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.
While the emerging amphibian disease chytridiomycosis is causing dramatic and ongoing biodiversity losses worldwide, sustainable strategies to mitigate this global threat to amphibians are currently ...missing. We here propose a conceptual framework for a novel biological mitigation strategy based on the increasing evidence that naturally occurring micropredators, such as protists, rotifers and crustaceans, are capable of using zoospores of the chytrid pathogens Batrachochytrium dendrobatidis (Bd) and Batrachochytrium salamandrivorans (Bsal) as a food source under controlled laboratory conditions. Pathogen predation may serve as a cost-efficient way to prevent chytridiomycosis outbreaks under natural conditions by reducing zoospore densities and thereby infection loads. This predator-pathogen relationship is not an isolated interaction, but is embedded in the aquatic food web structure that interacts with a wide range of environmental factors. Amphibian breeding ponds are increasingly associated to agricultural landscapes due to ongoing land use occupancy for food production, exposing these water bodies to a variety of environmental stressors such as agrochemical pollution, nutrient enrichment and cattle trampling. Environmental stressors may affect the composition and abundance of aquatic communities, while they can also exert sublethal effects that may reduce the zoospore removal efficiency of micropredators. By carefully controlling environmental stressors, trophic interactions may be steered to optimize chytrid predation with the aim of reducing zoospore densities to such extent that hosts and pathogens can sustainably coexist. We present a scientific outline of this novel concept and provide a framework for ongoing research to develop a complete mitigation strategy against chytridiomycosis based on such food web control.
•Pathogen predation may reduce infection pressure on amphibians.•The predator-pathogen interaction is embedded in the aquatic food web.•Amphibian breeding ponds are increasingly associated with agricultural land use.•Anthropogenic factors exert pressure on aquatic food webs.•Steering these factors may mitigate amphibian disease.
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.
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.
Although pesticides are frequently used for agriculture in the Galapagos Islands (Ecuador), there are, to date, no investigations of pesticide occurrences in its coastal waters. We examined the ...presence of pesticide residues in the coastal waters of urban areas in two islands of the Galapagos archipelago using a repeated sampling design. Quantification was performed by solid-phase extraction, followed by chemical analysis using liquid chromatography-tandem mass spectrometry (LC-MS/MS) and gas chromatography-electron capture detector (GC-ECD). The diversity and concentration of pesticide residues in Santa Cruz island were higher compared to Isabela island. In total, sixteen pesticides were detected, including three persistent organic pollutants. Carbendazim (23.93 μg·L−1), cadusafos (4.74 μg·L−1), DDT (2.99 μg·L−1), diuron (1.61 μg·L−1) and aldrin (1.55 μg·L−1) were detected with the highest concentrations between samples. Repetitions in locations show that concentrations of pesticide residues varied considerably in space and time. Comparison with local products indicated agricultural activities on the islands as a possible source. Furthermore, evaluation through ecological risk quotients showed that the observed concentration levels of seven pesticides pose a relatively high risk for three biotic groups (i.e. algae, invertebrates and fishes). Taken together, this study provides insights into the need to regulate, monitor and assess the presence of pesticides in the islands. At a global scale, this study is moreover valuable for the many islands that are facing the same challenges.
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•Pesticides occurrence was evaluated in coastal urban areas of Galapagos archipelago.•Sixteen pesticides were detected including three persistent organic pollutants.•Source of pesticides was associated with agriculture production in the islands.•Pesticide residues concentration varied considerably in space and time.
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.
While the amphibian disease chytridiomycosis is causing ongoing population declines and biodiversity losses around the globe, efficient mitigation strategies are lacking. The free‐living zoospores of ...the causative agents of this disease, the chytrid pathogens Batrachochytrium dendrobatidis (Bd) and Batrachochytrium salamandrivorans (Bsal), are a potential food source for filter‐feeding micropredators as part of the aquatic food web. While consumption of zoospores can lower environmental pathogen loads, alternative food sources may interfere with pathogen removal rates.
We compared the ability of three filter‐feeding zooplankton species, the cladoceran Daphnia magna, the rotifer Brachionus calyciflorus and the ostracod Heterocypris incongruens, to remove Bd zoospores in water and investigated the effect of alternative food sources, the green algae Pseudokirchneriella subcapitata and Chlorella vulgaris, on zoospore ingestion by D. magna.
Daphnia magna was the only micropredator candidate that effectively removed Bd zoospores from its environment, with an average removal rate of 1,012 ± 542 GE ind.−1 hr−1 within our test system. High concentrations (1 × 105 cells/ml) of large and easily ingestible P. subcapitata reduced pathogen removal rates, whereas the small and less edible C. vulgaris did not interfere with pathogen removal.
Synthesis and applications. We showed that Daphnia spp., which are keystone species in all sorts of aquatic habitats worldwide, are promising target agents for biologically mitigating chytridiomycosis infections and how natural food sources may interfere with this strategy. We also suggest potential management actions for biological disease mitigation, aiming to optimize environmental conditions for these target filter feeders, thereby reducing pathogen densities and eventually infection pressure in amphibian hosts. Examples of such management actions include, but are not limited to, removal of planktivorous fish, habitat restoration, nutrient control or agrochemical regulation in the vicinity of amphibian breeding ponds. Further studies, including field trials, are needed to confirm the effects of pathogen consumption on infection dynamics in natural situations and investigate the impact of intervention actions.
Samenvatting
Terwijl de amfibieziekte chytridiomycose wereldwijd populatieafnames en biodiversiteitsverlies veroorzaakt, ontbreekt het nogsteeds aan doeltreffende mitigatiestrategieën. Vrijlevende zoösporen van deziekteverwekkers, de Chytridiomycota Batrachochytrium dendrobatidis (Bd) en Batrachochytriums alamandrivorans (Bsal), zijn een mogelijke voedselbron voor filtrerende micropredatoren die deel uitmaken van het aquatische voedselweb. Hoewel predatie op zoösporen de aanwezigheid van pathogenen kan reduceren, kunnen alternatieve voedselbronnen deze predatie‐interactie verstoren.
Wij vergeleken het vermogen van drie filtervoedende organismen uit de zoöplanktongemeenschap, nl. de Cladocera Daphnia magna, derotifer Brachionus calyciflorus en de ostracod Heterocypris incongruens, om Bdzoösporen te verwijderen uit water en onderzochten het effect van alternatievevoedselbronnen, de groene algen Pseudokirchneriella subcapitata en Chlorellavulgaris, op de opname van zoösporen door D. magna.
D. magna was de enige kandidaat micropredator dat Bd zoösporen kon verwijderen uit zijn omgeving, met een gemiddelde verwijderingssnelheid van 1,012 ± 542 GE ind.−1 hr−1 in onze proefopzet. Hoge concentraties (1 × 105 cellen/ml) van de grote en makkelijk opneembare cellen van P. subcapitata verlaagden de verwijderingssnelheid van pathogene sporen, terwijl de kleine en minder eetbare cellen van C. vulgaris geen interactie vertoonden met het verwijderen van zoösporen.
Synthese en toepassingen. Wij tonen aan dat Daphnia spp., die een cruciale rol hebben in verschillende soorten aquatische ecosystemen wereldwijd, een veelbelovende doelgroep is voor biologische mitigatie van chytridiomycose infecties en hoe natuurlijke voedselbronnen deze strategie kunnen verstoren. Daarnaast stellen we ook een aantal mogelijke ingrepen voor om milieucondities te optimaliseren voor deze micropredatoren en zo het aantal ziekteverwekkers en de infectiedruk op amfibieën te verlagen. Voorbeelden van dergelijke ingrepen zijn o.a. de verwijdering van planktivore vissen, habitatherstel, nutriëntenbeheer en gecontroleerd gebruik van agrochemicaliën in de nabijheid van voortplantingspoelen van amfibieën. Verder onderzoek, inclusief veldproeven, is noodzakelijk om het effect van de consumptie van zoösporen op infectiedynamieken te onderzoeken in natuurlijke situaties en de impact van menselijke ingrepen te onderzoeken.
We showed that Daphnia spp., which are keystone species in all sorts of aquatic habitats worldwide, are promising target agents for biologically mitigating chytridiomycosis infections and how natural food sources may interfere with this strategy. We also suggest potential management actions for biological disease mitigation, aiming to optimize environmental conditions for these target filter feeders, thereby reducing pathogen densities and eventually infection pressure in amphibian hosts. Examples of such management actions include, but are not limited to, removal of planktivorous fish, habitat restoration, nutrient control or agrochemical regulation in the vicinity of amphibian breeding ponds. Further studies, including field trials, are needed to confirm the effects of pathogen consumption on infection dynamics in natural situations and investigate the impact of intervention actions.
•Bayesian Belief Network models were developed to assess the trade-off between ecosystem services.•Agricultural and water management optionscould be balanced and integrated.•Crop types and not ...farming scale and type are the maindrivers for economic returns.•Optimizing land use (LU) by considering the crops’ edaphoclimatic needs allows environmentalgains.•LU optimization integrated with agricultural intensification may mitigate productivity losses.
Food production often leads to environmental degradation. Consequently, insights into ecosystem functioning in relation to exploitation are needed as a basis for socioeconomically acceptable mitigation of these impacts. A Bayesian Belief Network (BBN) model is developed to link three major ecosystem services (ES), i.e. food production, water provision and ecotourism, and determine the effect of local agricultural practices and management on the ES in the Guayas Basin (Ecuador). Several data sources were integrated into the BBN model, including processed spatial data from primary and secondary sources, sampling and survey data, and expert knowledge. The model suggests that banana and sugar cane generate the highest yield but provide low ecotourism benefits. In contrast, cacao produces the lowest yields but contributes to better water quality. Scenario analyses suggest that environmental gains are possible by optimising the land use (LU) based on the edaphoclimatic requirements of crops. Moreover, the integration of LU optimisation with upscaling and farming intensification can allow for additional advantages in water provision and ecotourism while mitigating productivity losses. The BBN development approach can serve as a reference for other case studies, where data scarcity plays a limiting factor in the assessment of interactions between key ES.
Batrachochytrium dendrobatidis is responsible for amphibian declines worldwide. Decreasing the aquatic density of this chytrid through consumption of its infectious zoospores by Cladocera (water ...fleas) may mitigate the impact of chytridiomycosis. Understanding this predator-prey relationship requires insights in the zoospore ingestion rate of an average water flea, but such data are almost non-existent. We investigated the functional response of Simocephalus vetulus and Chydorus sphaericus feeding on B. dendrobatidis zoospores. These Cladocera commonly occur in farmland ponds, which may represent a major habitat for disease control. Both water fleas actively ingested zoospores and their per capita ingestion rate was best modelled in function of zoospore-to-Cladocera ratio, implying mutual interference among water fleas during zoospore feeding. The larger S. vetulus substantially consumed more zoospores, characterised by a maximum ingestion rate of 2.5 × 105 zoospores.Cladocera−1.h−1.mL−1, which is about 12 times higher than for C. sphaericus. These findings are useful to support model-based management of chytridiomycosis.
•Simocephalus vetulus and Chydorus sphaericus are common Cladocera in farmland ponds.•S. vetulus and C. sphaericus consume zoospores of B. dendrobatidis.•Zoospore ingestion rate for both Cladocera depends on zoospore-to-Cladocera ratio.•The larger S. vetulus has a significant larger per capita ingestion rate than C. sphaericus.
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