Satsuki Matsumura

Primary productivity in the offshore Oyashio in the spring and summer 1990

Primary productivity was measured byin situ method using13C in the offshore Oyashio region in the spring (May) and summer (September) of 1990. Most of the values were within the range of 0.1 to 4 μgC 1−1 h−1 although a very large value, 7.96 μgC l−1 h−1, was observed in summer. Most daily primary production fell within the range of 372 to 633 mgC m−2 d−1 although a very large value, 2,109 mgC m−2 d−1, was observed around the frontal area in summer. Chlorophylla (Chl.a) exceeded 1 μg l−1 in many cases, and the maximum was 4.61 μg l−1 in spring and 7.53 μg l−1 in summer. Most primary productivity per unit Chl.a (photosynthetic assimilation ratio) was within the range of 0.1 to 3 μgC μgChl.a−1 h−1 although higher values, 3–6 μgC μgChl.a−1 h−1, were observed where small-size phytoplanktons (<2 μm) were dominant. These results were compared with results obtained until now in the Oyashio region. The values beyond the range obtained so far in the offshore region were also observed in this study. Furthermore, it was pointed out that the size composition of phytoplankton community has significant influence on the results of Chl.a and photosynthetic assimilation ratio in the Oyashio region.

Kinetics of Nitrate and Ammonium Uptake by the Natural Populations of Marine Phytoplankton in the Surface Water of the Oyashio Region during Spring and Summer

The maximum uptake rate (ρmax) and affinity constant (Ks) for nitrate and ammonium were estimated in the surface water of offshore Oyashio in May (spring) and September (summer), 1990. The average ρmax/Chl.a for ammonium was 2.1 times larger than that of nitrate in both seasons. The average ρmax/Chl.a for both nitrogens were 3.5 times larger in summer than in spring. Water temperature and size composition of phytoplankton population were related to the seasonal difference in the ρmax/Chl.a. Phytoplankton population showed high affinity for both nitrogens in the spring and summer. In addition, the contribution of “new” production to total production was estimated by ρmax[ρmax−No3/(ρmax−NO3+ρmax−NH4)]. The spring value was in the range of 0.26 to 0.45 (mean±SD=0.35±0.092), and the values in spring bloom were especially a little over 0.4. The summer value was in the range of 0.30 to 0.37 (0.34±0.04).

Chlorophyll biomass off Sanriku, northwestern Pacific, estimated by Ocean Color and Temperature Scanner (OCTS) and a vertical distribution model

To estimate chlorophyll biomass from satellite-derived data, we established an empirical model for the estimation of the chlorophyll vertical profile as a function of surface chlorophyll for four separate regions of the Sanriku area, using algorithms based upon ship observations from 1986 to 1995. The modeled profiles compared well with observations during the Sanriku Field Campaign. Chlorophyll biomass in the Sanriku Area estimated by a combination of OCTS data and the model varied from 2.6×104 t in the Oyashio water to 8.2×103 t in the Kuroshio water.

Primary productivity in a cold water mass and the neighborhood area occurring off Enshu-Nada in the late summer of 1989

Primary productivity off Enshu-nada was measured by the13C method in September 1989. Primary productivity was estimated in a cold water mass developed off Enshu-nada for the first time. The obtained value was 469 mgC·m−2·d−1 and higher than those in the pelagic area of Kuroshio, but equivalent to those in the neritic and the Oyashio areas. It was indicated that cold water mass is the place where organic matter is produced actively. Extremely high chlorophylla of more than 5μg·l−1 were found in the cold water mass. The high productivity was due to high standing crop of phyoplankton. Furthermore, calculated light efficiency and quantum yield showed consistent increase with depth and showed a maximum at 10% light level. Both were larger on the coastal side than those on the oceanic side of the Kuroshio current.

Optical properties of inorganic suspended solids and their influence on ocean colour remote sensing in highly turbid coastal waters

The influence of the optical properties of inorganic suspended solids (ISS) on in-water algorithms was evaluated using an optical model in highly turbid coastal water, whose ISS concentration reached several hundred grams per cubic metre. The measurements were conducted in the upper Gulf of Thailand. The backscattering coefficient of the ISS was calculated using the Lorenz–Mie scattering theory. On the basis of the measurement, the ISS size distribution was parameterized as a function of ISS concentration, and both the spherical and non-spherical particle shape models were evaluated. For ISS concentrations of 10 g m−3, an estimate of the chlorophyll-a (chl-a) concentration within a factor of 2 on a logarithmic scale is possible in a [chl-a] range of 4–30 mg m−3. The differential coefficient of remote sensing reflectance was calculated to evaluate its respective sensitivities for chl-a and ISS concentrations. The use of radiometric data at 670 nm (700–900 nm) is valid for in-water algorithms used to estimate chl-a (ISS) concentration in highly turbid coastal waters.

Estimation of chlorophyll-a concentration from satellite ocean color data in upper gulf of Thailand

This study shows match-up analysis of chlorophyll-a concentration in coastal area in Upper Gulf of Thailand. An applicability of atmospheric correction are investigated in turbid area. When a suspended matter concentration is over 7 g/m3 in a mouth of Bangpakong river, atmospheric correction was failed, then chlorophyll-a concentration could not be estimated. Three algorithms which are MODIS (Moderate Resolution Imaging Spectroradiometer) standard, neural network for GLI (Global Imager) and regional empirical algorithm are compared using match-up data set. The regional algorithm has better correlation than other algorithms and its RMSE was minimum in three algorithms. MODIS standard algorithm has good performance in higher than 1mg/m3, however, CHL was overestimated in lower concentration.