Marine Heat Waves Hazard 3D Maps and the Risk for Low Motility Organisms in a Warming Mediterranean Sea

Abstract

Frequency and severity of heat waves is expected to increase as a consequence of climate change with important impacts on human and ecosystems health. However, while many studies explored the projected occurrence of hot extremes on terrestrial systems, few studies dealt with marine systems, so that both the expected change in marine heat waves occurrence and the effects on marine organisms and ecosystems remain less understood and surprisingly poorly quantified. Here we: (i) assess how much more frequent, severe, and depth-penetrating marine heat waves will be in the Mediterranean area in the next decades by post-processing the output of an ocean general circulation model; and (ii) show that heat waves increase will impact on many species that live in shallow waters and have reduced motility, and related economic activities. This information is made available also as a dataset of temperature threshold exceedance indexes that can be used in combination with biological information to produce risk assessment maps for target species or biomes across the whole Mediterranean Sea. As case studies we compared projected heat waves occurrence with thermotolerance thresholds of low motility organisms. Results suggest a deepening of the survival horizon for red coral (Corallium rubrum, a commercially exploited benthic species already subjected to heat-related mass mortality events) and coralligenous reefs as well as a reduction of suitable farming sites for the mussel Mythilus galloprovincialis. In recent years Mediterranean circalittoral ecosystems (coralligenous) have been severely and repeatedly impacted by marine heat waves. Our results support that equally deleterious events are expected in the near future also for other ecologically important habitats (e.g., seagrass meadows) and aquaculture activities (bivalvae), and point at the need for mitigation strategies.

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

“…In between these extremes, different levels of tolerance were found, including highly resistant species, for which 28°C represented the upper thermal limit that significantly reduced their probability of not suffering mortality, and intermediately tolerant species, which despite being affected at 26°C, did not suffer generalized necrosis until 1 week of exposure to 27°C. Bearing in mind that summer heat waves capable of sustaining temperatures between 26°C and 29°C for several days might become increasingly frequent during the next decades in diverse NW Mediterranean locations (Galli et al, 2017), our results suggest potential differences in climate change vulnerability among co-occurring species dwelling in coralligenous assemblages. Indeed, differences between the members of the community were observed in our experiments to the extent that even the two morphotypes of Parazoanthus axinellae presented contrasting thermal responses.…”

The park never born: Outcome of a quarter of a century of inaction on the sea‐floor integrity of a proposed but not established Marine Protected Area

“…The biological effects of seawater warming and frequent summer heat waves in the last two decades in the Ligurian Sea have been well documented (Bianchi, Caroli, Guidetti, & Morri, ; Galli, Solidoro, & Lovato, ; Parravicini et al, ). In the same period, however, human pressures (mostly through urbanization and tourism) on Mediterranean coastal marine ecosystems grew tremendously, so that it is difficult to identify the main driver of the change observed in epibenthic communities (Bianchi et al, ; Gatti et al, , ).…”

Cumulative Impact Index for the Adriatic Sea: Accounting for interactions among climate and anthropogenic pressures

“…As example, sea temperature parameter shows largescale variations with a clear seasonal cycle with values fluctuating from 22 to 30°C during summer and from 12 to 14°C during winter (Zore-Armanda, 1983). In particular, the frequency and severity of temperature extreme events are expected to increase in the next decades within the Mediterranean area, leading to significant impacts on marine benthic communities (Galli et al, 2017). Similar ranges of variabilities are observed as well for most biogeochemical parameters (Solidoro et al, 2009).…”

“…However, even though the SST increase contributes in a minor extent to drive the overall acute chemical hazard, the environmental impacts associated to this phenomenon cannot be underestimated. As observed by Galli et al (2017), frequency and severity of marine anomalously warm events is expected to increase in the next decades as a consequence of climate change, with important impacts on marine organisms and ecosystems health. Climate-induced changes has the potential to highly impact the state and dynamics of biological organisms exposing them to environmental conditions that are different from those they are used and adapted to, and potentially outside their tolerance boundaries.…”