No abstract

The main purpose of this study is to clarify the relation between characteristics of sediments and environmental conditions, based on the analysis of core samples from the South Yatsushiro Kai (Sea) which is located off the west coast of central Kyushu Island, Japan.Bottom sediment samples were collected at 74 stations in the southern part of the Yatsushiro Kai using gravity corers in March 1996. 62 core samples were used for the mechanical analysis by the settling-tube method, and Q-mode cluster analysis was carried out based on the proportion of grain size distribution (Wentworth size classes) . 61 core samples were available to estimate the sedimentation rates (during c. 50 years) which were recognized from the first appearance of high mercury contents of cores. On the other hand, the topmost one centimeter of 73 core samples, which is approximately 10 cc of wet sediments, was utilized for foraminifera) study.The general trend of the bottom current system in the area was discussed, based on the mechanical analysis data of bottom sediments, the distribution of sedimentation rates and the distributions of the number of individuals of planktic and living benthic foraminifera. Based on the results mentioned above, the South Yatsushiro Kai is subdivided into the following five areas:1) the area near the straits characterized by coarse sediments under the influence of strong tidal and bottom currents; 2) the southern part and the area off the mouth of the Minamata River, both of which are characterized by relatively coarse sediments under the influence of longshore currents and poorly sorted sediments supplied by the Komenotsu and Minamata Rivers; 3) the northwestern and eastern parts characterized by fine-grained sediments accumulated under conditions of rather stagnant water masses; 4) the central area, characterized by relatively fine sediments and a large number of planktic empty tests deposited on the sea bottom under the condition of rather weak tidal current systems; 5) the northern part characterized by gravels or gravelly sands which were derived from shallow coastal areas.Judging from the distribution pattern of the maximum mercury content at some horizons of each core, the fine-grained sediments polluted by mercury were transported northeastward and southward by weak longshore currents and spread toward north and west across the northern and southern parts of the South Yatsushiro Kai.

This study aims to determine the distribution of total suspended solid concentration (TSS) in the waters around TPI Dumai. Water samples were taken from 12 sampling point from the waters during high and low tides to determine TSS concentration. The concentration of total suspended solids ranges from 60-130 mg/l. The concentration is relatively higher (>80 mg/l) in the area that is close to residential areas and TPI. The highest concentration of total suspended solids was 117 mg/l found in waters with a depth of 1-3 m, while the lowest was 81 mg/l found at the sampling point of 5,9. The distribution of chlorophyll-a concentration is relatively higher around the coast which is around 0.476-0.178 mg/l, and it's lower off the shore which is around 0.080-0.090 mg/l. The chlorophyll-a concentration is lower in waters far from the coast because there is no direct nutrient supply from the land. The regression analysis indicate that Tss and chlorophyll-a has a weak relationship between the two variables relatively weak but they are still affecting each other.

The Malacca Strait is the importance waters for international shipping routes and more 200 cases of ship collisions in the period 1970-2015 in this strait. That is related to some a shallow depth waters with many small islands and strong current which is making this strait have a highest risk in certain seasons. The CMEMS data used to understanding of mechanism of current, illustrate the pattern and tranport volume. The research uses descriptive and the statistical methods to understanding of mechanism and variability of current. The analysis of current patterns and water level shows that during the monsoon winds active, the current always moves to the Andaman Sea, we called the southeast current system. The Northeast (NE) and Southwest (SW) monsoon wind is strongly influence to the mechanism of formation southeast current system, which causes the varition in sea level hight in eastern and western of Malacca Strait. During the NE monsoon season, the water masses of the South China Sea are push away into the Karimata Strait, causing the sea level in the eastern part to be higher than the western part and will increase the current speed. On the other hand, during the SW monsoon season, the water masses from the Karimata Strait is pushed away from the eastern part of the Malacca Strait which causes the sea level decrease and causes the current speed to weaken. Numbers eddies phenomenon were found at the Malacca Strait each season. The anticyclonic eddies occurred almost every season centered at 3° - 5° N, 97° - 100° E. Meanwhile anticyclonic eddies appear around the northern part of Sumatra centered at 4° - 5°N, 99° - 101°E during SW Monsoon season and the eddies formation also existed during the second transition monsoon season.