Mamoru Tanaka

Tokyo University of Science | TUS · Department of Civil Engineering

Microplastics (MPs), plastic particles <5 mm in diameter, are emerging ubiquitous pollutants in natural environments, including freshwater ecosystems. As rivers facilitate efficient transport among landscapes, monitoring is crucial for elucidating the origin, dynamics, and fate of MPs. However, standardized methodologies for in situ sampling in fre...

Meso- and microplastics have been collected via net sampling in marine and freshwater environments, but the effect of net clogging on evaluations of their concentrations (mPC) remains uncertain. We experimentally investigated the mPC uncertainties resulting from net clogging in the Ohori and Tone-unga Rivers, typical urban rivers in Japan, througho...

Microplastics (MPs), plastic particles <5 mm in diameter, have become an emerging ubiquitous concern for the environment. Rivers are the primary pathways that transport MPs from the land to the ocean; however, standardized methodologies for in-situ sampling in freshwater environments remain undefined. Notably, uncertainties in MP sampling methods l...

We deployed a turbulent microstructure profiler, Vertical Microstructure Profiler-eXpendable (VMP-X) near a cluster of seafloor massive sulfide deposits to directly observe deep-sea turbulence. Level of near-bed turbulence (~10⁻⁹ to 10⁻⁷ W kg⁻¹) roughly agreed with that indirectly estimated from Acoustic Doppler Current Profiler (ADCP) moored on th...

A recent linear stability analysis and a numerical simulation suggest that diffusive convection (DC), a regime of the double-diffusive convection, plays a potential role in onset of thermohaline–shear instability, implying that DC could contribute to turbulence production in the oceans. However, an existence of such a thermohaline–shear instability...

Despite suggestions that turbulence can affect the migration of zooplankton, field observations of such effects are scarce. This is especially the case for bottom-associated (demersal) zooplankton that reside in the typically turbulent near-bottom environment. Using moored sensors deployed at two coastal sites in the North Pacific and the Red Sea,...

The measurement of turbulence is necessary to quantify the vertical, diapycnal transport of heat, water and substances influencing climate, nutrient supply and marine ecosystems. As specialist instrumentation and ship-time are required to conduct microstructure measurements to quantify turbulence intensity, there is a need for more inexpensive and...

A multidecadal record of a local zooplankton community, stored in an open-access database, was analyzed with wind data to examine the impact of wind-induced turbulence on vertical distribution of zooplankton. Two major findings were made. First, the abundance of zooplankton assemblage (composed of copepods, cladocerans, etc.) in the upper layer (<1...

Rather than spatial means of biomass, observed overlap in the intermittent spatial distributions of aquatic predators and prey is known to be more important for determining the flow of nutrients and energy up the food chain. A few previous studies have separately suggested that such intermittency enhances phytoplankton growth and trophic transfer t...

Submersible fluorescence and turbidity sensors are widely used in studies of oceans and lakes. To reduce the instrument size, an overlapping interrogation volume is commonly used for the two sensors. Fluorescence sensors emit blue light for excitation and measure the red light emitted by excited chlorophyll pigments. However, during the night, many...

A field campaign was conducted around salmon cages, using a combination of a towed ADCP and a free‐fall multi‐parameter profiler, in order to investigate flow structures and the possible distribution of effluent materials. Two transect observations showed that hydrographic conditions changed dramatically within 5 days, from highly stratified open w...

While swimming organisms may cause turbulence, it is not clear how strong the turbulence is and if eddies are large enough to mix stratified water columns. We conducted an observational experiment in a large aquarium tank containing several thousand Japanese sardines Sardinops melanostictus. Turbulence data were collected from inside the sardine sc...

We have developed a free-fall multi-parameter profiler (YODA Profiler) to measure various physical and biological parameters in coastal ocean. We found internal bores create a strong mixing event. Sediment resuspension is associated with the mixing event and also AZFP detected fish school at the front of bore. We have deployed a cable observatory s...

Coastal ocean environment exhibits rapid change in time and space. Continuous long term measurements of environmental data are scarce. Environmental parameters, such as temperature and salinity, change due to multi-scale physical processes, such as Kuroshio and internal waves. A different scale of physical process affects planktonic ecosystem diffe...

near Joga-shima, Japan, we deployed two microstructure profilers, TurboMAP-L and the TurboMAP-Glider, to obtain vertical and quasi-horizontal measurements of turbulence and chlorophyll a fluor-escence. The deployments were clustered at two stations (one near the coast and another further offshore). Both instruments carried two fluorescence sensors...

See the attached file.

The measurement of phytoplankton distributions in ocean ecosystems provides the basis for elucidating the influences of physical processes on plankton dynamics. Technological advances allow for measurement of phytoplankton data to greater resolution, displaying high spatial variability. In conventional mathematical models, the mean value of the mea...