The Phytoplankton Community Structure of Taklong Island National Marine Reserve (Tinmar), Guimaras Before and After a Major Oil Spill Event

Abstract

A descriptive study was done to report the status of the phytoplankton community in Taklong Island National Marine Reserve (TINMAR), Guimaras approximately two months after the M/T Solar I oil spill. Baseline information on phytoplankton density, composition and diversity, and related ecological factors such as primary productivity through chlorophyll a and dissolved oxygen concentration, nutrient availability and polyaromatic hydrocarbon (PAH) concentration were determined. Quantification of PAH yielded undetectable results, while primary productivity, phytoplankton density and diversity values were higher as compared to samples before the oil spill and samples from the reference site. Sixty-nine genera representing six classes of phytoplankton were identified. Class distribution showed that diatoms composed of classes Coscinodiscophyceae, Bacillariophyceae and Fragilariophyceae were dominant in the area. Class Coscinodiscophyceae was the best represented class with 1,535 individuals/L seawater. The top ranked genera encountered were Chaetoceros, Protoperidinium, Skeletonema, Thalassionema, Rhizosolenia and Bacteriastrum. The shift in dominance of fast-growing centric diatoms over pennate diatoms was indicative of a stressed phytoplankton community. Simpsons (1/D’) values ranged from 0.873 - 1.236 while Shannon-Weiner (H’) values ranged from 1.196 - 1.400. The observed H’ and 1/D’ values of the oil impacted samples were also higher than samples before the oil spill and samples from the reference site. The parameters used in the study described the present phytoplankton community in TINMAR, Guimaras. Though the present findings could provide clues regarding the direct impact of the recent oil spill on phytoplankton community, long term biomonitoring is still needed to verily the said results.