Atrazine toxicity to Handroanthus heptaphyllus,a nontarget species from a Brazilian biome threatened by agriculture

The economic basis of the Brazilian midwest is agriculture, concentrating most of the grain production in the country. With the purpose of increasing yield, farmers have intensified land use and the use of atrazine among other pesticides, which can supposedly compromise human health and photosynthetic metabolism of plant species from Cerrado, such as Handroanthus heptaphyllus. The aim of this study was to determine experimentally the sensitivity level of H. heptaphyllus to atrazine, by measuring gas exchange, chlorophyll a fluorescence, chloroplastidic pigments, and membrane permeability. The experiment was conducted in a factorial scheme. Nine‐month‐old H. heptaphyllus plants were treated with six realistic doses of atrazine: 0, 25, 50, 100, 200, and 400 g a.i. ha^–1 (corresponding to 10, 20, 40, 80, and 100% of the commercial dose recommended for corn crops, respectively), with five replications. Evaluations were performed at 12, 36, 84, 180, and 276 h after treatment application. Photosynthesis, the effective quantum yield of photosystem II, and electron transport rate were gradually reduced by the action of atrazine. On the other hand, the nonphotochemical quenching increased gradually, which indicates that this mechanism was not sufficient to avoid oxidative stress and cellular damage in H. heptaphyllus treated plants. Based on these results, we concluded that the action of the herbicide in the photosynthetic reduction occurs by the electron transport rate limitation. Therefore, H. heptaphyllus trees are at risk in Cerrado areas next to agricultural lands.     

Temporal, spatial, and body size effects on growth rates of loggerhead sea turtles (Caretta caretta) in the Northwest Atlantic

In response to a call from the US National Research Council for research programs to combine their data to improve sea turtle population assessments, we analyzed somatic growth data for Northwest Atlantic (NWA) loggerhead sea turtles (Caretta caretta) from 10 research programs. We assessed growth dynamics over wide ranges of geography (9–33°N latitude), time (1978–2012), and body size (35.4–103.3 cm carapace length). Generalized additive models revealed significant spatial and temporal variation in growth rates and a significant decline in growth rates with increasing body size. Growth was more rapid in waters south of the USA (<24°N) than in USA waters. Growth dynamics in southern waters in the NWA need more study because sample size was small. Within USA waters, the significant spatial effect in growth rates of immature loggerheads did not exhibit a consistent latitudinal trend. Growth rates declined significantly from 1997 through 2007 and then leveled off or increased. During this same interval, annual nest counts in Florida declined by 43 % (Witherington et al. in Ecol Appl 19:30–54, 2009) before rebounding. Whether these simultaneous declines reflect responses in productivity to a common environmental change should be explored to determine whether somatic growth rates can help interpret population trends based on annual counts of nests or nesting females. Because of the significant spatial and temporal variation in growth rates, population models of NWA loggerheads should avoid employing growth data from restricted spatial or temporal coverage to calculate demographic metrics such as age at sexual maturity.     

Nuchal glands: a novel defensive system in snakes

Of the various chemical defensive adaptations of vertebrates, nuchal glands are among the most unusual. First described in a Japanese natricine snake, Rhabdophis tigrinus, in 1935, these organs are embedded under the skin of the neck region as a series of paired glands that have neither lumina nor ducts. The major chemical components of the glandular fluid are bufadienolides, which are cardiotonic steroids also found in the skin secretion of toads. Here we review early studies of nuchal glands and briefly introduce our recent findings on the sequestration of bufadienolides from consumed toads and the maternal provisioning of those sequestered compounds. We summarize behavioral studies associated with the antipredator function of the nuchal glands, which have been conducted during our more than decade-long collaboration. Results of preliminary analyses on the possible costs of toad-eating and on the ultrastructure of the nuchal glands are also presented. Finally, we discuss the evolutionary origin of the nuchal glands and suggest future directions designed to understand the biological importance of these novel vertebrate organs, which have evolved in a limited number of snake species.     

Continuous growth facilitates feeding and reproduction: impact of size on energy allocation patterns for organisms with indeterminate growth

Body size has great influence on feeding, reproduction, and ecological importance. This study measures growth, reproduction, and feeding for several northeastern Pacific intertidal invertebrates that have indeterminate growth. In all species studied, linear size (length, diameter) showed asymptotic growth fit by the von Bertalanffy growth function, supporting the notion that less energy is allocated to growth with age because of increased reproduction. However, these same species displayed a continuous, roughly linear increase in volume with age. Both reproductive output and food intake were shown to scale proportionally with volume. This indicates that some species with indeterminate growth do not reduce energy allocation to growth with age but instead display continuous volumetric growth that facilitates increases in feeding rate and reproductive output with age and size. A simple allometric model is proposed to describe constant volumetric growth rates and linear increases in reproduction with age.     

Removal of atrazine from river waters by indigenous microorganisms

We report the first data for atrazine removal in low-turbidity freshwaters. Atrazine is a globally applied herbicide, contamination by which may lead to direct and indirect ecotoxicological impacts. Although a common contaminant of surface waters, microbial biodegradation of atrazine in this environment has been little studied, with most work focused on soils by means of selected, atrazine-degrading bacteria-enriched cultures. Here, we measured atrazine removal from river water using a batch incubation system designed to represent environmental conditions, with water from two contrasting UK rivers, the Tamar and Mersey. Atrazine and bacterial inocula prepared from the source water were added to cleaned river water for 21-day incubations that were analysed directly by electrospray ionisation-mass spectrometry. The experimental approach was validated using peptides of different molecular mass. Results show that atrazine concentrations decreased by 11% over 21 days in Tamar samples, a rural catchment with low population density, when atrazine was the only substrate added. In contrast no removal was evident in Mersey samples, an urban catchment with high population density. When a tripeptide was added as a co-substrate, atrazine removal in the Tamar water remained at 11% while that for the Mersey water increased from 0 to 37%. Although degradation of atrazine in aerobic freshwaters is predicted according to its chemical structure, our data suggest that the composition of the bacterial population determines whether removal occurs under these conditions and at these environmentally realistic concentrations.     

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. In laboratory experiments we measured the pgr of Daphnia magna over a grid of values of pH and Ca2+, and so defined its "laboratory niche" in pH-Ca2+ space. The position of the laboratory niche boundary suggests that population persistence is only possible above 0.5 mg Ca2+/L and between pH 5.75 and pH 9, though more Ca2+ is needed at lower pH values. To see how well the measured niche predicts the field distribution of D. magna, we examined relevant field data from 422 sites in England and Wales. Of the 58 colonized water bodies, 56 lay within the laboratory niche. Very few of the sites near the niche boundary were colonized, probably because pgr there is so low that populations are vulnerable to extinction by other factors. Our study shows how the niche can be quantified and used to predict field distributions successfully.     

Detecting the order of population dynamics from time series: nonlinearity causes spurious diagnosis

Partial autocorrelation and partial rate correlation functions are frequently used to detect the order of the endogenous process generating an observed population time series. Here we uncover a problem with this approach: the diagnosis of spurious second order autocorrelation due to strong nonlinearity in a first order endogenous process, as exemplified by time series data from a population of Soay sheep. Causes and a possible solution are discussed.     

Potential interference bias in ozone standard compliance monitoring

The U.S. Environmental Protection Agency has established a federal reference method (FRM) for ozone (O3) and allowed for designation of federal equivalent methods (FEMs). However, the ethylene-chemiluminescence FRM for O3 has been replaced by the UV photometric FEM by most state and local monitoring agencies because of its relative ease of operation. Accumulating evidence indicates that the FEM is prone to bias under the hot, humid, and stagnant conditions conducive to high O3 formation. This bias may lead to overreporting hourly O3 concentrations by as much as 20-40 ppb. Measurement bias is caused by contamination of the O3 scrubber, a problem that is not detected by dry air calibration. An adequate wet test has not been codified, although a procedure has been proposed for agency consideration. This paper includes documentation of laboratory tests quantifying specific interferant responses, collocated ambient FRM/FEM monitoring results, and smog chamber comparisons of the FRM and FEMs with alternative scrubber designs. As the numbers of reports on monitor interferences have grown, interested parties have called for agency recognition and correction of these biases.     

A female-specific attractant for the codling moth,<Emphasis Type="Italic"> Cydia pomonella</Emphasis>, from apple fruit volatiles

Host plant-derived esters were investigated as potential female-specific attractants for the codling moth (CM), Cydia pomonella (L.), a key pest of apples worldwide. The behavioural effects of single and combined volatile compounds and of a natural odour blend were examined using olfactometry and wind-tunnel bioassays. The apple-derived volatile butyl hexanoate attracted mated females while it was behaviourally ineffective for males over a dosage range of more than three orders of magnitude in olfactometer assays. Female CM preferred this kairomone to the headspace volatiles from ripe apples. Both no-choice and choice trials in the wind-tunnel suggested that female moths might be effectively trapped by means of this compound. In contrast, headspace volatiles collected from ripe apple fruits as well as a blend containing the six dominant esters from ripe apples were behaviourally ineffective. A female-specific repellency was found for the component hexyl acetate in the olfactometer, but this ester had no significant effect in the wind-tunnel. Butyl hexanoate with its sex-specific attraction should be further evaluated for monitoring and controlling CM females in orchards.     

Application of a magnetic extraction technique to assess radionuclide-mineral association in Cumbrian shoreline sediments

An assessment has been made of the association of (239+240)Pu, 241Am and 210Po (in secular equilibrium with 210Pb) with iron minerals using a magnetic extraction technique. Grab samples of beach sand from the Cumbrian (UK) coastline were subjected to successive extractions with an approximately 0.1 T ferrite magnet and an approximately 0.3 T rare-earth magnet procedure to separate magnetic iron oxide minerals. Radionuclide concentrations in the magnetic extracts were enhanced (by approximately 4-6-fold) relative to the residue. Those in the approximately 0.1 T magnet extracts were broadly similar to those in the antiferromagnetic material extracted by the approximately 0.3 T magnet, despite the very large differences in magnetic property values between the two fractions (one to two orders of magnitude). The percentage of magnetic material in terms of mass was small and therefore, the majority of these radionuclides (on average 88%) were associated with the residue. Removal of stable Fe was incomplete. Given that the radionuclides may also bind to paramagnetic (nonmagnetic) Fe minerals, the data were extrapolated by normalising the results to quantitative Fe removal. This yielded average values of 37%, 45% and 46% for (239+240)Pu, 241Am and 210Po(210Pb), respectively, as upper limits for the fraction associated with magnetic + nonmagnetic Fe minerals. There are significant uncertainties inherent in quantifying data from this extraction technique. Nevertheless, it seems reasonable to conclude that radionuclide association with Fe minerals is unlikely to have a significant impact upon the physical dispersion of sediment contaminated by Sellafield discharges in the Irish Sea. However, it may be an important factor in governing Pu redox and redissolution behaviour.