15:00 〜 15:15
[ACG51-06] Responses of coral reef fish community to flow velocity and turbulence
キーワード：乱流、環境DNA、魚類群集、生物多様性
Coral reefs support approximately a quarter of global marine biodiversity despite covering only 0.2% of the ocean's surface. Their primary production per unit area is 10 to 100 times greater than that of tropical open oceans, even surpassing that of tropical rainforests, which hold the highest terrestrial primary production. Among coral reef systems, those in the Ryukyu Archipelago exhibit high biodiversity, partly due to the strong northerly Kuroshio current, which facilitates the recruitment of organisms from the Coral Triangle and provides favorable conditions for their growth. In this area, tourism and fisheries heavily rely on fish biodiversity, but increasing anthropogenic threats are a major concern. Thus, assessment of biodiversity in this region in a changing environment is urgent priority for conservation efforts.
While environmental factors such as temperature, acidity, and dissolved oxygen have been the primary focus in studies of fish communities, ocean turbulence is also an important factor that drives biogeochemical processes in coral reefs. Effects of turbulence on fish have been mainly investigated at an individual level. Studies on complex water flows including wake flow, turbulent flow and unsteady flow suggest that hydrodynamics influence fish behavior and metabolism. Fish adjust their behavior and energy expenditure in response to local hydrodynamic conditions, potentially leading to shifts in community composition. Due to anthropogenic activities, ocean turbulence is affected in various ways, such as intensified development of tropical cyclones due to global warming, shifts in tidal currents, and alterations to coastal structures caused by coastal development. Therefore, understanding turbulence effects on fish communities is essential. However, few studies have examined effects of turbulence on fish communities. Existing research suggests that faster flows enhance species richness and proportion of pectoral fin swimmers in the community, but further studies focusing on effects of not only mean flow velocities but turbulence on community dynamics is needed.
Here, we combined turbulence measurements with a fish community survey to investigate how fish community responds to changing flow velocity and turbulence. At a shallow coral reef site in Okinawa, a flow measurement was conducted for 63 days using an acoustic Doppler velocimeter. Mean flow velocities, turbulent kinetic energy (TKE), dissipation rates, and Reynolds shear stress over 10 mins every hour were estimated. Mean flow velocity reached up to ~0.4 m s-1, while the range of TKE, dissipation rates, and Reynolds shear stress corresponded well with previous observations in shallow coral reefs dominated by wave driven oscillatory flows. Fish community structure was estimated using environmental DNA metabarcoding every day for the same period. Time series of diversity indices, such as species richness and evenness were obtained to examine its relationship with hydrodynamic parameters. Additionally, temporal variation of community structure was examined using non-metric multidimensional scaling, and effects of different hydrodynamic parameters were tested. By integrating detailed turbulence measurements and fish community observations, our study provides key insights into how turbulence shapes fish communities in coral reefs.
While environmental factors such as temperature, acidity, and dissolved oxygen have been the primary focus in studies of fish communities, ocean turbulence is also an important factor that drives biogeochemical processes in coral reefs. Effects of turbulence on fish have been mainly investigated at an individual level. Studies on complex water flows including wake flow, turbulent flow and unsteady flow suggest that hydrodynamics influence fish behavior and metabolism. Fish adjust their behavior and energy expenditure in response to local hydrodynamic conditions, potentially leading to shifts in community composition. Due to anthropogenic activities, ocean turbulence is affected in various ways, such as intensified development of tropical cyclones due to global warming, shifts in tidal currents, and alterations to coastal structures caused by coastal development. Therefore, understanding turbulence effects on fish communities is essential. However, few studies have examined effects of turbulence on fish communities. Existing research suggests that faster flows enhance species richness and proportion of pectoral fin swimmers in the community, but further studies focusing on effects of not only mean flow velocities but turbulence on community dynamics is needed.
Here, we combined turbulence measurements with a fish community survey to investigate how fish community responds to changing flow velocity and turbulence. At a shallow coral reef site in Okinawa, a flow measurement was conducted for 63 days using an acoustic Doppler velocimeter. Mean flow velocities, turbulent kinetic energy (TKE), dissipation rates, and Reynolds shear stress over 10 mins every hour were estimated. Mean flow velocity reached up to ~0.4 m s-1, while the range of TKE, dissipation rates, and Reynolds shear stress corresponded well with previous observations in shallow coral reefs dominated by wave driven oscillatory flows. Fish community structure was estimated using environmental DNA metabarcoding every day for the same period. Time series of diversity indices, such as species richness and evenness were obtained to examine its relationship with hydrodynamic parameters. Additionally, temporal variation of community structure was examined using non-metric multidimensional scaling, and effects of different hydrodynamic parameters were tested. By integrating detailed turbulence measurements and fish community observations, our study provides key insights into how turbulence shapes fish communities in coral reefs.