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

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

Ecosystem services provided by marine and freshwater phytoplankton

Phytoplankton, the ecological group of microalgae adapted to live in apparent suspension in water masses, is much more than an ecosystem’s engineer. In this opinion paper, we use our experience as phytoplankton ecologists to list and highlight the services provided by phytoplankton, trying to demonstrate how their activity is fundamental to regulate and sustain Life on our Planet. Although the number of services produced by phytoplankton can be considered less numerous than that produced by other photosynthetic organisms, the ubiquity of this group of organisms, and their thriving across oceanic ecosystems make it one of the biological engines moving our biosphere. Supporting services provided by phytoplankton include almost half of the global primary and oxygen production. In addition, phytoplankton greatly pushes biogeochemical cycles and nutrient (re)cycling, not only in aquatic ecosystems but also in terrestrial ones. In addition, it significantly contributes to climate regulation (regulating services), supplies food, fuels, active ingredients and drugs, and genetic resources (provisioning services), has inspired artistic and craft works, mythology, and, of course, science (cultural services), and much more. Therefore, phytoplankton should be considered in all respects a true biosphere’s engineer

Analysis of morphological traits as a tool to identify the realized niche of phytoplankton populations: what do the shape of planktic microalgae, Anna Karenina and Vincent van Gogh have in common?

Understanding the dynamics of phytoplankton assemblages in various and variable aquatic ecosystems is of paramount importance, given the strategic supporting services offered by these organisms. Such knowledge is implicitly based on the analysis of the realized niche of the different populations, i.e. of the sets of conditions within which populations show a positive growth. The range of phytoplankton morphological traits variability is evolutionarily selected to maximize the ecological performance of species while they are entrained in the spectrum of turbulent flows. In addition, most phytoplankton species exhibit high morphological plasticity that can further optimize their performance under reduced environmental variability. Although this plasticity is well known, it is seldom considered in phytoplankton studies. Morphological analysis could therefore be used as a tool to estimate the environmental variability within which a species can persist and, ultimately, the niche width of phytoplankton populations. This opinion paper tries to answer the questions: to what extent can the morphological variability of phytoplankton offer a synthesis of the environmental variability of aquatic ecosystems?. Do the morphological traits contain sufficient information to describe the width of the realized niche of phytoplankton species? What can we do to fill eventual gaps in our knowledge

Limnology in Sicily: A history of fresh waters surrounded by the sea

The aim of this short article is to trace the history of limnology in Sicily, from the end of the last century up to the present, and pay a little homage to a scientist to whom limnology is deeply indebted: G.E. Hutchinson. Due to its insular and climatic conditions, Sicily is characterised by a drainage network formed by numerous short, torrent-like rivers, and by a few small, natural lakes. The geological characteristics of the island strongly condition the quality of these small waterbodies which generally have surface areas of less than 0.2 km super(2). The earliest observations on Sicilian lentic waters go back more than a century; in particular, at the end of the 19th century, some of the issues regarding the natural lakes had already been brought into focus. Subsequent studies on natural waterbodies concentrated on the geomorphology of landslide lakes or lakes created by the dissolution of the gypsum tableland. However, many of the waterbodies no longer exist because of land reclamation which took place up to the first half of the 1950s. During the last 35 years, there has been a notable increase in limnological publications. In addition, these studies show a more careful and integrated approach to the limnological aspects of waterbodies, compared with the early studies

Limnology in Sicily: A history of fresh waters surrounded by the sea

Although the practice of limnological sciences in an island located in themiddle of the Mediterranean Sea and characterised by a semi-arid climate couldappear, at a first sight, somewhat misplaced, limnology in Sicily is in some wayrelated to one of the finest scientists of this century who tightly linked his nameto limnology: G. E. Hutchinson. Actually, one of the excursions most requestedby those researchers involved in limnology who reach the island, and Palermoin particular, is to the sanctuary of Santa Rosalia and the nearby little pond (Fig.1) which was the scenario of one of the most famous papers by Hutchinson(1959). In addition, part of the second volume of his monumental work "ATreatise on Limnology" (Hutchinson 1967) was written while he was inPalermo as a guest at the Institute of Zoology of the University.The aim of this short article is to trace the history of limnology in Sicily,from the end of the last century up to the present, and pay a little homage to ascientist to whom limnology is deeply indebted