Morphological analysis of phytoplankton as a tool to assess ecological state of aquatic ecosystems: The case of Lake Arancio, Sicily, Italy

Phytoplankton requires a sufficient supply of light and nutrients to grow. At the same time it is largely entrained in water motion and is subject to grazing from planktonic herbivores. The pelagic life of lake phytoplankton is based on 4 pillars: living in suspension, light harvesting, nutrient uptake, and escape from grazing. Environmental variability and the uneven distribution of resources among and within the different aquatic ecosystems exert a selective pressure on these organisms, which are formed by a single cell or by colonies with either relatively low or high numbers of cells. Phytoplankton displays an amazing morphological variability representing an adaptation to spatial and temporal variability of their environments. Among functional traits of phytoplankton, morphological features such as shape and size represent an unavoidable starting point to fully understand the relationships between this group of organisms and its environment. The molding effect of environmental variables on phytoplankton morphology is particularly evident in highly dynamic environments such as reservoirs or ponds. The analysis of phytoplankton morphology can thus supply important information on the ecological conditions of a given waterbody. To support this hypothesis, data are presented on the main morphological features of phytoplankton from a 20-year limnological investigation carried out in a Mediterranean man-made lake. The results show that phytoplankton morphological variability reflects different environmental scenarios, and that the morphological features of phytoplankton represent a powerful tool to assess the ecological or trophic state of aquatic ecosystems. © International Society of Limnology 2013.Phytoplankton requires a sufficient supply of light and nutrients to grow. At the same time it is largely entrained in water motion and is subject to grazing from planktonic herbivores. The pelagic life of lake phytoplankton is based on 4 pillars: living in suspension, light harvesting, nutrient uptake, and escape from grazing. Environmental variability and the uneven distribution of resources among and within the different aquatic ecosystems exert a selective pressure on these organisms, which are formed by a single cell or by colonies with either relatively low or high numbers of cells. Phytoplankton displays an amazing morphological variability representing an adaptation to spatial and temporal variability of their environments. Among functional traits of phytoplankton, morphological features such as shape and size represent an unavoidable starting point to fully understand the relationships between this group of organisms and its environment. The molding effect of environmental variables on phytoplankton morphology is particularly evident in highly dynamic environments such as reservoirs or ponds. The analysis of phytoplankton morphology can thus supply important information on the ecological conditions of a given waterbody. To support this hypothesis, data are presented on the main morphological features of phytoplankton from a 20-year limnological investigation carried out in a Mediterranean man-made lake. The results show that phytoplankton morphological variability reflects different environmental scenarios, and that the morphological features of phytoplankton represent a powerful tool to assess the ecological or trophic state of aquatic ecosystems

A review on the animal xenodiversity in Sicilian inland waters (Italy)

This paper reviews the available knowledge about faunal xenodiversity in Sicilian inland waters (Italy). The aim is to provide an updated checklist and bibliography of those non-indigenous species (NIS) which occur in the island, and to identify possible threats to its native biological diversity. Data were collected through an extensive literature search which encompassed also local journals, books, congress abstracts, and other grey literature. All the collected data were critically revised and, when possible, verified by consulting available collections or through dedicated sampling surveys. Only those data contained in reports indicating precise occurrence localities, which were confirmed by our own observations and\or by at least two independent sources including at least a peer-reviewed publication, were considered as certain. Data in literature that did not meet these criteria were considered doubtful and reported separately as unverified data. The information provided by websites has been excluded as it often contains unfounded and\or erroneous data. The fauna of Sicilian inland waters host at present 31 confirmed NIS. In addition, the presence of further 11 taxa is dubious. Among the verified data, invertebrate and vertebrate taxa are nearly equally represented, with 15 and 16 taxa, respectively. With 16 species, the phylum Chordata is by far the most represented, followed by Mollusca (8 species) and Arthropoda (6 species). Most of these species were detected in the last 30 years due to the lack of previous regular studies on Sicilian freshwaters. With few exceptions (e.g., the recent introduction of Xenopus laevis, the African clawed frog), NIS' effects on native biota have not extensively studied in the island yet. Although the top-down effects caused by introduced vertebrate taxa are known to deeply modify the native structure of the biota, little information is available on the impacts caused by invertebrate taxa, especially the microscopic ones. The presence in Sicily of 11 non-native species of bony fish is probably the most impacting threat to autochthonous fauna through predation, competition and hybridisation. The results shown in the paper highlight the importance and the urgency of more exhaustive investigations on NIS in Sicilian inland waters with special regard to less charismatic taxa whose effects on the native biota have never been evaluated yet

Primo reperto di una lenticchia d'acqua alloctona in Sicilia: Lemna minuta KUNTH (Araceae Lemnoideae)

La presenza di Lemna minuta, una lenticchia d’acqua originaria delNord America, viene segnalata per la prima volta in Sicilia nel gorgo di Santa Rosalia, uno stagno temporaneo mediterraneo localizzato sul promontorio di Monte Pellegrino, Palermo. Lo specchio d’acqua risulta completamente ricoperto da questa pleustofita galleggiante, che impedisce la penetrazione della luce nella colonna d’acqua e non consente la crescita della vegetazione micro- e macroalgale. La repentina e perdurante invasione di Lemna minuta nello stagno, creando condizioni di ipossia nella colonna d’acqua, costituisce un potenziale rischio per l’intero biota del sito.Lemna minuta, an allochthonous duckweed from North America, has been collected for the first time in Sicily. This floating species completely covers the water surface of the Santa Rosalia pond, a small Mediterranean temporary water body located on Monte Pellegrino, Palermo, and inhibits the growth of algal vegetation because of its shading effect. The sudden and enduring invasion of Lemna minuta in the pond is causing hypoxic condition in the water column, which can potentially threaten the aquatic biota

First record of a representative of the subfamily Paradiaptominae (Copepoda Calanoida Diaptomidae) in Italy: Metadiaptomus chevreuxi (Guerne & Richard, 1894)

Metadiaptomus chevreuxi (Guerne & Richard 1894), a diaptomid calanoid copepod belonging to the subfamily Paradiaptominae, has been found in two neighbouring temporary pools in the Egadi Archipelago (Sicily, southern Italy). This finding constitutes the first record of a representative of this subfamily in Italy and the second known European record for this species. M. chevreuxi, commonly found in the arid areas of Maghreb, has already been reported to occur in Mallorca Island (Balearic Archipelago, Spain), while it seems to be rare in the eastern quadrants of the Mediterranean basin. The characteristics of the new Italian site are briefly described and drawings of morphological details of adult specimens are provided. The occurrence of M. chevreuxi in Western Sicily is in accordance with the supposed merging of North-eastern and South-western freshwater calanoid faunas in this area. Additional information on the distribution of calanoid species in the island and its biogeographic significance is also offered

A century of research on micro-organisms from the inland waters of the largest Mediterranean island

The first studies on the micro-organisms inhabiting Sicilian inland waters date back to the middle of the XIX century. However, these were based on single samples and mainly addressed at compiling faunistic and floristic inventories. It was in the first decades of the XX century that the first methodical studies were performed, which focussed on assessing microbial diversity in saline and hypersaline inland waters. Studies on plankton dynamics in ponds and reservoirs of the island started at the beginning of the 1980s and, since the end of the 1990s, temporary waters have also been intensively sampled, especially as regards phytoplankton and micro-crustaceans. These intensified sampling efforts contributed to increasing our knowledge of the composition, structure and functioning of the planktic compartment. On the contrary, studies on benthic microflora and fauna are still numerically scarce and mostly based on occasional collections. Also, running waters have received little attention and the methodical analysis of their micro-organisms is still in its infancy

First record and morphological features of Hemidiaptomus (Occidodiaptomus) ingens (Gurney, 1909) (Copepoda, Calanoida) in Italy

During a survey, carried out to assess the consistency of microcrustacean fauna inhabiting temporary ponds in Sicily, Hemidiaptomus (Occidodiaptomus) ingens (Gurney, 1909), a large calanoid copepod up to now known only for North-African ponds, Camargue and Corse, was found in the north-western part of the island. Due to its central location in the Mediterranean Sea, Sicily represents a transition zone where several chorological zones of the West Palearctic merge and converge. A brief summary of the existing literature regarding this taxon is given with some morphological considerations on the recently found population which represents the first record for Italy. In particular, the morphological features of the Sicilian population are closely related to those described by Gurney for the specimens collected in the locus typicus (Oued Tindja, Tunisia) and slightly differ from the other European populations

On Daphnia (Ctenodaphnia) similis Claus, 1876 and other interesting anomopods (Crustacea, Branchiopoda) from Apulia (Southern Italy)

The presence of Daphnia species in Apulia (southern Italy) freshwaters is update