different geological settings, the environments of these systems are much similar, having a high concentration of reduced compounds including methane, HS-, H2 and iron II in the fluids through the sedimentary column and supporting the thrive of local organisms. A series of studies are conducted on the biogeochemistry of the seeps and vents to characterize the reservoir and flux of key elements and figure out how the systems originate, evolve and support the biota community and global cycling of these elements. To date, studies on the biota community of deep-sea chemosynthetic ecosystems have mainly focused on the diversity, biochemistry and ecological significance of chemoautotrophs. Using cultivation dependent and independent methods, it has been found that a majority of the chemoautotrophs could obtain energy from diverse reduced compounds and fix inorganic carbon via multiple pathways. Moreover, it has been suggested that the chemosynthetic production by these microbes could be an important food source for deep-sea benthic consumers. However, it is also noticeable that only few studies have been conducted either in situ in the deep-sea or using genome-wide or transcriptome-wide approaches. Meanwhile, information about temporal and spatial changes of the free-living chemosynthetic microbial community is still rare, let alone the symbiotic population changes in deep-sea invertebrates. Besides studies focusing on the microbes, attention has also been paid to the megafauna inhabiting the chemosynthetic ecosystem. With more investigations into the biodiversity of deep-sea megafauna, it has been well known that the majority of megafauna could obtain the nutrients from not only endosymbiotic bacteria, but also episymbiotic bacteria. Besides the nutritional interactions, the tight symbiosis between host and symbionts could also shelter them from harsh environments such as heavy metals and high temperature. However, how these megafauna disperse, evolve and establish the symbiosis still needs to be elucidated. What’s more, the biogeography, succession and ecological function of these chemosynthetic holobionts are also less characterized. Finally, though deep-sea mining is still in its infancy, growing efforts have been made to clarify the influence of environment changes and human activities on deep-sea chemosynthetic ecosystems.
This Research Topic intends to present original research articles, mini-reviews and reviews providing a comprehensive perspective on the following aspects:
1. Biogeochemical processes of deep-sea chemosynthetic ecosystem;
2. Diversity, biochemistry and ecological significance of microbes (especially the chemoautotrophs) and virus in deep-sea chemosynthetic ecosystem;
3. Diversity, phylogeny, evolution and connectivity of deep-sea megafauna;
4. Nutritional and reproductive strategies of deep-sea organisms;
5. The physiological diversity of chemosynthetic symbiosis and the interaction between of invertebrate host and chemosynthetic symbionts (especially the mechanisms beneath the acquisition of symbionts of host);
6. The metabolic versatility of chemosynthetic symbionts to gain energy and build biomass and the ecological function of holobionts in the deep-sea ecosystems;
7. How deep-sea organisms evolve and adapt to the extreme environments and the biological responses of deep-sea organisms to stresses;
8. Impacts of global or regional environment changes and human activities on deep-sea chemosynthetic ecosystems.
9. The application of state-of-the art methods (such as single-cell sequencing, spatial transcriptomics, mass spectrometry imaging, in situ experiments and in situ detection) in revealing the phylogenetic or physiological diversity of deep-sea organisms.
