Ballast Water Management Implementation for Marine Biodiversity Conservation on the Tanker Thetis Leona

Ballast water management (BWM) supports vessel stability while preventing the transfer of harmful aquatic organisms and pathogens. This study analyzes BWM implementation on the oil/chemical tanker Thetis Leona and its relevance to marine biodiversity conservation. A descriptive qualitative case-study design was used with company and vessel documents, field documentation, and limited observation. Data were analyzed through data condensation, data display, and conclusion drawing/verification, supported by SWOT/TOWS analysis. The findings show that the vessel has a formal and managerial BWM foundation through its safety, health, environment, and quality system, pollution-prevention policies, organizational responsibilities, technical support, and deck-engine role allocation. However, the available evidence demonstrates administrative readiness more strongly than biological performance because direct ballast-water samples, a complete Ballast Water Record Book, full BWTS alarm history, and complete Planned Maintenance System records were unavailable. Comparative evidence from 228 ships showed that 49% of samples for organisms at least 50 micrometers exceeded the D-2 limit. The study concludes that installed systems and documentation do not automatically ensure biological compliance. Stronger implementation requires competency-based training, cross-verification of records, risk-based audits, integrated maintenance, periodic testing, and traceable ship-shore monitoring.