Chlorpyrifos (CPF) is an organophosphorus insecticide detected in aquatic environments considered harmful to living beings. The aim of this research was to evaluate the ecotoxicity of CPF for neotropical aquatic organisms of distinct trophic levels (Lemna minor, Azolla caroliniana, and Wolffia brasiliensis macrophytes; Pomacea canaliculata snail; Macrobrachium acanthurus shrimp; Xiphophorus maculatus and Hyphessobrycon eques fish), to verify the risk of environmental poisoning for each organism, and to determine the best bioindicator species of aquatic contamination by the insecticide. Ecotoxicological assays were carried out with different concentrations of CPF under controlled laboratory conditions standardized for each species. IC50;7d, LC50;7d, EC50;48h, and LC50;48h values were calculated using the Trimmed Spearman Karber software with 95% confidence limits. The toxicity data were used to classify the CPF according to the ecotoxicity categories for aquatic organisms. The risk of CPF environmental poisoning was determined by the quotient method considering different environmental scenarios. The sensitivity order of neotropical aquatic organisms to chlorpyrifos was Macrobrachium acanthurus (0.002 mg L⁻¹) > Xiphophorus maculatus (0.07 mg L⁻¹) > Hyphessobrycon eques (1.65 mg L⁻¹) > Pomacea canaliculata (30.66 mg L⁻¹) > Azolla caroliniana (849.72 mg L⁻¹) > Wolffia brasiliensis (1271.63 mg L⁻¹) = Lemna minor (1299.60 mg L⁻¹). The risk of poisoning by chlorpyriphos may vary according to the environmental concentration of the insecticide and the exposed trophic level. The best bioindicator and with the greatest risk of environmental poisoning was shrimp. The difference in CPF ecotoxicity for distinct aquatic trophic levels shows the relevance of evaluating the effects of contaminants considering food chains and highlights the importance of studying these levels in environmental monitoring programs.

The objectives of this study were to determine the acute toxicity of cadmium and to examine the bioaccumulation and elimination of cadmium in different tissues of the freshwater prawn Macrobrachium sintangese. It also evaluated the structural damage of gills and hepatopancreas of M. sintangese when administered to sublethal cadmium concentration and when exposed prawns were transferred to cadmium-free media. According to the mortality data, the 96 h LC₅₀ value of Cd to M. sintangese was 86 μg/L. The highest cadmium accumulation was observed in gills, followed by the hepatopancreas, and the abdominal muscle. After being transferred to cadmium-free media, the highest cadmium elimination was observed in abdominal muscle, followed by the gills and hepatopancreas. The gills of prawns exposed to cadmium exhibited a severe hyperplasia, vacuolization, and multiple necroses which resulted to the swelling of lamellae. After transferring the cadmium-exposed prawns into the control media, the histopathological effects decreased. Severe alterations to the hepatopancreatic tissue were observed in prawns exposed to cadmium. The tubular epithelial cells were heavily vacuolated and even ruptured. The number of large vacuoles and R cells appeared in the tubular epithelial cells of the hepatopancreas. After transferring to the control media, the histological alterations of the hepatopancreas decreased. The tubular epithelial cells began to rearrange to the normal structure. The number of R cells and B cells were noted in the epithelial cells. The thickness of tubular epithelial cells was comparable to the controls. Due to the sensitivity of M. sintangese to cadmium, therefore this species potentially can be used as a test organism in toxicity assays.

Aquaponics is a science that integrates animal aquatic production with vegetable culture in recirculating water systems. The performance of an aquaponics system using constructed semi-dry wetland with lettuce (Lactuca sativa L.) planted on treating wastewater of culture of shrimp Macrobrachium amazonicum was evaluated. Each aquaponics module consisted in four culture tanks (1 m³ tank⁻¹), conical sedimentation tank (0.1 m³), circular holding tank (0.2 m³), and constructed semi-dry wetland (0.2 m × 1.0 m × 4.0 m). Post larvae (PL) shrimps with an initial average mass of 314 ± 4.75 mg were stocked at density treatments in quadruplicate: (A) 40 shrimps m⁻², (B) 80 shrimps m⁻², and (C) 120 shrimps m⁻². Our results showed the average final mass of shrimps had a slight reduction at the density 80 and 120 shrimps. However, it did not differ significantly between the treatments. The ultimate survival and productivity were higher in density 80 and 120 shrimps. The maximum biomass productivity occurred at the treatment with density 120 shrimps. The aquaponics recirculation system using constructed semi-dry wetlands with lettuce adequately treated the water at the densities tested. Various water quality parameters were deemed suitable for shrimp culture, but for lettuce not, especially the temperature. The shrimp density was inappropriate which limited the system to accumulate and increase the concentration of nutrients to vegetables with lessening the yield. Nonetheless, the system with higher density has higher nutrient content that plants demonstrated significantly better growth and yield. The results showed the potential use of organics waste generated in a family lettuce hydroponic production, but for a commercial production is indicated supplementation with nutrients like calcium, magnesium, and potassium in the water.

INTRODUCTION: While the literature is replete with studies of the toxic potency of pentachlorophenol (PCP), site-specific criteria for native aquatic species that can be used in ecological risk assessments has been lacking and application of toxicity information for non-native species is controversial. MATERIALS AND METHODS: In the present study, acute and chronic toxicities of PCP to six aquatic species native to the Yangtze River were determined. The HC5 and HC50 (hazardous concentration for 5% and 50% of species) were derived from dose–response curves for these native aquatic species and were then compared with those derived for non-native species. RESULTS: The acute toxicity values for the native species ranged from 8.8 × 10−2 mg l−1 (Plagiognathops microlepis) to 1.1 mg l−1 (Soirodela polyrhiza), while chronic toxicity values based on no observed effect concentrations (NOECs) ranged from 0.01 mg l−1 (Macrobrachium superbum) to 0.25 mg l−1 (Soirodela polyrhiza). Native aquatic benthos was more sensitive to acute PCP exposure than non-native species. There was no significant difference in NOECs derived from native fish species and those based on non-native fish species. The median acute HC5 and HC50 derived from the toxicity data of native taxa were both less than those derived from non-native taxa. There was no significant difference between chronic HC5s derived from the two sets of taxa. However, the median chronic HC50 derived from native taxa was less than that derived from non-native taxa. CONCLUSION: The study upon which we report here provides site-specific toxicity information developed for native species which can be used for the protection of local aquatic life from a common contaminant, PCP.

The study’s objective was to evaluate the nitrate level safety for Macrobrachium amazonicum juvenile in the laboratory, a potential native species for culture in Brazil. The experiment consisted of six treatments with six replicates in a completely randomized block design: 0, 250, 500, 1,000, 1,500, and 2,000 mg L⁻¹. Physical and chemical water quality parameters were recorded every 12 h, while the shrimp mortalities in the 24-h interval. Except for nitrate, all physical and chemical water quality parameters remained within the ideal range rearing to this species. No deaths were observed during the first 6 h of exposure range 0-500 mg L⁻¹ concentrations. At 250 mg L⁻¹ N-NO₃⁻, the mortality (10%) started from 48 h. At 500 mg L⁻¹ N-NO₃⁻, shrimp mortalities occurred after 24 h, reaching 60% after 72 h. In the treatments with 1000 and 1500 mg L⁻¹ N-NO₃⁻ concentrations, dead shrimps can be observed after 24 h, with a mortality rate of 78% and 90% of the population in 96 h, respectively. All shrimps exposed at 2000 mg L⁻¹ died in 96 h. The LC50 values obtained decreased with increasing exposure time. Based on LC50 (96 h), the N-NO₃⁻ level safety to M. amazonicum is 48.5 mg L⁻¹.

Bioaccumulation of As, Cd, Cu, Pb and Zn by Macrobrachium prawns was observed to occur in the Strickland River downstream of a gold mine at Porgera, Papua New Guinea. This was despite the total metal concentrations of waters and sediments indicating no difference from reference sites within tributaries. To provide information on potential sources and bioavailability of metals to prawns, an extensive range of analyses were made on waters, suspended solids, deposited sediments and plant materials within the river system. Dissolved metal concentrations were mostly sub-micrograms per liter and no major differences existed in concentrations or speciation between sites within the Strickland River or its tributaries. Similarly, no differences were detected between sites for total or dilute acid-extractable metal concentrations in bed sediments and plant materials, which may be ingested by the prawns. However, the rivers in this region are highly turbid and the dilute acid-extractable cadmium and zinc concentrations in suspended solids were greater at sites in the Strickland River than at sites in tributaries. The results indicated that mine-derived inputs increased the proportion of these forms of metals or metalloids in the Strickland River. These less strongly bound metals and metalloids would be more bioavailable to the prawns via the dietary pathway. The results highlighted many of the difficulties in using routine monitoring data without information on metal speciation to describe metal uptake and predict potential effects when concentrations are low and similar to background. The study indicated that the monitoring of contaminant concentrations in organisms that integrate the exposure from multiple exposure routes and durations may often be more effective for detecting impacts than intermittent monitoring of contaminants in waters and sediments.