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Aquatic Ecotoxicology

aquatic ecotoxicology, aquatic ecotox, testing, analytical services, chemical studies

Aquatic toxicology tests (assays) are toxicity tests used to provide qualitative and quantitative data on adverse effects on aquatic organisms from a toxicant. Toxicity tests can be used to assess the potential for damage to an aquatic environment and provide a database that can be used to assess the risk associated within a situation for a specific toxicant. Aquatic toxicology tests can be performed in the field or in the laboratory. Field experiments generally refer to multiple species exposure and laboratory experiments generally refer to single species exposure.


There are different types of toxicity tests that can be performed on various test species.

Different species differ in their susceptibility to chemicals, most likely due to differences in accessibility, metabolic rate, excretion rate, genetic factors, dieteary factors, age, sex, health and stress level of the organism. Common standard test species are;
the fathead minnow (Pimephales promelas), daphnids (Daphnia magna, D. pulex, D. pulicaria, Ceriodaphnia dubia), midge (Chironomus tentans, C. riparius), rainbow trout (Oncorhynchus mykiss), sheepshead minnow (Cyprinodon variegatu), mysids (Mysidopsis), oyster (Crassotreas), scud (Hyalalla Azteca), grass shrimp (Palaemonetes pugio) and mussels (Mytilus).


Tier 1 Studies with full GLP Compliance

OECD 201

Freshwater Alga and Cyanobacteria, Growth Inhibition Test

The purpose of this test is to determine the effects of a substance on the growth of freshwater microalgae and/or cyanobacteria. Exponentially growing test organisms are exposed to the test substance in batch cultures over a period of normally 72 hours. The system response is the reduction of growth in a series of algal cultures exposed to, at least, five concentrations of a test substance. Three replicates at each test concentration should be used. The response is evaluated as a function of the exposure concentration in comparison with the average growth of control cultures. The cultures are allowed unrestricted exponential growth under nutrient sufficient conditions (two alternative growth media: the OECD and the AAP) and continuous fluorescent illumination. Growth and growth inhibition are quantified from measurements of the algal biomass as a function of time. The limit test corresponds to one dose level of 100 mg/L. This study includes: the determination, at least daily, of the algal biomass; the measure of the pH (at the beginning and at the end); microscopic observation. expand

OECD 221 & OECD 239/239

Aquatic Plant Growth Inhibition Tests using Lemna sp. (OECD 221), Myriophyllum spicatum (OECD 238/239)

OECD 221 - the purpose of this test is designed to assess the toxicity of substances to freshwater aquatic plants of the genus Lemna (duckweed). Exponentially growing plant cultures of the genus Lemna (Lemna gibba and Lemna minor usually) are allowed to grow as monocultures in, at least, five concentrations of the test substance over a period of seven days. The objective of the test is to quantify substance-related effects on vegetative growth over this period based on assessments of selected measurement variables. The limit test corresponds to one dose level of 100 mg/L. This study includes measurement of pH, light intensity, concentrations of the test substance, the counting of the frond number and measurement of at least one other variable (total frond area, dry weight or fresh weight). From the average specific growth rates (or yield) recorded in a series of test solutions, the concentration bringing about a specified x % inhibition of growth rate (or yield) is determined and expressed as the ErCx (or EyCx). An additional response variable used is yield. In addition, the lowest observed effect concentration (LOEC) and the no observed effect concentration (NOEC) may be statistically determined.

OECD 238 - the purpose of this test is designed to assess the toxicity of chemicals on the growth of submerged aquatic plants Myriophyllum spicatum growing in a sediment-free test system. In a modified Andrews' medium Myriophyllum spicatum plant cultures are exposed to at least five different concentrations of the test chemical over a period of 14 days. A minimum of 10 replicates for the controls and 5 replicates for each test concentration should be used. The measured variables include growth of shoot length, of lateral branches and roots, development of fresh and dry weight, increase of whorls. Both average specific growth rate (r) and yield (y) are determined and then used to expressed ErCx and EyCx respectively (x can be eg. 10,20,50). In addition, the lowest observed effect concentration (LOEC) and the no observed effect concentration (NOEC) may be statistically determined.

OECD 239 - the purpose of this test is designed to assess the toxicity of chemicals on the growth of the rooted aquatic plants (Myriophyllum spicatum) growing in water-sediment system. Shoot apices of healthy and non-flowering plant are potted in standardised, artificial sediment supplemented with additional nutrient and exposed to at least five concentrations of the chemical over a period of 14 days. A minimum of 6 replicates for the untreated control and 4 replicates for each test concentration should be used. The measured quantitative variables include growth of shoot length and development of fresh and dry weight, and the measured qualitative variables include presence or not of chlorosis and necrosis or growth deformities. Both average specific growth rate (r) and yield (y) are determined and then used to expressed ErCx and EyCx respectively (x can be e.g. 10, 20, 50.). In addition, the lowest observed effect concentration (LOEC) and the no observed effect concentration (NOEC) may be statistically determined.
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OECD 202 & OECD 211

Invertebrate testing using Daphnia magna, acute(OECD 202) and reproduction (OECD 211) including male induction (where necessary)

OECD 202 - the purpose of this test is designed to assess the effects of chemicals towards daphnids (usually Daphnia magna Staus). Young daphnids, aged less than 24 hours at the start of the test, are exposed to the test substance at a range of concentrations (at least five concentrations) for a period of 48 hours. Immobilisation is recorded at 24 hours and 48 hours and compared with control values. The results are analysed in order to calculate the EC50 at 48h. Determination of the EC50 at 24h is optional. At least 20 animals, preferably divided into four groups of five animals each, should be used at each test concentration and for the controls. At least 2 ml of test solution should be provided for each animal (i.e. a volume of 10 ml for five daphnids per test vessel). The limit test corresponds to one dose level of 100 mg/L. The study report should include the observation for immobilized daphnids at 24 and 48 hours after the beginning of the test and the measures of dissolved oxygen, pH, concentration of the test substance, at the beginning and end of the test.

OECD 211 - the purpose of this test is designed to assess the effect of chemicals on the reproductive output of Daphnia magna Straus. To this end, young female Daphnia are exposed to the test substance added to water at a range of concentrations (at least five). For semi-static tests, at least 10 animals at each test concentration and for flow-through tests, 40 animals divided into four groups of 10 animals at each test concentration are used. The test duration is 21 days. The total number of living offspring produced per parent animal which does not die accidentally or inadvertently during the test and the number of living offspring produced per surviving parent animal at the end of the test are reported. The study report also includes: the daily counting of the offspring, the daily recording of the parent mortality, the weekly measurement of oxygen concentration, temperature, hardness and pH values and the determination of the concentrations of test substance. Optionally other effects can be reported, including the sex ratio of the offspring. The reproductive output of the animals exposed to the test substance is analysed, by comparing it with that of the control in order to determine the lowest observed effect concentration (LOEC) and hence the no observed effect concentration (NOEC), and by estimating the concentration that causes an x % reduction in reproductive output by means of a regression analysis.

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OECD 218/219, OECD 235 & OECD 233

Invertebrate testing using Chironomus riparius (OECD 218/219), also
acute (OECD 235) and full life cycle tests (OECD 233)

OECD 218/219 - the purpose of this test is designed to assess the effects of prolonged exposure of chemicals to the sediment-dwelling larvae of the freshwater dipteran Chironomus sp. First instar chironomid larvae are exposed to at least five concentrations of the test chemical in sediment - water systems. The test substance is spiked into the sediment and first instar larvae are subsequently introduced into test beakers in which the sediment and water concentrations have been stabilised. Chironomid emergence and development rate is measured at the end of the test. The maximum exposure duration is 28 days for C. riparius, C. yoshimatsui, and 65 days for C. tentans. The limit test corresponds to one dose level of 1000 mg/kg. Larval survival and weight may also be measured after 10 days if required (using additional replicates as appropriate). The study report should include the development time and the total number of fully emerged midges (sex and number are recorded daily), the observation of any abnormal behaviour the number of visible pupae that have failed to emerge and any egg masses deposition. The data are analysed either by using a regression model in order to estimate the concentration that would cause x % reduction in emergence or larval survival or growth, or by using statistical hypothesis testing to determine a NOEC/LOEC.

OECD 235 - The purpose of this test is an acute immobilisation on chronomids and is designed to complement existing guidelines for chironomid chronic toxicity assays (OECD 218/219 & 233). The test method is based on TG 202: Daphnia sp. Acute Immobilisation Test. First instar Chironomus sp. larvae are exposed to a range of concentrations of the test substance in water-only vessels for a period of 48 hours. At least 20 larvae, preferably divided into four groups of five larvae each, should be used for each test concentration and for controls. In the definitive test, at least five test concentrations should be used, with a dilution water control and solvent control (if appropriate). Immobilisation is recorded at 24 and 48 hours, and if data allow, the EC50 is calculated at 24 and 48 hours. A limit test with a single concentration may also be performed at 100 mg/L of test substance or up to the practical limit of solubility (whichever is lowest) in order to demonstrate that the EC50 is greater than this concentration.

OECD 233 - the purpose of this test is designed to assess the effect of prolonged exposure of chemicals to the life-cycle of the sediment-dwelling freshwater dipteran Chironomus sp. First instar chironomid larvae are exposed to five concentrations of the test chemical in sediment-water systems. The test substance is spiked into the water or alternatively the sediment, and first instar larvae are subsequently introduced into test beakers in which the sediment and water concentrations have been stabilised. Chironomid emergence, time to emergence, and sex ratio of the fully emerged and alive midges are assessed. Emerged adults are transferred to breeding cages, to facilitate swarming, mating and oviposition. The number of egg ropes produced and their fertility are assessed. From these egg ropes, first instar larvae of the 2nd generation are obtained. These larvae are placed into freshly prepared test beakers (spiking procedure as for the 1st generation) to determine the viability of the 2nd generation through an assessment of their emergence, time to emergence and the sex ratio of the fully emerged and alive midges. All data are analysed either by a regression model to estimate the concentration that would cause X% reduction in the relevant endpoint, or by using hypothesis testing to determine a No Observed Effect Concentration (NOEC).

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OECD 203, OECD 210 & OECD 305

Fish testing with a range of species as listed in OECD guidelines, including acute (OECD 203), Early life stage (OECD 210) and Bioaccumulation (OECD 305)

OECD 203 - the purpose of this test is the fish are exposed to the test substance preferably for a period of 96 hours. Mortalities are recorded at 24, 48, 72 and 96 hours and the concentrations which kill 50 per cent of the fish (LC50) are determined where possible. One or more species may be used, the choice being at the discretion of the testing laboratory. At least seven fishes must be used at each test concentration and in the controls. The test substance should be administered to, at least, five concentrations in a geometric series with a factor preferably not exceeding 2.2. The limit test corresponds to one dose level of 100 mg/L. This study includes the observations of fish at least after 24, 48, 72 and 96 hours. The cumulative percentage mortality for each exposure period is plotted against concentration on logarithmic probability paper.

OECD 210 - The purpose of this test is intended to define the lethal and sub-lethal effects of chemicals on the early life stages of the species tested. The early-life stages of fish are exposed to five concentrations of the test substance dissolved in water, preferably under flow-through conditions, or where appropriate, semi-static conditions. The test starts with placing fertilised eggs (at least 80 per concentration level) in the test chambers (four at the minimum) and continues at least until all the control fishes are free-feeding. Lethal and sub-lethal effects are assessed and compared with control values to either determine the lowest observed effect concentration and the no observed effect concentration, or the effect concentration leading to x% change on organisms for the effect observed. The study report should include measurement of the concentrations of the test substance in water at regular intervals (five at least), the dissolved oxygen, the temperature, pH, total hardness and salinity, fish weight and length, observations of abnormal appearance, abnormal behaviour, hatching and survival, as well as the no-observed effect level or the effect concentration leading to x% change in the organisms for the effect observed.

OECD 305 - the purpose of this test is designed for characterising the bioconcentration potential of substances in fish, using an aqueous (standard and minimised tests) or dietary exposure, under flow-through conditions (but semi-static regimes are permissible). Independent of the chosen exposure method, the bioconcentration fish test test consists of two phases: exposure (uptake) and post-exposure (depuration). During the uptake phase (usually 28 days but can be extended), a group of fish of one species is exposed to the test substances at one or more chosen concentrations (depending on the properties of the test substance). For the depuration phase they are then transferred to a medium free of the test substance, or fed with clean, untreated feed. A depuration phase is always necessary unless uptake of the substance during the uptake phase has been insignificant. In addition to the test concentration, a control group of fish is held without the test substance. The minimised aqueous exposure test is not run over a shorter period than the standard test but comprises less fish sampling. The dietary exposure bioconcentration fish test is used for substances where the aqueous exposure methodology is not practicable. In the three test methods the concentration of the test substance in the fish is followed through both phases of the test: the aqueous exposure test yields a bioconcentration factor (BCF) and the dietary approach yields a biomagnifications factor (BMF); greater emphasis is put on kinetic BCF estimation (when possible) next to estimating the BCF at steady state. BCF and BMF are expressed based on the total concentration in fish, i.e. per total wet weight of the fish, and as normalised to a fish with a 5% lipid content.

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Our tests can be designed to meet EPA guidelines instead of, or as well as, the OECD guidelines as stated above, just get in touch on +44 (0)300 100 0324 or contact us here


Tier 2 Studies - Bespoke Capabilities

  • We can develop tests that address particular concerns or information gaps using additional aquatic plant, invertebrate or fish species to support the development of Species Sensitivity Distributions (SDD) or the Geomean approach
  • We are also able to refined Tier 1 tests, adapted to resemble pulsed exposures reflecting realistic to worst case scenarios
  • We have expertise in testing to assess the potential for endocrine disruption in fish, e.g. biomarkers and/ or reproduction tests (OECD 229/230) and the sexual development test (OECD 234), should this be a consideration in your Environmental Risk Assessment
tier3, environmental risk assessment, model ecosystems, flow-through ditch/stream, mesocosm, aquatic ecotoxicology, aquatic ecotox, testing, analytical services, chemical studies

Our laboratories

Our laboratories are equipped with state-of-the-art facilities that enable cost-effective performance of GLP compliant contract research environmental fate studies for pesticides, veterinary medicines, pharmaceuticals and industrial chemicals to satisfy regulatory requirements including:

  • Laboratory (GLP) analytical services for agrochemicals, REACH, veterinary medicinal products
  • Laboratory studies with radio-labelled and non-radiolabelled chemicals
  • Batch sorption including aged sorption and column leaching studies according to OECD guidelines and parameter estimation
  • Soil, water-sediment and manure/slurry biodegradation studies including estimation of degradation parameters and endpoints
  • Hard (man-made) surfaces fate studies including lab-scale sorption, wash-off, and field monitoring studies
  • Design, interpretation and analysis of lysimeter, field leaching, field dissipation and environmental (e.g. groundwater) monitoring studies

Contact Us

To speak with us about any of our aquatic ecotoxicology services, please contact our team on:

+44 (0)300 100 0324 or contact us here.


Contact Us - Aquatic Ecotoxicology

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Join Us at SETAC EUROPE BRUSSELS 2017

The SETAC Europe 27th Annual Meeting is dedicated to the use of multidisciplinary approaches to examine the impacts of stressors, chemicals, and technology on the environment. Also, to support the development of principles and practices for protection, enhancement and management of sustainable environmental quality and ecosystem integrity. Join us at 27th Annual SETAC EUROPE BRUSSELS 2017

Our Aquatic Ecotoxicology Capabilities

Fera can support our partners with an increasing testing capability in aquatic ecotoxicology for environmental risk assessments. All of our Aquatic Toxicology Testing is available with full GLP compliance.

Download our Latest Aquatic Ecotoxicology Leaflet

Come & Join Us at Chemicals Industries Regulations (CIR)

The CIR is dedicated to the advances in science and regulatory strategies to develop new biological and agrochemical products to meet the challenge of food security. Also, to support the development of principles and practices for protection, enhancement and management of sustainable environmental quality and ecosystem integrity. Join us at Chemicals Regulations Industry (CIR), 6-7 September 2017, Nice, France

Visit LIAISON website - Pesticide Approvals, Label Information & MRLs

Pesticide Approvals, Label Information and Maximum Residue Levels - LIAISON provides details of products approved for use on any crop you select

Case Study - Low Solubility (Water Sediment Study)

Fera can support our partners with the legal nature of the REACH authorisation process. Our latest case study illustrates a robust tailored study design that not only incorporated regulatory requirements, but also ensured the analytical challenges posed by the plasticizer were considered.

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Contact Us - Aquatic Ecotoxicology

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