Pollutants affecting sexual makeup of Laguna Lake fish

LOS BAÑOS, Laguna, Philippines  – Even the sexual composition of some fish species in Laguna de Bay are no longer safe from its polluted water.

This is exemplified by carp, which has been noted to suffer reproductive abnormalities caused by the contaminated waters of the 91,000-hectare lake, now described as the “world’s biggest septic tank.”

Attesting further the continued degradation of the country’s largest freshwater lake are results of a study done by Dr. Michelle Grace V. Paraso of the UP Los Baños-College of Veterinary Medicine (UPLB-CVM) here.

In her research titled “Estrogenic Disruption in Male Common Carp (Cyprinus carpio Linnaeus) to the East and West Sides of Laguna de Bay,” Paraso reported:

“Signs of estrogen exposure in the caged fish were evident in the changes in their sexual characteristics. These changes include reproductive abnormalities such as delay in maturation of germ cells, development of lesions in the testis, and presence of an egg yolk protein precursors called vittelogenin, which is usually found only in female fish.”

While the study confirmed estrogenic pollution in the lake and effects of exposure in male carps, one of the only about a dozen fish species surviving in the now heavily degraded lake, Paraso cautioned that it is too early to establish that the bio-pollutants adversely affect the overall fish population or raise any concern regarding fish consumption.

Estrogen is a substance, as sex hormones, that tends to promote estrus (state of sexual excitability) and stimulate the development of secondary sex characteristics in a female.

UPLB-based, Philippine government-hosted Southeast Asian Regional Center for Graduate Study and Research in Agriculture (SEARCA) supported Paraso’s research.

SEARCA, headed by Director Gil C. Saguiguit Jr., is one of the 20 “centers of excellence” of the Southeast Asian Ministers of Education Organization (SEAMEO), an intergovernment treaty body founded in 1965 to foster cooperation among Southeast Asian nations in the fields of education, science, and culture.

Paraso was among nationals of SEAMEO member-countries who earned their doctoral (PhD) and master’s (MS) degrees from UPLB in 2010-2011 as SEARCA scholars.

In her study, the UPLB-CVM scientist raised male common carps in fish cages along the lake. She later examined and compared them with a reference group raised in the UPLB Limnolgical Research Station in Los Baños.

She also analyzed water samples gathered from 16 sites in Laguna de Bay’s east and west sides, said to be among the highly polluted zones of the lake.

Results of the study showed the presence of high levels of a natural estrogenic endocrine-disrupting compound called 17-beta estradiol (E2) that poses a threat to fish health.

“Alarmingly,” the UPLB-CVM researcher said, “the levels of E2 found in Laguna de Bay were much higher than those in surface waters in other Asian countries. These bio-pollutants are correlated to the hormone excretions found in animal and human feces and urine carried as surface runoff that flow into the lake.”

With Laguna Lake being considered as a viable source of Metro Manila’s domestic water supply, Dr. Paraso recommended that “environmental laws, particularly these that focus on proper water management, as well as basic sewage treatment systems, need to be strictly enforced.”