Determining Macrophyte Primary Production and Nutrient Availability in LakePalacpaquen, San PabloCity, Laguna

de la Torre, Joseph Benjamin B.

Determining Macrophyte Primary Production and Nutrient Availability in LakePalacpaquen, San PabloCity, Laguna

Joseph Benjamin B. de la Torre

Department of Environmental Science

School of Science and Engineering

Ateneo de Manila University

LoyolaHeights, Quezon City

Abstract

LakePalacpaquen is a crater lake in San PabloCity, Laguna. It is the shallowest and the second largest among the seven lakes in the said city. Its water quality is influenced by the water from LakeCalibato as well as from sewage from the inhabitants and aquaculture practices by the various barangays in its vicinity.

This paper aimed to provide baseline data on macrophyte primary production and nutrient content in the said lake.

The water quality of the said lake was measured over a three-month period in terms of nitrate (NO3-), phosphate (PO43-), and total phosphorus (P) content. The macrophytes, namely: Pistia stratiotes, Ipomoea aquatica, and Hydrilla verticillata, and Eichhronia crassipes were sampled from the inlet, center, and outlet of the lake and were processed for primary production determination by measuring the ash-free dry weight. Moreover, on-site water quality parameters were measured. Sampling was done from November 2005 to January 2006.

The spatial and temporal variability of each factor were analyzed using t-test and ANOVA at 95% confidence interval. Furthermore, the correlation of NO3-and PO43- content with primary production were computed by determining the correlation values (r).

It was determined that the physico-chemical properties of the lake met the standards of DAO No. 34 for Class C waters in general. Also, it was found out that there was no significant difference (p0.05) in both the spatial and temporal data in the PO43- concentrations of the lake. In terms of NO3- content on the other hand, there was a significant difference (p<0.05) in the spatial variability of the samples taken during November and January and in the temporal variabilities of the inlet and outlet. Furthermore, there was no correlation between the PO43- and NO3- concentrations with the primary production (r=-0.13 and r=-0.01, respectively).

It was also determined that there was no significant difference in the spatial variability of the primary production for December and January and that there is a significant difference in the temporal variability of the center and outlet.

From these, it was concluded that LakePalacpaquen is suitable as a Class C water for aquaculture purposes. However, it is also polluted in terms of PO43- concentration, making it susceptible to eutrophication and algal blooms that could pose a threat to primary production and in the aquaculture industry in the long run.