Conservation status of Chirocephalus marchesonii Ruffo & Vesentini, 1957 in the Pilato Lake (Sibillini Mountains National Park, Central Italy)

Chirocephalus marchesonii is a fairy shrimp endemic to the Pilato Lake, a small temporary high-elevation lake (1948 m a.s.l.) located in the Central Apennines (Italy). The species is of particular conservation interest, since it has limited thermal tolerance, low dispersal capacity and is represented by a single population with a very restricted range. The anthropogenic pressure linked to summer tourism and the habitat’s vulnerability to climate change represent the main threats to the species. Concern over the population’s persistence has been increased by a period of total drying of the lake in summer 2017, which was attributed to earthquakes that occurred in 2016 and were judged to have altered the hydrogeological conditions. Our study aims were to: i) evaluate the conservation status of C. marchesonii and its habitat; ii) examine the influence of environmental parameters on the zooplankton community, with special reference to C. marchesonii population densities; and iii) provide information to underpin effective conservation strategies. The zooplankton community was monitored monthly from July to November 2018 and from June to August 2019, using a Ruttner bottle and an 80-µm mesh net within transects of known length. On each sampling occasion, 13 physicochemical parameters were measured, and water-level fluctuations and lake surface area were recorded. Higher air temperatures seem to be a key driver of drying events, whereas we identified no significant differences in water physicochemistry compared to the past. The mean estimated population density of C. marchesonii (0.06 individuals L–1) showed that, despite the 2017 drying event, the species completed its life cycle during the study period, although its population densities were lower than previously recorded. Our results can inform extinction risk assessment and associated management strategies, such as the identification of alternative habitats with the potential to support C. marchesonii populations.