The distribution of submerged macrophytes in the littoral zones of Lake Taal

Abstract

Macrophytes play an important role in the aquatic ecosystem since they are good bioindicators and serve as habitat for littoral fishes. This research involves the use of the hydroacoustic method aided by visual observation and quantification in determining the distribution and abundance of submerged macrophytes in the littoral zones of Lake Taal. The results were used to generate spatial distribution and percent cover maps of macrophytes in the lake. Based on the surveys, five macrophyte species were present in Lake Taal. Denser macrophyte beds were concentrated in the south basin of the lake. High nutrient levels in the south basin contributed to heavy macrophyte growth in this area, which usually come from run-offs from the residential, commercial, and agricultural watersheds. The lesser biomass of macrophytes in the north basin was attributed to clearing activities due to the construction of fish cages for aquaculture. Furthermore, we were able to observe that there were different dominant species in the north and south basins of the lake; Najas indica was more prominent in the north basin, while Vallisneria nana was more common in the south. This study shows that anthropogenic sources of excess nutrients and other activities such as aquaculture play a role in altering the distribution of macrophytes in Lake Taal and how these can have potential detrimental impacts to the littoral zones of the lake.