Special Nature Reserve “Lago di Pergusa”

The Kore University of Enna intends to promote and develop basic scientific research applicable in the sector of environmental and meteorological-climatic monitoring of protected natural environments and is interested in experimenting and applying the results obtained by collaborating with institutions and companies that operate directly in the specific sector, having the task among others:

• • a) to carry out collaborative activities through agreements, both with public bodies and private entities;

b) to design and implement research and services functional to the activities of both the Kore University and external clients with appropriate agreements; c) to assume an increasingly greater characterization of a University strongly linked to the interests of cultural and social development of its territory through exchanges with local institutional bodies, valorizing the scientific experiences developed and consolidated; from 2007 to 2015, the Regional Province of Enna (now the Free Municipal Consortium of Enna), managing body of the RNS “Lago di Pergusa”, and the University of Enna “Kore” have stipulated specific Agreements for the execution of the scientific research program on the RNS “Lago di Pergusa”.

Lake Pergusa is a Special Nature Reserve, whose managing body is the Libero Consorzio Comunale (formerly the Regional Province) of Enna; it is located in the center of Sicily (Municipality of Enna) between the Erei mountains at an altitude of 667 meters above sea level. It is the only endorheic lake in Sicily, characterized by wide fluctuations in level linked to the rainfall regime, and occupies the most depressed part of a Pliocene synclinal structure. Paleovegetation studies indicate that it was formed at least 20,000 years ago. Its main source of nourishment is represented by precipitation and groundwater; it, due to summer evaporation, is characterized by brackish water. Peculiar is the phenomenon of "Red Water" determined, in particular chemical-physical conditions, by red sulfur bacteria. Various human interventions, which began in the 1930s with reclamation works and were accentuated in the 1960s and 1970s with the extraction of water from the aquifers, have seriously endangered its existence, so much so as to determine the almost total reduction of the lake surface in the summer of 2002. Today, following the almost total reduction in the extraction and also thanks to some particularly rainy seasons, the lake has shown a significant recovery. The Protected Area is also part of the Natura 2000 Network (Special Protection Area - Site of Community Interest - Special Conservation Area "ITA060002") and as a geosite of the "Rocca di Cerere Geopark" it is included in the European Geopark Network (EGN) and Global Geopark Network (GGN).

Research program on environmental components (abiotic and biotic) through scientific processing, monitoring and parametric surveys of the computerized meteorological station.

The research program includes:

• monitoring of chemical, physical and bioecological parameters of water, with both in situ and laboratory analyses, including the detection of additional inorganic and organic parameters not only on the aqueous matrix but also on the lake bed sediments, bacteriological analyses and detailed studies of phytoplankton;
• monitoring of the hydrogeological system, through measurements of piezometric levels in the various sectors of the basin;
• continuous monitoring of climatic parameters, through a computerized weather station;
• the vegetation study and the continuous updating of the floristic list; as well as the aerobiological monitoring for the study of pollen;
• wildlife monitoring, including a detailed study on herpetofauna and ornithofauna, including through the scientific ringing technique, as well as on the tiger mosquito Aedes albopictus;
• the update of the dedicated web website: www.riserveenna.it;
• the photo reportage.

The monitoring activity of Lake Pergusa aims, in addition to creating a description of the characteristics of the basin, to create above all a description of the physical and biological factors that interact to determine the environmental peculiarities of the body of water and the entire ecosystem. For this purpose, it is useful to be able to document the average values of the various parameters and their ranges of variation to evaluate and model any changes taking place in the basin. In the future, it will also be possible to compare the situations that will occur with the current monitored situation. In this way, it will be possible to quantify the changes and, furthermore, there will be the basis for identifying their causes.

In light of the studies carried out so far, it can be stated that the main weak points of the Pergusa system are:

• for the aquatic environment and related habitats: drying up and silting up of the basin, oversaturation of the waters, drastic reduction of biocenoses;
• for the riparian environment: removal of territory from the reed bed, reduction of the carrying capacity of the habitat and invasion of alien species;
• for the hilly environment: reduction of habitats covered by native vegetation, invasion of alien plant species, withdrawal of groundwater, discharge of wastewater, herbicides and pesticides into the groundwater;
• for the entire biotope: general tendency towards desertification.

Instead, as regards the strong points, the results of this monitoring have highlighted that, as regards the quantity of water present in the lake basin, since 2003 the lake has been in clear recovery, so much so that the water level has reached approximately 4 metres; this process was favoured by the closure of the municipal wells in the 1980s. This is also evident from the control of the piezometric surface.

Restoring the lake level involved:

1. The reduction of water salinity and the increase of dissolved oxygen saturation, which consequently allowed the restoration of various forms of life.
2. Stabilization of the physical and chemical parameters of the lake waters on typical "normal" values of the ecosystem.
3. The reconstitution of the zooplanktonic biocenosis, formed essentially by Copepods, Cladocerans and Ostracods; together with the flourishing of large quantities of juvenile forms of Copepods, indicative of trophic conditions suitable for the development of the different benthic and planktonic communities, with activation of the recolonization processes, with the bottom sediments acting as a "bank" of planktonic diversity, storing forms of resistance that are released when favorable environmental conditions arise.
4. The non-occurrence of the red-purple colouring of the water (red water), which is of a scenic effect, but derives from an asphyxiated state with consequent abnormal development of sulphur bacteria, understood as a sign of a state of suffering.
5. Recolonization by aquatic plants. The study of phytoplankton has led to the detection, in certain periods (in 2008 and 2011), of the presence of an ichthyotoxic microalga Prymnesium parvum which has caused the death of hundreds of Carps Cyprinus carpio; although it has not caused mortality in bird populations, the bloom has indirectly produced a change in the composition of the community, causing a clear decrease in herbivorous species (Anatidae and Rallidae) and a significant increase in ichthyophagous species: Cormorant Phalacrocorax carbo, Yellow-legged Gull Larus michahellis and Grey Heron Ardea cinerea, which has also nested for the first time.
6. The recolonization of the lake environment by amphibians and reptiles, whose research has confirmed the presence of 12 species, 4 amphibians and 8 reptiles, with two strictly Sicilian endemic taxa: Bufotes siculus and Emys trinacris and the Sicilian-Maltese Discoglossus pictus pictus. Furthermore, the ecological and conservation importance of the protected area is confirmed for the endemic Bufotes siculus and Emys trinacris present with significant populations.
7. A significant increase in aquatic ornithofauna.

The zoological study allowed to census 299 species of which 177 ornithic species between nesting, wintering and migratory. Among the relevant species from the conservationist point of view and on which targeted studies have been carried out are the Purple Gallinule Porphyrio porphyrio and the Little Grebe Podiceps nigricollis. The first is a rail that became extinct in Sicily in the 60s and that today we can count again thanks to a reintroduction project in three different historical coastal sites, all at least 55 km from Pergusa km. The Purple Gallinule has spontaneously colonized Lake Pergusa and, since the first sighting in 2006, has now constituted a stable reproductive nucleus of over 50 couples. The Little-necked Grebe is of particular value because Pergusa is the only Italian locality where this species breeds regularly, counting the highest number of breeding pairs of the species (128 adults and 112 chicks and juveniles) for Italy. In Italy, for the Little-necked Grebe, the documented cases of reproduction after 1950, excluding the possible or probable ones, are about twenty, mostly relating to a few pairs. At Lake Pergusa, since 2010 the Little-necked Grebe has changed its status from "migrant, wintering and irregular breeder" to "regular breeder".

The scientific ringing activity of ornithofauna has allowed us to detect, in addition to elusive species that have escaped the censuses such as the Long-eared Owl (Asio otus) or the Long-tailed Tit (Aegithalos caudatus siculus), also species that are quite rare for this site such as the Pied Flycatcher (Ficedula hypoleuca), the Garden Warbler (Sylvia borin), the Common Warbler (Phylloscopus trochilus), the Sardinian Whitethroat (Sylvia conspicillata), the Fieldfare (Turdus pilaris) and the Savi's Warbler (Locustella luscinioides).

As regards the Tiger Mosquito Aedes albopictus, detected in Pergusa for the first time in the summer of 2010, constant monitoring shows a positive trend in its rooting in the territory. The data collected through ovitraps are "proxy" indicators, that is, able to approximate the degree of infestation and not directly indicative of the density of the vector present in the studied area; however, this methodology represents an indirect surveillance system able to obtain information on the development of the adult population. These studies have favored international collaboration with the Université Grenoble Alpes and the Unite Mixte de Recherche 5553-LECA (Laboratoire d'Ecologie Alpine) of the French CNRS (Comité National de la Recherche Scientifique) in order to contribute to the study of the invasion of the Tiger Mosquito through genetic typing (to investigate how its spread in the European continent occurred and therefore try to understand the relative future scenario).

The botanical study allowed us to count 358 species, including several orchids. From the elaboration of the biological spectrum it results that: therophytes represent 27.65%; helophytes 0.28%; hydrophytes 0.84%; geophytes 14.53%; hemicryptophytes 28.77%; chamaephytes 5.31%; nano-phanerophytes 2.51% and phanerophytes 20.11%. The endemic species counted in the area represent 2.23%. Among these are: Euphorbia ceratocarpa Ten., Senecio licopifolius Desf., Senecio squalidus Auct. Fl. Ital. var. chrysanthemifolius Poiret, Thymus spinulosus Ten., Crocus longiflorus Rafin. Finally, among the floristic species listed in Annex 2 of the Habitats Directive, Dianthus rupicola Biv.

The aeropalynological monitoring (volumetric type), which involved the preparation of 1,784 slides, confirmed the presence of pollens in the atmosphere almost continuously throughout the solar year; in fact, it begins in January (with pollens of the Oleaceae of the genus Fraxinus, of the Corylaceae and of the Cupressaceae) and ends in November (with pollens of the Compositae, of the Amaranthaceae/Chenopodiaceae and of the Graminaceae). Within the botanical families object of the research, it appears that in Pergusa it was the Urticaceae that had the greatest impact on the total concentration of allergenic pollens, in fact this taxon presented a five-year Pollen Index of 30,631 pollen grains per m³, equal to 24.6% of the total detected. The pollens of Urticaceae are also those that have been detected in the air for a longer period, in fact their Pollen Season in media has presented a duration of 145 days per year. The highest value, relative to the number of days with "high" pollen concentration (according to the AIA classification), was found for Oleaceae, which in the five-year period of the research showed a media measurement of 43 days per year. Aerobiology, in addition to being extremely useful in the health field, represents an excellent tool for monitoring the biodiversity of the protected area.

The study of pollen has opened a research collaboration with the Museum National d'Histoire Naturelle in Paris and the Unite Mixte de Recherche 7194-HNHP (Histoire Naturelle de l'Homme Prehistorique) of the French CNRS (Comité National de la Recherche Scientifique) on the IRN POLARISE project «POLlen et ARIdité, résilience de la végétation aux SÉcheresses récurrentes» with the aim of studying, through the pollen rain emitted by vegetation (for the past with fossil records, for the present with monthly and annual monitoring), the response of Mediterranean vegetation and its biodiversity to extreme drought events, past or present, and the impact of their recurrence in the long term.

The physiographic characteristics and high biodiversity make this ecosystem unique and valuable in the Sicilian context. The results underline the need to consider the functional aspects of ecological traits to improve management actions of conservation strategies, in order to preserve the diversity and functioning of the ecosystem.