The aim of this study is to determine the water quality, the particle size (mm) and the organic matter content sediment, the type and abundance of epipelic diatoms, and  the effect of particle size and organic matter content of the sediment on the abundance of epipelic diatoms at Bayur Bay Waters. This study was conducted in June - July 2019. The survey method was applied in this study and sampling location determine by purposive sampling. The resullt of measurement of water quality parameter ranged salinity 29 ‰ - 34 ‰, pH 7-8, current speed of 0,10 m/s – 0,53 m/s, temperature 30,330C - 31,670C. The sediment types are grouped into four types, namely gravel, sandy gravel, gravelly sand, and sand. The average of particle size (Mz) ranged -1,37 Ø - 0,80 Ø. The organic matter on sediment ranged 2,46% -6,36%. Eleven species of epipelic diatoms was recorded namely Amphora sp, Cocconeis sp, Diploineis sp, Halamphora sp, Melosira sp, Navicula sp, Nitzschia sp, Pinnularia sp, Stephanodiscus sp, Isthmia sp and Synedra sp. The average value of abundance range 2.836 – 10.812 ind/cm2. Epipelik diatom abundance was not significantly different between the stations. The effect of sediment particle size on the abundance of epipelic diatoms by 34,37%. The effect of content of organic matter sediment on abundance of epipelic diatoms in Bayur Bay Waters by 51,78%.

The high rate of bacterial diseases in fishes and shrimps has lead scientists seek for natural antibiotic products that would act as a solution. An example of this product is the secondary metabolic products from heterotrophic bacteria. These bacteria could easily be found in many water regions and estuaries, including the Siak District, Riau, Indonesia. Therefore, this study aims at determining the ability of bacterial isolates in inhibiting the growth of pathogens (Vibrio alginolyticus, Aeromonas hydrophila, and Pseudomonas sp.). The research was conducted from June to September 2018. It actuates the type of heterotrophic bacteria in the sampling area using the PCR technique. The phylogenetic structure of bacterial isolates obtained during this study was assessed by nucleotide sequencing of the 16S rRNA gene. The antagonism test showed that bacteria had the ability to inhibit the growth of pathogens (Vibrio alginolyticus, Aeromonas hydrophila, and Pseudomonas sp.). The results showed that 25 pure bacterial isolates were obtained, in which 10 of those were carried out by DNA sequencing; hence, it could be used as antimicrobes. Based on the analysis of 16S rDNA, 10 isolates were identified: 6 were Bacillus cereus and 2 were Pseudomonas aeruginosa with homology levels ranging from 97 to 99%, while the remaining two were suspected as the new species of isolates. From the result, it could be concluded that heterotrophic bacteria are found to be better used as antipathogens against Vibrio alginolitycus than hydrophila and Pseudomonas sp.

Input of nutrients into the waters from various human activities (residential, agriculture and industry) has the potential to cause changes in the physical, chemical and biological conditions of the waters. The study aims to determine the relationship of concentrations of nitrate, phosphate and silicate with the abundance of diatoms in the Tanjung Tiram waters. The method used is the survey method, the determination of the location of sampling is done by purposive sampling, data analysis (multiple regression). Based in the results of laboratory analysis nitrate concentrations ranged from 0,0819 – 0,1167 mg/l, the phosphate concentration ranged from 0,1002 – 0,1526 mg/l, and silicate concentration ranged from 0,04447 – 0,5418 mg/l. The abundance of diatoms in Tanjung Tiram waters ranged from 156,9 – 302,8 ind/l. The results of statistical analysis of the relationship of nitrate, phosphate and silicate with the abundance of diatoms are expressed in terms of equation Y = 350,906 – 58,065Nitrate– 2644,624phosphate+ 440,363Silicate. This statement explains the concentration of nitrate, phosphate related negative (-) to the abundance of diatoms and silicate positive (+) related to the abundance of diatom. This condition shows that the nutrient concentration in these waters is relatively high so that it affects the abundance of diatoms.

The study was conducted in July 2018. Sampling of sedut snails (Cerithidea obtusa) which was carried out in the waters of Mendol Island, Kuala Kampar District, Pelalawan Regency was aimed to determine the differences in the content of Pb, Cu and Zn between slugs and sediments and to know the consumption limits and the level of heavy metal pollution in the waters of Mendol Island. The method used in this study is the survey method. Sampling was determined using purposive sampling. The results of this study indicate the value of the metal content of Pb, Cu, and Zn in sedut snail highest at station 2, respectively: 9,2633 µg / g, 72,040 µg / g, 111,748 µg / g. Whereas for Pb, Cu, and Zn metals, the highest sediment was found at station 2, namely: 23.990 µg / g, 4.795 µg / g, 48.587 µg / g The results of linear regression analysis of Pb metal concentrations in snail meat showed negative results, and the concentration of Zn and Cu metals in snail meat showed positive results. namely Pb with a value of 14.1930 kg / week on Zn metal with a value of 111.7483 kg / week, while Cu metal at station 2 with a value of 72.0400 kg / week

Dinoflagellata was included in one of microalgae groups which are on waters of the sea and the river, it can be found on detritus floats, sediments, and also swim freely. This research done on May – June 2018 at waters of the mangrove bay village, Bintan Regency, Riau Island Province. The aims of this research was to know relationship between organic material concentration toward abundance of toxic benthic dinoflagellata on sediment. In addition, to analyzed organic material concentratin and amount of abundance of toxic benthic dinoflagellata on sediment in waters of Teluk Bakau. The method used was survey method which is the location of sampling is done by pursosive sampling. Measurement of water quality sampling done at any point, the surface water temperature range 31-33oC, 28-31 ‰ salinity, pH 8-9 and the current speed from 0.045 to 0.051 m / det.Perairan predominantly sandy gravel sediments, making an average of organic materials ditemukn at each station is 0.027%, 0.043%, 0.033%, 0.024%. The result of this research found 3 genus of toxic dinoflagellata, which are Prorocentrum, Gambierdiscus, and Ostreopsis. Poisonous dinoflagelatta can produced a several types of toxic that found the sea. The highest of abundance found at station 2 on 75,615 sel/m2 and the lowest found at station 1 on 35,176 sel/m2. the results of simple linear regression analysis the relationship between the concentration of organic material with the abundance of dinoflagellates has a positive relationship with the regression equation y = 32,913 + 556,13x