Temporal changes in environmental conditions of a mid-latitude estuary (southern Chile) and its influences in the cellular response of the euryhaline anemone Anthopleura hermaphroditica

The cellular response of the estuarine anemone Anthopleura hermaphroditica was assessed during a tidal cycle (low tide at noon) and compared between organisms acclimated to summer and winter environmental conditions (UV-B and PAR levels, salinity and temperature), with the aim of understanding the strategies used by this dominant invertebrate in an estuary of southern Chile. Anemones were gathered every two hours from 8:00 to 20:00 h from the low intertidal area of the Quempillén estuary and immediately snap frozen to carry out biochemical analyses (oxidative damage, antioxidant capacity, photo-protective compounds). Additionally, levels of environmental radiation (UV-B and PAR), salinity and water temperature were recorded during the field survey. Our results indicate that during summer, lipid peroxidation and protein carbonyl levels in A. hermaphroditica were 3.72 and 16.51 folds higher than during winter, respectively. Maximum lipid peroxidation levels in A. hermaphroditica during summer occurred after UV-B radiation peaked (14:00 h) when water temperatures reached 31 °C. Carbonyl protein levels increased progressively reaching maximum levels at the end of the day. On the contrary, during winter when radiation levels are low and water temperature remained almost constant in the estuary throughout the day, significant variation in salinity levels occurred due to oxidative damage levels that increased significantly at the end of the day. Surprisingly, the mean antioxidant capacity level in A. hermaphroditica during winter was 1.7 folds higher than in summer, a situation that was positively correlated to total phenolic compounds content. Mycosporine 2-glycine (λmax: 331 nm) was the only mycosporine like amino acid (MAA) found in A. hermaphroditica, a photo-protective compound with constant levels throughout the year. Anthopleura hermaphroditica, is an estuarine anemone that are adapted to tolerate rapid fluctuations in the environmental parameters during tidal changes. Those fluctuations are highly affected by seasonal components that expose this invertebrate to different intensity and duration of stress factors between summer and winter. Thus, an efficient antioxidant strategy added to the use of secondary metabolites (phenolic compounds and MAA) may efficiently intercept and neutralize ROS in this animal that lacks of physical protection, allowing it to succeed in a very unstable environment characterized by strong fluctuations of salinity, temperature and environmental radiation through the year.