ILIGAN CITY – Prof. Dr. Fema M. Abamo of the Mindanao State University in Marawi City has disclosed in a study that water in Lake Lanao is still clean.
“Our Lake Lanao from all sampling sites is still pristine; our water is still clean,” Abamo said during her webinar presentation for the regional basic research caravan for Bicol conducted by the Department of Science and Technology-National Research Council of the Philippines (DOST-NRCP).
The water quality of Lake Lanao in five sampling sites – Marawi City, Ramain, Balindong, Taraka, and Binidayan – was monitored for two years by using the abundance of one-celled protozoan ciliates as bio-indicators of organic pollution.
The highest ciliate abundance was observed in the littoral zone of Balindong at 0.0061cells/mL during the dry season.
The previous study of Beaver and Crisman (1989) categorized lakes as ultra-oligotrophic when their ciliate abundance is equal to or lower than 2.4cells/mL and Lake Lanao, therefore, is ultra-oligotrophic for having ciliate abundance below the set range in all sampling sites.
Such lake category has very low nutrients, scarce growth of plants and algae, and high dissolved oxygen indicative of a clean, healthy, good water quality, and not organically polluted lake.
Organic pollution occurs when large quantities of organic compounds are released into aquatic ecosystems, she said.
Sources of pollution usually come from wastes generated by agricultural, residential, and industrial activities. High levels of inorganic nutrients such as nitrogen and phosphorus in water can cause an overgrowth of plants and algae. As plants and algae die, they become organic materials in the water.
Decomposition of these organic materials uses up high amounts of oxygen, thus depriving the fish population of needed oxygen that causes fish kills in the lake.
These decaying organic compounds serve as substrates for the microorganisms, increasing the bacterial population which in turn supports the abundant growth of ciliates.
Ciliate abundance varied as the season changed, i.e., lower in the non-mixing season and higher in the dry season indicative of nutrient and organic load fluctuations in the lake as the season changed.
Abamo added that water samples for this study were obtained 50 to 100 meters away from the lakeshore in the shallower littoral zone and toward the deeper open water in the pelagic zone.
Their results were corroborated by the findings of another group in the same program conducting the physical and chemical characterization of the lake and also found out that the lake is not polluted but still healthy and has good water quality, she added.
The study, which was funded by the DOST-NRCP, was conducted during a three-year period, but was temporarily suspended and eventually allowed to resume after the Marawi siege.
“The lake was reportedly deteriorating due to increased human population and activities around the lake,” Abamo said, explaining why there’s a need to conserve the lake’s good condition, especially now that the people have resettled back near the lake after the Marawi siege.
The researchers suggested to the local government to strengthen their policies to maintain the healthy condition of the lake.
“We have recommended to the local government to create and implement stricter policies and ordinances to conserve the lake, and regulate and check both the residential and business establishments around the lake,” Abamo said.
Lake Lanao is estimated to be around 10 million years old (World Lake Database) and is listed as one of the 17 ancient lakes of the world with a tectonic-volcanic origin.
It is the second largest lake in the Philippines and the largest one in Mindanao, home to 18 endemic cyprinids (freshwater fishes related to the carps and minnows) that are found nowhere else in the world.
For generations, Lanao Lake has been a potent natural resource that breathes life to the Maranaos, as a source of their food and water, livelihood, religious practices, transportation, and sports.
Abamo is a member of DOST-NRCP’s 4,944 research pool involved in various scientific disciplines. For more webinars on basic research, interested parties can visit the NRCP’s Research Pod, a Facebook Page of the council.