The combined effects of anthropogenic pressures and climate change pose significant threats to key habitat-forming species, such as seagrasses. Understanding species' responses to environmental stressors and identifying their tolerance thresholds are essential for effective conservation and restoration efforts in coastal environments. Through a mesocosm experiment, we assessed Posidonia oceanica's metabolic responses under ecologically realistic conditions across three seasonal periods (February-March, June-July, and October-November) when plants were naturally acclimated to different temperature regimes. Within each period, we tested plant responses to small temperature variations (ambient and two increasing steps of 2°C) crossed with four turbidity levels (0-34 mg/L), enabling construction of ecologically realistic thermal performance curves. Our findings reveal that turbidity may impair P. oceanica functioning, including decreased thermal performance and narrowed thermal tolerance window, impairing photosynthesis and potentially limiting growth. Metabolism increased with temperature up to a thermal optimum (Topt) identified at 23 °C for all turbidity and exposure time treatment levels. We demonstrate the relevance of stressor properties on P. oceanica responses, with individuals exposed to the more extreme treatment (high turbidity (34 mg/L) and increased exposure time (7 days)) presenting a reduced optimal thermal tolerance with respect to control. We advocate integrating metabolic traits into monitoring protocols as early warning indicators of ecosystem stress. This approach can strengthen both conservation and restoration initiatives by informing policy decisions, particularly in the context of increasing coastal development and climate change.

# Metabolic traits and thresholds to inform marine ecological conservation and restoration [https://doi.org/10.5061/dryad.qfttdz0sv](https://doi.org/10.5061/dryad.qfttdz0sv) ## Description of the data and file structure The experiments aimed to assess the physiological responses of *Posidonia oceanica* under ecologically realistic conditions by exposing the plants to different temperature regimes and sediment-induced turbidity. A total of 324 healthy shoots were collected (108 per seasonal period, with 9 shoots per treatment combination). After acclimation in the laboratory, the plants were tested under controlled conditions to evaluate oxygen metabolism and photosynthetic performance. ### Files and variables #### File: Data\_JAPPL-2024-00618.R3.xlsx **Description:** The Excel file contains the data used to perform the analyses presented in the research article. ##### Variables * time = Treatment exprosure time, t1 = 2 days,t2 = 7 days * temp = Temperature (°C) * turb = Turbidity levels, 0 mg/L,4 mg/L, 16 mg/L, 34 mg/L * Rd = Dark Respiration (O2 mg gr-1 DW) * Pn = Net Photosynthesis (O2 mg gr-1 DW) * NPP = Net PrimaryProduction (O2 mg gr-1 DW) * ETR max =Maximum Electron Transport Rate (e -sec-1) * Fv.Fm = Maximum Quantum Yield (AFU) ## Code/software All analyses were performed using R software (v.4.4.2).