Effects of Barge and Tugboat Activities on Seawater Quality in the Geothermal Coastal Waters of Moinit Beach, South Minahasa

Abstract

This study aimed to analyze changes in seawater quality before and after vessel activity, evaluate their compliance with Indonesian marine water quality standards, and formulate implications for coastal environmental management. A descriptive-comparative quantitative approach with a before-after sampling design was applied at three stations: ST 1 as the vessel maneuvering zone, ST 2 as the geothermal and tourism-sensitive zone, and ST 3 as the control zone. In situ measurements included temperature and pH, with three replicates at each station. Ex situ analyses of turbidity, Total Suspended Solids (TSS), oil and grease, pH, Dissolved Oxygen (DO), and salinity were conducted at SGS-WLN Manado Laboratory, accredited by the National Accreditation Committee (KAN LP-433-IDN), under Analytical Report No. 1089379-1. Data were analyzed descriptively and using the Wilcoxon Signed-Rank Test for paired parameters that were eligible for statistical testing. The results showed that the seawater quality of Moinit Beach was generally in good condition, as indicated by low turbidity, TSS <10 mg/L, DO ranging from 7.71 to 7.92 mg/L, and pH ranging from 7.97 to 8.22. Temperature increased significantly after vessel activity (p = 0.011). The most critical finding was the oil and grease concentration at ST 1 after vessel activity, which reached 5 mg/L, or five times higher than the threshold of 1 mg/L, while ST 2 recorded 1 mg/L and ST 3 remained <1 mg/L. This pattern indicates that the impact of vessel activity was local and selective, particularly in the maneuvering zone. This study is important for environmental stakeholders because it provides initial laboratory-based evidence from an accredited laboratory to support oil pollution control, vessel operation zoning, and event-based monitoring in the geothermal coastal waters of Moinit Beach.

Keywords: barge; tugboat; oil and grease; seawater quality; geothermal coast; Moinit Beach

Absrak. Penelitian ini bertujuan menganalisis perubahan kualitas air laut sebelum dan sesudah aktivitas kapal, mengevaluasi kesesuaiannya terhadap baku mutu air laut Indonesia, serta merumuskan implikasi pengelolaan lingkungan pesisir. Penelitian menggunakan pendekatan kuantitatif deskriptif-komparatif dengan desain before-after sampling pada tiga stasiun: ST 1 sebagai zona manuver kapal, ST 2 sebagai zona sensitif geotermal dan wisata, serta ST 3 sebagai zona kontrol. Pengukuran in situ mencakup suhu dan pH dengan tiga ulangan per stasiun. Analisis ex situ terhadap kekeruhan, Total Suspended Solids (TSS), minyak dan lemak, pH, Dissolved Oxygen (DO), dan salinitas dilakukan di Laboratorium SGS-WLN Manado yang terakreditasi KAN LP-433-IDN berdasarkan Analytical Report No. 1089379-1. Data dianalisis secara deskriptif dan dengan Wilcoxon Signed-Rank Test untuk parameter berpasangan yang layak diuji. Hasil menunjukkan bahwa kualitas air Pantai Moinit secara umum masih berada dalam kondisi baik, ditunjukkan oleh kekeruhan rendah, TSS <10 mg/L, DO 7,71-7,92 mg/L, dan pH 7,97-8,22. Suhu meningkat secara signifikan sesudah aktivitas kapal (p = 0,011). Temuan paling kritis adalah minyak dan lemak di ST 1 sesudah aktivitas kapal sebesar 5 mg/L, atau lima kali lebih tinggi dari ambang 1 mg/L, sementara ST 2 tercatat 1 mg/L dan ST 3 tetap <1 mg/L. Pola ini menunjukkan bahwa dampak kapal bersifat lokal dan selektif, terutama pada zona manuver. Studi ini penting bagi pemerhati lingkungan karena menyediakan bukti awal berbasis laboratorium terakreditasi untuk pengendalian pencemaran minyak, pengaturan zona operasi kapal, dan pemantauan berbasis kejadian di pesisir geotermal Pantai Moinit.

Kata kunci: kapal tongkang; kapal tunda; minyak dan lemak; kualitas air laut; pesisir geotermal; Pantai Moinit