A higher tier flow-through toxicity test with the green alga Selenastrum capricornutum

Grade, R.; Gonzalez-Valero, Juan; Höcht, P; Pfeifle, Verena

doi:10.1016/s0048-9697(99)00504-5

Cited by 7 publications

(9 citation statements)

References 4 publications

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“…The use of flow‐through exposure systems allows pulsed exposure to be more realistically simulated with gradual changes in concentration. This approach has been used to simulate the effects of degradation of a herbicide on Selenastrum capricornutum 21. Three compounds were used in the simulation, namely the parent compound and two major metabolites, and the pulses of each mimicked the fate of the compound in the natural environment.…”

Section: Realistic Exposure Scenariosmentioning

confidence: 99%

Higher‐tier laboratory methods for assessing the aquatic toxicity of pesticides

Boxall

Brown

Barrett³

2002

Pest Management Science

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Registration schemes for plant-protection products require applicants to assess the potential ecological risk of their products using a tiered approach. Standard aquatic ecotoxicity tests are used at lower tiers and clearly defined methodologies are available for assessing the potential environmental risks. Safety factors are incorporated into the assessment process to account for the uncertainties associated with the use of lower-tier single-species ecotoxicity studies. If lower-tier assessments indicate that a substance may pose a risk to the environment, impacts can be assessed using more environmentally realistic conditions through the use of either pond mesocosms, artificial streams or field monitoring studies. Whilst these approaches provide more realistic assessments, the results are difficult to interpret and extrapolation to other systems is problematic. Recently it has been recognised that laboratory approaches that are intermediate between standard aquatic toxicity tests and field/mesocosm studies may provide useful data and help reduce the uncertainties associated with standard single-species tests. However, limited guidance is available on what tests are available and how they can be incorporated into the risk-assessment process. This paper reviews a number of these higher-tier laboratory techniques, including modified exposure studies, species sensitivity studies, population studies and tests with sensitive life stages. Recommendations are provided on how the approaches can be incorporated into the risk-assessment process.

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Section: Realistic Exposure Scenariosmentioning

confidence: 99%

Higher‐tier laboratory methods for assessing the aquatic toxicity of pesticides

Boxall

Brown

Barrett³

2002

Pest Management Science

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“…The applicability of experimental flow-through systems for algae as higher-tier tools in pesticide risk assessment has been investigated and proposed frequently [9][10][11][12][13][14][15]. In contrast to static experiments, it is possible to observe the inhibition of algae growth directly as visible loss of biomass as well as the recovery of populations by re-attaining a steady-state level of cell densities.…”

Section: Introductionmentioning

confidence: 99%

“…However, no combined use of higher-tier experiments and model predictions has been found in the literature thus far [9,13,[18][19][20][21]. However, no combined use of higher-tier experiments and model predictions has been found in the literature thus far [9,13,[18][19][20][21].…”

Section: Introductionmentioning

confidence: 99%

“…In addition, it is possible to investigate the extinction of populations which in the chemostat can happen if (due to algistatic or algicidal effects of a pesticide) the washout exceeds the growth rate. The applicability of experimental flow-through systems for algae as higher-tier tools in pesticide risk assessment has been investigated and proposed frequently [9][10][11][12][13][14][15].…”

Section: Introductionmentioning

confidence: 99%

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Combination of a higher‐tier flow‐through system and population modeling to assess the effects of time‐variable exposure of isoproturon on the green algae Desmodesmus subspicatus and Pseudokirchneriella subcapitata

Weber

Schaefer

Dorgerloh

et al. 2012

Enviro Toxic and Chemistry

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A flow-through system was developed to investigate the effects of time-variable exposure of pesticides on algae. A recently developed algae population model was used for simulations supported and verified by laboratory experiments. Flow-through studies with Desmodesmus subspicatus and Pseudokirchneriella subcapitata under time-variable exposure to isoproturon were performed, in which the exposure patterns were based on the results of FOrum for Co-ordination of pesticide fate models and their USe (FOCUS) model calculations for typical exposure situations via runoff or drain flow. Different types of pulsed exposure events were realized, including a whole range of repeated pulsed and steep peaks as well as periods of constant exposure. Both species recovered quickly in terms of growth from short-term exposure and according to substance dissipation from the system. Even at a peak 10 times the maximum predicted environmental concentration of isoproturon, only transient effects occurred on algae populations. No modified sensitivity or reduced growth was observed after repeated exposure. Model predictions of algal growth in the flow-through tests agreed well with the experimental data. The experimental boundary conditions and the physiological properties of the algae were used as the only model input. No calibration or parameter fitting was necessary. The combination of the flow-through experiments with the algae population model was revealed to be a powerful tool for the assessment of pulsed exposure on algae. It allowed investigating the growth reduction and recovery potential of algae after complex exposure, which is not possible with standard laboratory experiments alone. The results of the combined approach confirm the beneficial use of population models as supporting tools in higher-tier risk assessments of pesticides.

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“…Several laboratory approaches have been proposed, including the following: (1) static exposures accounting for dissipation processes (e.g., volatilization, hydrolysis, photolysis, and biodegradation); (2) static renewal exposures that can simulate any exposure pattern, provided the renewals are frequent enough (particularly useful for simulating square pulses); and (3) flow-through exposures in which continuous changes in exposure concentration can be achieved [46].…”

Section: Discussionmentioning

confidence: 99%

Effects of repeated pulsed herbicide exposures on the growth of aquatic macrophytes

Boxall

Fogg

Ashauer

et al. 2012

Enviro Toxic and Chemistry

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Abstract-Many contaminants are released into aquatic systems intermittently in a series of pulses. Pulse timing and magnitude can vary according to usage, compound-specific physicochemical properties, and use area characteristics. Standard laboratory ecotoxicity tests typically employ continuous exposure concentrations over defined durations and thus may not accurately and realistically reflect the effects of certain compounds on aquatic organisms, resulting in potential over-or underestimation. Consequently, the relative effects of pulsed (2 and 4 d) and continuous exposures of the duckweed Lemna minor to isoproturon, metsulfuron-methyl, and pentachlorophenol over a period of 42 d were explored in the present study. At the highest test concentrations, exposure of L. minor to pulses of metsulfuronmethyl resulted in effects on growth similar to those of an equivalent continuous exposure. For isoproturon, pulsed exposures had a lower impact than a corresponding continuous exposure, whereas the effect of pentachlorophenol delivered in pulses was greater. These differences may be explained by compound-specific uptake and degradation or dissipation rates in plants and the recovery potential that occurs following pulses for different pesticides. Given these results, use of a simple time-weighted average approach to estimate effects of intermittent exposures from short-term standard toxicity studies may not provide an accurate prediction that reflects realistic exposure scenarios. Development of mechanistic modeling approaches may facilitate better estimates of effects from intermittent exposures.

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A higher tier flow-through toxicity test with the green alga Selenastrum capricornutum

Cited by 7 publications

References 4 publications

Higher‐tier laboratory methods for assessing the aquatic toxicity of pesticides

Higher‐tier laboratory methods for assessing the aquatic toxicity of pesticides

Combination of a higher‐tier flow‐through system and population modeling to assess the effects of time‐variable exposure of isoproturon on the green algae Desmodesmus subspicatus and Pseudokirchneriella subcapitata

Effects of repeated pulsed herbicide exposures on the growth of aquatic macrophytes

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