Increase in Weather Patterns Generating Extreme Desiccation Events: Implications for Mediterranean Rocky Shore Ecosystems

Anthropogenic global climate change is anticipated to increase the frequency and intensity of transient extreme weather events that can be catastrophic to ecological communities. Here, we characterize an extremely stressful, transient phenomenon on southeastern Mediterranean (Israel) rocky shores: prolonged desiccation events (PDE). We also examined (during 2012–2014) its potential ecological impacts on the unique intertidal Mediterranean Sea ecosystem—vermetid reefs. In this region, where the tide is minimal but the rocky intertidal is extensive, high pressure and dry easterly winds generated by specific synoptic systems can suppress tidal flooding and create stressful desiccation conditions in the lower intertidal zones for many consecutive days (several days to weeks). Very long and strong PDEs resulted in extensive macroalgal bleaching and their eventual removal from the rocks and caused mortality of stranded topshell snails and partial collapse of the mid-shore limpet population. Dominant intertidal fleshy algae were shown to be more sensitive than calcareous algae to desiccation stress, but both die after 24 h of exposure in lab conditions. Re-analysis of climatic data for the period 1960–2010 showed a considerable increase in the frequency of PDE-generating synoptic systems, mainly during winter. This means that desiccation stress has already increased on southeastern Mediterranean vermetid reef ecological communities, and if this trend continues, we can expect further increases in aerial exposure and desiccation stress that could have long-term impacts on this fragile ecosystem. These results demonstrate the importance of change in patterns of synoptic systems and wind regimes to the integrity of coastal ecological communities.