No abstract

In the Mediterranean Sea, where biological invasions constitute a serious threat, the combination of citizen science and social networks amplified the power of proper field studies, recording species that would have otherwise presumably passed unnoticed. Based on data collected on several Facebook groups, we hereby first report the presence of five fish taxa (Kyphosus sp., Heniochus intermedius, Pomacanthus imperator, Pomacanthus maculosus and Abudefduf sp.) new for the Mediterranean Egypt, revise their distribution in the Mediterranean Sea and discuss their possible introduction pathways. Finally, we provide some considerations on the potentiality of social media for citizen science projects.

In a warming ocean, temperature variability imposes intensified peak stress, but offers periods of stress release. While field observations on organismic responses to heatwaves are emerging, experimental evidence is rare and almost lacking for shorter-scale environmental variability. for two major invertebrate predators, we simulated sinusoidal temperature variability (±3 °C) around todays' warm summer temperatures and around a future warming scenario (+4 °C) over two months, based on highresolution 15-year temperature data that allowed implementation of realistic seasonal temperature shifts peaking midpoint. Warming decreased sea stars' (Asterias rubens) energy uptake (Mytilus edulis consumption) and overall growth. Variability around the warming scenario imposed additional stress onto Asterias leading to an earlier collapse in feeding under sinusoidal fluctuations. Highpeak temperatures prevented feeding, which was not compensated during phases of stress release (low-temperature peaks). In contrast, increased temperatures increased feeding on Mytilus but not growth rates of the recent invader Hemigrapsus takanoi, irrespective of the scale at which temperature variability was imposed. This study highlights species-specific impacts of warming and identifies temperature variability at the scale of days to weeks/months as important driver of thermal responses. When species' thermal limits are exceeded, temperature variability represents an additional source of stress as seen from future warming scenarios.Global climate change is known to have profound impacts on marine ecosystems that range from distributional shifts and changes in species interactions to shifts in ecosystem function and diversity 1-4 . However, current knowledge on the impacts of climate change is based on experiments testing the effects of mean changes of stressors, rather than considering variability around means, or the role of climate extremes 5 .Environmental variability occurs at a variety of temporal (and spatial scales), from tidal to diurnal, over stochastic weekly to monthly patterns, and seasonal cycles, to large-scale inter-anneal variability. Irrespective of scale, this variability can impact organisms differently than changes in mean temperature (i.e. trends) 5,6 . High peaks of stressful temperatures might be lethal 7,8 , while excursions to below-stressful conditions can allow for stress relaxation 9 . Thus, in a warming ocean with already stressful mean temperature conditions 10 , environmental variability towards lower temperatures might create vital refuge from stress 9,11 . More theoretically, Jensen's inequality hypothesis postulates for non-linear functions (bell-shaped thermal performance curves, with an intermediate optimum), any variation around the mean should rise or lower the performance of an organism, when compared to constant environmental conditions 12 .Coastal waters are amongst the most valuable and productive ecosystems worldwide, providing a wide range of ecosystem services 1,13 . In the context of global climat...

No abstract