Biology of diatoms (class bacillariophyceae, genera: Nitzschia and Tryblionella) in the Philippines

Professorial Chair Lecture

Jose R. Velasco's inaugural Professorial Chair Lecture

Place

Institute of Biological Sciences, CAS, UPLB

Date

6-30-1999

Abstract

A total of 95 species and varieties of diatoms belonging to the genera Nitzschia and Tryblionella, class Bacillariophyceae are accounted for in the Philippines. The list includes 17 that are reported as new taxa. About 50% of the total species are found in marine habitat. The latter are typically of subtropical types that are predominantly large and elaborately ornamented and similar to the diatoms found in Campeche Bay in Mexico.

Paleolimnological studies along the shoreline of Laguna Lake show that the bulk of the diatom species were typical of eutrophic conditions that are tolerant to organic pollution, most notable of this is the abundance of Nitzschia palea. On the other hand, the Lake shows a consistent and persistent occurrence throughout the years of the centric diatoms, like species of Melosira, Cyclotella and Coscinodiscus that are not affected by some biotic and abiotic factors. While a pennate diatom, Nitzschia sigma var. rigida showed a significant inverse relationship of its population to that of the blue-green alga, Microcystis aeruginosa and the centric diatoms.

Ecological studies in rice paddies around the Philippines show that there is evolution of the types of algae in reference to the rice cultivation cycle, i.e., the planktonic algae predominate at the start of the cultivation cycle followed by the colony-forming algae as the rice matures up to maximum tillering stage. The planktonic algae consist mostly of diatom species, commonly Nitzschia palea. Likewise, the diatoms of Nitzschia types showed tolerance to high pesticide application.

Hence, the importance of Nitzschia's lies mainly in indicating the quality of a given aquatic ecosystem, especially the presence of Nitzschia palea.

Location

UPLB Main Library Special Collections Section (USCS)

College

College of Arts and Sciences (CAS)

Language

English

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