Time filter

Source Type

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 | 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.

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.

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.

Discover hidden collaborations