Effect of chronic UVR exposure on zooplankton molting and growth.

Molting is a crucial physiological process in arthropods development, growth, and adult reproduction, where the chitinolytic enzyme chitobiase (CB) and the apoptosis process (caspase-3 activity) play crucial roles. Both molecular endpoints have been observed to be affected by different toxics that may be present in aquatic environments. However, the role of ultraviolet radiation (UVR) in the molting process remains with poor evidence and the possible effect of the previous exposure on F1 generation is unknown. Here, we conducted laboratory experiments with chronic UVR exposure to test the effect on the molting process of Daphnia commutata. Our results showed a clear negative effect of the UVR that affected the molting process with a reduction in individual growth. This trend was also observed in CB and caspase-3 activities. Our results also suggest that the UV dose received by the mother and eggs has an additive effect with the dose received by the offspring. These results imply that the cumulative impact of small UVR doses (2 h per day, daily dose: 2520 J m-2 of 340 nm) on mothers and eggs (which cannot be discriminated in our experiments) can have an additive or synergistic effect along with the generations through a potential increase in lethal effect. Finally, the observed desynchronization in the molting process by UVR will affect the fitness of individuals and population dynamics.

Interactive effects of temperature, ultraviolet radiation and food quality on zooplankton alkaline phosphatase activity.

Ultraviolet Radiation (UVR) is a stressor for aquatic organisms affecting enzyme activities in planktonic populations because of the increase in reactive oxygen species. In addition, UVR exposure combined with other environmental factors (i.e. temperature and food quality) could have even higher detrimental effects. In this work, we aimed to determine the effect of UVR on somatic Alkaline Phosphatase Activity (APA) and Glutathione S-Transferase (GST) activity on the cladoceran Daphnia commutata under two different temperatures (10 °C and 20 °C) and under three food qualities (carbon:phosphorus ratios: 1150, 850 and 550). APA is a biomarker that is considered as a P deficiency indicator in zooplankton. Since recovery from UVR damage under dark conditions is an ATP depending reaction we also measured APA during recovery phases. We carried out a laboratory experiment combining different temperatures and food qualities with exposition to UVR followed by luminic and dark phases for recovery. In addition, we exposed organisms to H2O2, to establish if the response on APA to UVR was a consequence of the reactive oxygen species produced these short wavelengths. Our results showed that somatic APA was negatively affected by UVR exposure and this effect was enhanced under high temperature and low food quality. Consistently, GST activity was higher when exposed to UVR under both temperatures. The H2O2 experiments showed the same trend as UVR exposure, indicating that APA is affected mainly by oxidative stress than by direct effect of UVR on the enzyme. Finally, APA was affected in the dark phase of recovery confirming the P demands. These results enlighten the importance of food quality in the interacting effect of UVR and temperature, showing that C:P food ratio could determine the success or failure of zooplanktonic populations in a context of global change.

Low concentrations, potential ecological consequences: synthetic estrogens alter life-history and demographic structures of aquatic invertebrates.

Contraceptive drugs are nowadays found in aquatic environments around the globe. Particularly, 17α-ethinylestradiol (EE2) may act even at low concentrations, such as those recorded in natural ecosystems. We evaluated the physiological effects of EE2 on cyclopoids and calanoids, common copepods in both marine and freshwater communities. We used three EE2 concentrations and assessed its impact on activity of different physiological endpoints: Acetylcholinesterase (neurotransmission), Glutathione S-transferase (detoxifying system), and Caspase-3 (apoptosis). While EE2 exerts, distinctive effect on detoxifying and apoptotic systems, no effect on AChE was observed at environmental doses. Our results show that EE2 exposure affects differently copepod physiology endpoints, altering moulting process, adult recruitment in calanoids and calanoid to cyclopoid ratio. The ecological consequences of this underlying physiological process may affect since life history to population and community structures, and this represent a new aspects of this xenobiotic in natural systems.

Glacier melting and stoichiometric implications for lake community structure: zooplankton species distributions across a natural light gradient.

Glaciers around the globe are melting rapidly, threatening the receiving environments of the world's fresh water reservoirs with significant changes. The meltwater, carried by rivers, contains large amounts of suspended sediment particles, producing longitudinal gradients in the receiving lakes. These gradients may result in changes in the light : nutrient ratio that affect grazer performance by altering elemental food quality. Thus, glacial melting may induce a shift in the phytoplankton carbon : nutrient ratio and hence influence the dominance of herbivorous zooplankton through stoichiometric mechanisms. To test this hypothesis, we combined field and experimental data, taking advantage of a natural light intensity gradient caused by glacial clay input in a deep oligotrophic Patagonian lake. Across this gradient, we evaluated the abundances of two consumer taxa with different phosphorus requirements, the copepod Boeckella gracilipes and the cladoceran Daphnia commutata, using a six-station transect along the lake. We found significant differences in light : nutrient ratio and stoichiometric food quality of the seston, together with a switch from dominance of P-rich Daphnia in low carbon : nutrient stations to dominance of low-P copepods in high carbon : nutrient stations. The laboratory experiments confirmed that the difference in the carbon : nutrient ratio across the gradient is sufficient to impair Daphnia growth. The overall patterns are consistent with our prediction that shifts in the environmental light : nutrient ratio as a result of glacial melting would contribute to shifts in the dominance of stoichiometrically contrasting taxa in consumer guilds.

Rapid enzymatic response to compensate UV radiation in copepods.

Ultraviolet radiation (UVR) causes physical damage to DNA, carboxylation of proteins and peroxidation of lipids in copepod crustaceans, ubiquitous and abundant secondary producers in most aquatic ecosystems. Copepod adaptations for long duration exposures include changes in behaviour, changes in pigmentation and ultimately changes in morphology. Adaptations to short-term exposures are little studied. Here we show that short-duration exposure to UVR causes the freshwater calanoid copepod, Eudiaptomus gracilis, to rapidly activate production of enzymes that prevent widespread collateral peroxidation (glutathione S-transferase, GST), that regulate apoptosis cell death (Caspase-3, Casp-3), and that facilitate neurotransmissions (cholinesterase-ChE). None of these enzyme systems is alone sufficient, but they act in concert to reduce the stress level of the organism. The interplay among enzymatic responses provides useful information on how organisms respond to environmental stressors acting on short time scales.

Effect of ultraviolet radiation on acetylcholinesterase activity in freshwater copepods.

We analyzed the effects of UV radiation (UVR) effects on acetylcholinesterase (AChE) activity in two calanoid copepods, Boeckella gibbosa and Parabroteas sarsi that inhabit Patagonian shallow lakes. We studied the effect of experimental UVR (UV-B and UV-A) exposure on AChE activity in relation to basal antioxidant capacities of both copepods. Our experiments showed that UVR can effectively depress AChE activity, although with differences between species. In both copepods AChE was affected by UV-B, whereas UV-A only affected AChE in B. gibbosa. Both copepods also differed in body elemental composition (C:N:P), photoprotecting compound content (carotenoids and mycosporine-like amino acids) and enzymatic antioxidant capacity (glutathione S-transferase [GST]). Our results suggest that when exposed to UVR, AChE activity would depend more on the antioxidant capacity (GST) and P availability for enzyme synthesis than on the photoprotective compounds.

Biomarcadores para el monitoreo de la exposición intrauterina a plaguicidas en comunidades rurales / Biomarkers for monitoring in utero exposure to pesticides in a rural community

La prevención del daño por exposición acontaminantes ambientales requiere identificar biomarcadores que representen una medida del proceso toxicológico antes de la manifestación de daños irreversibles. Considerando la alta vulnerabilidad del período de gestación, este trabajo fue diseñadopara evaluar el impacto de la exposición in utero a plaguicidas organofosforados (OP) y la utilidad de biomarcadores de exposición/efecto en tejidos fácilmente accesibles. Se entrevistaron 342 embarazadas del área frutícola del Alto Valle de Río Negro y Neuquén donde se alternan períodos de 6 meses de fumigación y receso. Se registraron características, hábitos y lugar de residencia materna, parámetros del neonato y de la placenta a término. Los estudios analíticos incluyeron colinesterasas sanguíneas, hemograma de las embarazadas y enzimas placentarias. Los datos fueron analizados por ANOVA regresión y correlación. La actividad de colinesterasa plasmática en época de fumigación disminuyó significativamente (18 %) y presentó asociacióncon la duración de la exposición. Tanto la actividad de acetilcolinesterasa (AChE) como catalasa (CAT) placentariaaumentaron en dicho período (40%) y la edad gestacional disminuyó en dos semanas. El perímetro cefálico aumentó por la residencia rural materna y por la fumigación en el hogar. Este parámetro se asoció con la actividad de CAT. Estos resultados indican que el uso combinado de la AChE y CAT placentarias, enzimas involucradas en eventos adaptativos, serían herramientas útiles en programas de monitoreo ambiental. Asimismo, corroboran que este tejido, el más accesible de la tríada madre – placenta– feto, muestra efectos acumulativos que reflejan el ambiente intrauterino.

Improvement of children’s health requires preventing environmental exposures and identifying predictive biomarkers that represent the toxicological process before irreversibleinjury appears. Considering the high vulnerability of the intrauterine development, this study was designed to investigate the impact of in utero exposure to organophosphate pesticides and biomarkers of early effects in easily asequible tissues. A cohort of 342 women living in the agricultural area of High Valley of Río Negro and Neuquén, where 6 month spraying and non spraying periods are alternated, were interviewed in order to characterize their demographic characteristics and lifestyle habits. Morphometric information about the offspring and placentas were recorded. The analytical studies included pregnant womenhemogram, blood cholinesterases as well as placental enzymes activities. Data were analyzed by ANOVA, regression and correlation. During spraying season plasma cholinesterase diminished significantly (18%) and was associated to exposure length. Inthis period, placental acetylcholinesterase (AChE) and catalase (CAT) increased in a similar extent (40%) and gestational agediminished in two weeks. An increase in cephalic circumference was observed in newborns from women residents in rural areas and also in ones having indoors fumigation habits. This parameter was associated to CAT activity. These results indicate that the combined use of the placental AChE and CAT, enzymes involved in adaptative events, seems to be a useful tool in environmentalmonitoring programmes. Also, they corroborate that this tissue, the most accessible and available component of the triad mother-infant-placenta shows cumulative effects that reflect the intrauterine environment in which the newborn was developed.