研究者詳細 - 伴　修平

論文 - 伴　修平

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Cumulative reproduction model to quantify the production of the invasive species Arctodiaptomus dorsalis (Calanoida, Copepoda) 査読

Takahashi A., Ban S., Papa R.D.S., Tordesillas D.T., Dur G.

Ecological Modelling 482 2023年8月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Ecological Modelling

Arctodiaptomus dorsalis is an invasive calanoid copepod originally from America and has recently established a population in Lake Taal in the Philippines. It has been proposed that eutrophication due to aquaculture contributes to the establishment and success of this species. This study aimed to clarify this hypothesis by quantifying the effect of increasing food concentration on the reproduction of A. dorsalis using an Individual-Based Model. We parameterized food concentration-dependent equations to simulate the effect of different food concentration on the reproductive traits (latency time, embryonic development time, clutch size, and hatching success) of this species using data from the literature and simulated the reproduction of 1000 independent females for 20 days at different food concentration, taking into account the variability among individuals. The simulation results showed that the cumulative production of eggs and offspring increased continuously with time when the food concentration was above 3.2 × 104 cells mL−1, suggesting that this value was the threshold concentration required for stable reproduction of A. dorsalis. This value is not particularly low compared to other copepods. Hence, our result revealed that the food use efficiency of A. dorsalis is not particularly outstanding and urge the need of a comparison with native species to confirm a possible superiority. We suggest that A. dorsalis has filled the ecological niche left vacant by the disappearance of the original species due to the deterioration of water quality caused by the eutrophication of the lake. The reproductive cycle model developed in this study constitutes a necessary step in the development of a complete population dynamics model, which can help clarify the invasive abilities of A. dorsalis.

DOI： 10.1016/j.ecolmodel.2023.110398

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Sedimentary DNA can reveal the past population dynamics of a pelagic copepod 査読

Nakane K., Liu X., Doi H., Dur G., Kuwae M., Ban S., Tsugeki N.

Freshwater Biology 2023年1月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Freshwater Biology

Copepods play a key trophic role as secondary producers, transferring primary production to higher trophic levels such as fish. Copepod production contributes significantly to successful fish recruitment. Despite their importance, knowledge of copepod dynamics over several decades remains limited due to the lack of long-term data series with adequate sampling and analysis. However, an understanding of long-term copepod dynamics is urgently required to strive toward better management for sustainable aquatic ecosystems and fish recruitment. Sedimentary DNA (sedDNA) has been developing as a useful tool for reconstructing past plankton dynamics. This study evaluates whether sedDNA targeting the pelagic copepod, Eodiaptomus japonicus, in Lake Biwa (Japan) can be an effective tool for elucidating its past population dynamics. We applied a quantitative polymerase chain reaction method targeting the mitochondrial cytochrome c oxidase subunit I gene on two sediment cores and compared the detected sedDNA concentrations with the unique long-term dataset of demographic traits, biomass, specific growth rate, production, subitaneous eggs, and resting eggs of E. japonicus. The sedDNA concentration of E. japonicus recovered from sediment layers correlated significantly with in situ production, biomass, and production of immediately hatching eggs but not with resting eggs or specific growth rate. Our study provides evidence for the effective use of sedDNA as a tracking tool for assessing past copepod production dynamics.

DOI： 10.1111/fwb.14096

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The first report of the non-indigenous Chydorus brevilabris Frey, 1980 (Crustacea: Cladocera) in Asian freshwaters 査読

Makino, W., H. Suzuki, Y. Otake, S. Ban and J. Urabe

Limnology 2023年

Causal networks of phytoplankton diversity and biomass are modulated by environmental context 査読

Chang C.W., Miki T., Ye H., Souissi S., Adrian R., Anneville O., Agasild H., Ban S., Be’eri-Shlevin Y., Chiang Y.R., Feuchtmayr H., Gal G., Ichise S., Kagami M., Kumagai M., Liu X., Matsuzaki S.I.S., Manca M.M., Nõges P., Piscia R., Rogora M., Shiah F.K., Thackeray S.J., Widdicombe C.E., Wu J.T., Zohary T., Hsieh C.h.

Nature Communications 13 ( 1 ) 2022年12月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Nature Communications

Untangling causal links and feedbacks among biodiversity, ecosystem functioning, and environmental factors is challenging due to their complex and context-dependent interactions (e.g., a nutrient-dependent relationship between diversity and biomass). Consequently, studies that only consider separable, unidirectional effects can produce divergent conclusions and equivocal ecological implications. To address this complexity, we use empirical dynamic modeling to assemble causal networks for 19 natural aquatic ecosystems (N24◦~N58◦) and quantified strengths of feedbacks among phytoplankton diversity, phytoplankton biomass, and environmental factors. Through a cross-system comparison, we identify macroecological patterns; in more diverse, oligotrophic ecosystems, biodiversity effects are more important than environmental effects (nutrients and temperature) as drivers of biomass. Furthermore, feedback strengths vary with productivity. In warm, productive systems, strong nitrate-mediated feedbacks usually prevail, whereas there are strong, phosphate-mediated feedbacks in cold, less productive systems. Our findings, based on recovered feedbacks, highlight the importance of a network view in future ecosystem management.

DOI： 10.1038/s41467-022-28761-3

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A new sampling method with zirconium-loaded resin for phosphate oxygen isotope analysis in oligotrophic freshwater systems 査読

Ishida T., Tayasu I., Onodera S.i., Ban S., Okuda N.

Rapid Communications in Mass Spectrometry 36 ( 22 ) 2022年11月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Rapid Communications in Mass Spectrometry

Rationale: The phosphate oxygen isotope ratio ((Formula presented.)) is a useful technique to trace the sources and biogeochemical cycles of phosphorus (P) in aquatic ecosystems. However, (Formula presented.) has not been widely used in oligotrophic freshwater systems due to technical and methodological difficulties in collecting sufficient phosphate (PO4) for the (Formula presented.) analysis, which sometimes requires hundreds of liters of the water sample. In this study, a new approach (PaS-Zir) was developed for the (Formula presented.) analysis in oligotrophic freshwater systems using zirconium (Zr)-loaded (ZrIRC) resin, which has a high affinity for PO4. Methods: ZrClO2 was added to Amberlite IRC748 to obtain the ZrIRC resin. The adsorption/desorption experiment using KH2PO4 with a known value of (Formula presented.) was conducted to determine the adsorption/desorption properties of the resin and the likelihood of isotopic fractionation. By installing mesh bags filled with the resin, the PaS-Zir approach was used in two rivers with low PO4 concentrations (0.2 and 5.3 μmol/L). A conventional sampling method was also performed in the study river with a higher PO4 concentration to validate the efficacy of the PaS-Zir method. Results: The adsorption/desorption experiment demonstrated that the ZrIRC resin possessed a sufficient adsorption capacity (153 μmol/resin-mL) and exhibited little isotopic fractionation during the adsorption/desorption processes. Using the PaS-Zir method, we were able to collect sufficient PO4 samples for the (Formula presented.) analysis from the rivers within at least 4 days of mesh bag installation. The (Formula presented.) values (14.2‰ ± 0.2‰) obtained using the PaS-Zir method were comparable to those obtained using the conventional method (14.0‰ ± 0.03‰). Conclusion: We proved that the PaS-Zir method is applicable to oligotrophic freshwater systems and is generally more efficient than the conventional method. In addition, our method is useful for improving the understanding of the P dynamics of oligotrophic ecosystems because of the extremely low concentration of PO4 commonly found in them, which are often prone to P pollution.

DOI： 10.1002/rcm.9393

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Disrupted seasonal cycle of the warm-adapted and main zooplankter of Lake Biwa, Japan 査読

Dur G., Liu X., Sakai Y., Hsieh C.h., Ban S., Souissi S.

Journal of Great Lakes Research 2022年1月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Journal of Great Lakes Research

The seasonal cycle is an important feature of life, leading to the succession of different species and allowing them to share a common environment. Disruption in the seasonal cycle of many species has been reported, but the source of disruption varies from species to species. Lacustrine zooplankton species are widely acknowledged to respond to climate-induced, thermal and trophic variations. Here, we discuss the case of a warm-adapted copepod in Lake Biwa (i.e., Eodiaptomus japonicus), which experienced changes in trophic status and thermal regime over four decades (1966–2010). We investigated the phenological response of E. japonicus to these changes over this period and aimed to identify the sources of the observed variations. The combined results of wavelet analysis and cluster analysis indicated that E. japonicus exhibited different seasonal cycles during the study period. The common unimodal seasonal cycle of the copepod was disrupted on several occasions during which it presented sometimes two or three modes. Wavelet coherence analysis revealed a strong stationary correlation with lake temperature for the total abundance, the clutch size, and the birth rate, but a transient correlation with the body size of females at the annual scale. No coherence was found with food proxies. Discriminant analysis between unimodal and plurimodal seasonal cycles highlighted the effect of low temperature and high predation in leading to plurimodal cycles. Our study emphasizes the need for considering the seasonality of both lower and higher trophic levels for understanding zooplankton phenology.

DOI： 10.1016/j.jglr.2022.06.001

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Mate-seeking behavior in the calanoid copepod Eodiaptomus japonicus. 査読国際誌

Liu, X., Y. Nakamoto, D. Gaël and S. Ban

Journal of Plankton Research 44 961 - 965 2022年

Effect of acute acidic stress on survival and metabolic activity of zooplankton from Lake Biwa, Japan. 査読国際誌

Gao, H., X. Liu and S. Ban

Inland Waters 12 488 - 498 2022年

A new method for phosphate purification for oxygen isotope ratio analysis in freshwater and soil extracts using solid-phase extraction with zirconium-loaded resin 査読国際誌

Ishida, T., H. Kamiya, Y. Uehara, T. Kato, S. Sugahara, S.-i. Onodera, S. Ban, A. Payton, I. Tayasu and N. Okuda

Rapid Communications in Mass Spectrometry 36 ( e9384 ) 2022年

Enhancement of algal growth by Mg<sup>2+</sup> released from anaerobic digestion effluent of aquatic macrophytes through photolysis 査読

Qian J., Shimotori K., Liu X., Ban S., Akizuki S.i., Fujiwara M., Kodera T., Toda T., Imai A.

Biochemical Engineering Journal 172 2021年8月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Biochemical Engineering Journal

Anaerobic digestion effluent (ADE) from aquatic macrophytes (Egeria densa, Elodea nuttallii, Ceratophyllum demersum and Potamogeton maackianus) contains insufficient available magnesium ions (Mg2+) to achieve maximum algal yield and nutrient removal, although Mg concentrations are not scarce at 6–10 mg L−1. Unavailable Mg2+ may be bound into complexes with dissolved organic matter (DOM). We determined the effects of ADE exposure to ultraviolet C (UVC), and degradation of DOM, on Mg availability for growth of Chlorella sorokiniana. Molecular sizes of DOM binding Mg2+ were identified with high-performance size-exclusion chromatography. The results demonstrated that 3 h exposure to UVC can decompose DOM, and release sufficient amounts of available Mg2+, i.e. 0.09 mg from 1 mg of dissolved organic carbon, thus enhancing algal yield and nutrient removal. Almost 50 % of Mg in the ADE was bound by DOM with a molecular size of 400–1170 Da as organic complexes, and the remaining Mg was bound by DOM of < 240 Da and/or Mg2+ and inorganic Mg complexes.

DOI： 10.1016/j.bej.2021.108065

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Climate change drives widespread shifts in lake thermal habitat 査読

Kraemer B.M., Pilla R.M., Woolway R.I., Anneville O., Ban S., Colom-Montero W., Devlin S.P., Dokulil M.T., Gaiser E.E., Hambright K.D., Hessen D.O., Higgins S.N., Jöhnk K.D., Keller W., Knoll L.B., Leavitt P.R., Lepori F., Luger M.S., Maberly S.C., Müller-Navarra D.C., Paterson A.M., Pierson D.C., Richardson D.C., Rogora M., Rusak J.A., Sadro S., Salmaso N., Schmid M., Silow E.A., Sommaruga R., Stelzer J.A.A., Straile D., Thiery W., Timofeyev M.A., Verburg P., Weyhenmeyer G.A., Adrian R.

Nature Climate Change 11 ( 6 ) 521 - 529 2021年6月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Nature Climate Change

Lake surfaces are warming worldwide, raising concerns about lake organism responses to thermal habitat changes. Species may cope with temperature increases by shifting their seasonality or their depth to track suitable thermal habitats, but these responses may be constrained by ecological interactions, life histories or limiting resources. Here we use 32 million temperature measurements from 139 lakes to quantify thermal habitat change (percentage of non-overlap) and assess how this change is exacerbated by potential habitat constraints. Long-term temperature change resulted in an average 6.2% non-overlap between thermal habitats in baseline (1978–1995) and recent (1996–2013) time periods, with non-overlap increasing to 19.4% on average when habitats were restricted by season and depth. Tropical lakes exhibited substantially higher thermal non-overlap compared with lakes at other latitudes. Lakes with high thermal habitat change coincided with those having numerous endemic species, suggesting that conservation actions should consider thermal habitat change to preserve lake biodiversity.

DOI： 10.1038/s41558-021-01060-3

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Temporal variation in community structure of zoosporic fungi in Lake Biwa, Japan 査読

Song P., Yi R., Tanabe S., Goto N., Seto K., Kagami M., Ban S.

Aquatic Microbial Ecology 87 17 - 28 2021年1月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Aquatic Microbial Ecology

Zoosporic fungi play an important role in aquatic environments, but their diversity, especially that of parasitic fungi of phytoplankton, has still not been fully revealed. We conducted monthly analyses of the community structure of zoosporic fungi at a pelagic site in Lake Biwa, Japan, from May to December 2016. Metabarcoding analysis, targeted to a large subunit region of ribosomal DNA in the nano-size fraction of particles (2-20 μm), was carried out on the samples. We also counted large phytoplankton and chytrid sporangia attached to the hosts. We detected 3 zoosporic fungal phyla (Blastocladiomycota, Chytridiomycota and Cryptomycota) within 107 operational taxonomic units (OTUs), in which Chytridiomycota was the most diverse and abundant phylum. Few fungal OTUs overlapped between months, and specific communities were detected in each month. These results showed that diverse zoosporic fungi with high temporal variability inhabited the lake. Five large phytoplankton species were found to be infected by chytrids: Staurastrum dorsidentiferum, S. rotula, Closterium aciculare, Asterionella formosa and Aulacoseira granulata. Some chytrids were detected by metabarcoding analysis: Zygophlyctis asterionellae infecting A. formosa, Staurastromyces oculus infecting S. dorsidentiferum and Pendulichytrium sphaericum infecting A. granulata. One OTU detected in association with infected C. aciculare by microscopic counting might have been an obligate parasitic chytrid of C. aciculare. The results indicated that a combination of metabarcoding and microscopic analysis revealed more information on zoosporic fungi, including those that are parasitic.

DOI： 10.3354/AME01970

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Quasi-decadal periodicities in growth and production of the copepod Eodiaptomus japonicus in Lake Biwa, Japan, related to the Arctic Oscillation 査読

Liu X., Dur G., Ban S., Sakai Y., Ohmae S., Morita T.

Limnology and Oceanography 2021年1月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Limnology and Oceanography

Copepods are important secondary producers that support higher trophic levels in aquatic food webs. Large-scale climate events such as climate oscillations and global warming force on physical and chemical conditions in aquatic ecosystems might regulate copepod production through physiological and biochemical processes. We evaluated how large climatic and anthropogenic events impacted secondary production of copepods in Lake Biwa, the largest lake in Japan. We determined demographic traits such as body size, growth rate, biomass and production of the dominant copepod Eodiaptomus japonicus in this lake over four decades (1971–2010). To evaluate in situ food conditions and estimate growth and production for this omnivorous species, we firstly defined a size-based food index (f), that is the ratio of in situ body size to ideal body size in adult females. Values of f were mostly < 1 even during eutrophication (1970s to the early 1980s), suggesting that this copepod continuously suffered from a food shortage in this lake. Quasi-decadal periodicities were detected in f, growth and production (but not biomass) for this copepod throughout the study period. These periodicities were correlated with the Arctic Oscillation, implying that long-term trends in climate could regulate copepod food availability and production. This correlation weakened after 1990, which might be due to a regime shift in lake water temperature, which increased abruptly in the mid-1980s. Global warming might now be disrupting historical quasi-decadal periodicity in growth and production of copepods in Lake Biwa.

DOI： 10.1002/lno.11918

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Size-mediated temperature effect on embryonic development in Eodiaptomus japonicus (Copepoda, Calanoida) in Lake Biwa, Japan 査読

Liu X., Ban S.

Journal of Plankton Research 42 ( 6 ) 779 - 782 2020年11月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Journal of Plankton Research

Egg size has numerous ecological implications for zooplankton, and can influence hatching duration and female fecundity. In this study, temperature functions of embryonic development time (EDT) were determined in the copepod Eodiaptomus japonicus from Lake Biwa, in the cold and warm seasons, to clarify synergistic effects of egg size and temperature on EDT. EDT was longer for cold season eggs than warm ones, but both seasons were well fitted by Bělehrádek's function. Egg size was significantly correlated with female body size within seasons, but the relationship did not differ significantly between seasons. These results suggest that seasonal variation in EDT, which was associated with egg size, may result from temperature-mediated variation of female body size, because larger females produced larger eggs as temperature decreased. Larger eggs may enhance fitness under severe food conditions in winter due to high hatchability and naupliar survival.

DOI： 10.1093/plankt/fbaa045

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Are egg production and respiration of the marine pelagic copepod Acartia steueri influenced by crowding? 査読

Takayama Y., Hirahara M., Liu X., Ban S., Toda T.

Aquaculture Research 51 ( 9 ) 3741 - 3750 2020年9月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Aquaculture Research

© 2020 John Wiley & Sons Ltd The understanding of the biological responses of copepods under crowding conditions contributes to establish their stable cultures at high densities for aquaculture industry, which are preferred live feeds for fish larvae. The present study investigated survivorship, fecundity, hatching success and respiration rate, of Acartia steueri raised under five densities, from 100 to 2,000 ind. L−1, to clarify the biological responses of the copepod under dense culture. There were no significant differences in survival, fecundity and hatching success among all density conditions, whereas the respiration rate at 2,000 ind. L−1 decreased by 80% as compared with a condition at 100 ind. L−1. The female copepods raised under a copepod density of >500 ind. L−1 probably invested a larger proportion of energy in reproduction in relation to total assimilated energy as compared with females under lower copepod densities. This change of energy allocation may allow A. steueri under high densities to maintain high fecundity. Acartia steueri might be a promising species for dense culture because its mortality and fecundity were independent of the effect of crowding, and the density-dependent reduction in the metabolic rate might increase reproductive investment to maintain a constant rate of reproduction even under high densities.

DOI： 10.1111/are.14723

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Novel wet-solid states serial anaerobic digestion process for enhancing methane recovery of aquatic plant biomass 査読

Iweh N.S., Koyama M., Akizuki S., Ban S., Toda T.

Science of the Total Environment 730 2020年8月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Science of the Total Environment

© 2020 Elsevier B.V. Aquatic plant biomass is characterised by high moisture content and a lignocellulose structure. To apply the anaerobic digestion (AD) treatment to aquatic plants, the simultaneous achievement of high methane (CH4) recovery per biomass volume and high biodegradability have been a challenge owing to these characteristics. Herein, we propose a novel two-stage serial wet- and solid-state AD (SS-AD) system that quickly digests the labile cytoplasm fraction in the first wet AD reactor in a short retention time while slowly digesting the lignocellulosic fraction in the later SS-AD with long retention time. In this study, the effect of this serial AD on CH4 recovery and chemical oxygen demand (COD) balance from aquatic plant biomass was examined in a semi-continuous operation. Elodea nuttallii, which grows excessively in the southern basin of Lake Biwa, Japan, was used as the substrate. For comparison, single-stage AD with different hydraulic retention times (HRTs) (30 d and 15 d) was performed. The CH4 conversion efficiency in single-stage AD deteriorated from 47.6 to 33.1% COD with shortened HRT, probably owing to the low degradability of slowly degrading fraction (i.e. lignocellulose) in the short retention time. In contrast, the serial AD under the same HRT (15 d) as a single-stage AD exhibited higher CH4 conversion efficiency of 65.1% COD, mainly owing to the enhanced degradation of slowly degrading fraction because of the prolonged solid retention time (52.2 d) of the entire system. The CH4 recovery from the wet AD alone in the serial AD system surpassed that from the 30 d-HRT of the single-stage AD, possibly due to the appropriate HRT for labile fraction and/or the microbial recirculation. The serial wet and SS-AD was suggested as a suitable technology for the treatment of aquatic plant biomass with recalcitrant cell walls and a labile cytoplasm.

DOI： 10.1016/j.scitotenv.2020.138993

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Conditions for continuous cultivation of Chlorella sorokiniana and nutrient removal from anaerobic digestion effluent of aquatic macrophytes 査読

Liu X., Fujiwara M., Kodera T., Watanabe K., Akizuki S., Kishi M., Koyama M., Toda T., Ban S.

International Biodeterioration and Biodegradation 149 2020年4月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：International Biodeterioration and Biodegradation

© 2020 Elsevier Ltd Continuous cultivations of the microalga Chlorella sorokiniana using 10-L flat-panel bioreactors were conducted at different pH levels and hydraulic retention times (HRT) under natural light conditions to accomplish the maximum algal yields and high nutrient removal from anaerobic digestion effluent (ADE) of aquatic macrophytes, which contained high concentrations of ammonium-nitrogen and phosphate-phosphorus, but less available magnesium (Mg). In subsequent experiments, Mg was enriched directly or indirectly by lowering the pH in the original ADE as source medium of a flow-through system to increase the amount of available Mg for algal growth. In the Mg-enrichment experiment, a constant maximum algal yield, 0.7 g dry-weight L−1, was obtained at HRT of 5 days, and removal efficiencies in both ammonium-nitrogen and phosphate-phosphorus were >94%. The pH-controlled experiment was conducted at HRTs of 5 and 10 days at two different pH levels (5.0 and 6.5) of the source ADE. Finally, similar algal yields and nutrient removals were obtained using source ADE at pH 6.5 and 10 days HRT as those in the Mg-enrichment experiment. We demonstrated that pH control in the source ADE through continuous cultivation at the relatively longer HRT can help to maximize algal yield and improve nutrient removal without Mg enrichment.

DOI： 10.1016/j.ibiod.2020.104923

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琵琶湖南湖で過剰繁茂する水草を原料としたメタン発酵消化液の水耕栽培における培養液としての利用可能性査読

畑直樹, 刘鑫, 田口夏帆・金本良成, 吉田弦, 瀬山智博, 戸田龍樹, 伴修平

水資源・環境研究 2020年1月

Resting eggs of the perennial copepod Eodiaptomus japonicus in Lake Biwa (Japan) 査読

Liu X., Ban S., Beyrend D., Dur G., Kuwae M., Makino W., Urabe J.

Inland Waters 2020年1月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Inland Waters

© 2019, © 2020 International Society of Limnology (SIL). Egg dormancy is a key life history strategy in copepods to temporarily escape catastrophic or repetitive detrimental events and ensure permanent colonization. In Lake Biwa, although the copepod Eodiaptomus japonicus dominates the zooplankton community year-round, it has been known to produce resting eggs, yet little is known about its dormancy. To clarify the nature of dormancy in E. japonicus, we collected a sediment core from Lake Biwa, isolated resting eggs, and conducted hatching experiments to determine the life-cycle traits of the hatched individuals. We isolated 242 eggs (maximum age, 60 years) from the upper 17 cm depth sediments, and although no strict catastrophic event such as seasonal drying up was found, the findings implied that E. japonicus might have a “bet-hedging” strategy. Accumulated egg density above 17 cm was 2.5 × 104 m−2, and mean annual egg flux was 103 m−2 per year. Over the first 10 cm sediments, average egg hatching success was 17%. No egg hatchings were confirmed below 10 cm depth. Embryonic development times of the resting eggs were longer than those of subitaneous eggs, indicating that a lag phase existed until development resumed; 33% of hatched nauplii molted to adulthood, and 80% of females produced offspring. These results suggest potential recruitment from resting eggs in the bottom sediments, which partly serve as an egg bank in this copepod.

DOI： 10.1080/20442041.2019.1671766

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pH treatments in continuous cultivation to maximize microalgal production and nutrient removal from anaerobic digestion effluent of aquatic macrophytes 査読

Qian J., Liu X., Ban S., Fujiwara M., Kodera T., Akizuki S., Toda T.

Journal of Applied Phycology 2020年1月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Journal of Applied Phycology

© 2020, Springer Nature B.V. Green algae have great potential for removing inorganic nutrients from anaerobic digestion effluent (ADE), but there is insufficient available magnesium (Mg) in the ADE from aquatic macrophytes for effective algal growth. In this study, we determined suitable pH and hydraulic retention time (HRT) for maximizing growth of the alga Chlorella sorokiniana and nutrient removal efficiency with a flow-through continuous cultivation system. This used ADE from aquatic macrophytes, adjusted to pH 5.0, 6.0, 6.5 and 7.0 at two HRTs of 6 and 8 days. The highest C. sorokiniana biomass concentration was obtained in the pH 6.5 treatment, being 0.50 and 0.67 g L−1 at 6 and 8 days of HRT, respectively, without Mg enrichment. Both were equivalent to 83.6 mg L−1 day−1 of biomass productivity. Removal rates of both ammonium nitrogen and phosphate phosphorus were almost 100% in pH 6.5 and 7.0 treatments and declined to below 60% in pH 5.0 and 6.0 treatments during the study period. The results demonstrated that a source medium pH of 6.5 using a continuous cultivation system (irrespective of the two HRTs), and increasing available Mg, was suitable for maximizing C. sorokiniana biomass productivity and nutrient removal from the ADE.

DOI： 10.1007/s10811-020-02196-z

その他リンク： https://www.scopus.com/inward/record.uri?partnerID=HzOxMe3b&scp=85087610899&origin=inward

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