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Plant weight determines secondary fibre development in fibre hemp (Cannabis sativa L.)
Westerhuis, W. ; Delden, S.H. van; Dam, J.E.G. van; Pereira Marinho, J.P. ; Struik, P.C. ; Stomph, T.J. - \ 2019
Industrial Crops and Products 139 (2019). - ISSN 0926-6690 - 8 p.
Cannabis sativa L. - Day length sensitivity - Dual purpose - Fibre hemp - Secondary fibres - Textiles
In fibre hemp (Cannabis sativa L.) grown for the production of high‒quality textile yarns the presence of secondary fibres is unwanted. These fibres are too short for spinning and their presence hampers the production of fine and homogeneous yarns from the primary or long fibres. Primary fibres are present along the stem from bottom to top and hemp for fibres is traditionally harvested around the time of flowering, when the cell walls of these fibres are sufficiently thickened with cellulose to be extracted. In literature indications are found that the height up to which secondary fibres are present, moves upwards along the stem during the growing season, and that this process accelerates around flowering. To optimise the length of the stem part with primary fibres, but without secondary fibres, the background of secondary fibre development should be elucidated. It can be hypothesised that either flowering or the increasing plant size accelerates the formation of secondary fibres. To investigate this, an indoor experiment was conducted in greenhouses with mobile covers in which the day–length sensitivity of hemp was used to create size ranges of flowering and non–flowering plants for a single cultivar, Futura 75. Secondary fibre formation was recorded using microscopic techniques. The height up to which secondary fibres were present, depended on plant weight. The higher secondary fibre front in flowering plants was most likely caused by the higher weight of these plants as compared with non–flowering plants of the same height. As seed carrying inflorescences contribute to plant weight, dual use of fibre hemp for seed and high–quality textile fibres is not an option. Results from a field experiment confirmed the correlation between plant size and the height of the secondary fibre front. Therefore, to optimise the length of the stem part with primary fibres, but without secondary fibres above stubble height, for Futura 75 a relatively short crop of around 1.3–1.4 m should be harvested before flowering. This ideal crop height is likely to differ between varieties.
Intraspecific variability in response to phosphorus depleted conditions in the cyanobacteria Microcystis aeruginosa and Raphidiopsis raciborskii
Guedes, Iame Alves ; Pacheco, Ana Beatriz F. ; Vilar, Mauro C.P. ; Mello, Mariana M. ; Marinho, Marcelo Manzi ; Lurling, Miquel ; Azevedo, Sandra M.F.O. - \ 2019
Harmful Algae 86 (2019). - ISSN 1568-9883 - p. 96 - 105.
Cylindrospermopsis - Ecotypes - Phosphorus uptake - Strain variability
Phosphorus loading plays an important role in the occurrence of cyanobacterial blooms and understanding how this nutrient affects the physiology of cyanobacteria is imperative to manage these phenomena. Microcystis aeruginosa and Raphidiopsis raciborskii are cyanobacterial species that form potentially toxic blooms in freshwater ecosystems worldwide. Blooms comprise numerous strains with high trait variability, which can contribute to the widespread distribution of these species. Here, we explored the intraspecific variability in response to phosphorus depleted conditions (P-)testing five strains of each species. Strains could be differentiated by cell volume or genetic profiles except for those of the same species, sampling location and date, though these presented differences in their response to (P-). Although differently affected by (P-)over 10 days, all strains were able to grow and maintain photosynthetic activity. For most M. aeruginosa and R. raciborskii strains growth rates were not significantly different comparing (P+)and (P-)conditions. After ten days in (P-), only one M. aeruginosa strain and two R. raciborskii strains showed reduction in biovolume yield as compared to (P+)but in most strains chlorophyll-a concentrations were lower in (P-)than in (P+). Reduced photosystem II efficiency was found for only one R. raciborskii strain while all M. aeruginosa strains were affected. Only two M. aeruginosa and one R. raciborskii strain increased alkaline phosphatase activity under (P-)as compared to (P+). Variation in P-uptake was also observed but comparison among strains yielded homogeneous groups comprised of representatives of both species. Comparing the response of each species as a whole, the (P-)condition affected growth rate, biovolume yield and chlorophyll yield. However, these parameters revealed variation among strains of the same species to the extent that differences between M. aeruginosa and R. raciborskii were not significant. Taken together, these results do not support the idea that R. raciborskii, as a species, can withstand phosphorus limitation better than M. aeruginosa and also point that the level of intraspecific variation may preclude generalizations based on studies that use only one or few strains.
Combined Effect of Light and Temperature on the Production of Saxitoxins in Cylindrospermopsis raciborskii Strains
Mesquita, Marcella C.B. ; Lürling, Miquel ; Dorr, Fabiane ; Pinto, Ernani ; Marinho, Marcelo M. - \ 2019
Toxins 11 (2019)1. - ISSN 2072-6651 - 15 p.
cyanobacteria - cyanotoxins - intraspecific variability - saxitoxins
Cylindrospermopsis raciborskii is a potentially toxic freshwater cyanobacterium that can tolerate a wide range of light and temperature. Due to climatic changes, the interaction between light and temperature is studied in aquatic systems, but no study has addressed the effect of both variables on the saxitoxins production. This study evaluated the combined effect of light and temperature on saxitoxins production and cellular quota in C. raciborskii. Experiments were performed with three C. raciborskii strains in batch cultures under six light intensities (10, 40, 60, 100, 150, and 500 μmol of photons m-2 s-1) and four temperatures (15, 20, 25, and 30 °C). The growth of C. raciborskii strains was limited at lower temperatures and the maximum growth rates were obtained under higher light combined with temperatures equal or above 20 °C, depending on the strain. In general, growth was highest at 30 °C at the lower light intensities and equally high at 25 °C and 30 °C under higher light. Highest saxitoxins concentration and cell-quota occurred at 25 °C under high light intensities, but were much lower at 30 °C. Hence, increased temperatures combined with sufficient light will lead to higher C. raciborskii biomass, but blooms could become less toxic in tropical regions.
Managing Eutrophication in a Tropical Brackish Water Lagoon : Testing Lanthanum-Modified Clay and Coagulant for Internal Load Reduction and Cyanobacteria Bloom Removal
Magalhães, Leonardo de; Noyma, Natalia Pessoa ; Furtado, Luciana Lima ; Drummond, Erick ; Leite, Vivian Balthazar Gonçalves ; Mucci, Maíra ; Oosterhout, Frank van; Moraes Huszar, Vera Lúcia de; Lürling, Miquel ; Marinho, Marcelo Manzi - \ 2019
Estuaries and coasts 42 (2019)2. - ISSN 1559-2723 - p. 390 - 402.
Geo-engineering - Lake restoration - PAC - Phoslock - Phosphorus control - Sediment release
The release of phosphorus (P) stored in the sediment may cause long-term delay in the recovery of lakes, ponds, and lagoons from eutrophication. In this paper, we tested on a laboratory scale the efficacy of the flocculant polyaluminium chloride (PAC) and a strong P-binding agent (lanthanum-modified bentonite, LMB) on their ability to flocculate a cyanobacterial bloom and hamper P release from a hypertrophic, brackish lagoon sediment. In addition, critical P loading was estimated through PCLake. We showed that cyanobacteria could be effectively settled using a PAC dose of 2 mg Al L−1 combined with 400-mg L−1 LMB; PAC 8 mg Al L−1 alone could also remove cyanobacteria, although its performance was improved adding low concentrations of LMB. The efficacy of LMB to bind P released from the sediment was tested based on potentially available sediment P. A dose of 400 g LMB m−2 significantly reduced the P release from sediment to over-standing water (either deionized water or water from the lagoon with and without cyanobacteria). In sediment cores, LMB + PAC reduced sediment P flux from 9.9 (± 3.3) to − 4.6 (± 0.3) mg P m−2 day−1 for the experimental period of 3 months. The internal P load was 14 times higher than the estimated P critical load (0.7 mg P m−2 day−1), thus even if all the external P sources would be ceased, the water quality will not improve promptly. Hence, the combined LMB + PAC treatment seems a promising in-lake intervention to diminish internal P load bellow the critical load. Such intervention is able to speed up recovery in the brackish lagoon once external loading has been tackled and at a cost of less than 5% of the estimated dredging costs.
Cyanobacteria dominance drives zooplankton functional dispersion
Josué, Iollanda I.P. ; Cardoso, Simone J. ; Miranda, Marcela ; Mucci, Maíra ; Ger, Kemal Ali ; Roland, Fabio ; Marinho, Marcelo Manzi - \ 2019
Hydrobiologia 831 (2019)1. - ISSN 0018-8158 - p. 149 - 161.
Biodiversity - Eutrophication - Freshwater - Microbial food quality - Plankton
Accelerated eutrophication reduces water quality and shifts plankton communities. However, its effects on the aquatic food web and ecosystem functions remain poorly understood. Within this context, functional ecology can provide valuable links relating community traits to ecosystem functioning. In this study, we assessed the effects of eutrophication and cyanobacteria blooms on zooplankton functional diversity in a tropical hypereutrophic lake. Phytoplankton and zooplankton communities and limnological characteristics of a tropical Brazilian Lake (Southeast, Brazil) were monitored monthly from April 2013 to October 2014. Lake eutrophication indicators were total phosphorus, total chlorophyll-a, and chlorophyll-a per group (blue, green, and brown). The variation of major phytoplankton taxonomic group biomass was calculated and used as a proxy for changes in phytoplankton composition. Zooplankton functional diversity was assessed through functional dispersion and the community-weighted mean trait value. Regressions were performed between the lake eutrophication indicators, the phytoplankton biomass variation, and zooplankton functional dispersion. Our results suggest that eutrophication and cyanobacterial dominance change the composition of zooplankton traits and reduce functional dispersion, leading to zooplankton niche overlap. These findings are important because they provide a meaningful view of phytoplankton-zooplankton trophic interactions and contribute to an improved understanding their functional effects on aquatic ecosystems.
Response of natural cyanobacteria and algae assemblages to a nutrient pulse and elevated temperature
Lürling, Miquel ; Mello, Mariana Mendese ; Oosterhout, Frank van; Senerpont Domis, Lisette de; Marinho, Marcelo M. - \ 2018
Frontiers in Microbiology 9 (2018)AUG. - ISSN 1664-302X
Blooms - Climate change - Competition - Global warming - Optimum growth
Eutrophication (nutrient over-enrichment) is the primary worldwide water quality issue often leading to nuisance cyanobacterial blooms. Climate change is predicted to cause further rise of cyanobacteria blooms as cyanobacteria can have a competitive advantage at elevated temperatures. We tested the hypothesis that simultaneous rise in nutrients and temperature will promote cyanobacteria more than a single increase in one of the two drivers. To this end, controlled experiments were run with seston from 39 different urban water bodies varying in trophic state from mesotrophic to hypertrophic. These experiments were carried out at two different temperatures, 20°C (ambient) and 25°C (warming scenario) with or without the addition of a surplus of nutrients (eutrophication scenario). To facilitate comparisons, we quantified the effect size of the different treatments, using cyanobacterial and algal chlorophyll a concentrations as a response variable. Cyanobacterial and algal chlorophyll a concentrations were determined with a PHYTO-PAM phytoplankton analyzer. Warming caused an 18% increase in cyanobacterial chlorophyll-α, while algal chlorophyll-α concentrations were on average 8% higher at 25°C than at 20°C. A nutrient pulse had a much stronger effect on chlorophyll-α concentrations than warming. Cyanobacterial chlorophyll-α concentrations in nutrient enriched incubations at 20 or 25°C were similar and 9 times higher than in the incubations without nutrient pulse. Likewise, algal chlorophyll-α concentrations were 6 times higher. The results of this study confirm that warming alone yields marginally higher cyanobacteria chlorophyll-α concentrations, yet that a pulse of additional nutrients is boosting blooms. The responses of seston originating from mesotrophic waters seemed less strong than those from eutrophic waters, which indicates that nutrient control strategies -catchment as well as in-system measures- could increase the resilience of surface waters to the negative effects of climate change.
Assessment of possible solid-phase phosphate sorbents to mitigate eutrophication : Influence of pH and anoxia
Mucci, Maíra ; Maliaka, Valentini ; Noyma, Natalia Pessoa ; Marinho, Marcelo Manzi ; Lürling, Miquel - \ 2018
Science of the Total Environment 619-620 (2018). - ISSN 0048-9697 - p. 1431 - 1440.
Geo-engineering - Phosphate adsorption - Phosphorus control
Managing eutrophication remains a challenge to water managers. Currently, the manipulation of biogeochemical processes (i.e., geo-engineering) by using phosphorus-adsorptive techniques has been recognized as an appropriate tool to manage the problem. The first step in finding potential mitigating materials is conducting a sequence of upscaling studies that commence with controlled laboratory experiments. Here, the abilities of 10 possible solid–phase-sorbents (SPS) to adsorb P were examined. Four materials adsorbed P, and two of these materials were modified, i.e., a lanthanum-modified-bentonite (LMB) and an aluminum-modified-zeolite (AMZ), and had the highest adsorption capacities of 11.4 and 8.9 mg P g− 1, respectively. Two natural materials, a red soil (RS) and a bauxite (BAU), were less efficient with adsorption capacities of 2.9 and 3.4 mg P g− 1, respectively. Elemental composition was not related to P adsorption. Since SPS might be affected by pH and redox status, we also tested these materials at pH values of 6, 7, 8 and 9 and under anoxic condition. All tested materials experienced decreased adsorption capacities under anoxic condition, with maximum adsorptions of 5.3 mg P g− 1 for LMB, 5.9 mg P g− 1 for AMZ, 0.2 mg P g− 1 for RS and 0.2 mg P g− 1 for BAU. All materials were able to adsorb P across the range of pH values that were tested. The maximum adsorption capacities of LMB and RS were highest at pH 6, AMZ was higher at a pH of 9 and BAU at a pH of 8. Thus, pH influenced P adsorption differently. Given the effects of pH and anoxia, other abiotic variables should also be considered. Considering the criteria that classify a useful SPS (i.e., effective, easy to produce, cheap and safe), only the two modified materials that were tested seem to be suitable for upscaling to enclosure studies with anoxic sediments.
Effect of suspended clay on growth rates of the cyanobacterium Cylindrospermopsis raciborskii
Brasil, Jandeson ; Huszar, Vera L.M. ; Attayde, José L. ; Marinho, Marcelo M. ; Oosterhout, Frank Van; Lürling, Miquel - \ 2017
Fundamental and Applied Limnology 191 (2017)1. - ISSN 1863-9135 - p. 13 - 23.
Cyanobacteria - Inorganic turbidity - Light availability - Sedimentation - Suspended solids
Recent studies have shown that sediment resuspension may lead to the collapse of C. raciborskii dominance, which suggests that clay might have a negative effect on the growth of C. raciborskii. To test the hypothesis that suspended clay creates an unfavorable environment for growth of C. raciborskii, we exposed four different strains of this species to various concentrations of the clays kaolinite and bentonite, and monitored the biomass of each strain over the course of 1-week microcosm experiments. Contrary to our hypothesis, C. raciborskii was able to grow in suspensions of both clays. While kaolinite clay caused higher turbidity than bentonite, the growth rates of all four C. raciborskii strains were higher in kaolinite than in bentonite suspensions. C. raciborskii could still grow in clay concentrations that cause turbidity far above the levels found in natural lakes. Our study suggests that the reported collapse of C. raciborskii blooms with high concentrations of suspended sediments in tropical shallow lakes is probably not caused by the effects of suspended clay on light attenuation, but rather is a consequence of cell sinking or, possibly a response to disturbance events responsible for sediment suspension.
Coagulant plus ballast technique provides a rapid mitigation of cyanobacterial nuisance
Noyma, Natalia Pessoa ; Magalhães, Leonardo De; Miranda, Marcela ; Nunes Teixeira Mucci, Maira ; Oosterhout, Frank van; Moraes Huszar, Vera Lúcia de; Marinho, Marcelo Manzi ; Lima, Eduardo R.A. ; Lurling, Miquel - \ 2017
PLoS ONE 12 (2017)6. - ISSN 1932-6203 - 16 p.
Cyanobacteria blooms are a risk to environmental health and public safety due to the potent toxins certain cyanobacteria can produce. These nuisance organisms can be removed from water bodies by biomass flocculation and sedimentation. Here, we studied the efficacy of combinations of a low dose coagulant (poly-aluminium chloride-PAC-or chitosan) with different ballast compounds (red soil, bauxite, gravel, aluminium modified zeolite and lanthanum modified bentonite) to remove cyanobacterial biomass from water collected in Funil Reservoir (Brazil). We tested the effect of different cyanobacterial biomass concentrations on removal efficiency. We also examined if zeta potential was altered by treatments. Addition of low doses of PAC and chitosan (1±8 mg Al L-1) to the cyanobacterial suspensions caused flock formation, but did not settle the cyanobacteria. When those low dose coagulants were combined with ballast, effective settling in a dose-dependent way up to 99.7% removal of the flocks could be achieved without any effect on the zeta potential and thus without potential membrane damage. Removal efficacy was influenced by the cyanobacterial biomass and at higher biomass more ballast was needed to achieve good removal. The combined coagulant-ballast technique provides a promising alternative to algaecides in lakes, ponds and reservoirs.
Critical assessment of chitosan as coagulant to remove cyanobacteria
Lurling, Miguel ; Noyma, Natalia Pessoa ; Magalhães, Leonardo de; Miranda, Marcela ; Mucci, Maíra ; Oosterhout, F. van; Huszar, Vera L.M. ; Marinho, Marcelo Manzi - \ 2017
Harmful Algae 66 (2017). - ISSN 1568-9883 - p. 1 - 12.
Cyanobacterial blooms - Eutrophication - Flock and sink - Mitigation - Nuisance control
Removal of cyanobacteria from the water column using a coagulant and a ballast compound is a promising technique to mitigate nuisance. As coagulant the organic, biodegradable polymer chitosan has been promoted. Results in this study show that elevated pH, as may be common during cyanobacterial blooms, as well as high alkalinity may hamper the coagulation of chitosan and thus impair its ability to effectively remove positively buoyant cyanobacteria from the water column. The underlying mechanism is likely a shielding of the protonated groups by anions. Inasmuch as there are many chitosan formulations, thorough testing of each chitosan prior to its application is essential. Results obtained in glass tubes were similar to those from standard jar tests demonstrating that glass tube tests can be used for testing effects of coagulants and ballasts in cyanobacteria removal whilst allowing far more replicates. There was no relation between zeta potential and precipitated cyanobacteria. Given the well-known antibacterial activity of chitosan and recent findings of anti-cyanobacterial effects, pre-application tests are needed to decipher if chitosan may cause cell leakage of cyanotoxins. Efficiency- and side-effect testing are crucial for water managers to determine if the selected approach can be used in tailor-made interventions to control cyanobacterial blooms and to mitigate eutrophication.
Chitosan as coagulant on cyanobacteria in lake restoration management may cause rapid cell lysis
Nunes Teixeira Mucci, Maira ; Noyma, Natalia Pessoa ; Magalhães, Leonardo de; Miranda, Marcela ; Oosterhout, Frank van; Guedes, Iamê Alves ; Huszar, Vera L.M. ; Marinho, Marcelo Manzi ; Lürling, Miquel - \ 2017
Water Research 118 (2017). - ISSN 0043-1354 - p. 121 - 130.
Cell lysis - Cell viability - Cyanobacterial blooms - Eutrophication - Lake restoration - Photosystem II efficiency
Combining coagulant and ballast to remove cyanobacteria from the water column is a promising restoration technique to mitigate cyanobacterial nuisance in surface waters. The organic, biodegradable polymer chitosan has been promoted as a coagulant and is viewed as non-toxic. In this study, we show that chitosan may rapidly compromise membrane integrity and kill certain cyanobacteria leading to release of cell contents in the water. A strain of Cylindrospermopsis raciborskii and one strain of Planktothrix agardhii were most sensitive. A 1.3 h exposure to a low dose of 0.5 mg l−1 chitosan already almost completely killed these cultures resulting in release of cell contents. After 24 h, reductions in PSII efficiencies of all cyanobacteria tested were observed. EC50 values varied from around 0.5 mg l−1 chitosan for the two sensitive strains, via about 5 mg l−1 chitosan for an Aphanizomenon flos-aquae strain, a toxic P. agardhii strain and two Anabaena cylindrica cultures, to more than 8 mg l−1 chitosan for a Microcystis aeruginosa strain and another A. flos-aquae strain. Differences in sensitivity to chitosan might be related to polymeric substances that surround cyanobacteria. Rapid lysis of toxic strains is likely and when chitosan flocking and sinking of cyanobacteria is considered in lake restoration, flocculation efficacy studies should be complemented with investigation on the effects of chitosan on the cyanobacteria assemblage being targeted.
The efficiency of combined coagulant and ballast to remove harmful cyanobacterial blooms in a tropical shallow system
Miranda, Marcela ; Noyma, Natália ; Pacheco, Felipe S. ; Magalhães, Leonardo de; Pinto, Ernani ; Santos, Suzan ; Soares, Maria Fernanda A. ; Huszar, Vera L. ; Lurling, Miguel ; Marinho, Marcelo M. - \ 2017
Harmful Algae 65 (2017). - ISSN 1568-9883 - p. 27 - 39.
Chitosan - Cyanobacteria mitigation - Cylindrospermopsis - Eutrophication control - Microcystis
We tested the hypothesis that a combination of coagulant and ballast could be efficient for removal of positively buoyant harmful cyanobacteria in shallow tropical waterbodies, and will not promote the release of cyanotoxins. This laboratory study examined the efficacy of coagulants [polyaluminium chloride (PAC) and chitosan (made of shrimp shells)] alone, and combined with ballast (lanthanum modified bentonite, red soil or gravel) to remove the natural populations of cyanobacteria collected from a shallow eutrophic urban reservoir with alternating blooms of Cylindrospermopsis and Microcystis. PAC combined with ballast was effective in settling blooms dominated by Microcystis or Cylindrospermopsis. Contrary to our expectation, chitosan combined with ballast was only effective in settling Cylindrospermopsis-dominated blooms at low pH, whereas at pH ≥ 8 no effective flocculation and settling could be evoked. Chitosan also had a detrimental effect on Cylindrospermopsis causing the release of saxitoxins. In contrast, no detrimental effect on Microcystis was observed and all coagulant-ballast treatments were effective in not only settling the Microcystis dominated bloom, but also lowering dissolved microcystin concentrations. Our data show that the best procedure for biomass reduction also depends on the dominant species.
Efficacy of Coagulants and Ballast Compounds in Removal of Cyanobacteria (Microcystis) from Water of the Tropical Lagoon Jacarepaguá (Rio de Janeiro, Brazil)
Magalhães, Leonardo de; Noyma, Natália Pessoa ; Furtado, Luciana Lima ; Nunes Teixeira Mucci, Maira ; Oosterhout, Frank van; Huszar, Vera L.M. ; Marinho, Marcelo Manzi ; Lurling, Miguel - \ 2017
Estuaries and coasts 40 (2017)1. - ISSN 1559-2723 - p. 121 - 133.
Bloom control - Chitosan - Cyanobacteria - Eutrophication - Mitigation - PAC
Eutrophication is considered the most important water quality problem in freshwaters and coastal waters worldwide promoting frequent occurrence of blooms of potentially toxic cyanobacteria. Removal of cyanobacteria from the water column using a combination of coagulant and ballast is a promising technique for mitigation and an alternative to the use of algaecides. In laboratory, we tested experimentally the efficiency of two coagulants, polyaluminium chloride (PAC) and chitosan (made of shrimp shells), alone and combined with two ballasts: red soil (RS) and the own lagoon sediment, to remove natural populations of cyanobacteria, from an urban brackish coastal lagoon. PAC was a very effective coagulant when applied at low doses (≤8 mg Al L−1) and settled the cyanobacteria, while at high doses (≥16 mg Al L−1) large flocks aggregated in the top of test tubes. In contrast, chitosan was not able to form flocks, even in high doses (>16 mg L−1) and did not efficiently settle down cyanobacteria when combined with ballast. The RS itself removed 33–47 % of the cyanobacteria. This removal was strongly enhanced when combined with PAC in a dose-dependent matter; 8 mg Al L−1 was considered the best dose to be applied. The lagoon sediment alone did not promote any settling of cyanobacteria but removal was high when combined with PAC. Combined coagulant and ballast seems a very efficient, cheap, fast and safe curative measure to lessen the harmful cyanobacteria bloom nuisance in periods when particularly needed, such as around the 2016 Olympics in Jacarepaguá Lagoon.
Controlling cyanobacterial blooms through effective flocculation and sedimentation with combined use of flocculants and phosphorus adsorbing natural soil and modified clay
Pessoa Noyma, Natalia ; Magalhaes, L. de; Furtado, L.L. ; Nunes Teixeira Mucci, M. ; Oosterhout, M. van; Huszar, V.L.M. ; Marinho, M.M. ; Lurling, M.F.L.L.W. - \ 2016
Water Research 97 (2016). - ISSN 0043-1354 - p. 26 - 38.
Cyanobacteria bloom - Geo-engineering in lakes - Lake restoration - Local red soil - Phosphorus mitigation
Eutrophication often results in blooms of toxic cyanobacteria that hamper the use of lakes and reservoirs. In this paper, we experimentally evaluated the efficacy of a metal salt (poly-aluminium chloride, PAC) and chitosan, alone and combined with different doses of the lanthanum modified bentonite Phoslock® (LMB) or local red soil (LRS) to sediment positively buoyant cyanobacteria from Funil Reservoir, Brazil, (22°30’S, 44°45’W). We also tested the effect of calcium peroxide (CaO2) on suspended and settled cyanobacterial photosystem efficiency, and evaluated the soluble reactive P (SRP) adsorbing capacity of both LMB and LRS under oxic and anoxic conditions. Our data showed that buoyant cyanobacteria could be flocked and effectively precipitated using a combination of PAC or chitosan with LMB or LRS. The SRP sorption capacity of LMB was higher than that of LRS. The maximum P adsorption was lowered under anoxic conditions especially for LRS ballast. CaO2 addition impaired photosystem efficiency at 1 mg L-1 or higher and killed precipitated cyanobacteria at 4 mg L-1 or higher. A drawback was that oxygen production from the peroxide gave positive buoyancy again to the settled flocs. Therefore, further experimentations with slow release pellets are recommended.
Assessment of the Effects of Light Availability on Growth and Competition Between Strains of Planktothrix agardhii and Microcystis aeruginosa
Araujo Torres, C. de; Lurling, M.F.L.L.W. ; Manzi Marinho, M. - \ 2016
Microbial Ecology 71 (2016)4. - ISSN 0095-3628 - p. 802 - 813.
In this study, we tested the hypothesis that Planktothrix agardhii strains isolated from a tropical water body were better competitors for light than Microcystis aeruginosa strains. These cyanobacteria are common in eutrophic systems, where light is one of the main drivers of phytoplankton, and Planktothrix is considered more shade-adapted and Microcystis more high-light tolerant. First, the effect of light intensities on growth was studied in batch cultures. Next, the minimum requirement of light (I*) and the effect of light limitation on the outcome of competition was investigated in chemostats. All strains showed similar growth at 10 μmol photons m−2 s−1, demonstrating the ability of the two species to grow in low light. The optimum light intensity was lower for P. agardhii, but at the highest light intensity, Microcystis strains reached higher biovolume, confirming that P. agardhii has higher sensitivity to high light. Nonetheless, P. agardhii grew in light intensities considered high (500 μmol photons m−2 s−1) for this species. M. aeruginosa showed a higher carrying capacity in light-limited condition, but I* was similar between all the strains. Under light competition, Microcystis strains displaced P. agardhii and dominated. In two cases, there was competitive exclusion and in the other two P. agardhii managed to remain in the system with a low biovolume (≈15 %). Our findings not only show that strains of P. agardhii can grow under higher light intensities than generally assumed but also that strains of M. aeruginosa are better competitors for light than supposed. These results help to understand the co-occurrence of these species in tropical environments and the dominance of M. aeruginosa even in low-light conditions.
Light and Phosphate Competition Between Cylindrospermopsis raciborskii and Microcystis aeruginosa is Strain Dependent
Marinho, V.L.D. ; Souza, M.B. ; Lurling, M. - \ 2013
Microbial Ecology 66 (2013)3. - ISSN 0095-3628 - p. 479 - 488.
harmful algal blooms - cyanobacterium microcystis - genetic diversity - phytoplankton communities - environmental-conditions - growth - phosphorus - lake - temperature - model
The hypothesis that outcomes of phosphorus and light competition between Cylindrospermopsis raciborskii and Microcystis aeruginosa are strain dependent was tested experimentally. Critical requirements of phosphorus (P*) and of light (I*) of two strains of each species were determined through monoculture experiments, which indicated a trade-off between species and also between Microcystis strains. Competition experiments between species were performed using the weakest predicted competitors (with the highest values of P* and of I*) and with the strongest predicted competitors (with the lowest values of P* and of I*). Under light limitation, competition between the weakest competitors led C. raciborskii to dominate. Between the strongest competitors, the opposite was observed, M. aeruginosa displaced C. raciborskii, but both strains co-existed in equilibrium. Under phosphate limitation, competition between the weakest competitors led C. raciborskii to exclude M. aeruginosa, and between the strongest competitors, the opposite was observed, M. aeruginosa displaced C. raciborskii, but the systemdid not reach an equilibrium and both strains were washed out. Hence, outcomes of the competition depended on the pair of competing strains and not only on species or on type of limitation. We concluded that existence of different tradeoffs among strains and between species underlie our results showing that C. raciborskii can either dominate or be displaced byM. aeruginosa when exposed to different conditions of light or phosphate limitation.
Molecular detection of Papaya meleira virus in the latex of Carica papaya by RT-PCR
Araujo, M.M.M. de; Tavares, E.T. ; Silva, F.R. da; Marinho, V.L.D. ; Souza, M.T. - \ 2007
Journal of Virological Methods 146 (2007)1-2. - ISSN 0166-0934 - p. 305 - 310.
A RT-PCR assay was developed for early and accurate detection of Papaya meleira virus (PMeV) in the latex from infected papayas. The meleira disease is characterized by an excessive exudation of more fluidic latex from fruits, leaves and stems. This latex oxidises and gives the fruit a ¿sticky¿ texture. In the field, disease symptoms are seen almost exclusively on fruit. However, infected plants can be a source of virus for dissemination by insects. Primers specific for PMeV were designed based on nucleotide sequences of the viral dsRNA obtained using a RT-RAPD approach. When tested for RT-PCR amplification, one of these primers (C05-3¿) amplified a 669-nucleotide fragment using dsRNA obtained from purified virus particles as a template. The translated sequence of this DNA fragment showed a certain degree of similarity to the amino acid sequence of RNA-dependent RNA polymerases from other dsRNA viruses. When used as the single primer in two RT-PCR kits available commercially, primer C05-3¿ also amplified the DNA fragment from papaya latex of infected, but not from healthy plants. The RT-PCR-based method developed in this study could simplify early plant disease diagnosis, assist in monitoring the dissemination of the pathogen within and between fields, and assist in guiding plant disease management.