Mediterranean marine heatwave 2023: ecosystem and fisheries impacts in Italian waters

In 2023, the Mediterranean Sea experienced the longest recorded marine heatwave (MHW) in four decades, affecting marine biodiversity, fisheries and coastal livelihoods. In this study, we assess the effects of this extreme event on the spread of the invasive species Callinectes sapidus (Atlantic blue crab) and Hermodice carunculata (bearded fireworm) along the Italian coasts. We focus on the coastal area of the Po River Delta in the northern Adriatic and on the northern and southern coasts of Sicily and investigate to what extent the increased seawater temperatures contribute to the increase in the monthly biomass of these species. Considering that the spread of the Atlantic blue crab is responsible for significant economic losses in the shellfish fishery and that the spread of the bearded fireworm poses a health risk to the artisanal fishing industry, we also assess the socio-economic impact of this MHW by analysing fish market data and online surveys. Finally, we discuss possible strategies to mitigate the spread and ecological impact of these invasive species. We take into account the aggressive feeding behaviour of the fireworm and the thermophilic nature of the fireworm, whose toxic antennae also pose a health risk to humans. Overall, the sustainability of marine ecosystems and coastal communities in the Mediterranean requires robust interdisciplinary collaboration to address the challenges posed by biological invasions and climate change in this region.