L09 Ecotoxicology 2024 PDF

6/7/2024 L09 Ecotoxicology Timo Hamers 1 Ecotoxicology  Ecotoxicology is the study of the effects of toxic chemicals on biological organisms, especially at the population, community, ec...

6/7/2024 L09 Ecotoxicology Timo Hamers 1 Ecotoxicology  Ecotoxicology is the study of the effects of toxic chemicals on biological organisms, especially at the population, community, ecosystem, and biosphere levels. Ecotoxicology is a multidisciplinary field, which integrates biology, chemistry, toxicology and ecology 17 1 17  6/7/2024 Focus on effects populations, communities, ecosystem general community endpoints population individual organ tissue cellular molecular specific endpoints mechanistic ecological understanding relevance 18 18 Ecotoxicology vs Environmental Toxicology Environmental chemistry Environmental toxicology Environmental Uptake + direct Emission Exposure distribution effects on organisms Ecology Indirect effects on organisms Effects on structure and functioning of ecosystem Ecotoxicology 19 2 19  6/7/2024 Ecotoxicology is an integrated science  The study of harmful effects of chemicals on ecosystems, including effect on individuals, and consequent effects at the level of population and above  Ecotoxicology integrates different disciplines 20 20 Two approaches in ecotoxicity testing  To make a PROGNOSIS What is a safe environmental concentration for the ecosystem?  To make a DIAGNOSIS Is this field site polluted or clean? 1. Prognosis: Start in the lab, extrapolate to the field 2. Diagnosis: Assess the field directly 21 3 21  6/7/2024 Prognostic testing  Predictive: start in the lab, extrapolate to field  Indicator species cultured in the laboratory  Follows principles of human toxicity testing  Determine dose-response curve for single species and single chemical  Endpoints: survival, growth, reproduction, behaviour, biochemical parameters (biomarkers)  Test protocol development, harmonization of methods  Models for dose-response analysis  Use derived parameters for risk assessment  Applicable to new (and existing) chemicals 22 22 Test selection  The most sensitive species does not exist!  Depends on Species traits Life cycle Endpoint studied Position in the food chain Chemical behavior Mode of action Route of exposure Etc..  Therefore: you need a battery of test species! Various trophic levels Various endpoints Various taxonomic groups Various contributions to ecosystem functioning 23 4 23  6/7/2024 Same generic principles as in human toxicity testing  Routes of exposure  Phases in toxic response  Classification of toxic response 24 24 Animal exposure routes  Oral via GI track (all animals) via food and water  Contact (topical) influentialpoints.com via skin (dermal): vertebrates CC BY 3.0 via cuticle: arthropods via body wall (slugs, worms)  Respiratory https://lite.lstmed.ac.uk/ via lung or gills (vertebrates) via trachea (invertebrates)  Special routes, e.g. via injection via suppository Jun Chen; https://gochordates.weebly.com/lung-lung-derivatives.html 25 5 25  6/7/2024 Phases in toxic response  Exposure:  how does an organism get into contact with compound? Routes of exposure (previous slide)  to what extend does an organism get into contact with compound? External (concentration in air, (drinking) water, soil, food) Dose (quantity per bodyweight per day) Internal (concentration in body or body compartment)  Toxicokinetics: what does the body do to the compound? Absorption, Distribution, Metabolism, Excretion Qualitatively and quantitatively  Toxicodynamics: what does the compound do to the body? Hazard! Qualitatively: what type of effect? Quantitatively: dose-response relationship 26 26 Classification in toxic response  Possibility for repair Reversible (can be repaired) vs Irreversible (permanent)  Rate Acute (shortly after single exposure) vs Chronic (after prolonged and repeated exposure)  Site of action Local (at site of first contact) vs Systemic (at site distant from first contact) 27 27 6 27  6/7/2024 Acute vs chronic  Acute Effects upon short-term exposure (hours – days) Usually focus on mortality à LC50 Sometimes also sublethal endpoints  Chronic Effects upon long-term exposure (weeks – months) Duration depends on species and life cycle Effects due to cumulation of damage Focus on sublethal endpoints (growth, reproduction) EC50, EC10, NOEC Mortality also included 28 28 28 Toxicity tests – what endpoints?  Specific endpoints Gene expression Enzyme activity Neurotransmission Histological tissue examination Etc…  Generic endpoints, important for population Survival Growth / Metabolism Reproduction Behaviour 29 7 29  6/7/2024 Aquatic ecotoxicity test – what species?  Model for the aquatic ecosystem Algae (e.g. Scenedesmus sp.) Invertebrate (e.g. water flea Daphnia sp.) Fish (e.g. rainbow trout, zebrafish, medaka, fathead minnow)  Definition of acute and chronic depends on species and life cycle: Species Acute Chronic Daphnia magna 48 h 21 d Ceriodaphnia dubia 48 h 7d Fish (adult) 96 h 28 d Fish (ELS)* 96 h * Early life stage test 30 30 Sediment ecotoxicity testing – what species?  Chironomid larvae (Insects) (OECD)  Hyalella azteca (Amphipods)  Lumbriculus variegatus (Oligochaetes) 31 8 31  6/7/2024 Terrestrial ecotoxicity test – what species?  Model for the terrestrial ecosystem > Invertebrates – Earthworms (Eisenia) – Enchytraeids – Springtails (Collembola) – Plants > Soil microorganisms – Nitrification – Respiration Definition of acute and chronic depends on species and life cycle: Species Acute Chronic Eisenia foetida 7/14 d 28/56 d Folsomia sp 4d 21/28 d 32 32 Alternative test species (examples)  Terrestrial species Predatory mites Molluscs Insect Oribatid mites Isopods Carabid beetles Nematodes larvae  Aquatic species Bacteria Macrophyte (e.g. Aliivibrio fisheri) (e.g. Lemna minor) 33 9 33  6/7/2024 Ecotoxicity testing in practice  Negative control (C0) and positive control (Cp)  Series of increasing test concentrations (C1 – Cn) or doses, in replicates  Animals from standardized culture (same age, size, health)  Standardized test medium  Climate room (temperature, light-dark regime, etc) C0 C1 C2 C… Cn Cp C0 C1 C2 C… Cn Cp C0 C1 C2 C… Cn Cp 34 34 Diagnostic testing  Assess the impact of toxic compounds on the ecosystem directly in the field  Ecology and environmental chemistry become crucial chemistry Sediment, plant and animal concentrations TRIAD approach: integrated assessment of contaminated soils and sediments along risk three lines of evidence toxicity ecology Bioassays Field observations biomarkers & experimentation 35 10 35  6/7/2024 Diagnostic testing – in situ  Assess the impact of toxic compounds on the ecosystem directly in the field  Collect organisms from the field  Determine Species abundance/diversity Health condition Pathology Behavior Biomarkers (see L16) 36 36 Diagnostic testing in situ: field observations Structural and functional endpoints  Ecotoxicology studies not only effects on individuals but also on populations and communities: Structural Functional Structural effects endpoints endpoints Pattern description Abundance of Decomposition species Functional effects Species diversity Soil respiration Process characterization Biomass Nitrification Spatial distribution Nitrogen fixation Adult/juvenile ratio Primary production Sex ratio Humification Etc Etc 37 37 11 37  6/7/2024 Diagnostic testing in situ - Functional parameters Litter decomposition Feeding activity of the soil fauna 38 38 Structural and functional endpoints  Ecotoxicology studies not only effects on individuals but also on populations and communities: Structural Functional Structural effects endpoints endpoints Pattern description Abundance of Decomposition species Functional effects Species diversity Soil respiration Process characterization Biomass Nitrification Spatial distribution Nitrogen fixation Adult/juvenile ratio Primary production Most sensitive? Sex ratio Humification Most ecological relevant? Etc Etc Overlap among species in function: functional redundancy 39 39 12 39  6/7/2024 Diagnostic testing – ex situ  Bring a field sample to the lab soil, sediment, water, passive sampler  Perform toxicity test (bioassay) on field sample or its extract In the laboratory under controlled conditions Endpoints: survival, behaviour, growth, reproduction, etc.  Compare response on test sample with “non-polluted” reference sample, or least contaminated sample from gradient, or dilution required to obtain no effect 40 40 Why bioassays in addition to chemical analysis?  Chemical analysis Often restricted to a limited set of targeted compounds Does not account for transformation products Does not account for bioavailability Threshold values (environmental quality standards) only derived for single chemicals  In practice exposure is usually to a mixture of (many) pollutants with unknown composition → toxicity hard to predict  Bioassays may provide additional insight into actual ecological risk by integrating effects of bioavailable concentrations of different chemicals 41 13 41  6/7/2024 Diagnostic testing ex situ - examples of bioassays  Bacterial tests enzyme inhibition Bioluminescence inhibition (Aliivibrio fischeri) Mutagenicity (Ames test)  Cell-based assays Reporter gene assays (based on modes of action, e.g. Calux)  In vivo tests Laboratory-cultured test organisms (daphnids, earthworms, etc) Endpoints: survival, behaviour, growth, reproduction, biomarkers 42 42 Effect-directed analysis (see L18)  Identify compounds responsible for the observed bioassay response High-throughput bioassays combined with Advanced chemical analytical methods 43 14 43  6/7/2024 Learning goals: after this lecture you can…  Explain the difference between prognostic and diagnostic testing  Explain why a battery of ecotoxicity tests is needed  Mention typical test species for aquatic and terrestrial ecotoxicity testing  Name quality control criteria for ecotoxicity testing  Distinguish between structural and functional endpoints  Explain the value of effect-based bioassay testing in addition to chemical analysis 44 44 Right or wrong?  In diagnostic toxicity testing the impact of chemicals is determined directly in the field or in field samples  Fish is the most sensitive species for ecotoxicity testing  The duration of a chronic toxicity test depends on the life cycle of the test species  The TRIAD approach is based on three pillars: exposure, toxicokinetics, and toxicodynamics  A negative control shows a decrease in response and a positive control shows an increase in response  A changes in sex ratio is an example of a functional endpoint  Bioassay testing accounts for bioavailability, and chemical analysis not 45 15 45