Characteristics of Diatoms in Strait of Rupat Riau

Rupat Strait is one of small strait in Malacca Strait, which has a wide range of anthropogenic activities. The pressure of anthropogenic activities in Rupat Strait Riau could changed the conditions of aquatic environment which was took effects on marine organisms including an abundance of diatoms. This research was aimed to analyze the factors of physic and chemical of waters that affected an abundance of diatom on surface of water in Rupat Strait Riau. This research was conducted in Rupat Strait Riau at 5 stations with different environment characteristics during high and low tide. The measured parameters, consist of nitrate, phosphate, silicate, ammonia, light intensity, salinity, Pb, oils and fats, and then the abundance of diatoms. Principal component analysis (PCA) has used to analyze relations of physic and chemical of waters with abundance of diatoms. The study found 11 genus diatoms which has the highest value at high tide and low tide is Coscinodiscus, which ranged 10.693-197.160 sel.m^-3 at high tide and 8.020-186.466 sel.m^-3 at low tide, and Skeletonema (40.769-106.266 sel.m^-3 at high tide and 30.744-145.029 sel.m^-3 at low tide). The contents of NO3 ranged among (0.081–0.142 mg.L^-1 at high tide and 0.090-0.235 mgL^-1 at low tide), SiO2 ranged (0.054–0.075 mg.L^-1 at high tide and from 0.056–0.120 mg.L^-1 at low tide, the current ranged (0.3-0.5 m.s^-1 at high tide and 0.4-0.6 m.s^-1 at low tide), and light intensity ranged (37-113 lx at high tide and 37-233 lx at low tide). Those parameters of physics and chemical had contributions to an abundance of diatoms, but the tidal had no big effects to an abundance of diatoms. The anthropogenic activities had the effects to an abundance of diatoms that have impact on the food chain in aquatic ecosystem at Rupat Strait, so it needs to be managed well for maintain the balancing of aquatic ecosystem.