• Energy Research

Research to date has suggested that both individual marine species and ecological processes are expected to exhibit diverse responses to the environmental effects of climate change. Evolutionary responses can occur on rapid (ecological) timescales, and yet studies typically do not consider the role that adaptive evolution will play in modulating biological responses to climate change. Investigations into such responses have typically been focused at particular biological levels (e.g., cellular, population, community), often lacking interactions among levels. Since all levels of biological organisation are sensitive to global climate change, there is a need to elucidate how different processes and hierarchical interactions will influence species fitness. Therefore, predicting the responses of communities and populations to global change will require multidisciplinary efforts across multiple levels of hierarchy, from the genetic and cellular to communities and ecosystems. Eventually, this may allow us to establish the role that acclimatisation and adaptation will play in determining marine community structures in future scenarios.

The resilience of ecological communities is often defined by one or a few species that have disproportionately important roles influencing many other species in the community. This is true for some areas of the Mediterranean Sea that are characterized by large brown fucoid algae in the genus Cystoseira that form dense underwater forests structurally similar to the giant kelps of the Pacific. While shorter than the giant kelp, Cystoseira form dense underwater stands, contributing to the three‐dimensional complexity of the seascape (Fig. 1). These canopy‐forming seaweeds play a crucial role in primary production and nutrient cycling of temperate coastal ecosystems from the Mediterranean Sea to the Atlantic Ocean (Mineur et al., 2015) and act as ‘ecosystem engineers', providing food, nursery, and shelter for a rich associated biota. Our study highlighted potential disruptive effects of winter hot spells on reproductive timing, recruitment, and adult survival that could severely affect the persistence of Cystoseira populations. Because extreme climate episodes are increasing in intensity and frequency, implementing coordinated initiatives connecting centers for climate alerts and algologists may shed light on how these phenomena impact population dynamics of Cystoseira species, and help current attempts to restore algal forests.

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).