Aquatic risk assessment of pesticides in Latin America.

Latin America is anticipated to be a major growth market for agriculture and production is increasing with use of technologies such as pesticides. Reports of contamination of aquatic ecosystems by pesticides in Latin America have raised concerns about potential for adverse ecological effects. In the registration process of pesticides, all countries require significant data packages on aquatic toxicology and environmental fate.

A method to predict and understand fish survival under dynamic chemical stress using standard ecotoxicity data.

The authors present a method to predict fish survival under exposure to fluctuating concentrations and repeated pulses of a chemical stressor. The method is based on toxicokinetic-toxicodynamic modeling using the general unified threshold model of survival (GUTS) and calibrated using raw data from standard fish acute toxicity tests. The model was validated by predicting fry survival in a fish early life stage test.

Macroinvertebrate responses to insecticide application between sprayed and adjacent nonsprayed ditch sections of different sizes.

Under typical agricultural use of an insecticide, it is likely that only part of an edge-of-field drainage ditch will be directly contaminated by spray drift. The response, including recovery, of aquatic macroinvertebrates in sprayed ditch sections may be affected by immigration of organisms from adjacent nonsprayed ditch sections, but also the population dynamics in nonsprayed sections (refuges) may be affected by nearby contaminated patches (known as action at a distance). Experimental ditches were used to study the influence of the presence of nearby refuges on the responses of macroinvertebrates in ditch sections directly sprayed with the insecticide lufenuron, and vice versa.

Impact of a benzoyl urea insecticide on aquatic macroinvertebrates in ditch mesocosms with and without non-sprayed sections.

The long-term response, including recovery, of aquatic macroinvertebrates to short-term insecticide exposure may be affected by the presence of uncontaminated refuges in the stressed ecosystem. Experimental ditches were used to study the influence of non-sprayed ditch sections regarding the ecotoxicological effects on and the recovery of macroinvertebrates following treatment with the insecticide lufenuron. The treatment regimes differed in the proportion of the ditch (0, 33, 67, and 100% of surface area) that was sprayed to reach a lufenuron concentration of 3 microg/L in the water column of the sprayed ditch section.

The influence of simulated immigration and chemical persistence on recovery of macroinvertebrates from cypermethrin and 3,4-dichloroaniline exposure in aquatic microcosms.

Background: Chemical dissipation and organism immigration are considered important factors that influence recovery potential from perturbation of aquatic macroinvertebrates. Experiments were conducted to investigate the effect of simulated immigration on recovery of aquatic macroinvertebrates exposed in outdoor microcosms to ecotoxicologically similar concentrations of the rapidly dissipating pyrethroid insecticide cypermethrin (70 ng L(-1)) or the more persistent herbicide intermediate and degradate 3,4-dichloroaniline (10 mg L(-1)). Microcosms were covered with light-permeable mesh to prevent recolonisation.

The ecological niche of Daphnia magna characterized using population growth rate.

The concept of an organism's niche is central to ecological theory, but an operational definition is needed that allows both its experimental delineation and interpretation of field distributions of the species. Here we use population growth rate (hereafter, pgr) to define the niche as the set of points in niche space where pgr > 0. If there are just two axes to the niche space, their relationship to pgr can be pictured as a contour map in which pgr varies along the axes in the same way that the height of land above sea level varies with latitude and longitude.

Responses of zooplankton in lufenuron-stressed experimental ditches in the presence or absence of uncontaminated refuges.

Outdoor experimental ditches were used to evaluate the influence of untreated refuges on the recovery of zooplankton communities following treatment with the fast-dissipating insecticide lufenuron. Each experimental ditch was divided into three sections of the same surface area. The treatments differed in the proportion of ditch (0, 33, 67, and 100% of the surface area) to which the insecticide was applied at the same nominal treatment (3 mug/L).

Linking molecular and population stress responses in Daphnia magna exposed to cadmium.

DNA microarrays can be used to measure environmental stress responses. If they are to be predictive of environmental impact, we need to determine if altered gene expression translates into negative impacts on individuals and populations. A large cDNA microarray (14000 spots) was created to measure molecular stress responses to cadmium in Daphnia magna,the mostwidely used aquatic indicator species, and relate responses to population growth rate (pgr).

Systems biology meets stress ecology: linking molecular and organismal stress responses in Daphnia magna.

Background: Ibuprofen and other nonsteroidal anti-inflammatory drugs have been designed to interrupt eicosanoid metabolism in mammals, but little is known of how they affect nontarget organisms. Here we report a systems biology study that simultaneously describes the transcriptomic and phenotypic stress responses of the model crustacean Daphnia magna after exposure to ibuprofen.

Results: Our findings reveal intriguing similarities in the mode of action of ibuprofen between vertebrates and invertebrates, and they suggest that ibuprofen has a targeted impact on reproduction at the molecular, organismal, and population level in daphnids.

Agricultural intensity and landscape structure: influences on the macroinvertebrate assemblages of small streams in northern Germany.

The present study aimed to relate aquatic macroinvertebrate community composition to agricultural intensity and landscape structure. A total of 360 streams were investigated within the Aller river basin in northern Germany. The study area is typical of central German arable agricultural regions, but the small streams were of low dilution potential.

Chronic toxicity of ibuprofen to Daphnia magna: Effects on life history traits and population dynamics.

The non-steroidal anti-inflammatory drug (NSAID) ibuprofen (IB) is a widely used pharmaceutical that can be found in several freshwater ecosystems. Acute toxicity studies with Daphnia magna suggest that the 48h EC(50) (immobilisation) is 10-100 mgIBl(-1). However, there are currently no chronic IB toxicity data on arthropod populations, and the aquatic life impacts of such analgesic drugs are still undefined.

Expression of target and reference genes in Daphnia magna exposed to ibuprofen.

Background: Transcriptomic techniques are now being applied in ecotoxicology and toxicology to measure the impact of stressors and develop understanding of mechanisms of toxicity. Microarray technology in particular offers the potential to measure thousands of gene responses simultaneously. However, it is important that microarrays responses should be validated, at least initially, using real-time quantitative polymerase chain reaction (QPCR).

Ecological impact in ditch mesocosms of simulated spray drift from a crop protection program for potatoes.

Outdoor aquatic ditch mesocosms were treated with a range of pesticides to simulate various spray drift rates resulting from a typical crop protection program used in the cultivation of potatoes in The Netherlands. The main experimental aims of the present study were to provide information on the fate and ecological effects of drift of the pesticides into surface water and to evaluate the effectiveness of drift-reduction measures in mitigating risks. The pesticides selected and the dosage, frequency, and timing of application were based on normal agricultural practices in the potato crop.

Effects of lambda-cyhalothrin in two ditch microcosm systems of different trophic status.

The fate and effects of the pyrethroid insecticide lambda-cyhalothrin were compared in mesotrophic (macrophyte-dominated) and eutrophic (phytoplankton-dominated) ditch microcosms (approximately 0.5 m3). Lambda-cyhalothrin was applied three times at one-week intervals at concentrations of 10, 25, 50, 100, and 250 ng/L.

Ecotoxicogenomics: the challenge of integrating genomics into aquatic and terrestrial ecotoxicology.

Rapid progress in the field of genomics (the study of how an individual's entire genetic make-up, the genome, translates into biological functions) is beginning to provide tools that may assist our understanding of how chemicals can impact on human and ecosystem health. In many ways, if scientific and regulatory efforts in the 20th century have sought to establish which chemicals cause damage to ecosystems, then the challenge in ecotoxicology for the 21st century is to understand the mechanisms of toxicity to different wildlife species. In the human context, 'toxicogenomics' is the study of expression of genes important in adaptive responses to toxic exposures and a reflection of the toxic processes per se.

Partitioning, bioavailability, and toxicity of the pyrethroid insecticide cypermethrin in sediments.

The partitioning, bioavailability, and toxicity of cypermethrin in water-sediment systems was investigated. Cypermethrin adsorbed extensively and rapidly, with an overall mean organic carbon (OC) adsorption partition coefficient (Koc) of 350,000, and approximately 99% adsorption occurred within 24 h. Bioavailability was measured via body burdens of Daphnia magna and Chironomus tentans.

How realistic are outdoor microcosms? A comparison of the biota of microcosms and natural ponds.

This study investigated the extent to which aquatic plant and macroinvertebrate assemblages in small outdoor microcosms (cylinders 1.25-m diameter x 1.25 m deep) resembled assemblages found in natural ponds in Britain.