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Pesticides are widely applied in the agriculture sector to protect crops and pest control. The poisonous substance of pesticides will affect all of the organisms, either target and non-target organisms. Fish can play the role of an indicator of genotoxic presence in aquatic environments. Polysaccharide extracts from sargassum have promising anti-genotoxic potential. This study aimed to analyze the anti-genotoxic activity of brown seaweed (Sargassum polycystum) methanol extract against erythrocyte and micronuclei of tilapia exposed by methomyl-base pesticide. Brown seaweed (Sargassum sp.) purchased from farmers in Sumenep Regency, Madura, East Java, then macerated using methanol 1: 3 (w / v) for 3x24 hours at room temperature. The phytochemical screening was including flavonoids, alkaloids, triterpenes, saponins, and tannins. Tilapia fish (TL ± 9-12cm) purchased from the Technical Application Unit of Freshwater Fish (UPT Perikanan Air Tawar), Sumberpasir, Malang, East Java. The result of this study showed that exposure of methomylbased pesticides in the concentration of 4.015 ppm indicates the formation of micronuclei of 318.33 ‰. The increased concentration of extract treatment is directly proportional to the decrease of micronuclei. It means that sargassum extract can reduce the genotoxic effect on exposed tilapia by methomyl-based pesticides. The best concentration of Sargassum sp. extract that can reduce genotoxic was D (200 ppm).

Water pollution can make many problems such as, the incidence of disease and poisoning. Pollution in water can produce free radicals and it is can trigger of disease for aquatic organisms. There are some efforts that can be done to provide this problem, such as chemical compound that can reduce the reaction of free radicals. Antioxidants are one of the chemical compounds that can reduce the activity of free radicals. Eucheuma cottonii is the one of a seaweed that has many in antioxidant compounds, such as phenol compounds, but it is also rich in iodine fiber and other important minerals. The method used in this research is descriptive explorative and experimental method. This research was conducted with several stages of seaweed extraction. Identification of Eucheuma cottonii extract is using FTIR test. The last stage is an antioxidant activity test that includes DPPH test (1,1-diphenyl-2-picrilhidrazil) and Inhibition Concentration 50 (IC 50). The results obtained in this study were based on FTIR test of antioxidant compound in Eucheuma cottonii seaweed extract. The one of compounds that have antioxidant activity include galaktosa-4-sulfat. Based on the results of antioxidant activity test using DPPH obtained that seaweed extract Eucheuma cottonii active as an antioxidant to ward off free radicals in the waters. The concentration of Eucheuma cottonii seaweed extract for preventive 50% concentration of DPPH is 39,926 ppm.

The pathogenic bacterial infection is one of the problems in the cultivation of vannamei shrimp (Litopenaeus vannamei), causing a high mortality rate of cultured shrimp. The use of antibiotics or chemicals with inappropriate concentrations can harm the aquatic environment, cause resistance, and endanger consumer health because the residues from the chemicals used will periodically accumulate in the body of shrimp. One way to control and prevent shrimp disease is to increase the shrimp immune system by using immunostimulants from seaweed. This study aims to analyze the immunostimulant activity of seaweed extract (Gracilaria sp. and Padina sp.) against vannamei shrimp (L. vannamei) infected with Vibrio harveyi by observing the nonspecific immune system based on its hematological features, namely by counting the number of hemocytes and phagocytic activity. The research was conducted at the Hatchery Unit, Brackish Water Cultivation Development Center (BPAP) Situbondo, East Java. Seaweed sample Gracilaria sp. and Padina sp. purchased from seaweed farmers in Jepara, Central Java. The result of this study shows that supplementation of Gracilaria sp. and Padina sp. at a dose of 10 g/kg of feed can increase the total number of hemocytes and phagocytosis activity of L. vannamei shrimp. The best treatment is Gracilaria sp.