INVASIVE species of zooplankton affecting Philippine lakes and the synthesis of a medicinal compound highlighted the University’s golden year in scientific research.

These studies were presented in the “Ika-13 Panayam Pang-Agham” held by the UST Research Center for Natural and Applied Sciences (RCNAS) at the Thomas Aquinas Research Complex (TARC) Auditorium last Aug. 24 to commemorate the 50 years of contributions of Thomasian researchers in the field of science and technology. It was the 13th year that research papers were presented in Filipino.

Rey Donne Papa, an assistant professor from the College of Science, discussed how the increasing number of fish cages affects the plankton biodiversity and aquaculture in Taal Lake.

Planktons are minute aquatic organisms which are blown by water currents due to its incapability of swimming. Zooplanktons are microscopic animals seen in marine and freshwater environments and are very essential in the ecosystem being a source of nutrition for fishes and other aquatic animals.

“Fishes which are zooplanktivorous often eat these types of zooplankton. They are also important in sustaining primary production in the lakes,” Papa said.

He added that zooplankton population regulates the number of phytoplankton, or plant-like plankton and algae in the water by eating them.

“Without zooplanktons, the phytoplankton population will increase which will result in the overproduction of nutrients in the lakes which may lead to algal blooms,” Papa said.

An algal bloom is the increase in the population of phytoplankton in an aquatic ecosystem that produces toxins on water, resulting in fish kills and red tides.

While breeding freshwater fishes like tilapias serve as a source of revenue for the citizens of Taal, fish cages might have a negative implication on the lake’s ecosystem.

Papa said fish cages contribute to the increase of nutrients and plankton populations, resulting in competition of available oxygen between the fishes and the plankton.

Helter skelter

The 10,000 fish cages which had been built in 2008 are numerous, considering that Taal Lake has only the capacity to hold 6,000 fish cages.

“When people noticed the large population of fishes present in the lake, they increased the number of fish cages, but too much number of these cages caused a decrease in the fish population by 87 percent,” Papa said.

Majority of the dying fishes came from these fish cages. An example of which is an incident in 2011 where 2,000 metric tons of tilapia and bangus died in the lake. The endemic species of Sardinella tawilis, which can only be found in Taal, might also be affected, Papa said.

By identifying the zooplankton samples taken from the “open-water” and fish cage sites of Taal Lake, Papa discovered that fish cages contribute to the presence of excess nutrients in the lake. He also noticed from statistical records that high levels of certain types and populations of zooplanktons, like copepods, cladocerans, and rotifers, are found exclusively in fish cage sites as a result of eutrophication.

Eutrophication is the phenomenon when an increase in the level of nutrients like phosphates and nitrates occur in aquatic environments.

“The ratios we got [from the study] indicate that the lakes of Taal are eutrophic,” he said. “We recommend the reduction of fish cage areas there.”

Because of Papa’s study, Agham party-list representative Angelo Palmones issued a Writ of Kalikasan in Taal which orders the decrease of fish cages in the said lake.

According to Article II, Section 16 of the Constitution, the Writ of Kalikasan is a legal remedy that aims to protect the rights of the people to “a balanced and healthful ecology in accord with the rhythm and harmony of nature.”

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American invaders

Aside from the threats posed by fish cages, Papa also reported about another species of zooplankton trying to invade Philippine lakes.

Identified as Arctodiaptomus dorsalis, this zooplankton coming from North and Central America is believed to have reached the country’s waters through the American ships docking in Manila Bay.

“Reserve water from these ships is thrown in Manila Bay and from here, the water [carrying A. dorsalis] travels to Pasig River and reaches Laguna Bay,” Papa said.

He added that since Laguna Bay is the center of the largest aquaculture in the country, it might be possible that these dangerous zooplanktons are transported to other lakes through the fish cultures carrying them.

“[These] invasive species could either die as a result of being placed in a new habitat or grow in number because of the adequate environment which is favorable for their reproduction,” Papa said.

However, as the population of A. dorsalis increases, it displaces other calanoid copepods, a group of zooplanktons usually found in the Philippine lakes. Unfortunately, some of these copepods have not yet been fully studied and identified, and chances to discover other zooplanktons in the area are diminishing.

“Out of 27 lakes we surveyed, 18 lakes have been dominated by A. dorsalis and only 3 out of 12 species of calanoid copepods living in these lakes are no longer present,” Papa said. “It (A. dorsalis) has invaded other water bodies in America, as well and it has been discovered to grow in a dirty or eutrophic environment.”

Papa’s team is now focusing on the other possible effects that A. dorsalis could bring to the Philippine lakes to determine possible solutions for this problem.

Reliving the nightmare

Medicinal ingredient

Meanwhile, another researcher from RCNAS presented his study about a complex chemical compound that could possibly have a medical importance in the future.

Allan Patrick Macabeo, a chemistry professor also from the College of Science, discussed about his partial synthesis of ?-Butyrolactone. This compound that can be classified as lactones, which are natural products that can be isolated from plants and marine organisms, is of great pharmacological importance since it has known to have biological activities for cancer, inflammatory illnesses, malaria, and other infectious diseases.

Although these compounds can be found in plants belonging to family Asteraceae, like daisies and sunflowers and from marine animals like corals, he said only few amounts of ?-Butyrolactone can be isolated.

“So, you need to design reactions that could produce the same compound in larger amounts in order for it to be studied well,” Macabeo said.

While further research should still be done on the compound’s activity, Macabeo referred his research as a “marriage of sustainable chemistry and organic synthesis.”

“With organic synthesis, very expensive reagents are needed in producing this compound. However, with sustainable chemistry, we made use of resources abundant in nature, like sugarcane in creating the ?-butyrolactone,” he said.

This technique devised by Macabeo implies a cost-efficient way of creating large amount of chemical compounds which are relevant in creating drugs used to treat several diseases.

At present, continuous studies about ?-butrolactones are conducted by researchers around the world to further investigate other properties of this compound. With reports from Cez Mariela Teresa G. Versoza


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