Pesticide increases transgenerational cost of inducible defenses in a freshwater rotifer

© 2017, Springer International Publishing Switzerland. In addition to natural stressors such as predation risk, aquatic organisms receive the simultaneous impact of anthropogenic stressors like pollution. In order to advance our understanding of multiple stressor effects, we evaluated the potential costs in the population growth rate derived from the sub-lethal effect of exposure to the pesticide methamidophos and from the expression of morphological defenses front to predation risk, in the rotifer Brachionus calyciflorus. Costs were evaluated both in the organisms that were exposed to the stressors and in their offspring. Our hypotheses were (1) plastic morphological defenses under exposure to pesticides have fitness costs, which may be transmitted from the parental to the filial generation, and (2) interactive effects between pesticides and predation are dependent of the mother’s age. Our results indicate that pesticide exposure increased the costs, expressed as reduction in populat

Ontogenetic shift in Daphnia-algae interaction strength altered by stressors: revisiting Jensen’s inequality

Interaction strength among species plays a crucial role in shaping the functioning of ecological communities, but it is often assumed to be insensitive to inter-individual variation in underlying parameters such as attack rates or handling time. Ecological factors including stressors exert age/size-dependent effects on such behavioral parameters, promoting shifts in the distribution of parameter values over ages. Here we analyze the effects of the pesticide methamidophos on the Daphnia-microalga interaction strength. We first analyze age-dependent effects of the pesticide on the Daphnia functional response, and then decompose the population-level effects of the stressor into contributions of shifts in elevation (i.e., vertical effect) versus shifts in nonlinearity (i.e., nonlinear effect) of the response of interaction strength over consumer age. Our results show that (1) Rogers and Holling type II functional response models best fitted the empirical functional responses of Daphnia of different ages, (2) attack rate and handling time were affected by the pesticide, (3) these effects were age-specific, shifting the average attack rate and both the mean and coefficient of variation of handling time of different age classes, (4) population level interaction strength was affected by pesticide exposure by variation in both elevation and nonlinearity of its response over consumer age. We show that both vertical and nonlinear effects were important in magnitude but opposite in sign. The consequences of factors that exert age/size dependent effects can only be evaluated through properly considering inter-individual variation.Fondo Nacional de Desarrollo Cientifico y Tecnologico (Ministry of Education, Chile) FONDECYT 1150348 CONICYT Doctoral fellowship (CONICYT-PCHA/Doctorado Nacional) 2015-211521 CONICY

Aquatic community structure as sentinel of recent environmental changes unraveled from lake sedimentary records from the Atacama Desert, Chile.

The Atacama Desert (21-26°S) is currently one of the driest places on Earth and metal(loid)s are of special concern for this region, which hosts the largest-known porphyry copper deposits produced in Chile. Evidence of past environmental conditions is commonly preserved in natural archives, such as lacustrine sediments. Sediment records obtained from Inca Coya Lake (22°20'S-68°35'W, 2534 m.a.s.l.), a small lake located in the Atacama Desert, reflected the evolution of regional mining activity during the 20th century and sedimentation associated with decadal climate variability. We studied the aquatic community structure changes recorded in sediment records from Inca Coya Lake. By analysis of magnetic properties (susceptibility, hysteresis curves and Curie temperatures), grain size and geochemical composition of the sediments, we identified environmental periods and changes in the community of benthic and planktonic organisms (diatoms and diapausing egg bank). We identified three detrital episodes that we interpret as dry/wet phases during the last 90 years associated with the increase of flash flood events promoting hypoxia oscillations; anthropogenic (mining activity) signals were also identified. Invertebrate community structure (primary consumers) reflected the metal exposure, measured as changes in assemblage composition through species turnover. Diatom community composition was best associated with variables related to wetter/drier alternation and consequent changes in oxygen availability. Bioindicators analyzed (diatoms, diapausing egg bank and invertebrate community) demonstrated to be excellent indicators of the bioavailability of compounds in the aquatic ecosystem of Inca Coya Lake, allowing the environmental impact assessment of the water resources due to flash floods and mining activity in the driest desert of the world