Is your water clean? These algae are the ones to say

Marikina, known for its River Park, shows the importance of caring for freshwater. However, beneath it lives a creature too small to see with the naked eye, yet big enough to help the ecosystem thrive.

Researchers from the University of the Philippines Los Baños (UPLB), the University of Santo Tomas (UST), and partner institutions in Japan, discovered 17 tiny algae called Pinnularia (P.) in the Marikina River, Rizal—13 of which have never been seen in the country before.

“Using a microscope, scientists identified 17 different kinds of Pinnularia living in the river. Of these, 13 have never been officially recorded in the Philippines before. These microscopic organisms are important because they can help scientists understand the health of freshwater ecosystems,” the UP Office of the Vice President for Academic Affairs noted in their Facebook post.

Small but terrible

         According to the Diatoms of North America, an online database run by researchers specializing in recording information about diatoms, a typical size of a single Pinnularia is 10-300 micrometers, depending on the species; its size is usually similar to a dot you can make with a sharpened pencil, or a single grain of salt, but not smaller than a pore.

         They may widen to 2-20 micrometers, which is thinner than a strand of human hair. Meanwhile, its weight is so light that even a million Pinnularia would weigh far less than a sprinkle of flour.

         But don’t be fooled. Despite its tiny size, it has a remarkable purpose to help the ecosystem survive and thrive. 

An underwater detective

         Pinnularia can act as a natural water tester. Some species only thrive in clean freshwater, while others can tolerate polluted water. By looking at which species are present under a microscope—a scientific tool used to see tiny things that the human eye can’t—scientists can quickly get the water’s quality.

         “Generally, Pinnularia is a freshwater periphyton. The species in the genus can be used to indicate the characteristics of waters. They are predominantly found in oligotrophic waters with low electrolyte concentration and slightly acidic freshwater, but they also inhabit eutrophic, polysaprobic, or alkaline waters,” the researchers noted.

         When the water is healthy, P. divergens var. mesoleptiformis, P. substomatophora, P. rhombofasciata, P. saprophila, and P. latarea species thrive. While if it is rich with pollution, P. mesoleptiformis, P. cf. subcapitata, P. subgibba var. undulata, P. cf. vietnamogibba, P. cf. claasseniae, P. saprotolerans, P. subcapitata var. paucistriata, P. trivialiformis, P. aquaedulcis, P. borealis var. sublinearis, P. acrosphaeria, and P. reichardtii exist.

Pollution in the population

         But this remarkable discovery revealed a harsh reality.

         According to the researchers, out of the 30 sites where they conducted their study, Pinnularia were only found in 13 sites. Showing that parts of the river struggle to support life.

         “With the growing population and industrialization along the Marikina River, its water quality has been degrading as it goes downstream,” the researchers added.

         In a deeper understanding, this displays how the water in those areas may be so polluted that conditions are too harsh even for Pinnularia species known to tolerate polluted environments.

Nevertheless, though it’s invisible to the naked eye, these algae show a clear sight. An indicator that helps people know where to clean and act, whether big or small. Because even the smallest effort can have the biggest impact.