Unraveling Coastal Pollution: The Hidden Threats to Pekalongan's Estuarine Ecosystem

The various anthropogenic activities around the river in Pekalongan can influence the dynamics of the estuary. The estuary is important in fisheries, particularly small pelagic fish, related to plankton abundance and aquatic fertility. The recent tendency of the coastal development area raises the establishment of small-scale industries, textile industries, and ecotourism, which carry a significant amount of disposal waste as well as organic matter. The tidal flooding influenced the dynamic of organic matter in Pekalongan, which increased yearly due to climate change. This study aims to determine the content and distribution of nitrate, phosphate, total suspended solids (TSS), and chlorophyll-a (CHA) collected from 2021 to 2024 at four rivers in Pekalongan Regency based on a geospatial approach. The study results showed that the CHA contents from 2021 to 2024 varied from 0.196 to 2.473 µg/L, 0.022 to 0.379 µg/L, 0.002 to 2.414 µg/L, and 0.21 to 3.083 µg/L; TSS contents from 2021 to 2024 varied from 4 to 26 mg/L, 64.7 to 149 mg/L, 16.3 to 214 mg/L, and 19 to 299 mg/L; nitrate contents from 2023 to 2024 varied from 0.004 to 1.31 mg/L and 0.004 to 0.959 mg/L; and phosphate contents from 2023 to 2024 ranged from 0.003 to 0.767 mg/L and 0.001 to 1.017 mg/L. The concentration of CHA and TSS varied each year. However, the existing pattern shows an increase in TSS concentration and a decrease in CHA values, which indicates a reduction in water quality. The nitrate concentration tends to decrease, and the phosphate concentration has increased recently. The dynamic distribution of organic matter occurs due to the influence of tidal currents, longshore currents, and the east monsoon wind. The data collection showed the tendency for environmental quality degradation due to the limited carrying capacity and shortage of remediation.