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Li Y, Liao Z, Hui C, Zheng J, Yuan S, Zhang W. Hydraulic characteristics in channel confluence affect the nitrogen dynamics through altering interactions among multi-trophic microbiota. WATER RESEARCH 2023; 235:119882. [PMID: 36947927 DOI: 10.1016/j.watres.2023.119882] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/22/2022] [Revised: 03/12/2023] [Accepted: 03/13/2023] [Indexed: 06/18/2023]
Abstract
Identifying the distribution of multi-trophic microbiota under the complicated hydrodynamic characteristics of channel confluences and evaluating the microbial contributions to biogeochemical processes are vital for river regulation and ecological function protection. However, relevant studies mainly focus on bacterial community distribution in confluence, neglecting the essential role of multi-trophic microbiota in the aquatic ecosystems and biogeochemical processes. To address this knowledge gap, this study investigated the distribution of multi-trophic microbiota and the underlying assembly process under the hydraulic characteristics in the confluence and described the direct and indirect effects of multi-trophic microbiota on the nitrogen dynamics. Results revealed that, in a river confluence, eukaryotic communities were governed by deterministic processes (52.4%) and bacterial communities were determined by stochastic processes (74.3%). The response of higher trophic levels to environmental factors was intensively higher than that of lower trophic microbiota, resulting in higher trophic microbiota were significantly different between regions with varied environmental conditions (P < 0.05). Flow velocity was the driving force controlling the assembly and composition of multi-trophic microbiota and interactions among multi-trophic levels, and further made a significant difference to nitrogen dynamics. In regions with lower flow velocity, interactions among multi-trophic levels were more complex. There were intense nitrate and nitrite reduction and anammox reactions via direct impacts of protozoan and metazoan and the top-down control (protozoan and metazoan prey on heterotrophic bacteria) among multi-trophic microbiota. Results and findings reveal the ecological effect on river nitrogen removal in a river confluence under complex hydraulic conditions and provide useful information for river management.
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Affiliation(s)
- Yi Li
- Key Laboratory of Integrated Regulation and Resource Development on Shallow Lakes, Ministry of Education, College of Environment, Hohai University, Nanjing 210098, China.
| | - Ziying Liao
- Key Laboratory of Integrated Regulation and Resource Development on Shallow Lakes, Ministry of Education, College of Environment, Hohai University, Nanjing 210098, China
| | - Cizhang Hui
- Key Laboratory of Integrated Regulation and Resource Development on Shallow Lakes, Ministry of Education, College of Environment, Hohai University, Nanjing 210098, China.
| | - Jinhai Zheng
- Key Laboratory of Ministry of Education for Coastal Disaster and Protection, Hohai University, Nanjing 210024, China
| | - Saiyu Yuan
- State Key Laboratory of Hydrology-Water Resources and Hydraulic Engineering, Hohai University, Nanjing 210098, China
| | - Wenlong Zhang
- Key Laboratory of Integrated Regulation and Resource Development on Shallow Lakes, Ministry of Education, College of Environment, Hohai University, Nanjing 210098, China
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Recknagel F, Park HD, Sukenik A, Zohary T. Dissolved organic nitrogen, dinoflagellates and cyanobacteria in two eutrophic lakes: Analysis by inferential modelling. HARMFUL ALGAE 2022; 114:102229. [PMID: 35550299 DOI: 10.1016/j.hal.2022.102229] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/23/2021] [Revised: 02/17/2022] [Accepted: 03/14/2022] [Indexed: 06/15/2023]
Abstract
The Lake Suwa (Japan) has a history of non-N-fixing Microcystis blooms. Lake Kinneret (Israel) experienced multiannual periods of sole domination by the dinoflagellate Peridinium gatunense and periods dominated seasonally by P. gatunense or cyanobacteria. Extensive studies have been carried out in both lakes regarding the role of dissolved inorganic nitrogen and phosphorus as drivers of primary productivity. There is growing evidence that dissolved organic nitrogen (DON) compounds also influence not only biomass and structure of phytoplankton communities but also microcystin production. This study focuses on relationships of DON with: (1) population dynamics of Microcystis spp. and concentrations of microcystins in Lake Suwa, and (2) population dynamics of P. gatunense as well as N- and non-N-fixing cyanobacteria in Lake Kinneret. Modelling results for historical data of Lake Suwa by means of the hybrid evolutionary algorithm HEA revealed that the prediction of abundances of four Microcystis species and concentrations of cyanotoxins achieved higher coefficients of correlation when DON/DIN-ratios were included as drivers. Population dynamics of P. gatunense in Lake Kinneret appeared to have a strong inverse relationships with DON/DIN-ratios reflected by inferential models of HEA with higher coefficients of correlation when driven by DON/DIN-ratios. When DON/DIN-ratios were included as drivers, models of Microcystis spp. in Lake Kinneret performed higher coefficients of determination compared to models of N-fixing cyanobacteria. The study highlights the need to consider DON for improved understanding and management of population dynamics of cyanobacteria and dinoflagellates in freshwater lakes.
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Affiliation(s)
- Friedrich Recknagel
- School of Biological Sciences, University of Adelaide, 5000 Adelaide, Australia
| | - Ho-Dong Park
- Department of Environmental Sciences, Shinshu University, Matsumoto 390-8621, JAPAN
| | - Assaf Sukenik
- Kinneret Limnological Laboratory, Israel Oceanographic & Limnological Research, Migdal 14950, ISRAEL
| | - Tamar Zohary
- Kinneret Limnological Laboratory, Israel Oceanographic & Limnological Research, Migdal 14950, ISRAEL
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Gu L, Wu JY, Hua ZL. Benthic prokaryotic microbial community assembly and biogeochemical potentials in E. coli - Stressed aquatic ecosystems during plant decomposition. ENVIRONMENTAL POLLUTION (BARKING, ESSEX : 1987) 2021; 275:116643. [PMID: 33581629 DOI: 10.1016/j.envpol.2021.116643] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/21/2020] [Revised: 01/26/2021] [Accepted: 01/31/2021] [Indexed: 06/12/2023]
Abstract
Benthic microbes play a crucial role in maintaining the biogeochemical balance of aquatic ecosystems especially the material cycling during plant decomposition. However, those systems in agricultural area are always threatened by agricultural run-off containing a mass of typical pathogenic invader- Escherichia coli. It is therefore vital to clarify the turnover, assembly, and geochemical functions of the E. coli invaded benthic prokaryotic microbial community during plant decomposition. During the decaying process, the key filtering factors of benthic community assembly were NH4+-N (P < 0.001), NO2--N (P < 0.01), and Organic-N (P < 0.05). The E. coli colonized significantly in sediments (P < 0.001) and drove the turnover of the bacterial community (P = 0.001), which enhanced archaeal dominance in the benthic microbial network. E. coli also triggered niche structural variations. The biomass (%) of benthic nutrient cycling genera including Dechloromonas, Pseudomonas, Bacteroides, Candidatus_Methanofastidiosum, and Desulfomicrobium (P < 0.05) was altered by E. coli stress. The structural equation model illustrated that E. coli critically affected the benthic microbial geochemical functions in multiple pathways (P < 0.05). Our results provide new insights into benthic prokaryotic microbial community assembly and nutrient cycling and management under pollution stress.
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Affiliation(s)
- Li Gu
- Key Laboratory of Integrated Regulation and Resource Development on Shallow Lake of Ministry of Education, College of Environment, Hohai University, Nanjing, 210098, China; Yangtze Institute for Conservation and Development, Hohai University, Jiangsu, 210098, China.
| | - Jian-Yi Wu
- Key Laboratory of Integrated Regulation and Resource Development on Shallow Lake of Ministry of Education, College of Environment, Hohai University, Nanjing, 210098, China; Yangtze Institute for Conservation and Development, Hohai University, Jiangsu, 210098, China.
| | - Zu-Lin Hua
- Key Laboratory of Integrated Regulation and Resource Development on Shallow Lake of Ministry of Education, College of Environment, Hohai University, Nanjing, 210098, China; Yangtze Institute for Conservation and Development, Hohai University, Jiangsu, 210098, China.
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Picapedra PHS, Fernandes C, Taborda J, Baumgartner G, Sanches PV. A long-term study on zooplankton in two contrasting cascade reservoirs (Iguaçu River, Brazil): effects of inter-annual, seasonal, and environmental factors. PeerJ 2020; 8:e8979. [PMID: 32411516 PMCID: PMC7207214 DOI: 10.7717/peerj.8979] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2019] [Accepted: 03/25/2020] [Indexed: 11/30/2022] Open
Abstract
Background In reservoirs, zooplankton strongly interact with the physical and chemical characteristics of water, and this interaction is mainly influenced by climate variation and the different methods used to manage the dam water level. Therefore, the aim of this study was to evaluate how the distinct operating modes of two cascade reservoirs affected the richness, abundance, and composition of zooplankton, both spatially (intra and inter-reservoirs) and temporally (annual and seasonal). In this study, the upstream reservoir (Salto Santiago) operates using the storage method, with a water retention time (WRT) of 51 days, whereas the downstream reservoir (Salto Osório) operates using the run-of-river method, with a WRT of 16 days. Methods Zooplankton samples were collected for 16 consecutive years from the two reservoirs located on the Iguaçu River, Brazil. A total of 720 samples were collected. Four-way ANOVAs were used to determine the differences in richness and abundance of the zooplankton among years, periods, reservoirs, and environments. Multidimensional non-metric scaling (NMDS) and an analysis of similarities (ANOSIM) were used to describe similarity patterns in species composition. Finally, a canonical correspondence analysis (CCA) was used to select the environmental predictors that best explained the variation in zooplankton abundance data. Results We identified a total of 115 taxa in this study, and rotifers were the richest group. In contrast, the copepods were the most abundant. The four-way ANOVA results showed significant differences in the species richness and abundance of the zooplankton among years, periods, reservoirs, and environments. The NMDS ordination and ANOSIM test indicated that the largest differences in zooplankton species composition were annual and seasonal differences. Finally, the CCA showed that these differences were mainly associated with changes in water transparency, temperature, and the chlorophyll a, phosphorus, and total dissolved solids concentrations. Discussion Inter-annual changes in zooplankton species composition showed that over time, large filters-feeders (e.g., large daphinids and calanoid copepods) were replaced by small cladocerans (e.g., bosminids) and generalist rotifers. The highest species richness was associated with the fluvial environment, whereas the highest abundance was associated with the transitional and lacustrine reservoir environments. Variations in water temperature, nutrients, and food availability explained the annual and seasonal changes in community structure, whereas variations in the water flow characteristics of the environments explained the longitudinal changes in the richness and abundance of zooplankton in reservoirs. The differences in zooplankton structure between the two reservoirs can be explained by the functional differences between the two systems, such as their WRTs and morphometrics.
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Affiliation(s)
- Pablo H S Picapedra
- Programa de Pós-Graduação em Recursos Pesqueiros e Engenharia de Pesca, Universidade Estadual do Oeste do Paraná, Toledo, Paraná, Brazil
| | - Cleomar Fernandes
- Grupo de Pesquisas em Recursos Pesqueiros e Limnologia/Instituto Neotropical de Pesquisas Ambientais, Toledo, Paraná, Brazil
| | - Juliana Taborda
- Programa de Pós-Graduação em Recursos Pesqueiros e Engenharia de Pesca, Universidade Estadual do Oeste do Paraná, Toledo, Paraná, Brazil.,Grupo de Pesquisas em Recursos Pesqueiros e Limnologia/Instituto Neotropical de Pesquisas Ambientais, Toledo, Paraná, Brazil
| | - Gilmar Baumgartner
- Programa de Pós-Graduação em Recursos Pesqueiros e Engenharia de Pesca, Universidade Estadual do Oeste do Paraná, Toledo, Paraná, Brazil.,Grupo de Pesquisas em Recursos Pesqueiros e Limnologia/Instituto Neotropical de Pesquisas Ambientais, Toledo, Paraná, Brazil
| | - Paulo V Sanches
- Programa de Pós-Graduação em Recursos Pesqueiros e Engenharia de Pesca, Universidade Estadual do Oeste do Paraná, Toledo, Paraná, Brazil.,Grupo de Pesquisas em Recursos Pesqueiros e Limnologia/Instituto Neotropical de Pesquisas Ambientais, Toledo, Paraná, Brazil.,Programa de Pós-Graduação em Ciências Ambientais, Universidade Estadual do Oeste do Paraná, Toledo, Paraná, Brazil
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Yang N, Li Y, Zhang W, Lin L, Qian B, Wang L, Niu L, Zhang H. Cascade dam impoundments restrain the trophic transfer efficiencies in benthic microbial food web. WATER RESEARCH 2020; 170:115351. [PMID: 31810033 DOI: 10.1016/j.watres.2019.115351] [Citation(s) in RCA: 25] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/04/2019] [Revised: 11/26/2019] [Accepted: 11/27/2019] [Indexed: 05/25/2023]
Abstract
Determination of the effects of cascade dams on benthic microbial ecosystem is essential for dam regulation and ecological function protection. However, no comprehensive investigation has yet shown the ecosystem-level responses of microbiota to dam impoundments. This study conducted DNA metabarcoding and microbial food web analysis for multiple species and their interrelationships along a cascade dam-affected river. The composition, distribution and diversity of bacteria, protozoans and metazoans were obviously different between river and reservoirs, mainly controlled by hydrological (P < 0.01) and nutrient parameters (P < 0.05). Those three groups make up a co-occurrence network, with most edges direct from higher to lower trophic levels or vice versa and more than 50% keystones participate in the food web, indicating the significant role of predator-prey relationships. Based on the microbial food web analysis, the predator biomass, especially at higher trophic levels, decreased by about 10% from the riverine to the lacustrine system. The structural equation model illustrates that both bottom-up forces (environmental factors particularly velocity and nutrient concentrations) and top-down forces (higher trophic levels) critically control microbial food web patterns (P < 0.05). As a result of dam impoundments, the lower velocity in the reservoirs has direct negative effects on trophic transfer efficiencies that may be further magnified by nutrient accumulation, probably leading to an increase of eutrophication and posing a risk to water quality. The results suggest the potential ecological risk in the reservoirs and highlight the need to consider from the perspective of ecosystem during the operation of cascade dams.
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Affiliation(s)
- Nan Yang
- Key Laboratory of Integrated Regulation and Resource Development on Shallow Lake of Ministry of Education, College of Environment, Hohai University, Nanjing, 210098, China
| | - Yi Li
- Key Laboratory of Integrated Regulation and Resource Development on Shallow Lake of Ministry of Education, College of Environment, Hohai University, Nanjing, 210098, China.
| | - Wenlong Zhang
- Key Laboratory of Integrated Regulation and Resource Development on Shallow Lake of Ministry of Education, College of Environment, Hohai University, Nanjing, 210098, China
| | - Li Lin
- Department of Basin Water Environment, Changjiang River Scientific Research Institute, Wuhan, 430010, China; Hubei Provincial Key Laboratory of Basin Water Resources and Ecological Environment Sciences, Changjiang River Scientific Research Institute, Wuhan, 430010, China
| | - Bao Qian
- Hydrology Bureau of Changjiang Water Resources Commission, Wuhan, Hubei, 430010, China
| | - Longfei Wang
- Key Laboratory of Integrated Regulation and Resource Development on Shallow Lake of Ministry of Education, College of Environment, Hohai University, Nanjing, 210098, China
| | - Lihua Niu
- Key Laboratory of Integrated Regulation and Resource Development on Shallow Lake of Ministry of Education, College of Environment, Hohai University, Nanjing, 210098, China
| | - Huanjun Zhang
- Key Laboratory of Integrated Regulation and Resource Development on Shallow Lake of Ministry of Education, College of Environment, Hohai University, Nanjing, 210098, China
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Branco CWC, Leal JJF, Huszar VLDM, Farias DDS, Saint'Pierre TD, Sousa-Filho IF, de Palermo EFDA, Guarino AWS, Gomes AR, Kozlowsky-Suzuki B. New lake in a changing world: the construction and filling of a small hydropower reservoir in the tropics (Rio de Janeiro, Brazil). ENVIRONMENTAL SCIENCE AND POLLUTION RESEARCH INTERNATIONAL 2019; 26:36007-36022. [PMID: 31713132 DOI: 10.1007/s11356-019-06665-y] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/26/2019] [Accepted: 10/01/2019] [Indexed: 06/10/2023]
Abstract
Climate change has affected rainfall patterns in tropical regions, where simultaneous demands for water and energy, habitat loss, declining biodiversity, and spread of invasive species have reflected a rapidly changing world underway. In Brazil, hydropower generation accounts for 64% of the electricity matrix, which presently includes 1007 small hydropower plants (SHPs) having many others under construction or planned. This paper aimed to evaluate changes in water quality, plankton communities, and benthic macroinvertebrates during dam construction, filling, and the first year of operation of a SHP. Suspended solids, turbidity, and silica were variables that highlighted the impact of this construction on the river. Fast changes in water quality (increases in calcium, chlorides, and nitrate) and on aquatic communities (i.e. euglenophyceans and testate amoebae increased in numbers) were detected during the filling phase. Following SHP construction, the concentrations of metals and total phosphorus tended to decrease. Two striking findings observed in the aquatic communities from the riverine conditions to the new lake were the increase in picocyanobacteria abundance, expanding population stocks throughout the river basin, and the constant presence of the invasive mollusc Corbicula fluminea in the macroinvertebrate assemblage, revealing once again its resistance to environmental variability. The lake soon became a natural trap for ions from the drainage basin, as revealed by the increase in electrical conductivity, ammonium, potassium, and magnesium concentrations and the abundance of cyanobacteria, highlighting the need for watershed management to improve ecological conditions in the lake.
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Affiliation(s)
- Christina Wyss Castelo Branco
- Federal University of the State of Rio de Janeiro, Institute of Biosciences, Av. Pasteur 458, Prédio do IBIO/CCET Lab 403, Rio de Janeiro, RJ, 22290-240, Brazil.
| | - João José Fonseca Leal
- IFRJ-Federal Institute of Education Science and Technology of Rio de Janeiro, Campus/Nilópolis. RJ. Rua Lúcio Tavares 1045 - Centro Nilópolis, Rio de Janeiro, Brazil
| | | | - Daniel da Silva Farias
- Federal University of the State of Rio de Janeiro, Institute of Biosciences, Av. Pasteur 458, Prédio do IBIO/CCET Lab 403, Rio de Janeiro, RJ, 22290-240, Brazil
| | | | - Izidro Ferreira Sousa-Filho
- Federal University of the State of Rio de Janeiro, Institute of Biosciences, Av. Pasteur 458, Prédio do IBIO/CCET Lab 403, Rio de Janeiro, RJ, 22290-240, Brazil
| | | | - Alcides Wagner Serpa Guarino
- Federal University of the State of Rio de Janeiro, Institute of Biosciences, Av. Pasteur 458, Prédio do IBIO/CCET Lab 403, Rio de Janeiro, RJ, 22290-240, Brazil
| | - Adalto Rodrigues Gomes
- PCH PARACAMBI-LIGHTGER S.A. Company-Avenida Marechal Floriano, 168, bloco 1, 2°andar, corredor D, centro, Rio de Janeiro, RJ, 20.080-002, Brazil
| | - Betina Kozlowsky-Suzuki
- Federal University of the State of Rio de Janeiro, Institute of Biosciences, Av. Pasteur 458, Prédio do IBIO/CCET Lab 403, Rio de Janeiro, RJ, 22290-240, Brazil
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Yang Z, Tang C, Li X, Zhang H, Cai Y. Dynamics of dissolved greenhouse gas response to seasonal water mixing in subtropical reservoirs. ENVIRONMENTAL MONITORING AND ASSESSMENT 2019; 191:639. [PMID: 31529378 DOI: 10.1007/s10661-019-7772-x] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/24/2018] [Accepted: 08/27/2019] [Indexed: 06/10/2023]
Abstract
Although indispensable, significant uncertainty still exists in the underlying processes of the formation, dynamics, and emission of greenhouse gases (GHGs), the critical elements needed for the accurate estimation of greenhouse gas fluxes in inland lakes and reservoirs. Seasonal changes in water thermal stratification and turbulence strongly influence the concentration and emission of dissolved GHGs in water columns. Here, we studied the stratification and overturn processes of water column in the subtropical Lianhe Reservoir during different seasons and determined the dynamics of dissolved CO2, CH4, and N2O in the reservoir. Observation of temperature and analysis of chlorofluorocarbons (CFCs) clearly suggested that stratification of water column occurred in summer, but not in winter. The results showed that while dissolved oxygen (DO) was high in the top 5-m layer (the upper epilimnion layer), it dropped considerably especially below 10 m, resulting in an increase in concentration of CO2 and CH4. The high concentrations of dissolved N2O and CH4 were related to the decomposition of organic matter in the hypolimnion layer under anaerobic conditions after stratification. In winter overturn period, vertical circulants of water not only homogenized the concentration of DO in the water column, but also potentially moved CO2, CH4, and N2O from the bottom to the surface of the reservoir. The estimated GHG flux from the reservoir was - 7.13 mmol m-2 day-1 in summer and 2.14 mmol m-2 day-1 in winter. There was the potential that CO2 fluxes from subtropical lakes and reservoirs are overestimated by traditional geochemical models.
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Affiliation(s)
- Zhenglun Yang
- Graduate School of Horticulture, Chiba University, 648 Matsudo, Matsudo, 271-8510, Japan
| | - Changyuan Tang
- Graduate School of Horticulture, Chiba University, 648 Matsudo, Matsudo, 271-8510, Japan.
| | - Xing Li
- School of Environmental Ecology and Biological Engineering, Wuhan Institute of Technology, No. 206 Guanggu 1st road, Wuhan, 430205, China.
| | - Han Zhang
- Graduate School of Horticulture, Chiba University, 648 Matsudo, Matsudo, 271-8510, Japan
| | - Yangyang Cai
- School of Environmental Science and Engineering, Sun Yat-sen University, 135 Xingang Xi Road, Guangzhou, 510275, China
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Recknagel F, Zohary T, Rücker J, Orr PT, Branco CC, Nixdorf B. Causal relationships of Raphidiopsis (formerly Cylindrospermopsis) dynamics with water temperature and N:P-ratios: A meta-analysis across lakes with different climates based on inferential modelling. HARMFUL ALGAE 2019; 84:222-232. [PMID: 31128807 DOI: 10.1016/j.hal.2019.04.005] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/30/2018] [Revised: 04/10/2019] [Accepted: 04/10/2019] [Indexed: 06/09/2023]
Abstract
Raphidiopsis raciborskii is a tropical toxic cyanobacterium that is rapidly expanding to diverse lake habitats in different climate zones by sophisticated adaptation mechanisms. This meta-analysis investigated correlations of R. raciborskii with water temperature and N:P (nitrogen to phosphorus)-ratios across four lakes with different climates and trophic states by means of long-term time series and the hybrid evolutionary algorithm HEA. The results have shown that in the lakes with temperate and Mediterranean climate, R. raciborskii is strongly correlated with water temperature since germination and growth rely on rising water temperatures in spring. In contrast, there was a weaker correlation with water temperature in subtropical and tropical lakes where pelagic populations of R. raciborskii are overwintering, and are present all year round. However, the highest abundances of R. raciborskii coincided with highest water temperature for the Mediterranean, subtropical and tropical lakes, whilst in the temperate Langer See the highest abundances of R. raciborskii occurred at 24.1 °C, even though temperatures of up to 27 °C were recorded in 2013 and 2014. The correlation of R. raciborskii with N:P-ratios proved to be strongest for the meso- to eutrophic Lake Kinneret (r2 = 0.8) and lowest for the eutrophic Lake Paranoa (r2 = 0.16). However, the assumption has been confirmed that R. raciborskii is growing fastest when waters are N-limited regardless of trophic states. In terms of phenology, the temperate and Mediterranean lakes displayed "fastest growth" in spring and early summer. In contrast, the growing season in subtropical and tropical lakes lasted from spring to autumn most likely because of overwintering populations, and growing importance of direct and indirect biotic regulating factors such as competition, grazing, remineralisation of nutrients along warming climate. In order to carry out a meta-analysis of time series across four different lakes, HEA served as powerful tool resulting in inferential models with predictive capacity for population dynamics of R. raciborskii just driven by water temperature or N:P-ratios, whilst coefficients of determination r2 served as criteria for hypotheses testing.
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Affiliation(s)
| | - Tamar Zohary
- Israel Oceanographic and Limnological Research, Kinneret Limnological Laboratory, Migdal, Israel
| | - Jacqueline Rücker
- Brandenburg University of Technology, Department of Freshwater Conservation, Bad Saarow, Germany
| | | | | | - Brigitte Nixdorf
- Brandenburg University of Technology, Department of Freshwater Conservation, Bad Saarow, Germany
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