Composition and Abundance of Plankton Communities in Mangrove Estuary of Tubajon, Philippines

Tubajon has a semi-enclosed estuary characterized by shallow depth and slow water exchange being disrupted by a mangrove barrier. In an attempt to assess the environmental condition of the mangrove estuary of Tubajon, this study aimed to determine the composition and abundance of plankton as a bioindicator in the aquatic environment along with the physicochemical parameters. We determined the water depth using a sinker and the Surfer software processed the data to generate the bathymetric profile of the area. The use of sensor data logger determined the temperature, salinity, pH, and dissolved oxygen of water. Spectrophotometric method determined the chlorophyll-a content of water and the cadmium copper method measured the nitrate concentration. We identified the plankton species up to the generic level using the taxonomic keys. Results showed a total of 18 taxa of phytoplankton belonging to two taxonomic groups (dinoflagellates and diatoms) that were tolerant to the existing conditions and able to adapt the lower light conditions and nutrient-impoverished water. Dinoflagellates were the most numbered phytoplankton. There were nine taxa of zooplankton enumerated with copepods being the dominant species. Chlorophyll-a (<0.05µg/L) content, dissolved oxygen (<4mg/L) and nitrate concentration (<0.1mg/L) were relatively small indicating less productivity and oligotrophic condition.  The composition and abundance of plankton in the area along with the physicochemical condition might be due to less water exchange, high water retention, and the structure of the ecosystem. This study provides relevant information for any conservation effort in the area.

 

Keywords: bathymetric, bioindicator, oligotrophic, phytoplankton, productivity, zooplankton