High heavy metal load does not inhibit nitrogen fixation in moss-cyanobacteria associations Abstract Nitrogen (N2) fixation by moss-associated cyanobacteria is one of the main sources of new N input in pristine ecosystems such as boreal forests and arctic tundra. Given the non-vascular physiology of mosses, they are especially sensitive to e.g. increased N input and heavy metal deposition. While the effects of increased N input on moss-associated N2 fixation has been comprehensively assessed, hardly any reports exist on the effects of increased heavy metal load on this key ecosystem function. To address this knowledge gap, we made use of an extreme metal pollution gradient in boreal forests of Northern Sweden originating from a metal mine and its associated smelters. We collected the common moss Pleurozium schreberi, known to host cyanobacteria, along a distance gradient away from the metal source of pollution and measured moss-metal content (Fe, Cu, Zn, Pb) as well as N2 fixation. We found a strong distance gradient in moss-metal content for all investigated metals: a sharp decline in metal content with distance away from the metal pollution source. However, we found a similarly steep gradient in moss-associated N2 fixation, with highest activity closest to the metal source of pollution. Hence, while mosses may be sensitive to increased heavy metal inputs, the activity of colonising cyanobacteria seem to be unaffected by heavy metals, and consequently, ecosystem function may not be compromised by elevated metal input.

Rice busk biochar treatment to cobalt-polluted fluvo-aquic soil: speciation and enzyme activities Abstract Rice busk biochar was mixed with cobalt (Co)-polluted soil to examine the efficacy of biochar for Co immobilization and detoxification in fluvo-aquic soil. The Co speciation (modified BCR sequential extraction), fluorescein diacetate (FDA) hydrolysis and soil enzyme activities were investigated. In soil, the Co ions (acid-soluble fraction) could be uptake by biochar due to the microporous structure on the surface, as well as the oxygen-containing functional groups and conjugated structure in the molecular structure. Therefore, when the biochar concentration was lower than the optimum concentration (~6 g·kg−1), there was transformation of Co from the acid-soluble fraction to the oxidizable fraction, resulting in lower environmental risk. However, if the biochar concentration continued increasing, the distribution coefficient of Co in the acid-soluble fraction increased (P < 0.05). The biochar could also reduce the toxicity of Co, resulting in the negative correlations between soil enzyme activities (FDA hydrolysis, urease and alkaline phosphatases) and Co in the acid-soluble fraction (r = –0.816, –0.928 and –0.908, respectively, P < 0.01). When the biochar concentration ranged from 5.83 to 6.76 g·kg−1, the efficacy for Co immobilization and detoxification reached the maxima. To conclude, in fluvo-aquic soil, rice busk biochar is an effective amendment for immobilizing Co ions and reducing the toxicity of Co. The biochar concentration in soil should range from 5.83 to 6.76 g·kg−1 to reach the optimum efficacy.

Variation in Hg accumulation between demersal and pelagic fish from Puruzinho Lake, Brazilian Amazon Abstract Aquatic ecosystems in the Amazon are exposed to mercury, mostly from natural sources. Hg accumulation in fish tissues poses a risk to the local population since fish is one of the main sources of protein in the region. The aim of this study was to evaluate Hg distribution in demersal and pelagic carnivorous fish between seasons in Puruzinho Lake in the Brazilian Amazon. Total Hg was quantified in 221 individuals of 8 species obtained during the high water and low water seasons. Two-way ANOVA indicated an interaction between foraging habitat and season. During high water, total Hg concentrations were similar between demersal and pelagic fish, while in low water, total Hg levels were higher in demersal fish. Pelagic and demersal fishes’ Hg levels were similar between the two seasons.

Population recovery of peregrine falcons in central Norway in the 4 decades since the DDT-ban Abstract The breeding population of peregrine falcons (Falco peregrinus) in Norway was almost exterminated by the early 1970’s. Long-term monitoring of breeding pairs has been conducted since 1976 up to present. Peregrine falcons were first established at breeding sites in coastal habitats, where they remained at stable low numbers until the early 1990’s. Starting around 2000, numbers began to increase steadily, and current numbers have now reached historical population levels from the pre-DDT era. We documented a range expansion with increasing numbers of peregrines nesting in the fjords and inland valleys. We found that once a territory was colonized, the probability that a territory remained occupied was high (S > 0.958). During early stages of population recovery, the transitional probabilities of becoming or remaining a breeding territory were high (ψN–B > 0.40, ψB–B > 0.65) but declined over time, especially in coastal habitats. Moreover, the productivity per nest has also decreased over time at sites in coastal habitats in the former stronghold of the population. The levels of environmental pollutants in eggs of the peregrines have dropped sharply over the last few decades, and contaminant levels now seem to be below critical levels. Eggshells were relatively thin throughout the 1970s, 1980s, and 1990s, but have increased to almost normal levels during the last 2 decades. Reductions in levels of organochlorine pollutants, especially DDT, appear to have been the main factor in explaining the population recovery. The territory dynamics are consistent with density-dependence and the low breeding success of the coastal-breeding peregrines is believed to be caused by declining numbers of colonial seabirds and other prey species.

Historical control data for the interpretation of ecotoxicity data: are we missing a trick? Abstract Wildlife can be exposed to chemicals in the environment from various anthropogenic sources. Ecotoxicity studies, undertaken to address the risks from potential exposure to chemicals, vary in their design e.g. duration of exposure, effect types and endpoints measured. Ecotoxicity studies measure biological responses to test item exposure. Responses can be highly variable, with limited opportunity for control of extrinsic sources of variability. It is critical to distinguish between treatment-related effects and background ‘normal variability’ when interpreting results. Historical control data (HCD) can be a valuable tool in contextualising results from single studies against previous studies performed under similar conditions. This paper discusses the case for better use of HCD in ecotoxicology assessments, illustrating with case studies the value and difficulties of using HCD in interpretation of results of standard and higher-tier study designs. HCD are routinely used in mammalian toxicology for human health assessments, but not directly in ecotoxicology. The possible reasons for this are discussed e.g., different data types, the potential to mask effects, and the lack of guidance. These concerns are real but not insurmountable and we would like to see organisations such as OECD, EFSA and USEPA develop guidance on the principles of HCD collection. Hopefully, this would lead to greater use of HCD and regulatory acceptance. We believe this is not only a scientifically valid approach but also an ethical issue that is in line with societally driven legal mandates to minimise the use of vertebrate testing in chemical regulatory decision making.

Responses of Vallisneria natans (Lour.) Hara to the combined effects of Mn and pH Abstract Aquatic plants play a vital role in maintaining the health and stability of ecosystems and in ecological restoration of contaminated water bodies. Herein, a 21-day-long laboratory-scale experiment was designed to explore the growth and physiological responses of Vallisneria natans (Lour.) Hara (V. natans) to the combined effects of manganese (Mn, 5, 20, and 80 mg L−1) and pH (pH 4.0, 5.5, and 7.0). Our results showed the combined toxicity intensity was closely related to Mn concentration and the toxicity exhibited by Mn gradually strengthened with the decrease of pH level. High concentration of Mn stress significantly reduced plants leaf area, final leaf number, photosynthetic pigment content, RGR (relative growth rate) and biomass accumulation, but significantly increased the contents of malondialdehyde (MDA) and hydrogen peroxide (H2O2). At the same time, V. natans plants can resist the adverse stress by activating the antioxidant defense system, including superoxide dismutase (SOD), peroxidase (POD), catalase (CAT), and polyphenol oxidase (PPO) activities. Besides, V. natans tended to adjust the biomass allocation strategy and transferred more energy to the subsurface and the ramets and stolons parts under the combined stress. This experiment also showed that the increasing pH within a certain range could largely improve the removal rate of Mn (at highest by 84.28%). This may indicate the V. natans plant species can act as a promising tool for the Mn phytoremediation in aquatic environments which needs to be further explored by longer cycle field studies.

Secondary metabolites that could contribute to the monodominance of Erythrina fusca in the Brazilian Pantanal Abstract Erythrina fusca is a dominant species in the Brazilian Pantanal. We hypothesized that E. fusca possess allelopathic potential and we evaluated effects of extracts on germination and development of Lactuca sativa, a bioindicator species. We tested the effect of leaves, bark, roots, and seeds extracts of E. fusca on germination and speed index, using high, moderate and low concentration (0.2, 1 and 5 mg mL–1). To evaluate effects on development, we subjected seedlings of L. sativa to the same treatments and measured root and aerial part length. High concentration of extracts reduced L. sativa germination; leaves extract caused the maximum reduction on germination of L. sativa, similar to 2,4-Dichlorophenoxyacetic acid (2,4-D); this extract has flavonoids and saponins as main compounds, classes that also occur in the bark and roots extracts in lower concentrations; bark and roots (5 mg mL–1), leaves and roots (1 mg mL–1) decreased these traits as well, but in lower magnitude. A significant reduction in root length was induced by highest concentration of all extracts (5 mg mL–1); the results suggest that erythrinic alkaloids should interfere in the root length once the seeds accumulate almost exclusively this class of compounds. Our results showed that all parts of E. fusca had adverse effects on germination or development of L. sativa, showing that different class of compounds secondary metabolites is involved in this activity. Possibly, this phytotoxicity influences monodominance of E. fusca in Pantanal, but studies are essential to evaluate effects of it on other native species.

Evaluation of the sensitivity of Microhyla fissipes tadpoles to aqueous cadmium Abstract Cadmium (Cd) exposure is harmful to amphibians in natural environments and the Cd concentration is a key parameter in water monitoring. Cd pollution has been a severe issue in the Yangtze River and its southern reaches in recent years. Acute toxicity assays were employed to determine the tolerance limits of Cd for Microhyla fissipes tadpoles and five different concentrations of Cd (0, 50, 100, 200 and 300 μg/L) were involved to detect its chronic effects on metamorphosis, growth, locomotion, genotoxicity and enzymatic activities of M. fissipes tadpoles. The results showed that the 24-h and 48-h LC50 values of Cd on M. fissipes tadpoles were 2591.3 μg/L and 1567.9 μg/L, respectively, and the presumable non-lethal concentration obtained was 172.2 μg/L. During the 70-day chronic toxicity assays, Cd showed negative impacts on survival, growth, metamorphosis and the frequency of erythrocytes nuclear abnormality of M. fissipes tadpoles. However, the Cd exposure caused the increased body size and condition of tadpoles at complete metamorphosis (GS46). The tadpoles exposed to 200 μg/L of Cd exhibited degraded locomotor performance at GS46. Weight increments of tadpoles were inhibited at Day 14 and massive deaths were observed over the next 14 days. The enzymatic activities of tadpoles experienced a shock response stage (GS30-GS35) and a complete recovery stage (GS36-GS41) in all treatments. However, the enzymatic activities (except alkaline phosphatase) of tadpoles at GS46 increased after Cd exposure, especially at high concentrations. In summary, Cd is a threat to M. fissipes tadpoles as that causes reduced fitness.

Effect of azadirachtin on mortality and immune response of leaf-cutting ants Abstract Leaf-cutting ants are difficult pests to control because they have numerous defense strategies and are highly selective in their plant harvesting choices. The search for effective pest control methods that have minimal negative effects on the environment has been continuous. Azadirachtin, a compound extracted from the neem tree (Azadirachta indica), is a promising alternative for the control of various pests, as it is toxic to some insects but readily degrades in the environment. In this study, we evaluated the effects of azadirachtin on the mortality, through topical exposure to the compound, and immune response, by introducing an artificial antigen into leaf-cutting ants Atta sexdens and Acromyrmex subterraneus subterraneus. Azadirachtin caused death to minor and major workers of both species in a concentration-dependent manner. Topical application of the compound did not diminish the immune response of ants in a microfilament encapsulation assay. Azadirachtin showed no effect on the immune response of workers but increased worker mortality, which indicates its potential as an ant control agent.

Impacts of seven insecticides on Cotesia flavipes (Cameron) (Hymenoptera: Braconidae) Abstract The endoparasitoid wasp Cotesia flavipes (Cameron) (Hymenoptera: Braconidae) is inundatively released in Brazilian sugarcane plantations to control the sugarcane borers Diatraea saccharalis (Fabricius) and Diatraea flavipennella (Box) (Lepidoptera: Crambidae). In conjunction with these releases, several synthetic insecticides are used to control the neonate larvae of these pests. We assessed the lethal and transgenerational sublethal effects of seven of these insecticides on C. flavipes. Leaf discs were sprayed at the highest field concentrations of chlorantraniliprole, lambda-cyhalothrin + chlorantraniliprole, chlorfluazuron, triflumuron, lambda-cyhalothrin + thiamethoxam, tebufenozide, and novaluron. Distilled water was used as a negative control. Newly emerged females (24 h old) were placed in Petri dishes containing the treated leaves, and the lethal and transgenerational sublethal effects were assessed for the next two generations. Lambda-cyhalothrin + chlorantraniliprole and lambda-cyhalothrin + thiamethoxam caused 100% mortality of the parasitoid and were highly persistent, causing more than 30% mortality at 30 days after spraying. Chlorantraniliprole, chlorfluazuron, novaluron, and triflumuron did not cause significant mortality compared to the negative control, but did have transgenerational sublethal effects. The length of the tibia of the right posterior leg, used as a growth measurement, was reduced in the progeny (F1 generation) of exposed female parasitoids. In addition, chlorantraniliprole increased and chlorfluazuron reduced the proportion of females in the F1 generation, whereas novaluron reduced the proportion of females in the F2 generation. Overall, only tebufenozide was considered harmless to C. flavipes. The results of this study suggest that lambda-cyhalothrin + chlorantraniliprole and lambda-cyhalothrin + thiamethoxam are harmful to C. flavipes, although field studies are needed to obtain results for actual sugarcane crops.