Assessment of Water Quality, Primary Productivity, and Alpha Biodiversity in the Coastal Waters of Barangay Tambobong, Dasol, Pangasinan

Marine ecosystems are biodiversity-rich and crucial for ecological balance, yet many coastal areas lack baseline data to identify stressors and inform management. This study offers an initial dry season assessment of water quality, primary productivity, and alpha biodiversity in Barangay Tambobong, Dasol, Pangasinan, using transect-quadrat sampling at three stations. Water temperature, total dissolved solids (TDS), dissolved oxygen (DO), and pH were measured on-site using handheld multi-parameter equipment. For plankton analysis, 10L of seawater was collected from 0.5m depth in each quadrat and filtered through a 60 to 64µm plankton net. After three days, the 50mL sample was reduced to 10mL by decantation. A 1mL subsample was examined in a Sedgewick-Rafter chamber under a compound microscope for plankton identification and counting. Temperature ranged from 26.66 ± 0.41 to 28.04 ± 0.18°C, with peak DO at Station 3 (8.31 ± 0.56mg/ L). pH was stable (8.20 ± 0.00), while Station 1 recorded the highest TDS (905.80 ± 66.72mg/ L) and salinity (37.60 ± 3.36ppt). Light and dark bottle analysis showed low net (0.26 ± 0.11 mg/L/hr) and gross (0.43 ± 0.74 mg/L/hr) primary productivity, with higher respiration (0.97 ± 0.09 mg/L/hr), indicating ecosystem stress. A total of five plankton phyla were identified, with species from Heterokontohyta (9), Arthropoda (5), Rotifera (3), Chlorophyta (1), and Ciliophora (1). Diatoms and copepods dominated, with Entomoneis spp. (5,850.00 ind/mL) being the most abundant phytoplankton, followed by Nitzschia sigma (2,406.67 ind/mL) and Dactyliosolen fragilissimus (2,091.67 ind/mL). Diversity indices revealed a low and uneven phytoplankton community, with a Shannon Index of 1.40±0.65, Simpson Index of 0.60±0.31), and Margalef Richness of 0.21±0.07). Zooplankton analysis identified Paramecium caudatum (666.67 ind/mL) and Paracalanus parvus (666.67 ind/mL) as dominant, with a similar trend of low diversity and richness. Palmer's Pollution Index yielded a score of 6, indicating little or no organic pollution. In general, the study indicates moderate productivity with signs of stress possibly from anthropogenic activities, but diverse plankton suggest recovery potential. To support the long-term health of the coastal ecosystem in Barangay Tambobong, a sustained plankton monitoring program is recommended in partnership with academic institutions, government and private agencies, and other stakeholders. The program should involve seasonal sampling, species identification, and the integration of ecological data with records of human activities. It should also promote active community participation and include a comparative study during the wet season.