ALBERT

Description:    The heptageniid mayflies Epeorus latifolium and Epeorus l-nigrus are often the dominant species in the upper and midstream areas of Japanese rivers; as such, they play a significant role in river ecosystems. However, although these two species have been identified using the morphological characteristics of the male in its adult stage, it is impossible to differentiate them in their nymphal stage. We conducted a study to elucidate their distribution pattern, i.e., the current distribution of these two species in the Shinano-gawa River basin, based on quantitative field sampling and genetic analysis of nymphs and also some male adults; for these, it was possible to differentiate between the two species reliably. The data collected from the 30 study sites of the 1-year-long study revealed that the E. latifolium and/or E. l-nigrus mayflies are clearly distributed over a very broad area, and they appeared to be the dominant species at about a third of the study sites. Based on our genetic analysis, including several male adult specimens of E. latifolium and E. l-nigrus , it was clearly revealed that E. latifolium and E. l-nigrus respectively form two separate monophyletic clades. That is, E. latifolium and E. l-nigrus are clearly genetically differentiated, and they are considered to each represent a discrete species. Then, we plotted the collection sites of reliably identified specimens of E. latifolium and E. l-nigrus on the Shinano-gawa River basin map. This resultant map clearly displays that E. latifolium is distributed in the upper stream area rather than E. l-nigrus . To conclude, a pronounced ‘habitat segregation’ or ‘current distribution’ is clearly observable. Content Type Journal Article Pages 1-9 DOI 10.1007/s10201-010-0328-y Authors Masaki Ogitani, Shinshu University Department of Environmental System Science, Graduate School of Science and Technology 3-1-1 Asahi Matsumoto Nagano 390-8621 Japan Kazuki Sekiné, Shinshu University Department of Mountain and Environmental Science, Interdisciplinary Graduate School of Science and Technology 3-1-1 Asahi Matsumoto Nagano 390-8621 Japan Koji Tojo, Shinshu University Department of Biology, Faculty of Science 3-1-1 Asahi Matsumoto Nagano 390-8621 Japan Journal Limnology Online ISSN 1439-863X Print ISSN 1439-8621

Description:    As part of the Kushiro Wetland Restoration Project, we evaluated the effect of the tree-cutting (February 2003) on soil water chemistry for 3 years in an alder ( Alnus japonica ) shrubland on the peat soil in the Kushiro Wetland, the largest wetland in Japan. The alder stand was divided into two types; low stature and high stature stands, mean heights being 1.5 and 2.6 m, respectively. The treatment plot with tree cutting and the reference plot measuring 25 m × 25 m each were established in both stands, and a soil incubation experiment was also conducted by trenching the root zone of wetland vegetation in the treatment plots in both stands in the summer of 2004. The tree cutting did not substantially increase the concentrations of ammonium ion (NH 4 + ) and nitrate ion (NO 3 − ) in the soil water, although a gradual and slight increase of NO 3 − concentration was found after the tree-cutting only in the high stature stand (〈10 μmol/l). This increase in the NO 3 − concentration in the high stature stand was probably due to the rhizosphere oxidation of wetland herbaceous vegetation, and was accompanied by the increase of Ca 2+ concentration. The soil incubation experiment showed no significant change of the nitrogen concentration, suggesting that inorganic nitrogen was immobilized and NO 3 − was denitrified intensively in this wetland peat soil. The results of this study suggested that this wetland ecosystem had a high potential to stabilize the soil water chemistry. Content Type Journal Article Pages 1-10 DOI 10.1007/s10201-011-0350-8 Authors Yasunori Nakagawa, Northern Forestry Research and Development Office, Forest Research Station, Field Science Center for Northern Biosphere, Hokkaido University, 250 Tokuda, Nayoro, Hokkaido 096-0071, Japan Takatoshi Nakamura, Faculty of Bioindustry, Tokyo University of Agriculture, 196 Yasaka, Abashiri, Hokkaido 099-2463, Japan Hiroyuki Yamada, Research Faculty of Agriculture, Hokkaido University, Kita 9, Nishi 9, Kita-ku, Sapporo, 060-8589 Japan Futoshi Nakamura, Research Faculty of Agriculture, Hokkaido University, Kita 9, Nishi 9, Kita-ku, Sapporo, 060-8589 Japan Journal Limnology Online ISSN 1439-863X Print ISSN 1439-8621

Description:    We associated nymphs of three Tenuibaetis species with their imagoes by rearing. Herein we redescribe T. flexifemora and T. pseudofrequentus , and also provide description of a new species T. parvipterus . Tenuibaetis pseudofrequentus is morphologically similar to T. flexifemora in the imaginal stage, but we can distinguish these two species by the color patterns of their nymphs and their geographical distribution. Tenuibaetis parvipterus is distinguishable from the other two species by the fore femur, which is not bending distinctly, and abdominal sterna without distinct spots of male imago, reduced hind wing and abdominal sterna without distinct spots of female imago, and difference in color patterns of the abdomen of nymphs. Diagnostic characters of these species were tabulated. Content Type Journal Article Pages 1-11 DOI 10.1007/s10201-010-0342-0 Authors Toshihito Fujitani, Civil Engineering and Eco-technology Consultants Co., Ltd, Higashi-Ikebukuro, Toshima, Tokyo 170-0013, Japan Norio Kobayashi, Institute of River Biology, Yorii, Yorii-cho, Saitama 369-1203, Japan Toshiya Hirowatari, Entomological Laboratory, Graduate School of Life and Environmental Sciences, Osaka Prefecture University, Sakai, Osaka 599-8570, Japan Kazumi Tanida, Laboratory of Ecology, Graduate School of Science, Osaka Prefecture University, Sakai, Osaka 599-8570, Japan Journal Limnology Online ISSN 1439-863X Print ISSN 1439-8621

Description:    The active volcano El Chichón (Chiapas, Mexico) hosts a shallow acidic crater lake. During the period 2001–2007, 26 photographs of the crater lake were taken from the same spot at the eastern crater rim, ~160 m above the crater floor. The size of the lake was extremely variable. Using a GPS track from around the lake shore as a reference, 26 digitized lake outlines were corrected simultaneously for the perspective angle. The corrected lake outlines were superposed, leading to a “morphological map” of a large section of the lake bottom. This map provides insight into the erosive–sedimentary regime of the lake floor. The inner section of the lake is more stable due to the precipitation of sealing clays. This is probably one of the reasons why the El Chichón crater lake has never disappeared during the past 28 years. The sealing clays at the lake bottom can be considered the superficial analog of impermeable clay caps at the depths of hydrothermal systems. The photographic procedure presented here may be useful for other limnological and (volcanic) lake studies aimed at describing lake morphology, and for eventually deducing the surface area and volume of the lake. Content Type Journal Article Pages 1-9 DOI 10.1007/s10201-011-0343-7 Authors Dmitri Rouwet, Istituto Nazionale di Geofisica e Vulcanologia, Sezione di Palermo, Via Ugo La Malfa, 153, 90146 Palermo, Italy Journal Limnology Online ISSN 1439-863X Print ISSN 1439-8621

Description:    In 2003 and 2004, we conducted field investigations of a canal during the summer algal bloom to estimate the in-situ growth rate of Microcystis spp. and its limiting factors. Cellular RNA content (RNA/cell), determined by the real-time PCR method with a primer specific for amplification of Microcystis rRNA, was used as an index of in-situ growth rate. A Microcystis bloom was found in the canal in summer 2004 but not in summer 2003, because of its coldness. Corresponding to this, the average value of RNA/cell in 2004 was significantly higher than that in 2003. Water temperature, light intensity, and NO 3 and PO 4 concentrations were regarded as the factors limiting the in-situ growth rate of Microcystis in the canal, and their effects were quantified on the basis of laboratory experimental data. Effects of temperature and light intensity (photoinhibition by excessive photon flux density) were found to be important in limiting the growth rate, and more severe limitation was suggested in 2003. We then estimated the in-situ growth rate from the combined effect of these limiting factors. The estimated in-situ growth rates correlated significantly with RNA/cell in each year and in the combined (2003 + 2004) data. This agreement between our two different methods for estimation of in-situ growth rate suggests the validity of our approaches. This study was first field application of cellular RNA content as an index of algal growth rate in natural water samples. Content Type Journal Article Pages 1-9 DOI 10.1007/s10201-010-0339-8 Authors Takashi Nagai, National Institute for Environmental Studies, 16-2 Onogawa, Tsukuba, Ibaraki 305-0053, Japan Noriko Tomioka, National Institute for Environmental Studies, 16-2 Onogawa, Tsukuba, Ibaraki 305-0053, Japan Tatsuya Kawasaki, National Institute for Environmental Studies, 16-2 Onogawa, Tsukuba, Ibaraki 305-0053, Japan Akio Imai, National Institute for Environmental Studies, 16-2 Onogawa, Tsukuba, Ibaraki 305-0053, Japan Kazuo Matsushige, National Institute for Environmental Studies, 16-2 Onogawa, Tsukuba, Ibaraki 305-0053, Japan Journal Limnology Online ISSN 1439-863X Print ISSN 1439-8621

Description:    This study aimed at analyzing the phytoplankton structure and dynamics in Paso de las Piedras Reservoir, Argentina, through the study of dominant species, diversity and similarity in relation with the abiotic environment. Samples were collected weekly or biweekly (January 2004–June 2005) at four sampling stations. The reservoir experienced a seasonal progression in phytoplankton composition that underlines six successional periods, each one characterized by the dominance of one or a few species. Cyanobacteria, green algae and diatoms were the most important constituents of the reservoir’s phytoplankton. Cyanobacteria dominated during summer and early autumn, green algae during late autumn and early winter, and diatoms during winter and spring. A high abundance of R. lacustris (Cryptophyceae) was observed during late September and early October. The general pattern of species succession is coherent with the general model of plankton seasonal succession described by the PEG model; however, the major discrepancy is the extremely short clear water phase observed. Successional periods were associated with changes in abiotic variables, and they showed differences in ecological traits. Cyanobacteria-Dictyosphaerium, Cyclotella, Stephanodiscus and Anabaena-diatom periods were characterized by a low number of cells, high diversity, with both dominance and specific richness low. On the contrary, during Cyanobacteria and Cyanobacteria II periods, the highest abundance was observed associated with low diversity and high dominance. Content Type Journal Article Pages 1-13 DOI 10.1007/s10201-011-0347-3 Authors Carolina Fernández, CONICET-BB-IADO (Instituto Argentino de Oceanografía), CC 804, Camino La Carrindanga km 7.5, B8000FWB Bahía Blanca, Argentina Elisa R. Parodi, CONICET-BB-IADO (Instituto Argentino de Oceanografía), CC 804, Camino La Carrindanga km 7.5, B8000FWB Bahía Blanca, Argentina Eduardo J. Cáceres, Laboratorio de Ficología y Micología, Departamento de Biología, Bioquímica y Farmacia, Universidad Nacional del Sur, San Juan 670, B8000ICN Bahía Blanca, Argentina Journal Limnology Online ISSN 1439-863X Print ISSN 1439-8621

Description:    We examined the growth of testate amoebae preying on Microcystis whose physiological states were different in laboratory experiments and a hypertrophic pond. We prepared three experimental systems using water samples dominated by Microcystis aeruginosa : light incubation (control), dark incubation (dark), and light incubation with addition of nitrogen and phosphorus (+NP). In all the systems, the colony density of M. aeruginosa decreased slightly during incubation. Physiological activity of phytoplankton as determined by chlorophyll fluorescence was high and almost constant in the control and +NP systems, whereas it decreased in the dark system. Cell densities of testate amoebae increased in the control and +NP systems, whereas in the dark system they remained low. Thus, growth of the amoebae was low in the systems where physiological activity of Microcystis was low. In a hypertrophic pond, cell density of testate amoebae increased and remained high when M. aeruginosa predominated. Cell density of testate amoebae increased remarkably, simultaneously with the increases in M. aeruginosa colony density and phytoplankton physiological activity. We also found a significant correlation between densities of M. aeruginosa colonies and testate amoebae. We suggested that the physiological activity of Microcystis is one important factor affecting the growth of testate amoebae grazing on Microcystis . Content Type Journal Article Pages 1-7 DOI 10.1007/s10201-010-0341-1 Authors Seiko Mizuta, LAFWEDY, Ehime University, 3-5-7 Tarumi, Matsuyama, Ehime 790-8566, Japan Hiroyuki Imai, LAFWEDY, Ehime University, 3-5-7 Tarumi, Matsuyama, Ehime 790-8566, Japan Kwang-Hyeon Chang, LAFWEDY, Ehime University, 3-5-7 Tarumi, Matsuyama, Ehime 790-8566, Japan Hideyuki Doi, LAFWEDY, Ehime University, 3-5-7 Tarumi, Matsuyama, Ehime 790-8566, Japan Yuichiro Nishibe, LAFWEDY, Ehime University, 3-5-7 Tarumi, Matsuyama, Ehime 790-8566, Japan Shin-ichi Nakano, LAFWEDY, Ehime University, 3-5-7 Tarumi, Matsuyama, Ehime 790-8566, Japan Journal Limnology Online ISSN 1439-863X Print ISSN 1439-8621

Description:    Biological nitrogen fixation (BNF) is one of the major nitrogen inputs into the biosphere, and the nitrogenase iron protein ( nifH ) gene plays important roles in regulating the molecular nitrogen (N 2 ) fixation process. The nifH gene has also been extensively used to study the diversity and function of nitrogen-fixing microorganisms. In this study, we investigated the diversity of the nifH gene by culture-independent methods to analysis the planktonic nitrogen-fixing organisms in Lake Donghu, Wuhan, the largest urban lake in China. Results indicate that nifH gene sequences cloned from planktonic-community DNA showed high similarity to the uncultured cyanobacterial sequences deposited in the GenBank database. Phylogenetic analysis on the basis of the translated amino acid sequences further showed that most nifH clones were closely related to the reported cyanobacterial nifH gene sequences. Results also indicate that there are similar planktonic nitrogen-fixing organisms in the relatively independent areas of Lake Donghu, even though different regions showed a wide gradient in trophic status. These and other observations led us to believe that studies on nifH gene diversity and expression will increase our ability to understand the ecological function of target nitrogen-fixing groups in aquatic ecosystems. Content Type Journal Article Pages 1-7 DOI 10.1007/s10201-010-0340-2 Authors Qingyun Yan, Key Laboratory of Biodiversity and Conservation of Aquatic Organisms, Institute of Hydrobiology, Chinese Academy of Sciences, No. 7 Donghu South Road, 430072 Wuhan, China Yuhe Yu, Key Laboratory of Biodiversity and Conservation of Aquatic Organisms, Institute of Hydrobiology, Chinese Academy of Sciences, No. 7 Donghu South Road, 430072 Wuhan, China Weisong Feng, Key Laboratory of Biodiversity and Conservation of Aquatic Organisms, Institute of Hydrobiology, Chinese Academy of Sciences, No. 7 Donghu South Road, 430072 Wuhan, China Journal Limnology Online ISSN 1439-863X Print ISSN 1439-8621

Description:    To identify the geosmin-producing organisms in Lake Shinji, Japan, we conducted preliminary chemical and biological investigations from April to July 2008, during which odor occurrence was observed. Geosmin was mainly detected in the suspended substance (SS) of lake water, and its concentration corresponded to the cell numbers of Coelosphaerium kuetzingianum (Cyanophyceae) and Monoraphidium contortum . C. kuetzingianum and Pseudodictyosphaerium minusculum (Chlorophyceae; which occurred only in April) were separated from the lake water of 30 April to the lighter, interlayers in a step density gradient medium. The highest concentration of geosmin was detected in the portion of the lightest layer separated from the water sample by gas chromatography mass spectrometry (GC/MS). Observation under optical microscope confirmed that abundant C. kuetzingianum with some P. minusculum and a very rare unknown material was retained in this portion. Similarly C. kuetzingianum was separated by the step density gradient medium from the sediment of 7 May. Abundant C. kuetzingianum with rare bacteria was recognized in the portion of the lightest layer, which contained the highest concentration of geosmin. The cell numbers of C. kuetzingianum correlated with the concentration of geosmin in the separated portions of water samples. These results suggest that C. kuetzingianum probably produced geosmin, although there has been no report about this to now. Content Type Journal Article Pages 1-8 DOI 10.1007/s10201-011-0344-6 Authors Toshiyuki Godo, Shimane Prefectural Institute of Public Health and Environmental Science, 582-1 Nishihamasada, Matsue, Shimane 690-0122, Japan Shuji Ohtani, Faculty of Education, Shimane University, Nishikawatsu, Matsue, Shimane 690-8504, Japan Yukiko Saki, Shimane Prefectural Institute of Public Health and Environmental Science, 582-1 Nishihamasada, Matsue, Shimane 690-0122, Japan Yu Ishitobi, Shimane Prefectural Institute of Public Health and Environmental Science, 582-1 Nishihamasada, Matsue, Shimane 690-0122, Japan Journal Limnology Online ISSN 1439-863X Print ISSN 1439-8621

Description:    To identify the causes of the rapid expansion of the semi-emergent Phalaris arundinacea L. community in a nutrient-loaded river, we investigated the factors that determine the distribution of the Phalaris and other aquatic macrophyte communities and the shoot growth of P. arundinacea . The Phalaris community was distributed through areas with high organic nitrogen (Org-N), total phosphorus (T-P), PO 4 -P and suspended solids (SS) concentrations and low dissolved oxygen (DO). P. arundinacea shoots grow better in deep mud and high SS and T-P, all of which were strongly correlated with slower stream currents. Accordingly, although the concentration of total nitrogen constantly increased from 1985 to 1998, the determining nutrient for the expansion of the Phalaris community and P. arundinacea shoot growth stimulation was phosphorus rather than nitrogen. The Phalaris community increased rapidly between 1991 and 1996, when brief but prominent loadings of phosphorus were observed. We concluded that the Phalaris community was restricted due to phosphorus deficiency under nitrogen excess until 1991 and subsequently rapidly expanded over the channel due to the temporary excess phosphorus present during this period. Thereafter, the rapid expansion of the Phalaris community was maintained by the clogging effect of the floating mats formed by shoots and their remains of P. arundinacea , which results in slower currents. A slower current resulted in low DO, the sedimentation of degraded plant remains (high Org-N), and the adsorption of phosphorus by suspended matter (high SS and T-P). The anaerobic conditions caused by low oxygen and the accumulation of decomposable organic matter ensure the continuous development of the Phalaris community through the release of soluble phosphorus from the sediment. Content Type Journal Article Pages 1-11 DOI 10.1007/s10201-010-0335-z Authors Koji Katagiri, Graduate School of Agriculture, Hokkaido University, Kita-9, Nishi-9, Kitaku, Sapporo, 060-8589 Japan Kazuo Yabe, Graduate School of Design, Sapporo City University, Geijyutuno-mori, Minamiku, Sapporo, 005-0864 Japan Futoshi Nakamura, Graduate School of Agriculture, Hokkaido University, Kita-9, Nishi-9, Kitaku, Sapporo, 060-8589 Japan Yoshifumi Sakurai, Docon Co. Ltd., 1-5-4-1 Atsubetsu-chuo, Atsubetsuku, Sapporo, 004-8585 Japan Journal Limnology Online ISSN 1439-863X Print ISSN 1439-8621