Junaidi, Hafrijal Syandri and Azrita
Research loading of organic material, total organic matter (TOM) and the water quality and its impact on the ecosystem of the lake was conducted in the year 2013. Organic load of waste floating net cages from 2001 to 2013 as much as 111,889.84 tons with an average of as much as 9324.98 tons/year. Levels of total organic matter (TOM) in Koto Malintang station are 19.94 mg/l, Koto Kaciek 16.69 mg/l, Bayur 9.32 mg/l, Sigiran 14.10 mg/l and the outlet of the lake on Hydropower Intake 9.35 mg/l. TOM accumulation in Maninjau Lake amounted to 10.59 mg/l or 53.10% of the incoming load from the floating net cages. The quality of the surface water dissolved oxygen at each side research showed almost the same conditions ranged from 5.70 to 6.77 mg/l, except at a depth of 15 meters ranged from 3.26 to 4.12 mg/l, pH ranges from 8-10, brightness ranges from 1.2 to 2.0 m. Effect of organic matter accumulation has caused the status of heavily polluted lake water quality and mass mortality of fish in floating net cages every year.