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- Assessment of cyanobacterial biomass as sustainable agricultural fertilizer: soil experiment with plants in Pot †Publication . Massa, Anabella; Azevedo, Joana; Azevedo, Rui; Pinto, Edgar; Costa, Anabela; Vasconcelos, Vitor; Campos, Alexandre; Freitas, MarisaProviding food to the growing human population in a sustainable way is one of the greatest challenges of modern society. In this context, cyanobacterial biomass (CB) can function as a source of macronutrients to increase soil productivity. These organisms can be collected from the environment in considerable amounts, since they tend to grow in large blooms. However, some of these cyanobacterial strains produce toxins that need to be carefully monitored to avoid food accumulation. The objective of this work was to evaluate the possible use of toxic and non-toxic strains of CB as fertilizer supplement in the growth of economically relevant vegetables. One-month old Raphanus sativus (radish) and Spinacia oleracea (spinach) plants were grown in pots in indoor controlled conditions. Six experimental conditions were set: (1) a control with no nutrient addition, (2) a recommended dose of a NK commercial fertilizer (CF), 0.6g of lyophilized CB of (3) a non-toxic strain of Cylindrospermopsis raciborskii, (4) a toxin-producing strain of C. raciborskii, (5) Microcystis aeruginosa, and (6) Anabaena sp. Several variables were estimated: in CB, this included the NPK dose addition, and in plants, the height, dry weight (dw) of the shoot and root, and the mineral content of plant edible parts. The mineral content in CB was estimated and compared with the recommended dose of CF, according to the information given by the fabricant label. We found no significative differences in N composition; nevertheless, there was a significative higher content in P and significative lower content in K in the CB. In the plants, we found no significative statistical differences between the treatments for the dw of radish root and spinach height. In spinach, the dw of the shoot in the M. aeruginosa treatment was significantly lower than the control, CF, and both the toxic and non-toxic C. raciborskii biomass. Additionally, in radish, the plant height and dw of the shoot M. aeruginosa treatment were significantly lower than in the toxic strain of C. raciborskii treatment. When analyzing mineral content in edible parts, we found that spinach treated with control and CF showed a higher content of Ca, Mo, N, P, and K, while in radish, the same two treatments plus the C. raciborskii toxic had higher Co and Fe content. M. aeruginosa amendment seems to impair shoot growth in both plant species. On the contrary, the toxic C. raciborskii CB seems to have a beneficial effect on growth and in mineral uptake on radish plants.
- Bioaccessibility and changes on cylindrospermopsin concentration in edible mussels over storage and processing time.Publication . Freitas, Marisa; Azevedo, Joana; Carvalho, António Paulo; Mendes, Vera; Manadas, Bruno; Campos, Alexandre; Vasconcelos, VítorThe cyanotoxin cylindrospermopsin has been recognized of increased concern due to the global expansion of its main producer, Cylindrospermopsis raciborskii. Previous studies have shown that aquatic organisms, especially bivalves, can accumulate high levels of cylindrospermopsin. Based on the potential for human health risks, a provisional tolerable daily intake of 0.03 µg/kg body-weight has been recommended. However, human exposure assessment has been based on the cylindrospermopsin concentration in raw food items. This study aimed to assess the changes on cylindrospermopsin concentration in edible mussels over storage and processing time as well as cylindrospermopsin bioaccessibility. Mussels, (Mytilus galloprovincialis) fed cylindrospermopsin-producing C. raciborskii, were subjected to the treatments and then analyzed by LC-MS/MS. Mussels stored frozen allowed a significantly higher recovery of cylindrospermopsin (52.5%/48 h and 57.7%/one week). The cooking treatments did not produce significant differences in cylindrospermopsin concentration in mussel matrices (flesh), however, cylindrospermopsin was found in the cooking water, suggesting that heat processing can be used to reduce the availability of cylindrospermopsin in this food item. The in vitro digestion with salivary and gastrointestinal juices considerably decreased the cylindrospermopsin availability in uncooked and steamed mussels, highlighting the importance in integrating the bioaccessibility in the human health risk assessment.
- Cyanobacterial biomass used as biofertilizer in lettuce plants: effects on growth and cyanotoxin accumulation †Publication . Santos, Érica; Massa, Anabella; Azevedo, Joana; Martins, Diogo; Reimão, Mariana; Vasconcelos, Vitor; Campos, Alexandre; Freitas, MarisaThe use of cyanobacterial biomass as a biofertilizer is promising in terms of sustainable agriculture. Nevertheless, cyanobacteria can be considered a threat to human and environmental health due to the potential presence of cyanotoxins, since some studies report that the use of contaminated water for agricultural irrigation can impair plant growth and lead to contamination of food products. Interestingly, at environmentally relevant concentrations, cylindrospermopsin (CYN) seems to cause no deleterious effects in plants, and it might even promote their yield. However, studies assessing CYN accumulation in the edible tissues at environmental concentrations are lacking. The objective of this work was to evaluate the effects of cyanobacterial biomass CYN producing or non-producing on lettuce plant growth, and that of CYN accumulation in edible tissues. This study consisted of growing lettuce plants, under controlled conditions, for 25 days in soil (1) with no extra nutrient addition (control) and supplementation with (2) cyanobacterial biomass that did not produce CYN, (3) cyanobacterial biomass that produced CYN (~10 µg of dissolved CYN), and (4) cyanobacterial biomass that produced CYN, treated by boiling for 5 min (~25 µg of dissolved CYN). At the end of the exposure, lettuce growth was assessed, as well as CYN accumulation in tissues and soil. The results showed that leaf growth was significantly increased (p < 0.05) in lettuce plants supplemented with cyanobacterial biomass, especially at condition (3), which was five-fold higher compared with the control group. Regarding CYN accumulation, for conditions (3) and (4), the toxin was detected in the tissues of plants, as well as in soil at the following decreasing order of concentrations: soil > roots > leaves. Interestingly, the concentration determined in lettuce leaves in condition (4) was three-fold lower when compared with the condition (3). Nevertheless, for both conditions, although CYN has been detected in lettuce leaves, the concentration in the edible part did not exceed the proposed provisional tolerable daily intake (TDI) of 0.03 µg/kg/BW. In conclusion, these results suggest that the use of cyanobacterial biomass as lettuce biofertilizer, even containing CYN at environmentally relevant concentrations, can positively influence plant growth and development without compromising the safety of edible tissues.
- Effects of glyphosate and cylindrospermopsin at environmental concentrations on growth, photosynthesis and mineral content in lettuce plantsPublication . Sengupta, Soumi; Freitas, Marisa; Pinto, Edgar; Azevedo, Joana; Oliveira, Flávio; Campos, Alexandre; Vasconcelos, VítorGlyphosate is the most widely used herbicide, mainly due to the extensive cultivation of glyphosate resistant plants. The intensification of agriculture has increased water eutrophication and the presence of natural cyanobacterial toxins, such as ylindrospermopsin. Previous studies support the hypothesis that glyphosate and cylindrospermopsin can affect the yield of crop plants, depending on the exposure concentration. Lettuce (Lactuca sativa L.)
- Presence of microcystis sp. and microcystins in alqueva reservoirs assessed by chemical and molecular methodsPublication . Azevedo, Tomé; Azevedo, Joana; Martins, Joana; Freitas, Marisa; Vasconcelos, Vitor; Campos, AlexandreThe Alqueva reservoir, located in the Alentejo region, in the south of Portugal, is considered the largest artificial lake in Europe. It has been in operation since 2002, and it is used to produce energy and supply water for agriculture and to the populations in this region of Portugal. The water distribution system, starting from the main reservoir, includes 19 reservoirs of smaller capacity and a network of waterways totaling 382 km in length. Furthermore, the occurrence of cyanobacteria in water reservoirs has been recognized as an environmental concern due to the potential presence of their related toxins that can cause severe health effects. This work aimed to monitor the presence of cyanobacteria and the commonly associated cyanotoxin microcystin (MC) in three reservoirs belonging to the Alqueva water system, namely São Pedro, Magra, and Pisão, located in the district of Beja. These reservoirs were selected considering the historical data of phytoplankton provided by EDIA, the entity in charge of the management of this infrastructure. The field work was carried out in July, August, and September, the months with the highest risk of outgrowth of cyanobacteria, in the year 2020. Two or three samples of water (5 L) were collected in different locations of the reservoirs, once per month, by boat. Samples were collected at different depths in the photic zone using a Van Dorn bottle and pooled. The water samples were then processed in the laboratory. Molecular biology techniques were used to detect the presence of cyanobacteria (16S rRNA) and MC-related genes. Moreover, chemical analysis techniques based on liquid chromatography and mass spectrometry (MS) were used to identify and quantify MCs. The results revealed the presence of MCs in the three reservoirs in the three months monitored. Concentrations of this toxin varied between 0.01 µg/L and 0.1 µg/L, with São Pedro being the reservoir displaying the highest concentrations of MCs in all of the months monitored. These results are consistent with the molecular study based on the analysis of Microcystis sp. 16 rRNA and MC biosynthetic genes (mcya–mcyG), suggesting the presence of putative toxic Microcystis sp. strains in the three reservoirs. Despite the low concentrations of MCs detected in these reservoirs, their recurrent presence in Alqueva waters serve as a reminder of the need to monitor cyanobacteria and cyanotoxins on a regular basis.