Abstract
Wildlife diseases are contributing to the current Earth’s sixth mass extinction; one disease, chytridiomycosis, has caused mass amphibian die-offs. While global spread of a hypervirulent ...lineage of the fungus
Batrachochytrium dendrobatidis
(
Bd
GPL) causes unprecedented loss of vertebrate diversity by decimating amphibian populations, its impact on amphibian communities is highly variable across regions. Here, we combine field data with in vitro and in vivo trials that demonstrate the presence of a markedly diverse variety of low virulence isolates of
Bd
GPL in northern European amphibian communities. Pre-exposure to some of these low virulence isolates protects against disease following subsequent exposure to highly virulent
Bd
GPL in midwife toads (
Alytes obstetricans
) and alters infection dynamics of its sister species
B. salamandrivorans
in newts (
Triturus marmoratus
), but not in salamanders (
Salamandra salamandra
). The key role of pathogen virulence in the complex host-pathogen-environment interaction supports efforts to limit pathogen pollution in a globalized world.
The combination of rapid urbanization, industrialization, population growth, and low environmental awareness poses a major threat to worldwide valuable freshwater resources, which provide important ...ecosystem services to humans. There is an urgent need to monitor and assess these resources, as this information is indispensable for sustainable decision-making and management. In this context, we analyzed the chemical and ecological water quality of the riverine environment of a fast growing city in Southwest Ethiopia for which we proposed possible remediation options that were evaluated with an empirical model. The chemical and ecological water quality was assessed at 53 sampling locations using the oxygen Prati index and the ETHbios, which is a biotic index based on macroinvertebrates. In addition, a microbiological analysis was performed to estimate the degree of fecal contamination. Finally, we analyzed the relationship between the oxygen content and the organic pollution to simulate the effect of organics removal from waste streams on the chemical water quality. Our results showed that the average values for dissolved oxygen (4.2 mg DO·L−1) and nutrients (0.9 mg oPO43−·L−1 and 12.8 mg TAN·L−1) exceeded international standards. Moreover, high turbidity levels revealed that land erosion is a severe problem in the region. Along the rivers, a significant increase in oxygen consumption and in nutrient concentrations was observed, indicating organic pollution originating from different diffuse and point sources of pollution. The lack of proper sanitation also led to exceedingly high abundances of fecal coliforms in the surface water (>320 MPN·mL−1). However, fecal contamination was strongly reduced (>92%) after the polluted river water passed Boye wetland, indicating the purification potential of natural wetlands and the importance of conserving and protecting those ecosystems. The simulation results of the model showed that water quality could be substantially improved if municipal, industrial, and institutional wastewater was efficiently collected and transported to a treatment facility. Waste stabilization ponds and constructed wetlands are highly promising techniques, as they provide a cheap, effective, reliable, and sustainable way to purify wastewater. It is advised that the environmental awareness of the people via sensitization, education, and law enforcement is increased, as this is essential for sustainable development.
Mangroves are unique coastal ecosystems, located in tropical and subtropical regions. Yet, the functioning of these essential ecosystems is threatened by the presence of pollutants, including ...pesticides originating from agricultural activities. We investigated pesticide residues in the Guayas estuarine environment, since agricultural activities rapidly increased in the Guayas river basin over the past decades. A multi-residue analysis involving a selection of 88 pesticides was performed on the white meat and the hepatopancreas of the red mangrove crab (Ucides Occidentalis) at 15 sampling sites within the Guayas estuary along with water, sediment, and leaves samples. We found that 35 active compounds were present in the Guayas estuary, of which pyrimethanil was most commonly detected and had the highest concentrations in almost all compartments. Also, cadusafos was present in all studied compartments of the Guayas mangrove system and several prohibited pesticides (including carbendazim, carbofuran, and parathion) were detected. An ecotoxicological and probabilistic consumer risk assessment pointed out that current butachlor, carbendazim, and fludioxonil concentrations can cause adverse effects in aquatic organisms in the long term. Moreover, high potential acute and chronic risks of cadusafos residues on aquatic invertebrates and of diuron on algae in the Guayas wetlands were observed. Still, the exposure results indicated that the health risk for the consumers of the commercial red mangrove crab is low concerning cadusafos, chlorpyrifos, diuron, linuron, and pyrimethanil residues in crab tissues. The findings presented in this research can provide a useful basis for local water managers and environmental conservation groups to act and reduce the usage of pesticides, to avoid threatening aquatic and human health.
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•Thirty-five pesticides were detected in the Guayas mangroves.•Cadusafos had the highest Risk Quotient and Toxic Unit (15869 and 97 respectively).•Several prohibited pesticides were detected.•Cadusafos, diuron, and carbendazim pose the highest potential aquatic health risk.•The human health risk for the commercial mangrove crab consumers appeared to be low.
Patches of riparian woody vegetation potentially help mitigate environmental impacts of agriculture and safeguard biodiversity. We investigated the effects of riparian forest on invertebrate ...diversity in coupled stream-riparian networks using a case study in the Zwalm river basin (Flanders, Belgium). Agriculture is one of the main pressures in the basin and riparian forest is limited to a number of isolated patches. Our 32 study sites comprised nine unshaded “unbuffered” sites which were paired with nine shaded “buffered” sites on the same stream reach, along with five ‘least-disturbed’ sites and nine downstream sites. We sampled water chemistry, habitat characteristics and stream and riparian invertebrates (carabid beetles and spiders) at each site. Three methods were used to quantify riparian attributes at different spatial scales: a visually-assessed qualitative index, quantitative estimates of habitat categories in six rectangular plots (10 × 5 m) and geographic information system (GIS)-derived land cover data. We investigated relationships between invertebrates and riparian attributes at different scales with linear regression and redundancy analyses. Spiders and carabids were most associated with local riparian attributes. In contrast, aquatic macroinvertebrates were strongly influenced by the extent of riparian vegetation in a riparian band upstream (100–300 m). These findings demonstrate the value of quantifying GIS-based metrics of riparian cover over larger spatial scales into assessments of the efficacy of riparian management as a complement to more detailed local scale riparian assessments in situ. Our findings highlight the value of even small patches of riparian vegetation in an otherwise extensively disturbed landscape in supporting biodiversity of both terrestrial and freshwater invertebrates and emphasize the need to consider multiple spatial scales in riparian management strategies which aim to mitigate human impacts on biodiversity in stream-riparian networks.
The rapid increase and transition to more intensive agricultural activities in developing nations are often leading to misuse and overuse of pesticides, making their environment vulnerable for ...pesticide accumulation. In the present study, the Guayas river basin was taken as a representative case study to evaluate pesticide contamination of the Ecuadorean freshwater environment. Pesticide contamination was determined at 181 sampling sites by a multi-residue method using solid phase extraction (SPE) and pesticide residues were linked with agricultural land use activities to identify the main pollution sources. Moreover, the biological water quality status based on macroinvertebrate communities was determined at every location and the relation with the occurrence of pesticide residues was further investigated. Results showed that pesticide contamination of the freshwater environment was widely present in the Guayas river basin with detections at 108 sampling sites (60%). A total of 26 pesticide products were identified. Most frequently detected pesticides included cadusafos (62 locations), butachlor (21 locations) and pendimethalin (21 locations), with concentrations up to 0.081, 2.006 and 0.557 μg·L−1 respectively. Pesticide residues detected in this study did not significantly influence the biological water quality (p = 0.69), but were observed to be positively correlated with ammonium concentrations, supporting the assumed combined application of chemical fertilizers and pesticides in agriculture. These pesticide residues were also associated with one or more agricultural crops, with in particular the banana and rice industries identified as major pollution sources. Both high consumption rates and non-specific application methods, such as aerial spraying of banana plantations and application directly into the water layer of irrigated rice fields, may attribute to pesticide contamination of the freshwater environment of the Guayas river basin. It is therefore suggested that measures, e.g. legal regulations and awareness campaigns, taken to prevent environmental pollution and accumulation of pesticides primarily focus on these industries.
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•Pesticide residues were determined in Guayas river basin's freshwater environment.•Guayas river basin's freshwater environment was widely contaminated with pesticides.•Pesticide residues were linked to agricultural activities in the Guayas river basin.•Banana and rice industries were identified as main causers of pesticide pollution.•No direct relation was found between pesticide residues and biological water quality.
Mangrove wetlands provide essential ecosystem services such as coastal protection and fisheries. Metal pollution due to industrial and agricultural activities represents an issue of growing concern ...for the Guayas River Basin and related mangroves in Ecuador. Fisheries and the related human consumption of mangrove crabs are in need of scientific support. In order to protect human health and aid river management, we analyzed several elements in the Guayas Estuary. Zn, Cu, Ni, Cr, As, Pb, Cd, and Hg accumulation were assessed in different compartments of the commercial red mangrove crab Ucides occidentalis (hepatopancreas, carapax, and white meat) and the environment (sediment, leaves, and water), sampled at fifteen sites over five stations. Consistent spatial distribution of metals in the Guayas estuary was found. Nickel levels in the sediment warn for ecological caution. The presence of As in the crabs generated potential concerns on the consumers’ health, and a maximum intake of eight crabs per month for adults is advised. The research outcomes are of global importance for at least nine Sustainable Development Goals (SDGs). The results presented can support raising awareness about the ongoing contamination of food and their related ecosystems and the corresponding consequences for environmental and human health worldwide.
The alpine newt, Ichthyosaura alpestris, is very sensitive to habitat destruction and alteration which has led to declining populations across Europe. As this species is protected through the Bern ...Convention, it is essential to have a comprehensive understanding of its habitat requirements to ensure proper conservation measures. We trained, validated and optimized classification tree models based on data on local aquatic habitat conditions from 125 farmland ponds scattered over Belgium and Luxembourg where the alpine newt commonly occurs. To obtain user-friendly and representative models, data was pre-processed and stratified after which different degrees of pruning were applied for model optimization. In order to check the model’s applicability for management, we predicted alpine newt occurrence with an independent dataset. The most robust and reliable model revealed that fish absence was the major driving factor followed by the thickness of the sludge layer. We found that fish presence established alpine newt absence and that fishless ponds with a sludge layer of 15 cm or more were predicted to host no alpine newts. The latter provides quantitative information for decision makers. Moreover, our results indicated that the amount of sludge could be associated with eutrophication and erosion. Regarding management practices, it is advised to assure the absence of fish and reduce sludge accumulation in ponds designated for the conservation of alpine newts, for example by designing temporary ponds not fed through fish-containing surface waters. Furthermore, we recommend to install buffer strips around a pond to reduce nutrient and soil run-off from the terrestrial environment.
•Classification tree models can be valuable tools for conservation management.•Independent validation data ought to be used to verify a model’s applicability.•Fish create unsuitable habitats for alpine newts in an agricultural landscape.•The level of sludge defines habitat suitability for alpine newts in fishless ponds.•Sludge accumulation in farmland ponds can be linked to eutrophication and erosion.
Oceanic islands harbor unique yet fragile marine ecosystems that require evidence-based environmental management. Among these islands, the Galapagos archipelago is well known for its fish diversity, ...but the factors that structure communities within and between its islands remain poorly understood. In this study, water quality, physical habitats and geographical distance were assessed as potential predictors for the diversity and structure of fish assemblages. Differences in the structure of fish assemblages of the two studied islands (Santa Cruz and Floreana) were most likely driven by temperature and nutrient concentrations. In the relatively highly populated island Santa Cruz, the structure of fish assemblages was more affected by water conditions than physical habitats while the contrary was true for the more pristine area of Floreana. A wide variety of species with different geographical origins were distributed over the different islands, which indicates that most fish species are able to reach the islands of the archipelago. However, temperature gradients and elevated nutrient levels cause large differences in the structure of local fish assemblages. In addition, in Santa Cruz nutrient concentrations were negatively correlated with α diversity. Since pollution is a clear pressure on the fish assemblages of oceanic islands, environmental management of the coastal areas is of paramount importance.
Despite devastating effects on global biodiversity, efficient mitigation strategies against amphibian chytridiomycosis are lacking. Since the free-living pathogenic zoospores of Batrachochytrium ...dendrobatidis (Bd), the infective stage of this disease, can serve as a nutritious food source for components of zooplankton communities, these groups may act as biological control agents by eliminating zoospores from the aquatic environment. Such pathogen-predator interaction is, however, embedded in the aquatic food web structure and is therefore affected by abiotic factors interfering with these networks. Heavy metals, released from both natural and anthropogenic sources, are widespread contaminants of aquatic ecosystems and may interfere with planktonic communities and thus pathogen elimination rates. We investigated the interaction between zooplankton communities and chytridiomycosis infections in a Flemish agricultural region. Moreover, we also investigated the impact of heavy metal contamination, that was previously investigated in the region and presented in recent work, on zooplankton assemblages and chytridiomycosis infections. Finally, we tested the effect of sublethal concentrations of copper and zinc on Bd removal rates by Daphnia magna in a laboratory assay. Although zinc, copper, nickel and chromium were widely abundant pollutants, heavy metals were no driving force for zooplankton assemblages at our study locations. Moreover, our field survey did not reveal indirect effects of zooplankton assemblages on chytridiomycosis infections. However, sampling occasions testing negative for Bd showed a higher degree of copper contamination compared to positive sampling occasions, indicating a potential inhibitory effect of copper on Bd prevalence. Finally, whereas D. magna significantly reduced zoospore densities in its environment, sublethal concentrations of copper and zinc showed no interference with pathogen removal in the laboratory assay. Our results provide perspectives for further research on such a biological control strategy against chytridiomycosis by optimizing environmental conditions for pathogen predation.
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•Chytridiomycosis is causing worldwide mass extinctions of amphibian populations.•Zoospore predation by zooplankton may reduce environmental pathogen loads.•Interactions between heavy metals, zooplankton and pathogens were investigated.•Heavy metals were no driving factor for zooplankton assemblages.•Fungicidal effects of Cu on Bd may lower infection rates.
The sixth mass extinction is a consequence of complex interplay between multiple stressors with negative impact on biodiversity. We here examine the interaction between two globally widespread ...anthropogenic drivers of amphibian declines: the fungal disease chytridiomycosis and antifungal use in agriculture. Field monitoring of 26 amphibian ponds in an agricultural landscape shows widespread occurrence of triazole fungicides in the water column throughout the amphibian breeding season, together with a negative correlation between early season application of epoxiconazole and the prevalence of chytrid infections in aquatic newts. While triazole concentrations in the ponds remained below those that inhibit growth of Batrachochytrium dendrobatidis, they bioaccumulated in the newts' skin up to tenfold, resulting in cutaneous growth‐suppressing concentrations. As such, a concentration of epoxiconazole, 10 times below that needed to inhibit fungal growth, prevented chytrid infection in anuran tadpoles. The widespread presence of triazoles may thus alter chytrid dynamics in agricultural landscapes.
By combining an extensive field dataset with experimental trials, we examined the interaction between two globally widespread anthropogenic drivers of amphibian declines: the fungal disease chytridiomycosis and antifungal use in agriculture. We estimated the impact of triazoles use on B. dendrobatidis infection dynamics by determining its potential (1) to bioaccumulate in amphibians, (2) to effectively limit B. dendrobatidis growth and (3) to affect B. dendrobatidis infection dynamics in tadpoles. We showed that exposure to relevant field concentrations of epoxiconazole that are well below concentrations that limit fungal growth accumulate in amphibian skin and prevented infection with B. dendrobatidis, thus altering chytrid dynamics in agricultural landscapes.
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