Monitoring Portuguese Shellfish Continental Production Areas: Insights for Coastal Water Quality and Regeneration

The Portuguese Water Quality Policy, aligned with the Water Framework Directive, requires the monitoring of shellfish production in coastal and brackish water bodies and is based on the EC Shellfish Waters Directive; it preserves the environmental conditions necessary for shellfish growth and contributes to the production of a safe, high-quality sustainable animal food source. Between 2017 and 2021, quarterly measurements of physico-chemical and microbial parameters were conducted at 11 coastal stations and 21 estuarine/coastal lagoons stations along Portugal, to evaluate shellfish water quality and identify the environmental drivers influencing it. Results showed that estuaries and coastal lagoons were more vulnerable to fluctuations in salinity, oxygen and suspended matter and consistently exhibited higher faecal contamination in bivalves than coastal waters. These patterns were shaped by freshwater inputs, climate-driven variability, and local anthropogenic pressures, with contamination often increasing during rainy periods or under stressful environmental conditions. The study highlights the sensitivity of transitional waters to both natural and human-induced changes and underscores the need for targeted management strategies, such as improved wastewater treatment and integrated coastal management, to reduce pollution pressures. Strengthening these measures is essential for the long-term sustainability of Portugal’s shellfish industry and coastal ecosystems.