Permanent occurrence of Raphidiopsis raciborskii and cyanotoxins in a subtropical reservoir polluted by domestic effluents (Itupararanga reservoir, São Paulo, Brazil)

Abstract Toxic cyanobacteria blooms are a frequent problem in subtropical reservoirs and freshwater systems. The purpose of this study was to investigate the occurrence of potentially toxic cyanobacteria and the environmental conditions associated with the presence of cyanotoxins in a Brazilian subtropical reservoir. Five collections were carried out at seven sampling locations in the reservoir, during the rainy and dry seasons, between the years 2016 and 2017. There was permanent occurrence of Raphidiopsis raciborskii (Woloszynska) Aguilera, Berrendero Gómez, Kastovsky, Echenique & Salerno, ranging between dominant and abundant, with an average biomass of 38.8 ± 29.9 mg L− 1. Also abundant were D. solitarium, D. planctonicum, P. isothrix, and A. gracile. Saxitoxin (STX) was detected in all the collected samples (0.11 ± 0.05 µg L− 1). Microcystin (MC) was also detected, but at lower concentrations (0.01 ± 0.0 µg L− 1). Low availability of NO3− and phosphorus limitation had significant effects on the R. raciborskii biomass and the levels of STX and MC. It was observed that R. raciborskii was sensitive to thermal stratification, at the same time that STX levels were higher. This suggested that STX was produced under conditions that restricted the growth of R. raciborskii. These are important findings, because they add information about the permanent occurrence of STX and R. raciborskii in an aquatic ecosystem limited by phosphorus, vulnerable to climatic variations, and polluted by domestic effluents.

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The Assessment of Phytoplankton Dynamics in Two Reservoirs in Southern Africa with Special Reference to Water Abstraction for Inter-Basin Transfers and Potable Water Production

Water ◽

10.3390/w13213045 ◽

2021 ◽

Vol 13 (21) ◽

pp. 3045

Author(s):

Johannes Sirunda ◽

Paul Oberholster ◽

Gideon Wolfaardt ◽

Marelize Botes ◽

Christoff Truter

Keyword(s):

Phytoplankton Community ◽

Temporal Dynamics ◽

Phytoplankton Assemblages ◽

Water Abstraction ◽

The Public ◽

Toxic Phytoplankton ◽

Cyanobacteria Blooms ◽

Toxic Cyanobacteria ◽

Dry Seasons ◽

Depth Ranges

Toxic phytoplankton in the aquatic ecosystems are dynamic, affecting water quality. It remains unclear as to how possible toxic phytoplankton assemblages vary vertically and temporally in Swakoppoort and Von Bach dams, located in a dry subtropical desert region in central Namibia. The following variables were analyzed: pH, Secchi depths, turbidity, water temperature, total phosphorus, orthophosphate, chlorophyll-a, phytoplankton cells, and water depths. Cyanobacteria dominated the phytoplankton community in the autumn, winter and spring (dry) and summer (wet) seasons, at all the depth ranges in both dams. Microcystis dominated the vertical and temporal dynamics, followed by Dolichospermum. In the dry seasons, higher cyanobacteria cell numbers were observed in comparison to the rainy season in both dams. Spring blooms of cyanobacteria were evident in the Von Bach Dam while autumn and spring cyanobacteria blooms were observed in the Swakoppoort Dam. In the Swakoppoort Dam, the preferable depth ranges for toxic cyanobacteria species were at 5 to 10 m while in the Von Bach Dam at 0 to 5 m range. The findings of the current study indicate that the traditional selective withdrawal of water in the two dams should be performed with vertical and temporal dynamics of possible toxic cyanobacteria accounted for to aid the abstraction of water with the lowest possible toxic phytoplankton numbers, which could lower the public health risk.

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Detection of Microcystin (Mcye) Gene in Recreational Lakes in Miri, Sarawak, Malaysia

Current World Environment ◽

10.12944/cwe.11.3.02 ◽

2016 ◽

Vol 11 (3) ◽

pp. 690-699

Author(s):

Rohaslinda Mohamad ◽

Mohd Rafatullah ◽

Tengku Yusof ◽

Yi Sim ◽

Norli Ismail ◽

...

Keyword(s):

16S Rrna ◽

Pcr Amplification ◽

Cyanobacterial Toxins ◽

Cyanobacterial Toxin ◽

Cyanobacteria Blooms ◽

Toxic Cyanobacteria ◽

Mcye Gene ◽

Reverse Primer ◽

Polymerase Chain ◽

Encoding Gene

Toxic cyanobacteria blooms became a worldwide problems as many countries encounter the presence of the blooms in most of water bodies. As part to develop monitoring of cyanobacterial toxins in Malaysia, samples taken in twelve points in five different lakes in Miri, Sarawak. Polymerase chain reaction (PCR) amplification of cyanobacterial 16S rRNA were carried out to detect the presence of cyanobacteria in the water samples. Cyanobacterial 16S rRNA were detected in all the samples collected. While molecular analysis for detection of cyanobacterial toxin encoding gene were done using specific primers. PCR amplification of cyanobacterial toxin-encoding gene were carried using the combination of forward primer; mcyE-F2 and reverse primer; mcyE-R4 to amplify generic microcystin (mcyE) gene in the samples. Out of twelve samples collected, microcystin (mcyE) producing gene was detected in one of the samples tested. Presence of microcystin encoding gene indicates the risk of cyanobacterial toxins in Miri, Sarawak.

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Potential control of toxic cyanobacteria blooms with Moroccan seaweed extracts

Environmental Science and Pollution Research ◽

10.1007/s11356-019-04921-9 ◽

2019 ◽

Vol 26 (15) ◽

pp. 15218-15228 ◽

Cited By ~ 8

Author(s):

Soukaina El Amrani Zerrifi ◽

Zakaria Tazart ◽

Fatima El Khalloufi ◽

Brahim Oudra ◽

Alexandre Campos ◽

...

Keyword(s):

Potential Control ◽

Seaweed Extracts ◽

Cyanobacteria Blooms ◽

Toxic Cyanobacteria

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Natural events of anoxia and low respiration index in oligotrophic lakes of the Atlantic Tropical Forest

Biogeosciences ◽

10.5194/bg-9-2879-2012 ◽

2012 ◽

Vol 9 (8) ◽

pp. 2879-2887 ◽

Cited By ~ 1

Author(s):

H. Marotta ◽

M. L. S. Fontes ◽

M. M. Petrucio

Keyword(s):

Tropical Forest ◽

Thermal Stratification ◽

Tropical Lakes ◽

Oligotrophic Lakes ◽

Natural Event ◽

Deep Waters ◽

Anoxic Events ◽

Dry Seasons ◽

Average Standard Error ◽

Dry And Rainy Seasons

Abstract. Hypoxia is a well-recognized condition reducing biodiversity and increasing greenhouse gas emissions in aquatic ecosystems, especially under warmer temperatures of tropical waters. Anoxia is a natural event commonly intensified by human-induced organic inputs in inland waters. Here, we assessed the partial pressure of O2 (pO2) and CO2 (pCO2), and the ratio between them (represented by the respiration index, RI) in two oligotrophic lakes of the Atlantic Tropical Forest, encompassing dry and rainy seasons over 19 months. We formulated the hypothesis that thermal stratification events could be coupled to natural hypoxia in deep waters of both lakes. Our results indicated a persistence of CO2 emissions from these tropical lakes to the atmosphere, on average ± standard error (SE) of 17.4 mg C m−2 h−1 probably subsided by terrestrial C inputs from the forest. Additionally, the thermal stratification during the end of the dry season and the rainy summer was coupled to anoxic events and very low RI in deep waters, and to significantly higher pO2 and RI at the surface (about 20 000 μatm and 1.0, respectively). In contrast, the water mixing during dry seasons at the beginning of the winter was related to a strong destratification in pO2, pCO2 and RI in surface and deep waters, without reaching any anoxic conditions throughout the water column. These findings confirm our hypothesis, suggesting that lakes of the Atlantic Tropical Forest could be dynamic, but especially sensitive to organic inputs. Natural anoxic events indicate that tropical oligotrophic lakes might be highly influenced by human land uses, which increase organic discharges into the watershed.

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Using distribution models to estimate blooms of phytosanitary cyanobacteria in Brazil

Biota Neotropica ◽

10.1590/1676-0611-bn-2019-0756 ◽

2020 ◽

Vol 20 (2) ◽

Author(s):

Ariane Guimarães ◽

Pablo Henrique da Silva ◽

Fernanda Melo Carneiro ◽

Daniel Paiva Silva

Keyword(s):

Climate Scenario ◽

Environmental Data ◽

Support Vector ◽

Ecological Niche Models ◽

Distribution Models ◽

The North ◽

Cyanobacteria Blooms ◽

Toxic Cyanobacteria ◽

Bioclimatic Variables ◽

Number Of Publications

Abstract: The multiple uses of aquatic ecosystems by humankind and the continuous interference of their activities have contributed to the emergence of potentially toxic cyanobacteria blooms. Here, we firstly created a database of occurrences of cyanobacteria blooms in Brazil through a systematic review of the scientific literature available in online platforms (e.g. Web of Science, Capes Thesis Catalogue). Secondly, we carried out ecological niche models with occurrence data obtained from these studies to predict climatically suitable areas for blooms. We select 21 bioclimatic variables input environmental data. We used five modeling methods for the current climate scenario: (1) Maxent; (2) Support Vector Machines; (3) Random Forest; (4) Maximum Likelihood e (5) Gaussian. We found that the number of publications about bloom events was higher in 2009 with a decline in the years 2012, 2013 and 2017. Furthermore, the years with the higher records of blooms in freshwater environments were 2005, 2011 e 2014. These events occurring mainly in public supply reservoirs and are mostly of the genera Microcystis Lemmermann, 1907, Dolichospermum (Ralfs ex Bornet & Flahault) P.Wacklin, L.Hoffmann & J.Komárek, 2009 and Raphidiopsis F.E.Fritsch & F.Rich, 1929. Modeling the potential distribution of blooms, we found sampling gaps that should be targeting for future researches, especially in the Amazon biome. Overall, the models did not predict highly suitable areas in the /north of Brazil, while other regions were relatively well distributed with a higher number of occurrence records in the Southeast region.

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What are the factors leading to the success of small planktonic copepods in the Gulf of Gabes, Tunisia?

Journal of the Marine Biological Association of the United Kingdom ◽

10.1017/s0025315414001507 ◽

2015 ◽

Vol 95 (4) ◽

pp. 747-761 ◽

Cited By ~ 11

Author(s):

Thouraya Ben Ltaief ◽

Zaher Drira ◽

Imen Hannachi ◽

Malika Bel Hassen ◽

Asma Hamza ◽

...

Keyword(s):

Thermal Stratification ◽

Phosphorus Limitation ◽

Gulf Of Gabes ◽

Small Copepod ◽

Offshore Area ◽

Gulf Of Gabès ◽

Oithona Similis ◽

Copepod Abundance ◽

Planktonic Copepods ◽

Clausocalanus Furcatus

An oceanographic cruise conducted during June 2008 in the Gulf of Gabes revealed the existence of different water masses; the Modified Atlantic Waters (MAW) circulated in the upper 100 m in the offshore area, the Mixed Mediterranean Water (MMW) was confined to the inshore region and the Ionian Water (IW) was in deep offshore water. The thermal stratification was indicated by the vertical profiles of temperature generated from a coast-offshore section. Phosphorus limitation was induced by the thermal stratification as shown by the high N/P ratio. Heterotrophic and mixotrophic dinoflagellates were the major contributors to total phytoplankton biomass. Ciliates were less abundant and dominated by tintinnids. Small planktonic copepods (≤1.45 mm) contributed to 93.64% of total copepod abundance in the inshore area as a result of the high density of Oithona similis, Oithona nana, Clausocalanus furcatus and Euterpina acutifrons in this area characterized by warm and salty MMW. In fact, small copepods were significantly correlated to both temperature and salinity. Small copepod fraction prevailed also in the MAW contributing to 71.05% of total copepod abundance as a result of the dominance of O. nana and C. furcatus. Nonetheless, the large copepod Nannocalanus minor was more adapted to the deep IW where it contributed to 44.05% of total copepod abundance. Invasive species were encountered in the offshore region intruded by the Atlantic waters. The Atlantic copepods were scarce and less abundant reflecting the weakening of the Atlantic flow in the eastern basin of the Mediterranean.

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