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Cantonati M.,Limnology and Phycology Research Unit | Komarek J.,University of South Bohemia | Komarek J.,Academy of Sciences of the Czech Republic | Montejano G.,National Autonomous University of Mexico
Biodiversity and Conservation | Year: 2015

Although neglected for a long time by freshwater-ecology research, springs are very important habitats for biodiversity conservation. They are multiple ecotones, and are characterized by a remarkable variety of environmental conditions (e.g., from highly-shaded to UV exposed, from permanent discharge to intermittent flow, from still water to strong currents, from extremely-soft to carbonate-precipitating water, etc.). Moreover, springs are often amongst the last high-integrity, oligotrophic freshwater habitats in densely populated areas. Because of the high quality of their waters, the main impact affecting springs is capturing and water diversion. Climate-change driven reduction in precipitations in many areas is likely to determine an aggravation of this impact. It is thus important to document the rich and peculiar biodiversity of springs, also to establish reference conditions for bioassessment methods. Especially in non-acidic springs with running water, and coarse lithic substrata, cyanobacteria are often one of the most taxa-rich and abundant groups of photoautotrophs. The relatively-scarce information available in the literature is mostly referred to similar habitats, and not to spring habitats in the narrower sense. Papers dealing with the cyanobacteria of ambient springheads (=eucrenal) worldwide are still very rare. These were reviewed separating ambient springs in temperate and warm climate, and with special attention to key species, to cyanobacterial strategies allowing survival in oligotrophic headwaters (e.g., nitrogen fixation, phosphatases, anti-UV compounds, etc.), and to distribution patterns. The review also hopes to bolster new interest and research on this topic, and suggests some promising research directions. © 2015, Springer Science+Business Media Dordrecht.


Rosati M.,University of Parma | Cantonati M.,Limnology and Phycology Research Unit | Fenoglio S.,University of Piemonte Orientale | Segadelli S.,Geological | And 2 more authors.
Journal of Freshwater Ecology | Year: 2016

Sampling in springs has several technical problems due to their reduced dimensions and habitat heterogeneity. A standardized quantitative method for sampling crenic macroinvertebrates has never been proposed. The aim of this study was to compare different sampling methods and consider their environmental impacts. First, we present a review of sampling methods found in the literature and discuss their advantages and disadvantages with respect to selective collection of the target community and habitat disturbance. Altogether, 10 different methods have been reported, the use of nets being the most common protocol. Second, we report the results of macroinvertebrate samplings performed in three springs, each surveyed twice, using three different methods (multi-habitat proportional hand net, baited traps, and vegetation washing), in order to compare their effectiveness in collecting macroinvertebrates. Overall, 32 macroinvertebrate taxa, mostly identified at family level, were collected in the sampled springs. Significant differences in abundances were found using different methods, while results for community structure were comparable between the hand net sampling and the combined use of the other two methods, notwithstanding slight differences in the composition of Coleoptera and Diptera assemblages. The hand net, with a multi-habitat proportional approach, yielded more thorough results, making it suitable for biodiversity inventories but having some potentially negative effects on spring habitats. Traps and vegetation washing are also reliable methods with negligible impacts on spring ecosystems that can be conveniently used in ecological studies. © 2016 Taylor & Francis


Leira M.,University of Lisbon | Filippi M.L.,Geology Research Unit | Cantonati M.,Limnology and Phycology Research Unit
Journal of Paleolimnology | Year: 2015

Water-level fluctuations (WLF) often represent one of the greatest impacts on the development of lake ecosystems. In the year 1931, the Trentino Hydroelectric Company (SIT) requested the hydroelectric use of water bodies in the Upper and Middle Sarca basin. The largest and deepest lakes were dammed to increase lake volume and exploited since mid 1950s. This research uses the sediment record of two small lakes in close proximity to each other (Garzonè and Serodoli) in northern Italy, used for hydroelectric power generation to determine the dependence of diatom-assemblage dynamics on WLF that have taken place over the last 60 years. Historical WLF are clearly reflected in the lithological composition and grain-size variations of the sediment cores. During the regression and transgression phases, the boundaries between the erosion, transport and accumulation zones fluctuated, causing redistribution of previously accumulated sediments, and their return into the lake’s cycling of biogeochemical matter. The water-level changes not only caused distinct taxonomic shifts in the diatom communities, which were dominated by different species in the core sections of each lake, but also significant shifts in the composition of the diatoms’ ecological, morphofunctional and life-form groups. Diatoms with a low- and high-profile attachment type were the dominant morphological forms in the upper core levels, where the most extreme fluctuations in water level had occurred. Increased turbulent mixing caused by WLF favours the presence of large, heavily silicified centric diatoms, while more stable levels would select for smaller centric diatoms through thermal stratification. © 2015, Springer Science+Business Media Dordrecht.


Cantonati M.,Limnology and Phycology Research Unit | Guella G.,University of Trento | Spitale D.,Limnology and Phycology Research Unit | Angeli N.,Limnology and Phycology Research Unit | And 3 more authors.
Freshwater Science | Year: 2014

Lake Tovel is an oligotrophic, meromictic, mountain lake of the Dolomites that undergoes marked seasonal water-level fluctuations (WLFs). We used neo- and paleolimnological data collected since 1999 to test the utility of algal and cyanobacterial pigments and diatom and chironomid biodiversity as proxies for WLF and to highlight the contribution of benthic algae to the sediment record. We found that detailed knowledge of presentday spatiotemporal patterns of WLF is essential for a complete and correct interpretation of paleolimnological data. Scytonemin, a cyanobacteria-specific photoprotective pigment, was produced by epilithic cyanobacteria in the depth zone affected by WLF and should be considered a proxy for the extent of WLF. The phytobenthos was as important as phytoplankton as a source of sedimentary pigments. We used information gained on the detailed distribution of diatoms at different depths and on different substrata in the 2 basins to show the probable location in the lake from which taxa in sediment cores originated to aid in interpretation of the sediment archive (including identification of periods of active hydrology). We sampled present-day chironomids in springs and streams feeding the lake and along a depth transect in the main basin. The taxa found were all rheophilic, crenophilous, or typical of the littoral zone of oligotrophic lakes. We interpreted sections of the cores containing large numbers of Orthocladiinae and Diamesinae head capsules as indicative of periods of active hydrology (including sudden and marked WLF) because the littoral taxa found in the cores must have been derived from the littoral zone by sediment focusing or slumps. Thus, we identified useful proxies of WLF in mountain, carbonate lakes. © 2014 by The Society for Freshwater Science.


Mares J.,University of South Bohemia | Mares J.,Academy of Sciences of the Czech Republic | Cantonati M.,Limnology and Phycology Research Unit | Guella G.,University of Trento | And 2 more authors.
Freshwater Science | Year: 2014

An unknown green alga (order Ulvales) was a dominant macroalga in the rocky littoral zone of Lake Garda (southeastern Alps). Morphological and phylogenetic analyses indicated the alga was in the genus Jaoa, considered endemic to China. The alga in Lake Garda had numerous rhizoids, a subspherical hollow thallus with irregularly lobate - saccate morphology, and 3 layers (an outer layer of small cells with distinct chloroplasts, 2 pseudoparenchymatous, large, round, and mainly hyaline cell layers). Most characteristics were in agreement with the description of Jaoa bullata, 1 of 2 species belonging to the genus Jaoa. Phylogenetic analysis based on 3 loci (rbcL, nrDNA 18S, and ITS) placed the alga in a clade with a sample identified as Jaoa prasina from a Chinese population, but with a considerable sequence distance, a result suggesting it might be a separate species. The Lake Garda alga is a siphonaxanthin-type species that possesses only nonP lipids as structural components of chloroplast (monogalactosyl diacylglycerols, digalactosyl diacylglycerols, and sulfoquinovosyl diacylglycerols) and other cell membranes (diacylglyceryl-N,N,N- trimethylhomoserine lipids). The alga is easily detected with the naked eye, occupies a characteristic belt in the eulittoral zone, and can be found wherever hard substrata are available. Neither this species nor similar taxa are mentioned in historical (end of the 19th century) papers on benthic algae of Lake Garda, so the alga probably was introduced to the lake in relatively recent times. This alga belongs to a little-known genus, but is easily observed and was discovered in Italy's largest lake, a tourist resource of outstanding importance. It is a striking example of the degree to which lake benthic algae are understudied in many areas. © 2014 by The Society for Freshwater Science.


Cantonati M.,Limnology and Phycology Research Unit | Guella G.,University of Trento | Komarek J.,University of South Bohemia | Komarek J.,Academy of Sciences of the Czech Republic | Spitale D.,Limnology and Phycology Research Unit
Freshwater Science | Year: 2014

Lake benthic cyanobacteria and algae are distributed along a depth gradient. At the extremes of the gradient, irradiance is a selecting factor because of excess (UV exposure in shallow waters) or extreme reduction (light limitation at the bottom of the euphotic zone). We tested whether, how, and to what extent epilithic cyanobacteria assemblages change with depth in a carbonate meromictic lake (Lake Tovel, southeastern Alps) that undergoes marked water-level fluctuations. Fixed stations were placed along a transect at 2- to 3-m depth intervals from 0 to 24 m and were sampled by SCUBA divers. Three depth-distribution zones were identified based on the composition of cyanobacterial assemblages and primary benthic algal pigments: shallow, middepth, and deep. The autecological traits of the cyanobacteria indicators identified by indicator value (IndVal) analysis suggested that the shallow, mid-depth, and deep zones were disturbed by water-level fluctuations, highly stable with favorable growth conditions, and severely light-limited, respectively. The shallow zone was colonized mainly by pseudaerial cyanobacteria and by UV-resisting phenoecodemes with yellow - brown sheaths (scytonemin). Shannon - Wiener diversity was highest in the shallow zone, probably because taxa characteristic of periodically inundated habitats mixed with lacustrine taxa. The most unique morphospecies were in the lower part of the mid-depth and in the deep zone. These species frequently had colorless sheaths or pink - red - violet cell contents. We found clear patterns in the depth distribution of benthic cyanobacteria and algal pigments that indicated adaptation to the principal evolutionary pressures at the extremes of the depth gradient: water-level fluctuation and light attenuation. These features have implications for quality assessments, biodiversity inventories, and identification of areas affected by water-level fluctuations. © 2014 by The Society for Freshwater Science.


Cantonati M.,Limnology and Phycology Research Unit | Komarek J.,University of South Bohemia | Komarek J.,Academy of Sciences of the Czech Republic | Hernandez-Marine M.,University of Barcelona | Angeli N.,Limnology and Phycology Research Unit
Freshwater Science | Year: 2014

The deep littoral zone hosts a unique but understudied subset of lake periphyton. We investigated epilithic cyanoprokaryotes in a carbonate meromictic lake (Lake Tovel, southeastern Alps) to obtain information on 2 poorly known, deep-dwelling coccoid species (one new to science) and to analyze their distribution in light of the current understanding of the depth distribution of lake periphyton. Cyanoprokaryotes in Lake Tovel have distinct depth distributions among 3 zones: shallow (0-4 m), mid-depth (6-12 m), and deep (15-24 m). The mid-depth and deep zones are characterized by high stability with favorable growth conditions and by severe light limitation, respectively. Both zones have unique taxa that frequently possess colorless sheaths or pink - red - violet cell contents. The 2 most poorly known cyanoprokaryotes found in Lake Tovel (both pink - red - violet) were a species of Geitleribactron new to science (Geitleribactron purpureum sp. nov. Cantonati et Komárek) and the rare Chlorogloea purpurea. We described and documented, respectively, these 2 species by means of light microscopy, careful comparison with the most-similar morphospecies, transmission electron microscopy (TEM), and ecological characteristics. We are the first to describe the TEM ultrastructure of a Chlorogloea species and to characterize the autecology and distribution of C. purpurea, which, in spite of its very specific habitat requirements (deep waters of carbonate oligotrophic mountain lakes), has been reported in several studies from disparate habitats and geographic locations. © 2014 by The Society for Freshwater Science.


Cantonati M.,Limnology and Phycology Research Unit | Lowe R.L.,Bowling Green State University
Freshwater Science | Year: 2014

Lake phytoplankton studies outnumber studies on lake periphyton by an order of magnitude, and most periphyton research has been done in streams. Most benthic algal taxa found in lakes also can be found in lotic systems, but assemblages and taxa differ in a number of ways. The ecological characteristics of some lake benthic algae reflect habitat coupling. Littoral zones (benthic areas above the light compensation depth) are areas of high productivity and biodiversity. The proportion of benthic and planktonic primary production (autotrophic structure) is a key ecosystem property. The distribution of lake benthic algae is markedly influenced by the depth gradient and substratum, and assemblages change with depth from epilithic and epiphytic rheobionts to epipsammic and epipelic limnobionts. At shallow depths, periphyton must cope with the effects of high radiation, water-level fluctuations, wave action (e.g., desiccation, ultraviolet radiation exposure, shear stress), and seasonal shifts in temperature. This situation selects for widely distributed rheophilic species. In contrast, the deeper littoral zone is stable and hosts a distinct subset of lentic periphyton. However, species experience low light intensity, which becomes increasingly severe with increasing depth, and are often threatened by eutrophication-driven increased shading by phytoplankton. Besides change across depths and substrata, adaptations to disturbance levels, competition, microdistribution of phenological stages, and physiomorphological regulation generate multiple and complex spatial patterns at different scales. Lake shores are the focus of human activities with significant consequences for periphyton. In this review, we introduce a series of 15 papers on the topic and suggest directions for future research. Overall, this special series illustrates that, despite the many important ecosystem services provided by lake benthic algae, the topic is understudied. © 2014 by The Society for Freshwater Science.


Spitale D.,Limnology and Phycology Research Unit | Angeli N.,Limnology and Phycology Research Unit | Lencioni V.,Invertebrate Zoology and Hydrobiology Research Unit | Tolotti M.,Instituto Agrario Of S Michele Alladige Fondazione E Machinery
Biologia (Poland) | Year: 2015

Many lakes in mountain regions have been used for hydropower generation since the 1950s. It has been estimated that as many as 79% of the rivers in the Alps have been affected by the presence of hydropower plants. In this context, the shutting down of hydropower plants on a group of Alpine lakes represented a good opportunity to study the ecological impact on them. We selected nine lakes that had been affected and nine that had not, and analysed the differences in environment, littoral diatoms and zoobenthos, phytoplankton, zooplankton, and fish. Results showed that benthic biota -diatoms and zoobenthos- were the most affected by water-level drawdown during winter months. Even six years after the end of hydroelectric operations, diatom species richness and diversity were lower in impacted lakes. Assemblage structure was different for both diatoms and zoobenthos. Phytoplankton and zooplankton were similar in impacted and unaffected lakes in terms of both species richness (and diversity) and assemblage structure. The degree of impact on fish was unclear because illegal stocking of lakes with allochthonous fish species had taken place. This study showed that compared to limnetic biota, littoral communities were the most affected by the decrease in water volume every winter. Six years after the end of hydroelectric operations, diatoms, and to lesser extent zoobenthos, were still different compared to those in natural (unaffected) lakes. Planktic communities seem to be either more resistant to the disturbances, or else able to recover more quickly to their former condition. © 2015 Institute of Botany, Slovak Academy of Sciences.


PubMed | IRSTEA, CNR Institute of Ecosystem Study, University of Helsinki, Limnology and Phycology Research Unit and 5 more.
Type: | Journal: The Science of the total environment | Year: 2014

In the presence of different environmental stressors, diatoms can produce frustules presenting different types of deformities. Metals and trace elements are among the most common causes of these teratological forms. Metal enrichment in water bodies can be attributed to the geological setting of the area or to pollution. The widespread benthic diatom Achnanthidium minutissimum (ADMI) is one of the most metal-tolerant species. In the present study, ADMI teratologies were defined from samples taken from eight very diverse, widely-distributed inland-water habitats: streams affected by active and abandoned mining areas, a metal-contaminated stream, a spring in an old chalcopyrite mine, a mineral-water fountain, and a sediment core taken from a lake affected by metal contamination in the past. Deformed frustules of ADMI were characterised mainly by one (sometimes two) more or less bent off ending, conferring to the specimens a cymbelloid outline (cymbelliclinum-like teratology, CLT). Marked teratologies were distinguished from slight deformities. Hydrochemical analyses, including metals and trace elements, were carried out and enrichment factors (EF) relative to average crustal composition were calculated. To improve our knowledge on the potential of different metals and trace elements to trigger the occurrence of ADMI CLT, we carefully selected 15 springs out of 110 (CRENODAT dataset) where both ADMI and above-average metal or metalloid concentrations occurred, and re-analysed these samples. The results from the eight widely-distributed core sites as well as from the 15 selected CRENODAT springs led to the hypothesis that two metals (copper and zinc) and a metalloid (antimony) were the most likely triggers of ADMI CLT formation. From a quantitative point of view, it is worth noting that the lowest concentrations triggering ADMI CLT can be fairly low, particularly in the case of copper contamination. The antimony-rich site was characterised by a marked-teratology variant where both ends of ADMI were bent off.

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