A risk assessment of Tributyltin (TBT) in Tokyo Bay was conducted using the
Margin of Exposure (MOE) method. Risk to marine life of Tokyo Bay exists when
no-observed effect levels are less than estimated environmental concentrations (i.e.
when MOE values are less than one). Sources of TBT in this study were assumed
to be commercial vessels in harbors and navigation routes. Concentrations of TBT
in Tokyo Bay were estimated using a three-dimensional hydrodynamic model,
ecosystem model, and chemical fate prediction model. These models calculate
temporal and spatial distributions of TBT concentrations at a fine scale: 1 km x
1 km grids and at a time step of one day. The risk assessment was conducted at the
species level using a common marine species of the Bay: the Japanese short-neck
clam, Ruditapes philippinarum. The assessment endpoint was detined as TBT
induced growth reduction on the Japanese short-neck. NOEC for the Japanese
short-neck clam with respect to the endpoint was estimated from experimental
results published in the scientific literature. MOEs for Japanese short-neck clams
were estimated for the years 1990, 2000, and 2007. There was no risk for these cases,
and the risk from TBT decreased temporally in Tokyo Bay.
To detect slight changes of oceanic carbon cycle in response to atmospheric
C02 increase, high precise measurements of oceanic C02-system properties are
necessary. For the purpose, we examined to improve a coulometer (model 5012,UIC),
which is generally used to detect a temporal increase of total dissolved inorganic
carbon (TC02) in the ocean. In addition, we produced in-house reference materials
(RM), which are traceable to certified reference materials (CRM), to monitor
performance of a TC02 measuring system.
For the coulometer improvement, we improved the photometric detection part
of a coulometer to minimize variations of light source intensity. The repeatability
was improved to be 0.03%(relative standard deviation), which was previously
0.08%. Measurements of RMs showed no statistically significant changes over
approx. 2 years. The RM was judged to be useful as a standard for monitoring
TC02, It is also useful for reducing systematic erros of TC02 values, which are
Habitat information on aquatic animals can be acquired easily using under
water acoustic biotelemetry. The biotelemetry has been developed recently along
with developments of micro-electronics. In this paper, an attempt to track red
tilefish using ultrasonic coded transmitter and receiver system both in the Wakasa
Bay and the Maizuru Bay was introduced. The Wakasa Bay is open to the Japan
Sea and the Maizuru Bay is the typical semi-closed waters. Tracking in the
Maizuru Bay was easier than in the Wakasa Bay, and some fish were passively
tracked more than 100 days. The result indicated that the biotelemetry study in
semi-closed water has a big advantage in order to study fish ecology. Some fish
stayed relatively longer periods in the Maizuru Bay showed circadian rhythm.
Successive tracking records can reveal the ecology of fish as well as their position.
Behavior of hatchery-reared fish was different from that of wild fish. The under
water acoustic biotelemetry may be a tool to evaluate the fish quality for release.
Wavelet spectrum analysis was applied to sea surface temperature images
derived from NOAA/AVHRR for the area around Japan. A two-dimensional
wavelet spectrum for each scale (wave number) was computed at each position
using the Haar wavelet basis, and then a specially-averaged wavelet spectrum was
calculated for each scale. The wavelet spectral slope derived from the averaged
wavelet spectra was approximately -2.0 in the wavelength range between 4 and 280
km in the Kuroshio area and the East China Sea, while in the Japan Sea and the
Perturbed area (between the Kuroshio and the Oyashio), the slope was approximate
ly -5/3. However, the calculation of the slope at every position showed the values
of the slope were randomly distributed, and even in the Japan Sea and the Perturbed
area, the number of positions where the slope was -5/3 was very small (about 10%).
The results gave insight into the structure of horizontal turbulence, which would be
impossible using a traditional Fourier transform approach.
TRITON buoy system consists of unmanned mooring system in the ocean. In
some areas where the buoy are moored, observational instruments are detached and
stolen. Such destructive acts are called Vandalism. Japan Marine Science and
Technology Center (JAMSTEC) tries to prevent Vandalism, of course. Since the
cycle of deployment and recovery of each buoy is about one year, only once a year
prevention can be tested. So far, the following prevention was proved to be
remarkably effective; (1) Change of towers in material from alminium to stainless,
(2) Change of antennas in shape from a whip to a disk.