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 15 proposal of low-dose quicklime (CaO; 1–3% w/w) as a remediation strategy to improve 16 microbiological quality in highly contaminated areas. After application, CaO is converted 17 into calcium carbonate (CaCO₃), yet the ecological effects of this residual compound on 18 benthic fauna remain poorly understood. This study evaluated the short-term impact of 19 CaCO₃-enriched sediment (3% w/w) on the Manila clam Ruditapes philippinarum under 20 controlled mesocosm conditions. Adult clams were exposed for one week, and survival, 21 burrowing behavior, feeding- and metabolism-related parameters (clearance, ingestion, 22 absorption efficiency and rate, ammonia excretion), and oxidative stress (malondialde-23 hyde, MDA) were assessed using a hierarchical design with tank as the experimental unit. 24 No significant differences were detected between control and CaCO₃-enriched treatments 25 for any measured endpoint. Survival remained high, functional responses showed over-26 lapping ranges, and MDA levels did not differ significantly between groups. Although 27 limited to short-term exposure and a single concentration, these findings suggest that re-28 sidual CaCO₃ derived from quicklime application did not induce detectable adverse ef-29 fects in adult R. philippinarum under the tested conditions. Further long-term and multi-30 species studies are needed to confirm ecological safety.