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Water temperature plays a critical role in mediating energy budgets and influencing the behavior of marine ectotherms. Previous research has demonstrated that marine ectotherms such as sea turtles conserve energy by decreasing activity levels in colder water—often at or near the latitudinal limits of their range. San Diego Bay is near the northern edge of the range for eastern Pacific green turtles and is home to a year-round foraging population. Turtles in San Diego Bay experienced a significant decrease in ambient water temperature following the closure of a fossil-fuel-based power plant and corresponding loss of the plant’s warm-water effluent. Time-depth recorders were placed on 13 turtles before (n = 5) and after (n = 8) the closure of this plant to determine how changing water temperature influenced dive duration. Deployments lasted 2-25 d, with a mean deployment of 7.5 d. Green turtle behavior in different thermal regimes revealed a strong relationship between dive duration and water temperature; dive duration was significantly longer when water temperatures were colder, especially when water was below 14.4°C. Establishing the inactivity threshold for this population is critical to future management in light of temperature variability in coastal habitats and the impacts this may have on sea turtle energetics. Understanding organismal response to relatively rapid shifts in thermal conditions is relevant to assessments of the direct and indirect anthropogenic effects on aquatic environments.

Green sea turtles Chelonia mydas use coastal areas as foraging grounds for the majority of their lives. Human development of coastlines is increasing, but the effects of urban development of foraging grounds on green turtles are poorly understood. We used acoustic telemetry to determine home ranges of green turtles during 2009 to 2011 in San Diego Bay, Cali- fornia, USA, which is a highly urbanized temperate foraging area. Adult and juvenile turtles (n = 25, straight carapace length = 54.9 to 102.5 cm) were tracked for up to 370 d. Based on the fixed kernel densities of 15 turtles, we found individual home range areas (95% utilization distribution) were 2.09 to 8.70 km 2 (mean ± SE = 5.51 ± 0.57 km 2 ), where each turtle used 1 or 2 core activity areas (50% utilization distribution). The home ranges of all turtles were exclusively in the south- ern portion of San Diego Bay, where eelgrass Zostera marina is abundant and where human activ- ity is the lowest within the bay. Core activity areas coincided with eelgrass distribution or occurred adjacent to the warm water-effluent outfall of a power plant. Results from our study suggest that south San Diego Bay serves as important turtle habitat within the bay. Future monitoring is required to document the potential effects of changing environmental conditions, including closure of the power plant, on green turtles residing in San Diego Bay.