An Integrated Physiological Assessment of the Symbiotic Sea Anemone Anemonia viridis Using Metabolic, Antioxidant and Symbiosis-Related Biomarkers

Anemonia viridis is an ecologically and commercially important sea anemone whose natural populations have declined due to overexploitation, climate change, and the expansion of the invasive alga Rugulopteryx okamurae. Therefore, the recovery of natural populations is necessary through the development and optimization of zootechnical techniques for rearing and maintaining sea anemones in captivity. This requires the identification of reliable indicators of physiological status, which remains poorly understood. This study evaluated the suitability of metabolic, antioxidant, and symbiosis-related parameters to assess the physiological status of A. viridis under two distinct experimental stress scenarios: acute aerial exposure (6 h) and prolonged starvation and darkness (10 days). Acute aerial exposure induced rapid metabolic adjustments, characterized by increased glucose and lactate concentrations, reduced superoxide dismutase activity, and unchanged glutathione peroxidase activity, with no significant changes in the measured symbiosis-related parameters. In contrast, prolonged starvation and darkness altered glucose and cholesterol levels and antioxidant responses, and was accompanied by numerical decreases in Symbiodiniaceae density and total chlorophyll a content normalized to host protein, although without reaching statistical significance. Thus, while the metabolic and antioxidant biomarkers revealed distinct physiological responses to the two experimental stress scenarios, evidence for changes in the cnidarian–Symbiodiniaceae symbiosis remained limited. Overall, the combined assessment of metabolic, antioxidant, and symbiosis-related biomarkers provided a more comprehensive evaluation of holobiont physiological status than individual biomarkers alone. This integrative biomarker panel represents a practical tool for optimizing rearing conditions and supporting the recovery of A. viridis.