Journal of Limnology https://jlimnol.it/index.php/jlimnol <p>The <strong>Journal of Limnology</strong> publishes peer-reviewed original papers, review papers and notes about all aspects of limnology. The scope of the Journal of Limnology comprises the ecology, biology, microbiology, physics, and chemistry of freshwaters, including the impact of human activities, management and conservation. Coverage includes molecular-, organism-, community-, and ecosystem-level studies both applied and theoretical. Proceedings of workshops, specialized symposia, conferences, may also be accepted for publication. The <strong>Journal of Limnology</strong> is published in three issues per year, open access online and each article is available for downloading for free. A printed version is also available at the annual subscription rate of € 160. For further information on subscription terms, rates, modes of payment and shipping, etc. please contact the Publisher at <a href="mailto:info@pagepress.org">info@pagepress.org</a></p> <h3 style="color: #194480;">The Special Issue <strong><a href="/index.php/jlimnol/issue/view/57">Aquatic biomonitoring: Lessons from the past, challenges for the future</a></strong> is now available</h3> en-US <p><strong>PAGEPress</strong> has chosen to apply the&nbsp;<a href="http://creativecommons.org/licenses/by-nc/4.0/" target="_blank" rel="noopener"><strong>Creative Commons Attribution NonCommercial 4.0 International License</strong></a>&nbsp;(CC BY-NC 4.0) to all manuscripts to be published.<br><br> An Open Access Publication is one that meets the following two conditions:</p> <ol> <li>the author(s) and copyright holder(s) grant(s) to all users a free, irrevocable, worldwide, perpetual right of access to, and a license to copy, use, distribute, transmit and display the work publicly and to make and distribute derivative works, in any digital medium for any responsible purpose, subject to proper attribution of authorship, as well as the right to make small numbers of printed copies for their personal use.</li> <li>a complete version of the work and all supplemental materials, including a copy of the permission as stated above, in a suitable standard electronic format is deposited immediately upon initial publication in at least one online repository that is supported by an academic institution, scholarly society, government agency, or other well-established organization that seeks to enable open access, unrestricted distribution, interoperability, and long-term archiving.</li> </ol> <p>Authors who publish with this journal agree to the following terms:</p> <ol> <li>Authors retain copyright and grant the journal right of first publication with the work simultaneously licensed under a Creative Commons Attribution License that allows others to share the work with an acknowledgement of the work's authorship and initial publication in this journal.</li> <li>Authors are able to enter into separate, additional contractual arrangements for the non-exclusive distribution of the journal's published version of the work (e.g., post it to an institutional repository or publish it in a book), with an acknowledgement of its initial publication in this journal.</li> <li>Authors are permitted and encouraged to post their work online (e.g., in institutional repositories or on their website) prior to and during the submission process, as it can lead to productive exchanges, as well as earlier and greater citation of published work.</li> </ol> nadia.moscato@pagepress.org (Nadia Moscato) tiziano.taccini@pagepress.org (Tiziano Taccini) Tue, 28 Aug 2018 00:00:00 +0200 OJS 3.1.1.4 http://blogs.law.harvard.edu/tech/rss 60 Cyanobacterial blooms in freshwaters bodies in a semiarid region, northeastern Brazil: A review https://jlimnol.it/index.php/jlimnol/article/view/jlimnol.2017.1646 <p>Harmful cyanobacterial blooms have caused several problems in freshwater environments due to their prolific growth and the harmful cyanotoxins produced by some species. The occurrence of these organisms has increased in recent decades due to climate change and eutrophication, although most studies are from temperate regions in the Northern hemisphere. This review presents data about cyanobacteria occurrence, dominance, and toxicity events in freshwater bodies in a semiarid region of Northeast Brazil, in the tropical Southern hemisphere. We performed a literature survey of cyanobacteria publications from 1930 to 2016. We made a list of all the dominant species registered in each state, noted their distribution and occurrence of dominance events involving one or more species, and the registered records of toxic blooms, including information about the toxins involved and the range of values. We selected 102 publications that described cyanobacteria occurrence from states in Northeast Brazil; these publications included relevant contributions regarding cyanobacteria distribution, richness, density, and biomass. Forty-nine dominant species were recorded, with the most representation found in the state of Pernambuco (30 spp.). The genera with the highest occurrences were <em>Microcystis</em>, <em>Cylindrospermopsis</em>, <em>Planktothrix</em>, <em>Dolichospermum</em> (=<em>Anabaena</em>), and <em>Geitlerinema</em>, especially the species <em>Cylindrospermopsis raciborskii</em>, <em>Microcystis aeruginosa</em>, and <em>Planktothrix agardhii</em>. Episodes of toxic blooms were observed in four states. Microcystins, cylindrospermopsin, saxitoxins, and anatoxin-a(S) were found to be associated with these blooms. In Northeast Brazil, harmful cyanobacterial blooms are common in urban and public reservoirs. However, in recent years, cyanobacterial blooms in this region have been more intense and perennial, with high biomass occurring throughout the year.</p> Ariadne do Nascimento Moura, Nisia K. C. Aragão-Tavares, Cihelio A. Amorim ##submission.copyrightStatement## http://creativecommons.org/licenses/by-nc/4.0 https://jlimnol.it/index.php/jlimnol/article/view/jlimnol.2017.1646 Wed, 27 Dec 2017 00:00:00 +0100 Effect of temperature on behavior, glycogen content, and mortality in Limnoperna fortunei (Dunker, 1857) (Bivalvia: Mytilidae) https://jlimnol.it/index.php/jlimnol/article/view/jlimnol.2017.1658 <p><em>Limnoperna fortunei</em> (Dunker 1857) is a freshwater mussel with physiological tolerance to different environmental conditions, which may explain its success as an invasive species. The role of abiotic factors in its establishment, abundance and projections of risk of further spread into several areas has been studied. These mussels may respond to multiple environmental stressors, such as temperature, through physiological mechanisms, behavioral responses, mortality or some combination of these. The aim of this study was to investigate the behavioral responses (valve closing), glycogen concentrations and mortality of <em>L. fortunei</em> under four different temperatures (5°C, 10°C, 20°C and 30°C) during a chronic test (30 days). Two-way analysis of variance (ANOVA) was used to compare glycogen concentrations across days of the experiment and at the different temperatures. Differences in valve-closing behavior and mortality among temperatures were tested using repeated-measures ANOVA. We observed that most of the mussels maintained at 5°C closed their valves (74.7±15.3%), indicating that they remain inactive at low temperatures. The glycogen levels significantly differed among the temperatures tested. These differences occurred mainly due to the high glycogen values observed in mussels exposed to 10°C. Stability in glycogen concentrations was observed within each particular temperature. The cumulative mortality was higher at extreme temperatures (5°C and 30°C). The ideal temperature for laboratory maintenance and tests is approximately 20°C. Our data also show that <em>L. fortunei </em>can survive and maintain their energy reserves (glycogen) for several days at 5°C, an important feature related to its invasion success.</p> Jennifer T.M. Andrade, Nelmara I.S. Cordeiro, Lângia C. Montresor, Dalva M.R. Luz, Renata C.R. Luz, Carlos B. Martinez, Jairo Pinheiro, Adriano P. Paglia, Teofânia H.D.A. Vidigal ##submission.copyrightStatement## http://creativecommons.org/licenses/by-nc/4.0 https://jlimnol.it/index.php/jlimnol/article/view/jlimnol.2017.1658 Fri, 22 Dec 2017 00:00:00 +0100 Contribution to the knowledge on the distribution of freshwater sponges – the Danube and Sava rivers case study https://jlimnol.it/index.php/jlimnol/article/view/jlimnol.2017.1677 <p>Sponges in the large rivers within the Danube River Basin (DRB) have not been adequately studied. Hence, the aim of this work was to undertake an investigation on the distribution of sponge species in the Danube and Sava rivers. Out of 88 localities covered by the study, sponges were found at 25 sites only (46 samples in total). By using morphological (light and scanning electron microscopy) and genetic (28S rDNA sequencing) analysis, four species were determined: <em>Ephydatia fluviatilis </em>(Linnaeus, 1759), <em>Spongilla lacustris </em>(Linnaeus, 1759),<em> Eunapius fragilis </em>(Leidy, 1851)<em>, Trochospongilla horrida </em>Weltner, 1893.<em> </em>In the Danube, the predominant species was found to be<em> E. fluviatilis </em>making approximately 80% of collected samples, while in the Sava River <em>S. lacustris</em> dominated, representing 46% of the river sponges. Our work represents one of the few studies on freshwater sponges within the DRB from long stretches of the large lowland rivers (more than 2500 km of the Danube River and about 900 km of the Sava River). Moreover, molecular analysis for the identification of freshwater sponges was applied on the material collected from a wide area, thus contributing to the systematic studies on the distribution and abundance of the European freshwater invertebrate fauna in general.</p> Stefan Andjus, Nadja Nikolic, Valerija Dobricic, Ana Marjanovic, Zoran Gacic, Goran Brankovic, Maja Rakovic, Momir Paunovic ##submission.copyrightStatement## http://creativecommons.org/licenses/by-nc/4.0 https://jlimnol.it/index.php/jlimnol/article/view/jlimnol.2017.1677 Thu, 21 Dec 2017 00:00:00 +0100 Calcite production by the calcifying green alga Phacotus lenticularis https://jlimnol.it/index.php/jlimnol/article/view/jlimnol.2018.1692 <p>The importance of carbonate precipitation by phytoplankton in fresh water lakes has not been sufficiently considered in global carbon cycles and climate change scenarios. The objective of this study was to determine the influence of the calcifying bivalved phytoflagellate <em>Phacotus lenticularis</em> (Ehrenberg) Deising 1866 on the total calcite precipitation in five European hard-water lakes. For this purpose, an accurate mass determination of single <em>Phacotus lenticularis </em>shells was required. We developed a novel methodological approach to precisely determine the volume and mass of the calcified shells. Focused ion beam (FIB) techniques were employed to investigate internal structural features. Thin layer cross-sections of the shell profiles were reproduced and perforation as well as the crystalline structure of the calcite plates were monitored. 3D-shell models were computed by 360° rotation of the shell cross-sections using a CAD 3D imaging software to calculate precise volumes and estimate realistic masses. In contrast to previous estimates, we determined a 2.8-fold higher shell mass of 0.86 ng CaCO<sub>3</sub> (standard deviation SD = 0.18) for the highly massive shells at a mean volume per individual of 334.1 µm³ (SD = 70). An initial shell porosity of less than 5% was derived from thin layer cross-section images, resulting in a presumed mean shell density of 0.0026 ng µm<sup>−3</sup>. The shell diameter was significantly influenced by the lake’s origin. The shells from each lake displayed substantial variations in diameter and shape. The pores in the shells showed two variations. Wider pore canals penetrated the whole shell wall, whereas small, elongated pores were located along the interspaces between calcite crystals with tabular habit. The approximate average dimensions of these calcite plates were 1.0 × 1.6 × 0.2 µm. The mean lateral wall thickness at the rim and centre of the shell were 1.98 µm (SD = 0.42) and 0.79 µm (SD = 0.17), respectively. The average carbonate precipitation by <em>Phacotus lenticularis </em>in relation to the total epilimnetic suspended calcite precipitation was 6.0% in the oligotrophic lake Großer Ostersee (Bavaria, Germany). During the growing season, <em>Phacotus lenticularis </em>contributed up to 21% of the particulate calcium carbonate in the epilimnion. These findings suggest that <em>Phacotus lenticularis </em>should be considered in the assessment of hard-water lake carbon cycling.</p> Sebastian Lenz, Uta Gruenert, Juergen Geist, Michael Stiefel, Maren Lentz, Uta Raeder ##submission.copyrightStatement## http://creativecommons.org/licenses/by-nc/4.0 https://jlimnol.it/index.php/jlimnol/article/view/jlimnol.2018.1692 Thu, 04 Jan 2018 00:00:00 +0100 Geochemistry and mineralogy of a complex sedimentary deposit in the alkaline volcanic Lake Specchio di Venere (Pantelleria Island, south Mediterranean) https://jlimnol.it/index.php/jlimnol/article/view/jlimnol.2018.1722 <p>Specchio di Venere is a peculiar, ambient temperature, geothermal, alkaline lake, with lake water oversaturated in carbonate phase where siliceous stromatolites actively grow despite the undersaturation of silica phases. The most of the main sedimentary structures of this lake have been investigated in recent years, with the exception of the carbonate bank running along the south-western margin of the lake, which is the object of this study. Here we report on the mineralogical and geochemical characterisation of the carbonate bank, based on the study of two cores taken in the area mostly affected by the circulation of fluids of different origin. The ultimate results of our study suggest that silica gel deposits form inside the carbonate bank, following an Alkali-Silica Reaction. These new findings complete the general overview on the sedimentary processes acting in a Lake Specchio di Venere, whose origin is sometimes chemico-physical and sometimes strongly conditioned by microbial activity. </p> Marianna Cangemi, Paolo Madonia, Sergio Speziale ##submission.copyrightStatement## http://creativecommons.org/licenses/by-nc/4.0 https://jlimnol.it/index.php/jlimnol/article/view/jlimnol.2018.1722 Thu, 04 Jan 2018 00:00:00 +0100 Multi-year succession of cyanobacteria blooms in a highland reservoir with changing nutrient status, Guizhou Province, China https://jlimnol.it/index.php/jlimnol/article/view/jlimnol.2018.1636 <p>Over the last 22 years significant phytoplankton changes in Hongfeng lake reservoir have been observed with multiple years of harmful cyanobacteria blooms (cHABs). Fish farming and other anthropogenic activities from 1994-2001 triggered the harmful blooms. Nine years after the cessation of aquaculture, a conversion from problematic species (<em>Microcystis</em> spp, <em>Aphanizomenon flos-aquae</em>) to the less problematic species <em>P</em>. <em>limnetica </em>and other associated non-cyanobacteria taxa was recorded. Through this period of change, trophic factors (bottom-up) were re-examined, and correlations between cHABs and selected environmental variables were observed. Higher temperatures, nutrients (TN, TP) and available light significantly favored the development of <em>Microcystis</em> spp blooms. With declining nutrient loads, and a decline in TP relative to TN there was a competitive shift from <em>Microcystis</em> summer blooms to the growth of <em>Pseudanabaena</em> <em>limnetica </em>and other non-cyanobacteria<em>.</em> <em>Pseudanabaena limnetica </em>was favored over <em>Microcystis</em> spp when temperatures were &lt;20°C and TP was &lt;0.03 mg L<sup>-1</sup>. The apparent species succession to <em>P. limnetica</em> was enhanced by a competitive advantage under varied light conditions. Multiple environmental and biotic conditions (not always nutrients) were driving cHABs. Although only a selected number of environmental variables were examined, the CCA analysis supports observations that temperature and nutrients were associated with the species shift. The replacement of cHABs with the growth of less toxic cyanobacteria like <em>P</em>. <em>limnetica</em>, and other algae creates an interesting scenario (new community condition) for the removal of problematic taxa in reservoir systems. Diverting or controlling blooms will have direct implications on water quality and economic remediation initiatives in reservoir and lake management.</p> Shengxing Long, Paul B. Hamilton, Yang Yang, Jianrong Ma, Ondhoro C. Chobet, Chuan Chen, Anzhi Dang, Zhiwei Liu, Xian Dong, Jiangan Chen ##submission.copyrightStatement## http://creativecommons.org/licenses/by-nc/4.0 https://jlimnol.it/index.php/jlimnol/article/view/jlimnol.2018.1636 Fri, 26 Jan 2018 00:00:00 +0100 Leaching of carbon from native and non-native leaf litter of subtropical riparian forests https://jlimnol.it/index.php/jlimnol/article/view/jlimnol.2018.1662 <p>We evaluated the leaching of dissolved organic and inorganic carbon (DOC and DIC, respectively) from leaf litter of plant species of the native Atlantic Forest and<em> </em>of <em>Pinus elliottii</em> (Engelm.) and <em>Eucalyptus grandis</em> (Hill ex Maiden) forests. We carried out experiments in which leaves from each forest system (native, <em>E. grandis</em>, and <em>P. elliottii</em>) were placed in reactors with sterile water. After 1/4 h, 1 h, 4 h, 12 h, 24 h, and 48 h of incubation, we quantified the concentrations of DIC and DOC of each leachate. The greatest quantity of DIC was leached in the native forest system, whereas the greatest quantity of DOC was leached in the <em>E. grandis </em>forest system. With respect to the period of year, the greatest quantity of DIC was leached in autumn, whereas that of DOC was leached in the summer. Our results demonstrated that the replacement of native species in riparian zones, by non-native forest monocultures, could alter the chemical composition of the water. Finally, the results presented in this paper reinforce the need for a more careful look at ecological processes.</p> Daniel J. da Silva, Alice T. Valduga, Joseline Molozzi, Rodrigo Fornel, Rozane M. Restello, Luiz U. Hepp ##submission.copyrightStatement## http://creativecommons.org/licenses/by-nc/4.0 https://jlimnol.it/index.php/jlimnol/article/view/jlimnol.2018.1662 Wed, 31 Jan 2018 00:00:00 +0100 Interaction between simulated dense Scenedesmus dimorphus (Chlorophyta) bloom and freshwater meta-zooplankton community https://jlimnol.it/index.php/jlimnol/article/view/jlimnol.2018.1742 <p class="MDPI17abstract">Algal bloom has been a subject of much research, especially the occurrence of blue-green algae (cyanobacteria) blooms and their effects on aquatic ecosystems. However, the interaction between green algae blooms and zooplankton community was rarely investigated. In the present study, the effects exerted by <em>Scenedesmus dimorphus</em> (green alga) bloom<em> </em>on the community structure of zooplankton and the top-down control of the bloom process mediated by the zooplankton were evaluated using a series of laboratory cultures. The results showed that a dense <em>S. </em><em>dimorphus</em><em> </em>bloom could change the zooplankton community structure by decreasing its diversity indices, leading to the enrichment of a particular zooplankton species, <em>Brachionus calyciflorus</em>. In the presence of mixed species of zooplankton, the density of <em>S. dimorphus </em>in the <em>culture was decreased as determined by a change in total chlorophyll </em><em>a</em><em> (</em><em>Chl </em><em>a</em><em>) concentration, which was</em><em> about 20</em><em>0</em><em> </em>μg L<sup>-1</sup><em> lower than that of </em><em>the </em><em>zooplankton-free culture.</em><em> </em>Furthermore, the number of species belonging to Cladocera, Copepoda and Rotifera all decreased, with all the cladocerans disappeared in the co-culture within 2 weeks of culturing, while the density of rotifers increased from 818 (±243) ind L<sup>-1</sup> at the time of inoculation to 40733 (±2173) ind L<sup>-1</sup> on the 14<sup>th</sup> day post-inoculation.<em> </em>Grazing of <em>S. </em><em>dimorphus</em><em> </em>by the rotifer <em>B.</em><em> </em><em>calyciflorus</em><em> </em>neutralized its growth, and the gradual increase in <em>B. calyciflorus</em> density eventually led to the collapse of the bloom. Furthermore, grazing by <em>B. calyciflorus</em><em> </em>also led to a decrease in the maximal photochemical efficiency (F<sub>v</sub>/F<sub>m</sub>) of photosystem II (PSII). The combined changes occurring in the zooplankton community structure during the process of <em>S. </em><em>dimorphus </em>bloom and the negative effects of grazing on algal growth, morphology and photosynthetic activities confirmed the key role of zooplankton in the control of algal bloom. The results of the study therefore indicated that dense algal blooms caused by non-toxic algae could still remain a threat to aquatic ecosystems.</p> Zengling Ma, Hengguo Yu, Ronald Thring, Chuanjun Dai, Anglv Shen, Min Zhao ##submission.copyrightStatement## http://creativecommons.org/licenses/by-nc/4.0 https://jlimnol.it/index.php/jlimnol/article/view/jlimnol.2018.1742 Thu, 08 Mar 2018 00:00:00 +0100 Long-term fish monitoring underlines a rising tide of temperature tolerant, rheophilic, benthivore and generalist exotics, irrespective of hydrological conditions https://jlimnol.it/index.php/jlimnol/article/view/jlimnol.2018.1745 <p>The invasion of exotic species is one of the main threats to worldwide biodiversity and can be aided by changes in environmental conditions. We hypothesized that a temporal trend of decreasing discharge and increasing temperature might have favored the invasion of warm-adapted, lentic exotic fish species in the lower Po River, northern Italy. We used presence/absence data over a long-term period (over 20 years) to investigate the dynamics of exotic fish invasion along water temperature and discharge gradients. Mean annual discharge and temperature did not show a clear trend and did not affect exotic fish species invasion, which progressed with time irrespective of these factors. The total number of species fluctuated without a clear trend, which underlined a progressive substitution of native species with exotic ones. Perhaps surprisingly, the community composition changed over time towards more temperature tolerant but also rheophilic, benthivore and generalist fish species. These results highlight how species interactions could be one of the main factors driving the invasion. Furthermore, our data underlines a continuously rising tide of exotics, which questions the success of past control strategies. Considering the current conservation resources limitations, priority should be given to the development of prevention strategies in order to avoid new species introductions.</p> Marco Milardi, Mattia Lanzoni, Anna Gavioli, Elisa Anna Fano, Giuseppe Castaldelli ##submission.copyrightStatement## http://creativecommons.org/licenses/by-nc/4.0 https://jlimnol.it/index.php/jlimnol/article/view/jlimnol.2018.1745 Wed, 21 Feb 2018 00:00:00 +0100 Feeding patterns in Eubranchipus grubii (Dybowski 1860) (Branchiopoda: Anostraca) and its potential influence on the phytoplankton communities of vernal pools https://jlimnol.it/index.php/jlimnol/article/view/jlimnol.2018.1705 <p>Filtration patterns in the fairy shrimp <em>Eubranchipus grubii</em> were analysed under laboratory conditions using water containing phytoplankton from their actual locality in western Poland. After 48 hours of feeding, we compared the structure of algal communities in water samples in treatments with males, females and control. The mean filtration rate for <em>E. grubii</em> was relatively high (14,488 mL h<sup>-1</sup>) in comparison to other crustacean filter feeders and was higher for females than for males. Fairy shrimps grazed effectively on all 11 dominant phytoplankton taxa and there was no sign of overall preferences with regard to taxon, cell volume, length or shape. Female fairy shrimps removed significantly more cells of three taxa (<em>Cryptomonas erosa</em>, <em>C. ovata</em> and <em>Trachelomonas volvocina</em>). The differences between sexes did not depend on the cell volume or length of particular phytoplankton taxa but were significantly related to their initial abundance, initial biomass and shape. The higher the abundance and biomass of the algal taxa, the more intensively it was grazed by females than by males. Females were also observed to graze more on spherical and elongated cells. In conclusion, our results show <em>E. grubii</em> to be an effective, generalist filter feeder capable of significantly influencing the phytoplankton community of a vernal pool. Possible implications of such grazing pressure are also discussed.</p> Sofia Celewicz, Michał Jan Czyż, Bartłomiej Gołdyn ##submission.copyrightStatement## http://creativecommons.org/licenses/by-nc/4.0 https://jlimnol.it/index.php/jlimnol/article/view/jlimnol.2018.1705 Thu, 29 Mar 2018 00:00:00 +0200 Copepods act as omnivores in a (sub)tropical reservoir: Implication for the top-down effect on phytoplankton https://jlimnol.it/index.php/jlimnol/article/view/jlimnol.2018.1748 <p class="a">Tropical reservoirs in China receive a high input of organic matter from surrounding watersheds and this represents a significant resource for zooplankton consumers. Copepods are often the dominant zooplankton group in the tropical systems. Whether copepods tend to be omnivorous and their potential cascading effect on phytoplankton are subjects of debate. We used stable carbon and nitrogen isotope analyses to elucidate the allochthony and trophic positions of two copepod species (<em>Phyllodiaptomus tunguidus</em> and <em>Mesocyclops thermocyclopoides</em>)<em> </em>and one cladoceran species (<em>Diaphanosoma orghidani</em>) over a one-year period in a tropical oligo-mesotrophic reservoir in China. We assumed the filter-feeding <em>D. orghidani</em> was herbivorous and we used it<em> </em>as a baseline indicator of δ<sup>15</sup>N to estimate the trophic position of the two copepods. <em>P. tunguidus</em> and <em>M. thermocyclopoides</em> had an average trophic level that was 0.7 and 0.5 higher, respectively, than that of <em>D. orghidani</em>. <em>M. thermocyclopoides</em> showed seasonal differences in trophic position and an increase in trophic position with rising temperatures, whereas <em>P. tunguidus</em> remained omnivorous throughout the year. All three zooplankton species had a much higher degree of allochthony in the flood season than in the dry season, and their allochthony was positively related to the allochthony of the particulate organic matter input. The two copepods’ omnivorous behavior suggests their allochthony was primarily linked to microbial food web based on the input of terrestrial organic matter. The chlorophyll a to total phosphorus ratio was much higher when <em>P. tunguidus </em>dominated the zooplankton community<em> </em>than when <em>D. orghidani</em> dominated. The ratio was positively related to the ratio of omnivorous adult copepods to cladoceran biomass but not to the zooplankton:phytoplankton biomass ratio. Our results suggest that copepods tended to be omnivorous and relied heavily on allochthonous material in the study reservoir. The indirect cascading effect is likely to be stronger than the direct grazing effect, resulting in a positive effect of copepods on the phytoplankton.</p> Qiuqi Lin, Liang Peng, Yang Yang, Bo-Ping Han ##submission.copyrightStatement## http://creativecommons.org/licenses/by-nc/4.0 https://jlimnol.it/index.php/jlimnol/article/view/jlimnol.2018.1748 Wed, 18 Apr 2018 00:00:00 +0200 Genetic diversity and population differentiation of the freshwater copepod Sinocalanus tenellus (Calanoida, Centropagidae) in China https://jlimnol.it/index.php/jlimnol/article/view/jlimnol.2018.1731 <p>Copepods, present in a wide range of water bodies, are an important component of freshwater ecosystems and their biodiversity has been much studied in marine and freshwater ecosystems. However, no previous genetic data are available that allow an assessment of population-genetic diversity and differentiation of the copepod <em>Sinocalanus tenellus</em> from Chinese freshwaters. We analyzed DNA sequences of the mitochondrial cytochrome c oxidase subunit I (<em>COI</em>) gene from eleven <em>S. tenellus</em> populations (individual lakes) from China, ten of which exhibited a high genetic diversity. Low to high population differentiation was detected among the populations. Interestingly, substantial genetic divergence was detected between WLS (Wuliangsu, in Inner Mongolia) and other locations, indicating the presence of two lineages of <em>S. tenellus</em> in East Asia. Moreover, we found that two distinct clades of <em>S. tenellus</em> were separated by the reference “<em>S. sinensis</em>” clade, suggesting they were parts of a complex of cryptic species of<em> S. tenellus</em>. This study will contribute to an understanding of the diversity and biogeography of copepods in freshwater ecosystem in China.<strong></strong></p> Xiaoyu Wang, Xiaolin Ma, Wei Hu, Mingbo Yin ##submission.copyrightStatement## http://creativecommons.org/licenses/by-nc/4.0 https://jlimnol.it/index.php/jlimnol/article/view/jlimnol.2018.1731 Thu, 12 Apr 2018 00:00:00 +0200 Degree of high phenotypic plasticity in wild populations of Daphnia in early spring https://jlimnol.it/index.php/jlimnol/article/view/jlimnol.2018.1709 <p>Inducible defenses have been empirically known as defensive phenotypes that are triggered by predator kairomones. We hypothesized that morphological defense of wild <em>Daphnia</em> varies not only with predator density, but also with the predator regime in the field. We observed how the morphological defenses of two <em>Daphnia </em>species (<em>D. ambigua</em> and<em> D. pulex</em>) changed according to the population density in the water column at daytime of predatory insect larvae <em>Chaoborus flavicans</em> in Lake Fukami-ike, Japan, from February to July. In both <em>Daphnia</em> species, the inducible defense morphology was highly expressed in March and April. Its degree of expression decreased, and did not change with increases in predator density from May to July. These seasons are generally considered as when the number of the larvae and fish increases, and predation becomes more active due to their growth and breeding. We suggest that the degree of inducible defense of <em>Daphnia</em> is higher at the end of the overwintering season, when <em>Chaoborus</em> larvae began to inhabit the water column during the daytime and is constant in other seasons regardless of predators regime changes. Field observation of wild populations is important for understanding the seasonal changes in the morphology, and to provide more realistic explanations of phenomena in inducible defense.</p> Mariko Nagano, Hideyuki Doi ##submission.copyrightStatement## http://creativecommons.org/licenses/by-nc/4.0 https://jlimnol.it/index.php/jlimnol/article/view/jlimnol.2018.1709 Wed, 21 Mar 2018 00:00:00 +0100 Do environmental variables predict the trophic structure of fish fauna in a subtropical river (Uruguay River Ecoregion)? https://jlimnol.it/index.php/jlimnol/article/view/jlimnol.2018.1738 <p>Trophic interactions represent the routes through which energy flows upwards within ecosystems and the understanding of such structuring under varying environmental conditions is still challenging. Here we test the hypothesis that differences in environmental variables act as environmental filters on the composition and trophic structure of local the fish fauna of a subtropical mountain river. We predict that differences in the trophic structure of the fish fauna occur along the river continuum. Main environmental parameters have been measured and fishes were sampled quarterly between August 2013 and May 2014 at six sampling sites in the main channel of the Pelotas River, Upper Uruguay ecoregion. We collected 3848 individuals belonging to 38 species, 4 orders and 11 families. The most (82.1%) consisted of small- and medium-sized individuals. The species were classified into eight trophic guilds: aquatic insectivorous, carnivorous, detritivorous, detritivorous/aquatic insectivorous, herbivorous, iliophagous, omnivorous and piscivorous. In general, herbivorous and piscivorous guilds were the most representative in both number and biomass. Significant differences detected by Permanova were for richness, numerical abundance and biomass between all the sites sampled. Relationships between the environmental variables and the composition of trophic guilds were observed along the longitudinal gradient by RLQ and fourth-corner analyses. The abundance of guilds omnivorous, aquatic insectivorous and herbivorous increases with higher values of chlorophyll-<em>a</em> and vegetation cover, especially characterizing the upstream sites (S1, S2 and S3). On the other hand, the abundance of the iliophagous, detritivorous/insectivorous and piscivorous guilds increases with greater values of width, temperature, inorganic phosphorus and total solids, a fact observed in downstream sites (S4, S5 and S6). Thus, it was possible to identify a clear variation in the trophic structure of the fish fauna along the Pelotas River (upstream-downstream), in which the local variables were efficient in predicting environmental filters that influence the trophic organization. In this scenario, our study follows the longitudinal model and evidences a greater accumulation of energy in food webs in the upstream-downstream direction, which favors the greatest abundance of piscivorous, detritivorous and iliophagous verified in stretches of greater volume and dimensions of river. These results highlight the importance of the local variables and the interrelationships in the lateral connectivity processes along the river continuum.</p> Mayara P. Neves, Dirceu Baumgartner, Gilmar Baumgartner, Rosilene L. Delariva ##submission.copyrightStatement## http://creativecommons.org/licenses/by-nc/4.0 https://jlimnol.it/index.php/jlimnol/article/view/jlimnol.2018.1738 Wed, 28 Mar 2018 00:00:00 +0200 The impact of global warming on lake surface water temperature in Poland - the application of empirical-statistical downscaling, 1971-2100 https://jlimnol.it/index.php/jlimnol/article/view/jlimnol.2018.1707 <p>The paper presents historical (1971-2015) and scenario-based (2006-2100) changes in surface water temperatures in 10 lakes of Poland. The analysis of historical measurement (1971-2015) showed that mean annual lake surface water temperature (LSWT) was characterised by an increasing tendency by 0.37°C∙dec<sup>-1 </sup>on average, and was higher by 0.01°C∙dec<sup>-1</sup> than air temperature in the analogical period. The highest increase in LSWT was recorded in spring months (April, May) and in summer (July). The future changes in LSWT was based on simulations of 33 AOGCMs available in the scope of CMIP5 project for RCPs: 2.6, 4.5, 6.0, and 8.5. The developed empirical-statistical downscaling models (ESD) use the air temperature field as predictors, with consideration of autocorrelation for two preceding months. ESD models are characterised by high quality of reconstruction of water temperatures in the historical period, with correlation from 0.82 (December, February) to 0.93 (July). The future CMIP5 scenarios for the period 2006-2100 assume an increase in air temperature at the end of the 21<sup>st</sup> century from +1.8°C (RCP 2.6) to +5.1°C (RCP 8.5) in reference to the period 1971-2005. According to the downscaling models, this corresponds to an increase in water temperature in the analysed lakes ranging from +1.4°C (RCP 2.6) to +4.2°C (RCP 8.5) in the years 2081-2100, respectively, with evident variability between the adopted emission paths beginning from the period 2041-2060. At a monthly scale, water temperature will increase the slowest in February (2081-2100: RCP 2.6 = +0.5°C, RCP 8.5 = +1.8°C). The highest increase in temperature will occur from May to August (RCP 8.5 = +6°C in June).</p><p>Substantial effects of transformations of the thermal regime are already observed today, e,g. in the reduction of the ice season length. According to developed scenarios, a further considerable increase in water temperature will be the primary factor determining the transformation of lake ecosystems. The obtained results provide a theoretical basis for further research conducted in the scope of many disciplines, among others hydrology, hydrobiology, ecology, water management, energy production, etc. In the case of Poland, issues related to low water resources per capita are particularly important. Contemporary studies concerning changes in water resources showed that the natural factor playing the key role in their reduction is temperature increase and therefore it should constitute for the possibly fast development of multidisciplinary concepts of mitigation policy to potential impact of climate change.</p><p class="western" lang="en-GB" align="justify"> </p> Bartosz Czernecki, Mariusz Ptak ##submission.copyrightStatement## http://creativecommons.org/licenses/by-nc/4.0 https://jlimnol.it/index.php/jlimnol/article/view/jlimnol.2018.1707 Wed, 02 May 2018 00:00:00 +0200 Erratum - Daphnia magna fitness during low food supply under different water temperature and brownification scenarios https://jlimnol.it/index.php/jlimnol/article/view/jlimnol.2018.1849 <p>This corrects the article entitled “<em>Daphnia magna</em> fitness during low food supply under different water temperature and brownification scenarios" by the authors Andrea Gall, Martin J. Kainz and Serena Rasconi, published with DOI 10.4081/jlimnol.2016.1450. The data on somatic growth rates reported in the results section, paragraph "Life history traits", page 165, were incorrect and the rectified data are presented. Figure 4 has also been corrected accordingly.</p> Andrea Gall, Martin J. Kanz, Serena Rasconi ##submission.copyrightStatement## http://creativecommons.org/licenses/by-nc/4.0 https://jlimnol.it/index.php/jlimnol/article/view/jlimnol.2018.1849 Fri, 31 Aug 2018 08:33:09 +0200