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The estuarine anemone Anthopleura hermaphroditica and its symbiont Philozoon anthopleurum are continuously exposed to intense fluctuations in solar radiation and salinity owing to tidal changes. The aim of this study was to evaluate the effects of the tidal cycle, solar radiation, and salinity fluctuations on the photosynthetic and cellular responses (lipid peroxidation, total phenolic compounds, and antioxidant activity) of the symbiont complex over a 24 h period in the Quempillén River Estuary. Additionally, laboratory experiments were conducted to determine the specific photobiological responses to photosynthetically active radiation (PAR), ultraviolet radiation (UVR), and salinity. Our field results showed that the photosynthetic parameters of the symbiont complex decreased with increasing ambient radiation; however, no relationship was observed with changes in salinity. Increased peroxidative damage, total phenolic compound levels, and antioxidant activity were mainly related to increased UVR and, to a lesser extent, PAR. During the dark period, only PAR-exposed organisms returned to the basal levels of photosynthesis and cell damage. Laboratory exposure confirmed the deleterious effects of UVR on the photosynthetic response. The present study suggests that the ability of A. hermaphroditica to acclimate to natural radiation stress is mediated by the concerted action of various physiological mechanisms that occur at different times of the day, under varying levels of environmental stress.

Azamethiphos is used in the salmon industry to treat sea lice and is subsequently discharged into the sea, which may affect non-target species (NTS). A rise in seawater temperature could enhance the sensitivity of NTS. Thus, in the present investigation, the combined effects of azamethiphos (0 µg L−1, 15 µg L−1 and 100 µg L−1) and temperature (12 °C and 15 °C) was assessed over time (7 days) in the gonads and gills of the oyster Ostrea chilensis, assessing its oxidative damage (lipid peroxidation and protein carbonyls) and total antioxidant capacity. Our results indicated that in gonads and gills, lipid peroxidation levels increased over time during exposure to both pesticide concentrations. Protein carbonyl levels in gills increased significantly in all experimental treatments; however, in gonads, only pesticide concentration and exposure time effected a significant increase in protein damage. In both, gill and gonad temperature did not influence oxidative damage levels. Total antioxidant capacity in gonads was influenced only by temperature treatment, whereas in the gills, neither temperature nor azamethiphos concentration influenced defensive responses. In conclusion, our results indicated the time of pesticide exposure (both concentrations) had a greater influence than temperature on the cellular damage in this oyster.