ALBERT

Description:    In the past decade, extreme hydrological events were expressed with extreme droughts and floods in temperate regions. The aim of this paper is to explain how such changes in hydrology can influence cyanobacterial populations in floodplain ecosystems. We therefore analyzed a 6-year (2003–2008) study of the phytoplankton in the Kopački Rit floodplain, one of the largest natural floodplains in the middle section of the Danube River (Europe). During the studied period, the shallow floodplain lake shifted between a state of turbid water, characterized by high phytoplankton biomass and regular appearance of cyanobacteria blooms, to a state of clear water with very low phytoplankton biomass and absence of cyanobacteria, and back to the turbid state. Apparently, the major forces driving the cyclic shift were closely related to extremely high and long-lasting flood events. Significant increase in water level, low hydraulic residence time of water, decrease in transparency and low-light climate, together with mass developed aquatic macrophyte vegetation in the whole inundated floodplain were unfavorable conditions for growth and proliferation of cyanobacteria. With the establishment of the flood regime characterized by long-lasting periods without flooding, in-lake processes prevailed leading to cyanobacterial bloom. The most successful were filamentous non-N-fixing cyanobacteria tolerant to mixed and low-light conditions ( Planktothrix and Limnothrix ) and invasive species Cylindrospermopsis raciborskii. Their massive development led to the establishment of a phytoplankton steady state. All our results demonstrate that the altered intensity and frequency of flood events will have pronounced effects on the appearance of cyanobacterial blooms and generally on alternative stable states in the floodplain. Relating to this, management objectives should be focused on qualifications of changes in hydrology and projecting those effects for potential floodplain restoration. Content Type Journal Article Pages 1-15 DOI 10.1007/s10452-011-9357-9 Authors Melita Mihaljević, Department of Biology, Josip Juraj Strossmayer University of Osijek, Trg Ljudevita Gaja 6, 31000 Osijek, Croatia Filip Stević, Department of Biology, Josip Juraj Strossmayer University of Osijek, Trg Ljudevita Gaja 6, 31000 Osijek, Croatia Journal Aquatic Ecology Online ISSN 1573-5125 Print ISSN 1386-2588

Description:    Barriers (culverts and dams) can impede fish passage and affect the overall habitat connectivity of rivers. However, a challenge lies in how to conceptualize and adequately measure passability at barriers. We hypothesize that estimates of barrier and watershed connectivity are dependent on assumptions about the nature of passability, and how it is measured. Specifically, we compare passability estimates in Terra Nova National Park, Canada for individual barriers for two barrier assessment methods (a rapid assessment and one based on FishXing software), two salmonid species, different fish sizes and swimming speeds, and varying hydrological conditions. Watershed connectivity was calculated using the Dendritic Connectivity Index (DCI). Lastly, we test to see what the impact of the various factors is on the practical goal: prioritizing barriers for restoration. Our results show that barrier passability estimates can vary drastically for some barriers (0–100%). In general, the rapid field-based assessment tended to give more conservative estimates of passability than those based on FishXing. Estimates of watershed connectivity were not as sensitive to the assumptions and methods used (DCI: 40–83). Fish size had the greatest effect on DCI. Importantly, variation in DCI had little impact on the restoration priorities. The same barrier was retained as the top priority 〉96% of the time. Thus, managers wishing to assess barriers for restoration need to carefully consider how passability is to be measured, but can reduce the impact of these decisions by considering barriers in their watershed context using a connectivity index such as the DCI. Content Type Journal Article Pages 1-15 DOI 10.1007/s10452-011-9362-z Authors Christina M. Bourne, Department of Biology, Memorial University, St. John’s, NL A1B 3X9, Canada Dan G. Kehler, Atlantic Service Center, Parks Canada, 1869 Upper Water St., Halifax, NS B3J 1S9, Canada Yolanda F. Wiersma, Department of Biology, Memorial University, St. John’s, NL A1B 3X9, Canada David Cote, Terra Nova National Park, Parks Canada, General Delivery, Glovertown, NL A0G 2L0, Canada Journal Aquatic Ecology Online ISSN 1573-5125 Print ISSN 1386-2588

Description:    The study assessed the composition and abundance of insect assemblages associated with two submerged macrophytes, Lagarosiphon ilicifolius and Vallisneria aethiopica , in fishless ponds. Six ponds were used, with each plant occurring singly in two ponds, whilst the remainder had both plants. The insects were sampled using a 500-μm mesh. The number of insect taxa, diversity and total abundance on Lagarosiphon were greater than on Vallisneria when the plants occurred in separate ponds. In ponds comprising both plants, the total insect abundance on Lagarosiphon was greater than on Vallisneria . In all ponds, anisopteran naiads were dominant. Hemicordulia , Diplacodes and Trithemis made up 36.2, 27.1 and 15.2%, respectively, of the total number of insects on Lagarosiphon in single plant ponds. Trithemis was the only odonate in ponds comprised exclusively of Vallisneria and made up 68.7% of insects. In ponds that were cultured with both plants, four anisopteran taxa, Hemicordulia , Diplacodes , Trithemis and Tramea, were collected. In single plant ponds, the body-size class distribution of naiads on Lagarosiphon was characterised by a broader range, with significantly greater numbers of smaller and larger size classes than on Vallisneria (Kolmogorov–Smirnov test, P  〈 0.05). The study shows that in fishless waters, epiphytic insect assemblages may differ between the two plant species, especially when they are widely separated in space, probably due to greater predator–prey interactions on Vallisneria than on Lagarosiphon . The two plants may also differentially affect water physicochemical conditions, which may possibly influence insect ovipositing behaviour, and so affect insect community assemblage. Content Type Journal Article Pages 1-12 DOI 10.1007/s10452-011-9363-y Authors Crispen Phiri, University Lake Kariba Research Station, P.O. Box 48, Kariba, Zimbabwe Albert Chakona, South African Institute for Aquatic Biodiversity, Private Bag 1015, Grahamstown, 6140 South Africa Jenny A. Day, Freshwater Research Unit, Zoology Department, University of Cape Town, 7707 Rhodes Gift, Western Cape, South Africa Journal Aquatic Ecology Online ISSN 1573-5125 Print ISSN 1386-2588

Description:    The impact of different land-use types on species is traditionally estimated by correlating landscape proportions recorded in buffer areas around focal points with species data observed at these sites. If a high proportion of a specific land-use type exists within a small radius, it will be accumulated in larger buffers and may confound the interpretation at larger scales. We sampled freshwater invertebrates in ten streams using cages with artificial substrate and compared the effects of arable land proportions calculated in disc-shaped buffers of increasing radius versus areas calculated from non-overlapping rings of increasing radius. We hypothesize that (1) the accumulative disc-based approach leads to confounding effects across increasing buffer size and that (2) the use of ring-based methods facilitates the identification of relevant scales for conservation measures. The abundance of crustaceans showed a positive relationship with arable land proportions, but Plecoptera abundance and the taxonomic richness of Ephemeroptera and Plecoptera decreased with increasing arable land proportions in the surrounding landscape. Our results further support the presence of confounding effects in disc-based analyses, as correlations between arable land proportions and Crustacea, or Plecoptera, respectively, were affected by the accumulation of small-scale area proportions. The distance at which arable land proportions significantly affected benthic fauna in freshwater streams was consistently shorter if calculated from rings rather than from discs. Although an a priori definition of ring width introduces new challenges, a combined use of disc- and ring-based techniques for the estimation of land-use effects may substantially improve the realization of conservation and protection measures in terrestrial and aquatic systems. Content Type Journal Article Pages 1-6 DOI 10.1007/s10452-011-9358-8 Authors Christine Schneider, Department of Animal Ecology, Justus Liebig University Giessen, Heinrich-Buff-Ring 26-32, 35392 Giessen, Germany Klemens Ekschmitt, Department of Animal Ecology, Justus Liebig University Giessen, Heinrich-Buff-Ring 26-32, 35392 Giessen, Germany Volkmar Wolters, Department of Animal Ecology, Justus Liebig University Giessen, Heinrich-Buff-Ring 26-32, 35392 Giessen, Germany Klaus Birkhofer, Department of Animal Ecology, Justus Liebig University Giessen, Heinrich-Buff-Ring 26-32, 35392 Giessen, Germany Journal Aquatic Ecology Online ISSN 1573-5125 Print ISSN 1386-2588

Description:    Climate change has been suggested to lead to higher temperature and increased heterotrophy in aquatic systems. The aim of this study was to test how these two factors affect metazooplankton and food web efficiency (FWE was defined as metazooplankton production divided by basal production). We tested the following hypotheses: (1) that lower metazooplankton production and lower FWE would be found in a food web based on heterotrophic production (bacteria) relative to one based on autotrophic production (phytoplankton), since the former induces a larger number of trophic levels; (2) the metazooplankton in the heterotrophic food web would contain less essential fatty acids than those from the autotrophic food web; and (3) that higher temperature would lead to increased FWE. To test these hypotheses, a mesocosm experiment was established at two different temperatures (5 and 10°C) with a dominance of either autotrophic (NP) or heterotrophic basal production (CNP). Metazooplankton production increased with temperature, but was not significantly affected by differences in basal production. However, increased heterotrophy did lead to decreased fatty acid content and lower individual weight in the zooplankton. FWE increased with autotrophy and temperature in the following order: 5CNP 〈 10CNP 〈 5NP 〈 10NP. Our results indicate that in the climate change scenario we considered, the temperature will have a positive effect on FWE, whereas the increase in heterotrophy will have a negative effect on FWE. Furthermore, the quality and individual weight of the metazooplankton will be reduced, with possible negative effects on higher trophic levels. Content Type Journal Article Pages 1-17 DOI 10.1007/s10452-011-9355-y Authors Kristin Dahlgren, Department of Ecology and Environmental Sciences, Umeå University, 90187 Umeå, Sweden Ann-Kristin Eriksson Wiklund, Department of Applied Environmental Science, Stockholm University, 10691 Stockholm, Sweden Agneta Andersson, Department of Ecology and Environmental Sciences, Umeå University, 90187 Umeå, Sweden Journal Aquatic Ecology Online ISSN 1573-5125 Print ISSN 1386-2588

Description:    We checked whether the induced anti-predator defences of zebra mussels are able to affect the predation success of roach, being one of the most efficient zebra mussel predators in Europe. Previously, several anti-predator defences of mussels have been observed in the presence of roach, including stronger attachment, aggregation forming and inhibition of upward movement. However, the actual efficiency of these responses to reduce the mussel vulnerability to predation was unknown. To check the effectiveness of attachment strength, we exposed mussels for 6 (strong attachment), 1 (weak attachment) or 0 (unattached) days in ceramic trays and then presented the trays to fish in an experimental tank. To test the effectiveness of aggregation, we glued mussels to the trays in groups of three (touching one another) or singly using denture glue and exposed them to fish. To check the effect of the vertical position, we glued mussels with denture glue to the bottom and 10, 20 and 30 cm above the bottom of the tank with fish. After 1-h exposure, we determined the percentages of consumed mussels. Roach predation rate was lowest on strongly attached mussels, intermediate on weakly attached mussels and highest on unattached mussels. Aggregated mussels were less frequently consumed than singletons. Conversely, the vertical position of mussels did not affect the roach predation success. Our study demonstrates that the behavioural defences exhibited by zebra mussels can increase their survival in the presence of predators and thus emphasizes the importance of the anti-predator behaviour of this species. Content Type Journal Article Pages 1-10 DOI 10.1007/s10452-011-9359-7 Authors Jarosław Kobak, Department of Invertebrate Zoology, Institute of General and Molecular Biology, Nicolaus Copernicus University, Toruń, Poland Tomasz Kakareko, Department of Hydrobiology, Institute of Ecology and Environmental Protection, Nicolaus Copernicus University, Toruń, Poland Journal Aquatic Ecology Online ISSN 1573-5125 Print ISSN 1386-2588

Description:    The impacts that predators have on prey behavior, growth, survival, and ultimately the composition of many ecological communities are mediated by prey defenses and the susceptibility of prey to predators. We hypothesized that prey populations inhabiting short-lived, species-poor, aquatic environments should lack significant morphological, developmental, and behavioral responses to predators and are therefore highly susceptible to predation. Furthermore, we predicted that the resultant decrease in prey density and increase in per capita resources due to high susceptibility to predators should enhance overall cohort survival because of enhanced growth of surviving prey. To test these ideas, we performed laboratory and outdoor mesocosm experiments to disentangle multiple effects of predators on an anuran ( Scaphiopus couchii ); a species highly adapted to breeding in ephemeral habitats and that has one of the shortest larval periods of all anurans. Chemical (presence of predator) and lethal predator cues (predator plus consumed conspecific) elicited no response in behavior, development, or morphology, indicating a lack of defensive mechanisms. Survivorship was significantly reduced in treatments where tadpoles were exposed to predators. However, this reduction in prey density led to accelerated time to metamorphosis, conferring an advantage to survivors who must metamorphose before ephemeral ponds dry. Our experiments demonstrated that in short-lived environments, prey may exhibit little or no response to the presence of predators presumably because selection for anti-predator defenses is countered by selection for rapid metamorphosis. However, predation actually resulted in an increase in overall cohort survival. Although predators are relatively rare in highly ephemeral aquatic environments, they may play an important role in facilitating the long-term persistence of their prey by reducing prey density. Content Type Journal Article Pages 1-9 DOI 10.1007/s10452-011-9356-x Authors Gage H. Dayton, Interdisciplinary Research Program in Ecology and Evolutionary Biology, Department of Wildlife and Fisheries Sciences, Texas A&M University, Tamus 2258, College Station, TX 77843-2258, USA Lee A. Fitzgerald, Interdisciplinary Research Program in Ecology and Evolutionary Biology, Department of Wildlife and Fisheries Sciences, Texas A&M University, Tamus 2258, College Station, TX 77843-2258, USA Journal Aquatic Ecology Online ISSN 1573-5125 Print ISSN 1386-2588

Description:    The economic value of ecosystem services of vegetated habitats (seagrass and macroalgal beds) has been estimated to be among the highest of the various ecosystems on earth. However, fish production has not been included in the evaluations due to the difficulty of quantitative estimation of fish production in the field. In the present study, annual production and economic value of wild juvenile black rockfish, Sebastes cheni , a dominant fish species in seagrass and macroalgal beds in the central Seto Inland Sea were estimated. Juvenile S. cheni migrated into vegetated habitats at about 20 mm total length (TL) and grew up to about 60 mm TL by late May. Juvenile abundance was highest in April (2007) or March (2008). Eight cohorts with the same extrusion period (each cohort covering a 10-day period) were identified using otolith daily increments. The annual estimates of S. cheni juvenile production were 13,080 g ha −1 year −1 in 2007 and 18,360 g −1  year −1 in 2008. Based on the unit price of artificially raised S. cheni juveniles, the economic value of the annual wild juvenile production was converted to 654,000 JPY (Japanese yen: 100 JPY = ca. 1 USD) ha −1 year −1 for 2007 and 918,000 JPY ha −1 year −1 for 2008. Analyses of stomach contents and stable isotope (δ 13 C or δ 15 N) showed that juvenile S. cheni were highly dependent on copepods. The planktonic trophic pathway originating from phytoplankton supports the majority of the juvenile black rockfish production during the post-migration period (20–60 mm TL) in the seagrass and macroalgal beds through the production of copepod zooplankton. The total economic value of the ecosystem services of the vegetated habitat is suggested to be much higher than estimates in previous studies if the provisioning and regulating services which originate from fish production were included in the estimates. Content Type Journal Article Pages 1-10 DOI 10.1007/s10452-011-9360-1 Authors Yasuhiro Kamimura, Takehara Marine Science Station, Center for Education and Research of Setouchi Field Science, Graduate School of Biosphere Science, Hiroshima University, 5-8-1 Minato-machi, Takehara, Hiroshima, 725-0024 Japan Akihide Kasai, Division of Applied Bioscience, Graduate School of Agriculture, Kyoto University, Sakyo, Kyoto, 606-8502 Japan Jun Shoji, Takehara Marine Science Station, Center for Education and Research of Setouchi Field Science, Graduate School of Biosphere Science, Hiroshima University, 5-8-1 Minato-machi, Takehara, Hiroshima, 725-0024 Japan Journal Aquatic Ecology Online ISSN 1573-5125 Print ISSN 1386-2588

Description:    In aquatic ecosystems, fish play a key role in parasite accumulation and transmission to predacious animals. In the present study, realized on seven populations of a small cyprinid fish species, the European bitterling Rhodeus amarus , we investigated (1) the role of the European bitterling as a potential intermediate or paratenic host, (2) the ability of the fish to accumulate parasites with similar final host group, and (3) its significance as a potential source of parasite infection in the ecosystem in respect to habitat characteristics. A total of 36 parasite species were recorded; 31 species (90% of all parasite specimens) were classified as endoparasites. Most of the endoparasites were found in the larval life stage, using bitterling as an intermediate or paratenic host. In particular, parasite community structure showed significantly higher proportions of allogenic parasites in comparison with autogenic. The supposed co-occurrence of parasite species with identical final host groups showed only a weak association. The adjacent reservoir areas were a significant determinant of both the total and infracommunity parasite species richness and for the mean parasite abundance. No relationship between the distance of sampling site from the adjacent reservoir and parasite community characteristics was found. As a small-sized fish with a wide distribution range and high local abundances, the European bitterling can represent a natural prey for a wide range of piscivorous predators. Due to its susceptibility to the number of larval endoparasites, this fish species may therefore fulfill the role as important transmitter of parasites to their final hosts. Content Type Journal Article Pages 1-11 DOI 10.1007/s10452-011-9361-0 Authors Martina Dávidová, Department of Botany and Zoology, Faculty of Science, Masaryk University, Kotlářská 2, 611 37 Brno, Czech Republic Radim Blažek, Department of Botany and Zoology, Faculty of Science, Masaryk University, Kotlářská 2, 611 37 Brno, Czech Republic Teodora Trichkova, Institute of Biodiversity and Ecosystem Research, Bulgarian Academy of Sciences, Gagarin str. 2, 1113 Sofia, Bulgaria Emmanuil Koutrakis, Fisheries Research Institute, National Agricultural Research Foundation, Nea Peramos, 640 07 Kavala, Greece Özcan Gaygusuz, Faculty of Fisheries, Istanbul University, Ordu Cad. No 200, Laleli, 34470 Istanbul, Turkey Ertan Ercan, Faculty of Aquaculture and Fisheries Biology, University of Mugla, 48000 Kötekli, Turkey Markéta Ondračková, Department of Botany and Zoology, Faculty of Science, Masaryk University, Kotlářská 2, 611 37 Brno, Czech Republic Journal Aquatic Ecology Online ISSN 1573-5125 Print ISSN 1386-2588

Description:    We tested the hypothesis that structural complexity is an important factor influencing the abundance and taxon richness of microfauna (e.g., rotifers, copepods, cladocerans) in littoral habitats. Research on littoral microfauna has to date focused mainly on field observations, which commonly show microfauna have preference for some macrophytes over others. However, while such studies commonly conclude that macrophyte architecture is a major determinant of these variations, independent factors may also be responsible (e.g., differences in macrophyte ages, differences in macrophyte bed densities and the depth of the respective macrophyte beds sampled). We used artificial macrophytes with three levels of complexity to keep the surface area and mass of the substrate sampled constant, and to control for confounding factors not related to the complexity of the plants. Our results support the hypothesis that structural complexity is an important factor influencing abundance and taxon richness, independent of other potential confounding factors. Microfaunal (mainly rotifer) abundance and richness were generally greater on more complex artificial macrophytes, likely a result of more complex substrates (1) providing a greater variety of habitat, (2) supporting a greater concentration or variety of food and/or (3) affording greater protection against predators. Less mobile surface-associated (i.e., benthic/periphytic) taxa were found to discriminate among substrates, whereas the abundance and richness of planktonic species were not affected by complexity level. Relatively low abundances and taxon richness of microfauna recorded in control samples, which did not contain artificial macrophytes, supports the contention that vegetated areas sustain a higher abundance and variety of species than non-vegetated areas. Content Type Journal Article Pages 1-9 DOI 10.1007/s10452-011-9353-0 Authors Paloma Lucena-Moya, Department of Ecology and Animal Biology, Faculty of Sciences, University of Vigo, 36310 Vigo, Spain Ian C. Duggan, Department of Biological Sciences, Centre for Biodiversity and Ecology Research, The University of Waikato, Private Bag 3105, Hamilton, New Zealand Journal Aquatic Ecology Online ISSN 1573-5125 Print ISSN 1386-2588