[M-IS24] Biogeosciences of cold seeps, mud volcanoes, and hydrothermal vents

[MIS24-06] Does subsurface fluid emission affect the plankton community? A case study at a hydrothermal vent

*Hiromi Kayama WATANABE¹, Shino Yamamoto¹, Mehul Sangekar¹, Takashi Hosono¹, Dhugal Lindsay¹ (1.Japan Agency for Marine-Earth Science and Technology)

Keywords:chemosynthesis-based community, image analyses

Subsurface fluid emission in oceanic environments, including mud volcanos and hydrothermal vents, can drastically affect marine ecosystems. The distribution patterns in biological communities, though only thoroughly investigated for benthic or sessile animals on the seafloor using video transects and mosaic analyses, are known to be correlated with geochemical characteristics. For planktonic animals, as their distributions are mostly defined by water masses and they flow, correlations between their distributions and that of subsurface fluids has not yet been well-examined. However, plankton are recognized as an important vector carrying minerals, chemicals and organic matter originating in subsurface fluids to the wider oceanic ecosystem. In this presentation, we summarize our recent plankton surveys in the Nansei-shoto island area, where many hydrothermal vent fields are located.
The plankton surveys were carried out both inside and outside of deep-sea calderas associated with and without hydrothermal fluid emissions, to detect the differences in plankton communities attributable to subsurface fluid emissions. The surveys consisted of net sampling using a vertical multiple plankton sampler (VMPS) net and in situ image analyses, including the Visual Plankton Recorder (VPR). The plankton community compositions and distributions were compared. We will show the details of our results and discuss how subsurface fluid can affect the marine ecosystem, as well as discuss the difference between methods used to analyze plankton communities.