Federico Quattrocchi1,2, Marco Milazzo1,2, Antonio Di Franco3,2, Manfredi Di Lorenzo3,2, Giacomo Milisenda3,2, Elena Desiderà3,2, Paolo Guidetti3,2, Antonio Calò3,2
1University of Palermo, Italy - 2National Biodiversity Future Center (NBFC), Italy - 3Stazione Zoologica Anton Dohrn, Italy
Ocean warming (OW) is causing species distributions to shift poleward, thereby increasing the abundance of the warm-water biota in many ecosystems worldwide. In the Mediterranean Sea, for instance, OW is leading native thermophilic species, such as the bearded fireworm Hermodice carunculata (Amphinomida), to become invasive. This species, historically common in the warm Central Mediterranean Sea, is now expanding its range northward in the Tyrrhenian and Adriatic Seas. Recent laboratory studies have shown that adults of this species can tolerate low seawater temperatures, being inactive but not dying below 19°C, whereas during the larval stage, which occurs in late summer/early autumn, the larvae perish when seawater cools down to 22°C. Our study was aimed at understanding the factors responsible for the fast expansion of this species in the Mediterranean region. To this end, underwater visual censuses were conducted in the summers of 2021 and 2023. These spanned 8.5 degrees of latitude in 10 Marine Protected Areas. The species’ thermal habitat was characterised as: 1) the temperature during the survey, 2) the historical mean temperature (last 20 years) during the larval stage (August-October), 3) the mean number of days during the larval stage at <22°C temperature in the last 20 years. We then related the log(x+1) fireworm abundance to these thermal characteristics, using linear and segmented mixed models including MPAs as random intercept, to assess which was the best in shaping its range expansion. The number of days below 22°C in the segmented model was the only significant factor, acting as a bottleneck for the survival of its early life stages when low temperature days exceeded approx. 13% of the total larval period (i.e. 92 days). Ground-truthing previous laboratory tests, our results underline the urgency of developing seawater temperature monitoring systems to anticipate the spread of H. carunculata and its impacts on Mediterranean benthic communities.
Biography
Federico Quattrocchi is a researcher at the University of Palermo, focusing on both marine populations and communities. His work investigates how marine populations fluctuate in response to environmental changes and the role of connectivity in explaining population dynamics. Additionally, he studies how climate change affects marine communities’ biodiversity (alpha, beta, and gamma diversity), providing insights into ongoing shifts in marine ecosystems