Sandra M.F.O. Azevedo

Microcystin contamination in fish from the Jacarepaguá Lagoon (Rio de Janeiro, Brazil): ecological implication and human health risk.

Chronic and subchronic toxicity from exposure to microcystins, cyclic peptide liver toxins from certain cyanobacteria, poses an important hazard, which has received little study. No in vivo information exists on accumulation and transfer of microcystin from the food chain to humans. This paper present results of a 3-year study that demonstrates bioaccumulation of microcystins by fish and potential rates of microcystin ingestion by humans. The study was carried out in a shallow coastal lagoon in the city of Rio de Janeiro (Jacarepaguá Lagoon). Fish (Tilapia rendalli) were collected every 2 weeks from August 1996 to November 1999. Microcystins were analyzed by HPLC in phytoplankton, fish liver and viscera while fish muscle tissue was analyzed by enzyme linked immunosorbant assay (ELISA). Phytoplankton samples, dominated by the genus Microcystis, were confirmed to contain microcystins as were fish livers, viscera and muscle tissue. During the entire study period, including times of low water bloom densities, fish muscle tissue contained concentrations of microcystins close to or above the recommended limit for human consumption (0.04 microg x kg(-1) day). Our findings demonstrate that microcystins can accumulate in fish tissue used for human consumption. Rates of ingestion routinely exceed the TDI guidelines as set by the WHO for drinking water. Appropriate epidemiology and risk assessment should be undertaken so that an acceptable TDI and appropriate risk management decisions can be made for human consumption of fish which are harvested from cyanobacterial blooms that contain cyanotoxins.

Toxins in the freshwater cyanobacterium Cylindrospermopsis raciborskii (Cyanophyceae) isolated from Tabocas reservoir in Caruaru, Brazil, including demonstration of a new saxitoxin analogue

Abstract Cyanobacteria can produce biotoxins that are significant hazards to humans. After the intoxication incident in 1996 at the city of Caruaru, Brazil, a phytoplankton-monitoring programme was established at its main water supply, the Tabocas reservoir. Data obtained during 1997 and 1998 revealed the dominant species at Tabocas to be Cylindrospermopsis raciborskii, which was responsible for a massive bloom observed in July–October 1998. Laboratory cultures of isolate ITEP-018 demonstrated highly toxic properties, mice inoculated with this strain exhibited the same symptoms as those of paralytic shellfish poisoning, with an acute lethal effect of 9.3 mouse units mg−1 of dry cells. Several saxitoxin analogues were identified in these cultures, specifically saxitoxin (3.3 mol% total toxin content), gonyautoxin 6 (6.4 mol%), decarbamoyl-saxitoxin (8.5 mol%), neosaxitoxin (17.1 mol%), and a new saxitoxin analogue, which proved to be the major product of the Tabocas strain, accounting for 64.6 mol% of the toxin present in the sample analysed. Additionally, decarbamoylneo-saxitoxin was detected by liquid chromatography-mass spectrometry. Cylindrospermopsis raciborskii strain ITEP-018 thus produces at least five saxitoxin analogues, including the most toxic ones as assessed by mouse bioassay.

First report of microcystins from a Brazilian isolate of the cyanobacteriumMicrocystis aeruginosa

This is the first report on microcystins, cyclic heptapeptide hepatotoxins, from Brazilian water supplies. A colony isolate (NPJB-1) of the colonial cyanobacteriumMicrocystis aeruginosa from Lagoa das Garças, São Paulo, was cultured under non-axenic conditions. Exponential phase cells were harvested, concentrated and lyophilized for mouse bioassays and toxin extraction. The LD100 of lyophilized cell suspensions was approximately 31 mg kg−1 (dry cell weight/animal weight). Isolation, purification and characterization of the toxins were carried out by reversed phase HPLC, HPLC amino acid analysis and fast atom bombardment mass spectrometry. Strain NPJB-1 produces two different hepatotoxic heptapeptide microcystins. The main one was microcystin-LR, the most commonly reported microcystin from cyanobacteria. The other was microcystin-LF, the phenylalanine variant of microcystin-LR. This is the first published report for microcystin-LF.

Limnological features in Tapacurá reservoir (northeast Brazil) during a severe drought

The drastic interactions of weather as El Niño events with catchment and hydrological processes can cause unexpected changes in physical, chemical and biological properties of freshwater aquatic ecosystems. The severe drought during 1998–1999 in the northeastern region of Brazil induced ecological changes in numerous reservoirs as in Tapacurá reservoir, one of the biggest drinking-water suppliers in Pernambuco state. Investigations were based on monthly sampling over 2 years (May 1998–May 2000) conducted at 3 representative stations with 3 sampled depths through the water column (0.5 m, middle and 0.5 m above the bottom). Temporal changes in ecological processes, especially stratification, were driven by two major precipitation patterns, with an initial marked dry period (period 1) followed by a rainy season (period 2). Dissolved oxygen and pH variations, higher conductivity and alkalinity values, higher concentrations of particulate organic material (carbon, nitrogen and phosphorus) and higher levels of algal biomass (chlorophyll a) characterized the dry period (May 1998–May 1999). During this phase of low water level when the reservoir storage capacity reached a minimum of 3.9%, the concentrations of chlorophyll a gradually increased with a cyanobacterial bloom (Cylindrospermopsis raciborskii) noted in April 1999. The decline in chlorophyll a and particulate organic matter were observed as a result of the first rains in May–June 1999, with the drastic changes of quality of matter (higher particulate C/N ratio). After a phase characterized by the entire water column turning anoxic, a second phase in the stratification process could be identified from June 1999 with the pronounced rainfalls accompanied by an overturn event. Annual rainfall deficit and lack of reservoir water renewal in 1998–1999 linked to the 1997 El Niño consequences were important determinants of high eutrophication levels and drastic ecological modifications in Tapacurá reservoir.

Occurrence of toxin-producing cyanobacteria blooms in a Brazilian semiarid reservoir.

We report the occurrence of cyanobacterial blooms and the presence of cyanotoxins in water samples from the Armando Ribeiro Gonçalves reservoir (06 degrees 08 S and 37 degrees 07 W), located in the state of Rio Grande do Norte, in the semiarid region of northeastern Brazil. The cyanobacterial species were identified and quantified during the rainy and dry seasons in the year 2000. Cyanotoxins such as microcystins, saxitoxins and cylindrospermopsins were analyzed and quantified using HPLC and ELISA methods. The mixed toxic blooms of Cylindrospermopsis raciborskii, Microcystis spp (M. panniformis, M. protocystis, M. novacekii) and Aphanizomenon spp (Aphanizomenon gracile, A. cf. manguinii, A. cf. issastschenkoi) were persistent and represented 90-100% of the total phytoplankton species. Toxic cyanobacterial blooms from the Armando Ribeiro Gonçalves reservoir were analyzed and found to have three phases in relation to the annual cycle. During the rainy season, an intense toxic bloom of Cylindrospermopsis raciborskii was recorded along with saxitoxins (3.14 microg.L(-1)). During the transition period, between the rainy and dry seasons, different species of Microscytis occurred and microcystin as high as 8.8 microg.L(-1) was recorded. In the dry season, co-dominance of Cylindrospermopsis raciborskii, Microcystis spp and Aphanizomenon spp occurred and the concentrations of saxitoxin remained very low. Our results indicate the presence of microcystins (8.8 microg.L(-1)) and saxitoxins (3.14 microg.L(-1)) into the crude water, with increasing concentrations from the second fortnight of April to late May 2000. The occurrence of toxic blooms in this reservoir points to a permanent risk of cyanotoxins in supply waters, indicating the need for the implementation of bloom control measures to improve the water quality. Exposure of the local population to cyanotoxins through their potential accumulation in fish muscle must also be considered.

First report of microcystin production by picoplanktonic cyanobacteria isolated from a northeast Brazilian drinking water supply

Seven strains (NPCA‐5, ‐10, ‐15, ‐16, ‐19, ‐23, and ‐29) of picoplanktonic cyanobacteria from Caruaru reservoirs were identified and analyzed for toxicity. We tested the toxicity of these strains by mouse bioassay, by HPLC, and by enzyme‐linked immunosorbent assay (ELISA). Strains NPCA‐15 and ‐23 were toxic when tested by mouse bioassay (LD100=600 mgDW/kg body weight). The toxin from strain NPCA‐15 had the same UV spectrum as microcystin‐LR. All of the strains showed the presence of microcystin by ELISA analysis. The microcystin concentration varied between 0.08 ng/mgDW (NPCA‐5) and 3.7 ng/mgDW (NPCA‐15). Confirmation of microcystin production by picoplankton opens the possibility that these organisms may have contributed to human poisoning in Caruaru and defines a new source of microcystin in water supplies. ©1999 John Wiley & Sons, Inc. Environ Toxicol 14: 31–35, 1999

Accumulation of microcystins by a tropical zooplankton community

In the current study, the hepatotoxic peptide microcystins, were measured in the zooplankton community of Jacarepaguá Lagoon during a 6-month period. Concurrent phytoplankton and seston samples were obtained. Microcystins were measured in seston and phytoplankton by High Performance Liquid Chromatography (HPLC), and in zooplankton by an Enzyme-Linked Immunosorbant Assay (ELISA). Zooplankton community was comprised mainly by the rotifers Brachionus angularis and B. plicatilis, the cladocerans Moina micrura and Ceriodaphnia cornuta and the copepod Metacyclops mendocinus. Phytoplankton was dominated by Microcystis aeruginosa during all the studied period. Microcystins in zooplankton ranged from 0.3 to 16.4 microg g(-1) DW, while in the sestonic samples they ranged from undetectable values to 5.8 ng g(-1) DW. Microcystins in net phytoplankton ranged from 0.3 to 3.9 mg g(-1) DW. We conclude that zooplankton from Jacarepaguá Lagoon were efficient accumulators of microcystins from seston and that these animals can be potential vectors in the transferring of such toxins to higher trophic levels in the aquatic food chain.

Effects of unicellular and colonial forms of toxic Microcystis aeruginosa from laboratory cultures and natural populations on tropical cladocerans

Three life-table experiments, two growth experiments and one feedinginhibition experiment, were performed to study the effects of the toxiccyanobacterium Microcystis aeruginosa on the cladoceransofa tropical lagoon (Jacarepaguá Lagoon, Rio de Janeiro, Brazil).Differentexperimental designs were used to estimate toxic effects of both field samplesand laboratory cultures of Microcystis aeruginosa oncladoceran life history parameters and juvenile growth rates. Effects ofnutritional deficiency could be distinguished from toxic effects in experimentswhere green algae in high carbon concentration were mixed withMicrocystis. Our results show that natural assemblages ofMicrocystis caused much less pronounced toxic effects thanlaboratory cultures and that unicellular forms were more toxic than colonialforms, even though both contained high concentrations of toxins. One possibleexplanation is that colonies were too large to be ingested by the smallMoina micrura and Ceriodaphniacornuta. Feeding inhibition by single cells and small colonies seemsto be another mechanism that contributes to the harmful effects ofMicrocystis on cladocerans, both in the laboratory and inthe field. Thus, caution is needed in extrapolating results from the laboratoryto the field. We did find, however, that toxic algae in natural seston caninhibit growth and reproduction of native cladocerans populations.

Biomonitoring of cyanotoxins in two tropical reservoirs by cladoceran toxicity bioassays

This study evaluates the potential for the use of cladocerans in biomonitoring of cyanobacterial toxins. Two zooplankton species (Daphnia gessneri and Moina micrura) were cultivated in the laboratory for use in acute (48 h) and chronic (10 days) bioassays. Water samples were collected from two reservoirs and diluted in mineral water at four concentrations. Survivorship in the acute bioassays was used to calculate LC50, and survivorship and fecundity in chronic bioassays were used to calculate the intrinsic population growth rate (r) and the EC50. Analysis of phytoplankton in the water samples from one reservoir revealed that cyanobacteria were the dominant group, represented by the genera Anabaena, Cylindrospermopsis, and Microcystis. Results of bioassays showed adverse effects including death, paralysis, and reduced population growth rate, generally proportional to the reservoir water concentration. These effects may be related to the presence of cyanobacteria toxins (microcystins or saxitoxins) in the water.

Microcystins in South American aquatic ecosystems: occurrence, toxicity and toxicological assays.

The acute poisoning of chronic renal patients during hemodialysis sessions in 1996 in Caruaru City (Pernambuco State, Brazil) stimulated an intensive search for the cause of this severe complication. This search culminated in the identification of microcystins (MC), hepatotoxic cyclic heptapeptides produced by cyanobacteria, as the causative agents. More than ten years later, additional research data provides us with a better understanding of the factors related to cyanobacterial bloom occurrence and production of MC in Brazil and other South American countries. The contamination of water bodies and formation of toxic blooms remains a very serious concern, especially in countries in which surface water is used as the main source for human consumption. The purpose of this review is to highlight the discoveries of the past 15 years that have brought South American researchers to their current level of understanding of toxic cyanobacteria species and that have contributed to their knowledge of factors related to MC production, mechanisms of action and consequences for human health and the environment.