Correlation of Chlorophyll-a and Dissolved Oxygen in the Phytoplankton Abundance in Leyte Gulf, Philippines

Abstract

Leyte Gulf is an important fishing ground in the Philippines that serves as a livelihood and food source for many coastal communities. This study aimed to determine the composition, abundance, and diversity of phytoplankton, examine the chlorophyll-a (chl-a) and dissolved oxygen (DO) concentration and distribution, and correlate the results of phytoplankton abundance to the examined water parameters in the Leyte Gulf. Samples were collected at 20 established oceanographic stations from April 24 to May 8, 2020, using 10 liters (L) of Niskin bottles at a depth of 10 meters (m), 25 m, 50 m, and 75 m. Phytoplankton were categorized into three classes, namely diatoms, dinoflagellates, and blue-green algae. Results of this study showed that diatoms were the most dominant class comprising about 89% abundance. Of all the identified phytoplankton taxa, Leptocylindrus spp., Rhizosolenia spp., and Coscinodiscus spp. were the most abundant. Leptocylindrus spp. was found to have a higher density in all sampling stations. Based on the diversity index and density-depth analysis, the phytoplankton abundance has a similar distribution in Leyte Gulf. A high concentration of phytoplankton abundance in the Leyte group was observed, wherein a high concentration of chl-a and DO occurred. Additionally, the status of water parameters throughout the study area was tolerable. Results further revealed that the relationship between the chl-a and DO was strongly positively correlated to phytoplankton. Therefore, continued monitoring of phytoplankton and other important water parameters within the gulf must be done.