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(1 - 5 of 5)
Zooplankton community turnover in response to a novel TiO2-coated nano-formulation of carbendazim and its constituents
Nederstigt, T.A.P.; Bode, B.; Ommen J..R. van; Peijnenburg, W.J.G.M.; Vijver M.G. 2023
Zooplankton community turnover in response to a novel TiO2-coated nano-formulation of carbendazim and its constituents
Article / Letter to editor
open access
Novel nanomaterial-based pesticide formulations are increasingly perceived as promising aids in the transition to more efficient agricultural production systems. The current understanding of... Show moreNovel nanomaterial-based pesticide formulations are increasingly perceived as promising aids in the transition to more efficient agricultural production systems. The current understanding of potential unintended (eco)toxicological impacts of nano-formulated pesticides is scarce, in particular with regard to (non-target) aquatic organisms and ecosystems. The present study reports the results of a long-term freshwater mesocosm experiment which assessed responses of individual zooplankton taxa and communities to a novel TiO2-coated nano-formulation of the fungicide carbendazim. Population- and community trends were assessed and compared in response to the nano-formulation and its constituents applied individually (i.e. nano-sized TiO2, carbendazim) and in combination (i.e. nano-sized TiO2 & carbendazim). Minimal differences were observed between effects induced by the nano-formulation and its active ingredient (i.e. carbendazim) when applied at equivalent nominal test concentrations (4 μg L−1). Nano-sized TiO2 was found to affect zooplankton community trends when applied separately at environmentally realistic concentrations (20 μg L−1 nominal test concentration). However, when nano-sized TiO2 was applied in combination with carbendazim, nano-sized TiO2 was found not to alter effects on community trends induced by carbendazim. The findings of the current study provide an extensive and timely addition to the current body of work available on non-target impacts of nano-formulated pesticides. Show less
Plant traits and environment: floating leaf blade production and turnover of Nymphoides peltata (SG Gmel.) O. Kuntze (Menyanthaceae)
Klok, P.F.; Velde, G. van der 2022
Plant traits and environment: floating leaf blade production and turnover of Nymphoides peltata (SG Gmel.) O. Kuntze (Menyanthaceae)
Annotation
open access
Background: Nymphaeid macrophytes, rooting in the sediment of water bodies and characterized by floating leaves, play an important role in wetland ecosystems. The present research deals with the... Show moreBackground: Nymphaeid macrophytes, rooting in the sediment of water bodies and characterized by floating leaves, play an important role in wetland ecosystems. The present research deals with the effects of limited space, limited nutrient availability, water temperature and an unexpected inundation on the production, turnover and plasticity of floating leaves of the globally widespread species Nymphoides peltata (Fringed waterlily).Methods: The effects of these environmental conditions were studied in two plots in outdoor concrete tanks (CT1, CT2, mesocosms simulating occurrence in small ponds) and in two plots in the floodplain oxbow lake Bemmelse Strang (BS1, BS2). Plot CT1 was situated in a stand coexisting with helophytes, plot CT2 in a monospecific stand, plot BS1 in the center and plot BS2 at the open water border of a monospecific stand. All floating leaf blades within the plots were marked at appearance at the water surface and subsequently length, width and damage of each leaf and maximum and minimum water temperatures were measured bi-weekly. Area and biomass of leaf blades were calculated based on leaf length and width and were used to calculate turnover rates and production.Results: The growth period started in May and ended mid-October with continuous production of floating leaves during nearly the whole vegetation period. In the tanks the water level was very stable, but the lake underwent an inundation by river water, causing a sudden loss of existing leaves. Considering environmental conditions and based on the assumed ranking from low to high nutrient availability, the ranking of the plots was CT1, CT2, BS1, BS2. This order was found for maximum leaf life span and maximum leaf length, and the reverse order was found for number of leaves, new leaves per day and duration of the vegetation period. Turnover rates appeared to be relatively similar for plots CT1, CT2 and BS1, but for the deeper border plot BS2 lower ratios were found. These results indicate that increased enclosure with expected nutrient limitation causes (1) the production of high numbers of small leaves with larger totals for leaf area and biomass, (2) a shift towards increased sexual reproduction by the production of more flowering stem leaves. Show less
Impacts of a novel controlled-release TiO2-coated (nano-) formulation of carbendazim and its constituents on freshwater macroinvertebrate communities
Nederstigt, T.A.P.; Peijnenburg, W.J.G.M.; Schrama, M.J.J.; Ommen; J.R. van; Vijver, M.G. 2022
Impacts of a novel controlled-release TiO2-coated (nano-) formulation of carbendazim and its constituents on freshwater macroinvertebrate communities
Article / Letter to editor
open access
Recently, the delivery of pesticides through novel controlled-release (nano-)formulations has been proposed intending to reduce (incidental) pesticide translocation to non-target sites. Concerns... Show moreRecently, the delivery of pesticides through novel controlled-release (nano-)formulations has been proposed intending to reduce (incidental) pesticide translocation to non-target sites. Concerns have however been raised with regards to the potentially enhanced toxicity of controlled-release (nano-)formulations to non-target organisms and ecosystems. We evaluated long-term (i.e. 1 and 3 month-) impacts of a novel controlled-release pesticide formulation (nano-TiO2-coated carbendazim) and its individual and combined constituents (i.e. nano-sized TiO2 and carbendazim) on naturally established freshwater macroinvertebrate communities. In doing so, we simultaneously assessed impacts of nano-sized TiO2 (nTiO2), currently one of the most used and emitted engineered nanomaterials world-wide. We determined ecological impacts on diversity (i.e. β-diversity), structure (i.e. rank abundance parameters), and functional composition (i.e. feeding guilds & trophic groups) of communities and underlying effects at lower organizational levels (i.e. population dynamics of individual taxa). Freshwater macroinvertebrate communities were negligibly impacted by nTiO2 at environmentally realistic concentrations. The controlled-release (nano-)formulation significantly delayed release of carbendazim to the water column. Nevertheless, conventional- (i.e. un-coated-) and nTiO2-coated carbendazim induced a similar set of adverse impacts at all investigated levels of ecological organization and time points. Our findings show fundamental restructuring of the taxonomic- and functional composition of macroinvertebrate communities as a result of low-level pesticide exposure, and thereby highlight the need for mitigating measures to reduce pesticide-induced stress on freshwater ecosystems. Show less
Improving estimations of life history parameters of small animals in mesocosm experiments
Dellar, M.E.; Boerlijst, S.P.; Holmes, D.S.T. 2022
Improving estimations of life history parameters of small animals in mesocosm experiments: a case study on mosquitoes
Article / Letter to editor
open access
  1. Mesocosm experiments enable researchers to study animal dynamics, but determining accurate estimates of survival and development rates of different life stages can be difficult, especially as the...

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  1. Mesocosm experiments enable researchers to study animal dynamics, but determining accurate estimates of survival and development rates of different life stages can be difficult, especially as the subjects may be hard to sample and mortality rates can be high. We propose a new methodology for estimating such parameters.
  2. We used an experimental set-up with 48 aquatic mesocosms, each with 20 first instar mosquito larvae and under 1 of 12 treatments with varying temperatures and nutrient concentrations. We took daily subsamples of the aquatic life stages as well as counting the emerging adults. We developed a method to estimate the survival and development probabilities at each life stage, based on optimising a matrix population model. We used two different approaches, one assuming the difference between predictions and observations was normally distributed, and the other using a combination of a normal and a multinomial distribution. For each approach, the resulting optimisation problem had around 100 parameters, making conventional gradient descent ineffective with our limited number of data points. We solved this by computing the formal derivatives of our matrix model.
  3. Both approaches proved effective in predicting mosquito populations over time, also when compared against a separate validation dataset, and the two approaches produced similar results. They also both predicted similar trends in the survival and development probabilities for each life stage, although there were some differences in the actual values. The approach which only used the normal distribution was considerably more computationally efficient than the mixed distribution approach.
  4. This is an effective approach for determining the survival and development rates of small animals in mesocosm experiments. We have not found any other reliable methodology for estimating these parameters, especially not from incomplete data or when there are many different experimental treatments. This methodology enables researchers to gain a much more detailed understanding of the life cycles of small animals, potentially leading to advances in a wide range of areas, for example in mosquito-borne disease risk or in considering the effects of biodiversity loss or climate change on different species.

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Neonicotinoids in nature: The effects on aquatic invertebrates and their role in ecosystems
Barmentlo S.H. 2020
Neonicotinoids in nature: The effects on aquatic invertebrates and their role in ecosystems
Doctoral Thesis
open access
2021-11-03T00:00:00Z; 2021-11-03T00:00:00Z; 2021-11-03T00:00:00Z
This thesis describes the role of pollution, specifically neonicotinoid insecticides, as an actor of the ongoing biodiversity decline. Using a new research facility, the Living Lab, the effects of... Show moreThis thesis describes the role of pollution, specifically neonicotinoid insecticides, as an actor of the ongoing biodiversity decline. Using a new research facility, the Living Lab, the effects of field relevant concentrations of neonicotinoids and fertilizers to aquatic invertebrates was assessed in 36 experimental ditches. This showed that neonicotinoids had profound impacts on both single species as well as macroinvertebrate biodiversity and had severe consequences for the ecosystem processes the invertebrates fulfilled. Many of the results found in this thesis have not been discovered before because of the simplicity of standardized ecotoxicological testing, which not fully incorporates the myriad of ecological factors governing toxicity. It was found that the addition of fertilizers directly stimulated primary production which in turn reduced toxic effects indirectly. In addition, the neonicotinoid thiacloprid induced indirect effects on aquatic biodiversity which persisted much longer than the presence of this insecticide in the ditch ecosystem. The results in this thesis therefore show how the inclusion of environmentally realistic testing is essential to predict the actual risks of agrochemicals in the actual environment. Show less