Stress Marker Response in the Manila Clam, Ruditapes philippinarum, After Exposure to Sediment Liming

Beach sands may harbor human pathogens and antibiotic resistance genes, prompting the proposal of low-dose quicklime (CaO; 1–3% w/w) as a remediation strategy to improve microbiological quality in highly contaminated areas. After application, CaO is converted into calcium carbonate (CaCO3), yet the ecological effects of this residual compound on benthic fauna remain poorly understood. This study evaluated the short-term impact of CaCO3-enriched sediment (3% w/w) on the Manila clam, Ruditapes philippinarum, under controlled mesocosm conditions. Adult clams were exposed for one week, and survival, burrowing behavior, feeding- and metabolism-related parameters (clearance, ingestion, absorption efficiency and rate, ammonia excretion), and oxidative stress (malondialdehyde, MDA) were assessed using a hierarchical design, with a tank as the experimental unit. No significant differences were detected between control and CaCO3-enriched treatments for any measured endpoint. Survival remained high, functional responses showed overlapping ranges, and MDA levels did not differ significantly between groups. Although limited to short-term exposure and a single concentration, these findings suggest that residual CaCO3 derived from quicklime application did not induce detectable adverse effects in adult R. philippinarum under the tested conditions. Further long-term and multi-species studies are needed to confirm ecological safety.