Diatom record in Laguna de Bay, Philippines for the past 3,000 years
2006
Pineda, R.P.L. | Paleo-Alampay, A.M. | Siringan, F.P.
Diatoms are unicellular algae that thrive in most aquatic environments. They are characterized by their distinctive siliceous cell walls, which are very well preserved in the sediment record. These cell walls, as well as the organisms' sensitivity to their environement, make the one of the most utilized proxies in paleolimnological reconstruction. This study attempts to use diatoms to determine the paleo environmental history of Laguna Lake, based on an 11.5m core sample collected from the central basin. Several samples were taken from the upper part of the core for preliminary diatom analysis. The diatom content per sample was identified and counted, then correlated with historical silica and phosphorous records of the same core. Initial results have shown that the diatom Aulacosiera granulata was the most dominant species in the examined samples. Several other diatoms species such as Cyclotella meneghiniana and Stephanodiscus sp., were observed in significant amounts. An abundance of A.granulata shows a general reversal in trend compared to the phosphorous curve, while correlations with the silica curve show some positive correlation with silica at depths below 60 cm. Results also show that a decline in the number of A. granulata corresponds to an abundance peak in Stephanodiscus sp. The Cyclotella menegliniana abundance curve follows the phosphorous curve to a certain degree. For full understanding of the environmental history of the lake, a correlation with other variables that could affect diatom abundance is recommended.
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