Thermal tolerance of Mediterranean marine macrophytes: Vulnerability to global warming

Abstract

The Mediterranean Sea is warming at three times the rate of the global ocean raising concerns about the vulnerability of marine organisms to climate change. Macrophytes play a key role in coastal ecosystems, therefore predicting how warming will affect these key species is critical to understand the effects of climate change on Mediterranean coastal ecosystems. We measured the physiological performance of six dominant native Mediterranean macrophytes under ten temperature treatments ranging from 12 to 34°C to examine their thermal niche, and vulnerability to projected warming in the western Mediterranean up until 2100. Among the macrophytes tested, Cymodocea nodosa was the species with the highest thermal optima and it was beyond current summer temperature. Therefore, C. nodosa may benefit from projected warming over the coming century. The optimal temperature for growth of the other species (Posidonia oceanica, Cystoseira compressa, Padina pavonica, Caulerpa prolifera, and Halimeda tuna) was lower. Similarly, the species presented different upper lethal limits, spanning at least across 5.1°C between 28.9°C (P. oceanica) and >34°C (C. nodosa). Our results demonstrate the variable physiological responses of species within the same local community to temperature changes and highlight important potential differences in climate change vulnerability, among species within coastal marine ecosystems.

Response diversity in Mediterranean coralligenous assemblages facing climate change: Insights from a multispecific thermotolerance experiment

“…Forecasting temperature effects on ecological communities require a deep understanding of how temperature may influence the physiology of their different members. Thus, as oceans keep warming, community‐wide thermal sensitivity studies are becoming a powerful tool for reducing the uncertainty about the future composition, structure and functionality of marine communities facing climate change (Beveridge, Petchey, & Humphries, ; Fey & Cottingham, ; Iles, ; Savva et al, ; Stuart‐Smith, Edgar, Barrett, Kininmonth, & Bates, ). In this study, we explored the ranges of thermal sensitivity among structurally, functionally and taxonomically different components of Mediterranean coralligenous assemblages, showing contrasting responses to warming and suggesting the presence of potential “winners” and “losers” in the face of climate change.…”

“…Eventually, although statistical analyses could not be performed regarding the growth form given the low number of species in each group, the different upper thermal limits shown by the species with an equivalent morphology suggests that contrasting responses to warming also occur between species with similar structural roles (Figures 2 and 3). (Beveridge, Petchey, & Humphries, 2010;Fey & Cottingham, 2012;Iles, 2014;Savva et al, 2018;Stuart-Smith, Edgar, Barrett, Kininmonth, & Bates, 2015). In this study, we explored the ranges of thermal sensitivity among structurally, functionally and taxonomically different components of Mediterranean coralligenous assemblages, showing contrasting responses to warming and suggesting the presence of potential "winners" and "losers" in the face of climate change.…”

“…Exploring species-specific thermal sensitivities among different components of benthic communities is, therefore, a key step toward forecasting the future composition and functionality of these communities in the face of climate change. However, while important efforts in this direction have been taken in shallow tropical reefs, thermotolerance analyses in temperate benthic communities largely lag behind (Kersting et al, 2015;Linares, Cebrian, Kipson, & Garrabou, 2013;Savva, Bennett, Roca, Jordà, & Marbà, 2018;Torrents, Tambuté, Caminiti, & Garrabou, 2008).…”

Adaptive evolution shapes the present-day distribution of the thermal sensitivity of population growth rate

“…Within the original MTE framework [6][7][8], the shape of the TPC 16 is expected to reflect the effects of temperature on the kinetics of a single rate-limiting 17 enzyme involved in key metabolic reactions. Thus, according to the MTE, the 18 exponential rise in trait values up to T pk can be mechanistically described using the 19 Boltzmann-Arrhenius equation:…”

“…Indeed, there is now overwhelming empirical evidence for variation in E (thermal 47 sensitivity) far exceeding the narrow 0.6-0.7 eV range [14][15][16][17][18][19]. Furthermore, the 48 distribution of E values across species is not Gaussian but typically right-skewed.…”