Mesocosm Testing Research Articles

MESOCOSM: A mesocosm database management system for environmental nanosafety

Engineered nanomaterials (ENMs) are intentionally designed and produced by humans to revolutionize the manufacturing sector, such as electronic goods, paints, tires, clothes, cosmetic products, and biomedicine. With the spread of these ENMs in our daily lives, scientific research have generated a huge amount of data related to their potential impacts on human and environment health. To date, these data are gathered in databases mainly focused on the (eco)toxicity and occupational exposure to ENMs. These databases are therefore not suitable to build well-informed environmental exposure scenarios covering the life cycle of ENMs. In this paper, we report the construction of one of the first centralized mesocosm database management system for environmental nanosafety (called MESOCOSM) containing experimental data collected from mesocosm experiments suited for understanding and quantifying both the environmental hazard and exposure. The database, which is publicly available through https://aliayadi.github.io/MESOCOSM-database/, contains 5200 entities covering tens of unique experiments investigating Ag, CeO2, CuO, TiO2-based ENMs as well as nano-enabled products. These entities are divided into different groups i.e. physicochemical properties of ENMS, environmental, exposure and hazard endpoints, and other general information about the mesocosm testing, resulting in more than forty parameters in the database. The MESOCOSM database is equipped with a powerful application, consisting of a graphical user interface (GUI), allowing users to manage and search data using complex queries without relying on programmers. MESOCOSM aims to predict and explain ENMs behavior and fate in different ecosystems as well as their potential impacts on the environment at different stages of the nanoproducts lifecycle. MESOCOSM is expected to benefit the nanosafety community by providing a continuous source of critical information and additional characterization factors for predicting ENMs interactions with the environment and their risks.

Indirect Effects of Iron Oxide on Stream Benthic Communities: Capturing Ecological Complexity with Controlled Mesocosm Experiments.

Ferric iron (Fe(III)) oxyhydroxides commonly precipitate at neutral pH and in highly oxygenated conditions in waterways receiving acid mine drainage, degrading stream benthic communities by smothering of habitat, primary producers, and aquatic invertebrates. Stream mesocosms were used to expose naturally colonized benthic communities to a gradient of ferric Fe (0-15 mg/L) for 14 days to estimate the effects of Fe precipitates on primary production, larval and emerging adult aquatic insects, and the macroinvertebrate community structure. Community composition was significantly altered at concentrations near or below the US Environmental Protection Agency chronic Fe criterion (1.0 mg/L). Iron exposure significantly decreased larval and emerging adult abundances of Baetidae (mayfly) and Chironomidae (Diptera); however, while Simuliidae (Diptera) larvae were not reduced by the Fe treatments, abundance of emerged adults significantly decreased. Iron substantially decreased the colonization biomass of green algae and diatoms, with estimated EC20 values well below the Fe criterion. In contrast, cyanobacteria were stimulated with increasing Fe concentration. By integrating environmentally realistic exposure conditions to native benthic communities that have complex structural and functional responses, the ability to predict the effects of Fe in the field is improved. Traditional toxicity testing methodologies were not developed to evaluate indirect effects of contaminants, and modernized approaches such as community mesocosm experiments better characterize and predict responses in aquatic ecosystems outside the laboratory. Therefore, the development of water quality standards would benefit by including mesocosm testing results.

Monitoring the Environmental Aging of Nanomaterials: An Opportunity for Mesocosm Testing?

Traditional aging protocols typically examine only the effects of a limited number of stresses, and relatively harsh conditions may trigger degradation mechanisms that are not observed in actual situations. Environmental aging is, in essence, the complex interaction of multiple mechanical, physicochemical and biological stresses. As yet, there is no (pre)standardized procedure that addresses this issue in a satisfactory manner. Mesocosm experiments can be designed to specifically cover the aging of nanomaterials while characterizing the associated exposure and hazard. The scenario of exposure and the life time of the nanomaterial appear as the predominant factors in the design of the experiment, and appropriate precautions need to be taken. This should the subject of guidance that may be divided into product/application categories.

Contribution of mesocosm testing to a single-step and exposure-driven environmental risk assessment of engineered nanomaterials

Environmental risk assessment of nanomaterials generally relies on a decision-tree based strategy which provides guidance and protocols for the determination of a collection of hazard end-points. Mesocosm testing is based on a different approach. This method consists in monitoring the evolution of a re-created miniature ecosystem subsequent to a nanomaterial contamination. The only decision in this risk assessment strategy is the definition of an environmentally relevant exposure scenario (incl. dose), which, given current analytical capabilities, may unfavorably affect the nature and precision of parameters and endpoints to be determined. Despite these limitations, mesocosm testing bears clear advantages for the determination of both exposure and hazard in a single experiment, and for producing dependable and intercomparable data.

Performance assessment of laboratory and field-scale multi-step passive treatment of iron-rich acid mine drainage for design improvement.

Multi-step passive systems for the treatment of iron-rich acid mine drainage (Fe-rich AMD) perform satisfactorily at the laboratory scale. However, their field-scale application has revealed dissimilarities in performance, particularly with respect to hydraulic parameters. In this study, the assessment of factors potentially responsible for the variations in performance of laboratory and field-scale multi-step systems was undertaken. Three laboratory multi-step treatment scenarios, involving a combination of dispersed alkaline substrate (DAS) units, anoxic dolomitic drains, and passive biochemical reactors (PBRs), were set up in 10.7-L columns. The field-scale treatment consisted of two PBRs separated by a wood ash (WA) reactor. The parameters identified as possibly influencing the performances of the laboratory and field-scale experiments were the following: AMD chemistry (electrical conductivity and Fe and SO42- concentrations), flow rate (Q), and saturated hydraulic conductivity (ksat). Based on these findings, the design of an efficient passive multi-step treatment system is suggested to consider the following: (1) Fe pretreatment, using materials with high ksat and low HRT. If a PBR is to be used, the Fe load should be < 26g/m3 substrate/day (Fe < 200mg/L) and SO42- < 110g/m3 substrate/day; (2) PBR/DAS filled with a mixture with at least 20% of neutralizing agent; (3) include Q and ksat (> 10-3cm/s) in the long-term prediction. Finally, mesocosm testing is strongly recommended prior to construction of full-scale systems for the treatment of Fe-rich AMD.

Evaluation of Multiple Herbicides for Control of Sponge Plant (Limnobium laevigatum)

Sponge plant is an emerging threat that has spread throughout California including the Sacramento-San Joaquin Delta, which is an important water resource for agriculture as well as critical habitat for a variety of threatened and endangered species. More data are needed on effective control methods for this spreading invader, as current management practices are not preventing proliferation. The overall objectives of this research were to evaluate imazamox, penoxsulam, topramezone, florpyrauxifen-benzyl, and carfentrazone-ethyl for control of sponge plant using three testing scales, as well as compare image analysis software to traditional biomass response for measuring herbicide performance. Overall, 280 g imazamox ha?1 (with one-percent methylated seed oil surfactant) was found as a potent solution for all different growth stages of sponge plant, and 70 g penoxsulam ha?1 as an alternative for control of sponge plant in the seedling and rosette growth stage. The image analysis software yielded similar measurement of herbicide effects as traditional biomass measure. Mesocosm testing indicated imazamox treatment sites should be inspected at four week intervals to identify plants missed by prior applications. This research provides water resource managers critical information for identification of an aquatic invasive species, and selecting an effective rapid management program.

Reference scenarios for exposure to plant protection products and invertebrate communities in stream mesocosms

Higher tier aquatic risk assessment for plant protection products (PPPs) is often based on pond-like mesocosm studies in which transient and dynamic PPP exposure scenarios as observed in lotic systems are hardly achievable. Thus, the present study presents dynamic PPP exposure scenarios at different time scales under flow-through conditions as typical for streams in agricultural landscapes. The stream mesocosm setup allows testing the influence of spatial gradients of exposure over the length of the mesocosms. The use of the fluorescent tracer uranine revealed the hydraulic processes generally underlying peak- and hour-scale exposure scenarios and demonstrated an optimized application technique to achieve stable day-scale exposures. Furthermore, to account for potential reactions of invertebrates to PPP exposures in streams (e.g. avoidance behavior and drift), the present study thus aimed at a comprehensive evaluation on how PPP exposure and the establishment of invertebrates can be advanced within stream mesocosm testing. For both, peak- and hour-scale exposure as well as the experiments considering the establishment of invertebrates, the presented compilation of experiments was able to highlight the influence of aquatic macrophytes within stream mesocosms. Since the field relevance of the higher tier aquatic risk assessment for PPPs relies qualitatively on the presence of potentially sensitive or vulnerable species, those species were especially considered. Thus, the establishment of aquatic invertebrates in non-dosed streams was evaluated with respect to (i) the presence of different aquatic macrophytes and (ii) the duration of the pre-experimental period. The present study highlights the beneficial influence of complex-structured macrophytes and prolonged pre-experimental periods on the abundance of invertebrate taxa. Furthermore, population dynamics were evaluated statistically by simulating PPP-related declines of 30, 50 and 70%. Thereby, minimum detectable difference (MDD) classes of mostly ≥III were found for 12 out of 15 taxa for at least two consecutive sampling dates.

Using stable isotope analysis in stream mesocosms to study potential effects of environmental chemicals on aquatic-terrestrial subsidies.

While recent research has provided evidence that the emergence of merolimnic insects (species with an aquatic larval stage) provides a considerable energy subsidy to riparian food webs, it has also shown that merolimnic insects may serve as a vector for contaminants. Therefore, riparian food webs may be at risk from either an aquatic-terrestrial transfer of contaminants or from the contaminant-driven reductions of emerging merolimnic insects. The objective of the present study was to develop an integrated stream mesocosms test design capable of identifying these inter-ecosystem boundary effects and to provide a comprehensive approach as a basis for ecotoxicological testing. We chose the widely distributed web-building spider Tetragnatha extensa as a representative species for riparian predators. Trophic aspects of riparian food webs were investigated by stable isotope analysis of carbon (δ(13)C) and nitrogen (δ(15)N). Utilization of stable isotope ratios provided detailed information on the riparian food web structure and the dietary composition of T. extensa. Merolimnic invertebrates (mainly Cloeon spp. and Chironomidae) were found to contribute up to 71% of T. extensa's diet, demonstrating their importance in riparian food webs in ecotoxicological mesocosm testing. This study provides a conceptual and methodological basis for assessing aquatic insect emergence-related pollutant transfer or effect translation from aquatic to adjacent terrestrial systems.

Forced Diffusion soil flux: A new technique for continuous monitoring of soil gas efflux

AbstractMeasurements of soil carbon dioxide efflux provide critical information on soil carbon balance. In light of increasing interest in monitoring carbon balance of northern soils, it is important that we develop new methodologies that are better suited to long-term, remote, and off-grid deployments. In this study, we describe a Forced Diffusion (FD) dynamic chamber, in which a gas permeable membrane passively regulates mixing of atmosphere and soil air in the chamber, in place of the active pumping system inside a regular dynamic efflux chamber system. We use a combination of methodologies to explore the FD chamber technique, including numerical modelling, laboratory benchmarking, mesocosm testing, and year-round field studies in northern temperate ecosystems. Not surprisingly, FD chambers are functionally similar to regular dynamic chambers, but the passive regulation of gas flow means that internal concentration sensors can be switched off between measurements, thereby achieving very low power consumption and high reliability. In numerical modelling experiments and controlled lab tests, FD chambers deliver data that is comparable to commercially available instruments. As with other efflux techniques, calibration, design geometry, and deployment methodology are critical issues for generating good accuracy and precision with FD chambers.

Aquatic and terrestrial mesocosms in amphibian ecotoxicology

Aquatic and terrestrial mesocosms have been used successfully to examine ecological and ecotoxicological questions with amphibians. Mesocosms represent a bridge between the laboratory and the natural world, and allow for experimental research on factors that influence amphibian populations and communities. In this manuscript, we review the current literature utilizing mesocosms for ecotoxicology, evaluate the role that mesocosm studies could play in ecotoxicology, and suggest future research directions. Mesocosms are advantageous relative to other experimental systems because treatments are easily replicated, multiple environmental factors can be manipulated, food webs can be established, direct and indirect effects can be examined, and contamination effects can be evaluated. This allows for the examination of contaminant effects on multiple trophic and taxonomic levels in an ecologically relevant context. Standard guidelines for mesocosm testing with amphibians should be created to aid new researchers, make studies more comparable, and facilitate risk assessment.

Modular estuarine mesocosm validation: ecotoxicological assessment of direct effects with the model compound endosulfan

This study represents the first in a series of validation experiments for the modular estuarine mesocosm testing direct pesticide effects. Endosulfan, an agricultural insecticide, was selected as a model contaminant for studying direct toxic effects as well as uptake of this model contaminant by estuarine biota. The grass shrimp, Palaemonetes pugio, and the mummichog, Fundulus heteroclitus, showed significant mortality (96 h LC 50: 0.12 and 2.2 μg/l, respectively) to endosulfan as predicted by laboratory bioassays. There was no effect on fiddler crabs and eastern oysters. The mesocosm was also useful in demonstrating the bioconcentration of endosulfan by eastern oysters (bioconcentration factor [BCF]=375) similar to results reported in field studies. This study illustrates the modular estuarine mesocosms' ability to detect direct effects of pesticide exposure and the uptake of a pesticide by estuarine fauna.

Ten Years of Research by the U.S. Oil Industry to Evaluate the Ecological Issues of Dispersant Use: An Overview of the Past Decade

ABSTRACT The Marine Spill Response Corporation (MSRC) and the American Petroleum Institute (API) recently completed a multiyear research program on dispersants and dispersed oil consisting of four elements: information synthesis and dissemination, improved laboratory methods for toxicity evaluation, mesocosm testing, and field experiments. These research efforts contributed to the recent changes in the way dispersants are viewed in the United States. When combined with other research findings from the last 10 years, this information, now available to response planners, greatly improved and contributed to a growing interest in the use of dispersants, including the potential for the extension of preauthorization areas. The primary objectives of this paper are to summarize the objectives of the program, highlight major findings, and identify the sources where the results can be examined in detail.

The use of engineered wetlands to treat recalcitrant wastewaters

Constructed wetlands provide good removals of BOD, COD, suspended solids, heavy metals, and pathogens from wastewaters being treated in them. However, although they are widely used in cold climates, winter operability often presents problems, and they normally only remove part of nitrogen and phosphorus nutrients in wastewaters being treated in them. What is needed was a new type of constructed wetland which removes nutrients as well as it does other contaminants, which operates better in cold weather, and which is able to handle especially difficult‐to‐treat wastewaters. The answer may be found with engineered wetlands, a type of constructed wetland in which process conditions and/or operations are modified, manipulated and/or controlled, in contrast to the more passive operation of ordinary constructed wetlands. Although the names ≪engineered wetland≫ and ≪constructed wetland≫ are sometimes used interchangeably, it is appropriate to define the former more narrowly by limiting the engineered wetland designation to apply only to the less passive situation. All engineered wetlands are constructed wetlands, but not all constructed wetlands are engineered ones. Constructed wetland systems may be ≪engineered≫ in many ways. For example, influent streams may be varied in flow rate (or periodically turned off); effluents from various points in the wetland system may be recycled to other points, ordinary substrates may be replaced with special ones having specific qualities (e.g., the ability to permanently chemically adsorb certain pollutants from wastewaters passing through them); things may be added at certain points (e.g., heat, chemicals, air); and/or wetland vegetation may be selected for its phytoremediating properties. This paper describes a new sub‐surface flow (SSF) engineered wetland biological/environmental technology (ecotechnology) known as BioReactor Engineered Wetland for wastewater treatment (BREW). It presents the results from bench scale, mesocosm testing which show that ammonia nitrogen and phosphate removals can be increased greatly with engineered wetlands.