BAN Syuhei




Research Fields, Keywords

Aquatic Ecology

Mail Address

E-mail address

Graduate School 【 display / non-display

  • Hokkaido University  Graduate School, Division of Fisheries  Doctor's Course  1991.02

Campus Career 【 display / non-display

  • University of Shiga Prefecture  School of Environmental Science  Department of Ecosystem Studies  Professor   2008.02 - Now

  • University of Shiga Prefecture  School of Environmental Science  Department of Ecosystem Studies  Associate Professor   2007.04 - 2008.01

  • University of Shiga Prefecture  School of Environmental Science  Department of Ecosystem Studies  Associate Professor (as old post name)   2001.05 - 2007.03

Academic Society Affiliations 【 display / non-display

  • Association for the Sciences of Limnology and Oceanography

  • Japan Society on Water Environment

  • JpGU

Field of expertise (Grants-in-aid for Scientific Research classification) 【 display / non-display

  • Ecology/Environment

  • Aquatic bioproduction science

  • Environmental dynamic analysis


Research theme 【 display / non-display

  • Biodiversity-driven nutrient cycling and human-wellbeing in socio-ecological systems (lake ecosystem)

  • Sustainable management in lake ecosystem using macrophyte biomass

    macrophyte biomass, conservation in lake ecosystem, freshwater environments, methane fermentation, microalgal culture

  • Diversity and function of Chytrid fungi in lakes and oceans

    Chytrid fungi, diversity, phytoplankton, lakes

  • Long-term study on zooplankton biomass in Lake Biwa

    Lake Biwa, zooplankton, biomass, long-term analysis

  • Effects of internal wave on phytoplankton production in Lake Biwa

    internal wave, material flux, phytoplankton production, wind direction and speed

Papers 【 display / non-display

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

    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  Nature Communications  13 (1)    2022.12

    10.1038/s41467-022-28761-3  Joint Work  


    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.

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

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

    Journal of Great Lakes Research  Journal of Great Lakes Research    2022.01

    10.1016/j.jglr.2022.06.001  Joint Work  


    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.

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

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

    Biochemical Engineering Journal  Biochemical Engineering Journal  172    2021.08

    10.1016/j.bej.2021.108065  Joint Work  


    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.

  • Climate change drives widespread shifts in lake thermal habitat

    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  Nature Climate Change  11 (6)   521 - 529  2021.06

    10.1038/s41558-021-01060-3  Joint Work  


    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.

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

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

    Aquatic Microbial Ecology  Aquatic Microbial Ecology  87   17 - 28  2021.01

    10.3354/AME01970  Joint Work  


    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.

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

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

    Limnology and Oceanography  Limnology and Oceanography    2021.01

    10.1002/lno.11918  Joint Work  


    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.

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

    Liu X., Ban S.

    Journal of Plankton Research  Journal of Plankton Research  42 (6)   779 - 782  2020.11

    10.1093/plankt/fbaa045  Joint Work  


    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.

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

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

    Aquaculture Research  Aquaculture Research  51 (9)   3741 - 3750  2020.09

    10.1111/are.14723  Joint Work  


    © 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.

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

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

    Science of the Total Environment  Science of the Total Environment  730    2020.08

    10.1016/j.scitotenv.2020.138993  Joint Work  


    © 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.

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

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

    International Biodeterioration and Biodegradation  International Biodeterioration and Biodegradation  149    2020.04

    10.1016/j.ibiod.2020.104923  Joint Work  


    © 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.

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Review Papers 【 display / non-display