Evidence of cylindrospermopsin uptake and clearance in fish (Oreochromis niloticus) under laboratory conditions.

Cylindrospermopsin (CYN) is a cyanotoxin that has raised serious concerns about public health in many parts of the world. It can bioaccumulate and affect the health of aquatic organisms, but despite this, few studies have been conducted on CYN uptake and clearance in fish. In this paper, the authors evaluate the uptake and clearance of CYN in the muscle tissue and viscera of juvenile tilapia (Oreochromis niloticus) after exposure to aqueous extracts and whole cells of Cylindrospermopsis raciborskii (CYN-producer). CYN blended with commercial fish food, and three experiments were conducted. In the first trial, fish food, and aqueous extracts containing 0.31 µg CYN g-1 of food per day, was administered to tilapia for 15 days. In the second trial, fish were provided food and intact cells (5.4 µg CYN g-1 of food per day) for 15 days. In the last trial, they were provided fish food and aqueous extracts (0.8 µg CYN g-1 of food per day) for 12 days, and for the next 10 days, the animals were fed food without toxic cell extracts (to simulate a clearance period). The concentration of CYN in muscle tissue and viscera was analysed using ELISA. In the case of juvenile tilapia, the presence of CYN was higher in viscera than in muscle tissue, and the toxin remained in the tissues even after 10 days without the addition of contaminated food. The results suggest that tilapia represents a potential source of CYN transfer through the food web, and this shows the need for a continuous monitoring of this compound in organisms that are used for human and animal consumption.

Multiple biomarkers response in a Neotropical fish exposed to paralytic shellfish toxins (PSTs).

The Alagados Reservoir (Southern Brazil) is used as water supply, and since 2002 there have been reports with a presence of cyanobacterial blooms and cyanotoxins. In order to assess the water quality and the ecological integrity of the reservoir, we evaluated biochemical, genotoxic and osmoregulatory biomarkers in the freshwater cichlid fish (Geophagus brasiliensis) that were exposed to PSTs. The fish were sampled in the Alagados Reservoir in February 2016 (Summer) and were divided in three groups: 1) Reservoir group (RES): fish were collected immediately after sampling; 2) Depuration group (DEP): fish were submitted to the depuration experiment for 90 days in the laboratory; and 3) Reproduction group (REP): fish were kept in the laboratory until the fertilization and the chemical analyses were performed on the offspring (F1 generation). In the RES and DEP the blood, brain, muscle, liver and gills were collected for biochemical, genotoxic and osmoregulatory biomarkers analysis. Our results showed that the fish from the Alagados Reservoir (RES) presented oxidative stress and DNA damage; and after 90 days (DEP), the antioxidant system and DNA damage were recovered. Although PSTs were considered a risk to the ecological integrity of this water body; PSTs concentrations were not found in the tissues of the F1 generation. In addition, the biomarkers used were useful tools to evaluate the effects of environment contamination. Therefore, it is necessary to develop new technologies and monitoring programs in order to reduce cyanobaterial blooms, cyanotoxins and human activities that cause the contamination in aquatic environments.

The accumulation dynamics, elimination and risk assessment of paralytic shellfish toxins in fish from a water supply reservoir.

Paralytic shellfish Toxins (PSTs) or saxitoxins are neurotoxins that block the neural transmission by binding to the voltage-gated sodium channels in the nerve cells. There are >50 analogues described, which could be biotransformed into a molecular form of greater or lesser toxicity. The Alagados Reservoir is used for water supply, and persistent cyanobacterial blooms as well as PSTs concentrations have been found in this water body since 2002. The aims of this study were to quantify the concentrations of PSTs in the water and fish samples from the Alagados Reservoir. In addition, we evaluated the elimination of PSTs for 90 days in fish and estimated the potential risk to human health. Water and fish samples were collected from the reservoir. For the water samples the phytoplankton and chemical analyses were carried out. Fish were divided into two sample times: Field Samples (FS) and Elimination Experiment Samples (EES), which were maintained for 90 days in filtered and dechlorinated water. For chemical analysis, the muscles of FS were collected on the fish sampling day and the muscles and feces of EES were collected at 7, 15, 30, 45, 60, 75 and 90 days. PSTs concentrations were present in water and fish samples, and they were estimated as a potential risk to humans; mainly for children. In addition, toxins were accumulated, biotransformed to other analogues and excreted by the fish. However, after 90 days, the toxins were still present in the water and fish muscle. Therefore, PSTs can remain for a long period in water, and fish can be a carrier of these neurotoxins. New approaches of monitoring and management are necessary in the actual global context of cyanobacteria and cyanotoxins.

Depuration time and sublethal effects of microcystins in a freshwater fish from water supply reservoir.

Microcystins (MCs) are hepatotoxins that have been considered to be a worldwide problem due the effects that they can cause to environmental and human health systems. The Iraí Reservoir, located in the South of Brazil, is used as a water supply and MCs concentrations have been reported in this ecosystem. This study aimed to determine the MCs concentrations in the Iraí Reservoir and to evaluate the MCs depuration time and the health of Geophagus brasiliensis using biomarkers. Water and fish samples were collected in the Iraí Reservoir from August 2015 to May 2016. Phytoplankton and chemical analyses were conducted using water samples and the fish were divided into two groups; the Immediate Group (IMM) and the Depuration Group (DEP). In the IMM group, the blood, liver, muscle, brain and gills were collected, in order to evaluate the genotoxic, biochemical and chemical biomarkers. The DEP group was used in the depuration experiment for 90 days, and after this period the fish were submitted to the same procedure as the IMM group. Our results suggested that fish accumulated MCs and it may have caused oxidative stress, neurotoxicity and molecular damage. Furthermore, MCs concentrations increased during the depuration time and it resulted in molecular damage over the first 30 days. After 90 days, the recovery of the antioxidant system occurred. The depuration started on the 15th day, however, the toxins were still present in the samples. Therefore, the effects and the persistence of MCs are a risk to environmental systems and human health.

Neurotoxins in a water supply reservoir: An alert to environmental and human health.

Reservoirs are important source of power generation, recreation, and water supply. Nevertheless, human activities have favored the bloom of toxic cyanobacteria in many reservoirs, which has resulted in environmental, social, and economic problems. This study aims to evaluate the water quality of a reservoir in South Brazil through the analysis of cyanobacteria and cyanotoxins PSTs (Paralytic Shellfish Toxins) and biomarkers of environmental contamination in fish. For this purpose, water samples and fish (Geophagus brasiliensis) (Perciformes: Cichlidae) were collected from September 2013 to May 2014. The fish G. brasiliensis were separated in two groups. The first one "site group" was euthanized after the sampling and their weight and length were measured. The blood, brain, muscle and liver were collected for chemical, biochemical and genetics biomarkers analysis. The second group "depuration group" was submitted to depuration experiment for 40 days in clean water. After that, the same procedures as for the first group were carried out. Cylindrospermopsis raciborskii was the dominant cyanobacteria found in the reservoir, and it showed a density above the recommended limit by Brazilian legislation of 20,000 cells/mL. Results showed that the fish accumulate PSTs in the Reservoir and these were not eliminated after 40 days. The biochemical and genotoxic biomarkers showed a significant difference between "site groups" and "depuration groups", which suggests a recovery of the antioxidant system and a reduction of cellular damage after 40 days in clean water. In conjunction with results reported earlier by others, Alagados Reservoir, in South Brazil, appears to have a persistent contamination of cyanotoxins. Moreover, the mixture of contaminants which may be present in the water body can explain the seasonal differences in fish at the sampled points.