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Plankton in large rivers ecological and ecotoxicological importance C. Joaquim-Justo LABORATORY OF ANIMAL ECOLOGY AND ECOTOXICOLOGY Pr. J.P. Thomé UNIVERSITY OF LIÈGE BELGIUM Water quality : definition Reference system sustainable and self regulated systems system where human influence is minimal (historic data) Physical, chemical and biological characteristics defined as suitable for a certain use of a water resource Main surface water uses: Domestic use (human consumption and hygienic purposes) Recreational use (bathing, boating, aesthetic aspects of landscape, …) Aquatic life Most demanding uses in terms of water quality. Compliance of a water body to criteria defined for these uses allow all other uses. Agricultural use Fishing Aquaculture Industrial use Energetic uses Transport Aquatic life preservation Need to determine what organisms found in ecosystems Need to understand ecosystem functionality Organisms at the base of food chains particularly important Plankton in large rivers Bacteria Phytoplankton Small species (0,5 - 20 m) with high growth rates adapted to important light variations Diatoms Many pigments • Broad absorption spectrum • Significant growth rates even in dim light ( Cyanobacteria ) Chlorophytes Dictyosphaerium sp. Scenedesmus sp. Plankton in large rivers - Metazooplkanton Cladocerans Daphniidae • • • • From Amoros 1984 Bosminidae Filter feeders (Daphniidae) Bigger preys ingested compared to rotifers Selective predation (Bosminidae) Parthenogenesis Longer development time Development during summer (low flow, lowland reaches) Plankton in large rivers - Metazooplkanton Copepods Nauplius larvae Copepodites & Adult • Wide variety of diet depending on species ( herbivores, omnivores, highly selective predators, …) • Active capture of prey often very selective (chemical detection or sensitivity to prey movements) • Sexual reproduction longer life span Molluscs larvae Dreissena veliger Plankton in large rivers Protozooplankton • High numbers of biomass up to 30 % of total zooplankton • High turn-over rates Flagellates Ciliates (Heterotrophs and mixotrophs) Auto Hetero Amoebozoa, Heliozoa, ... Mixo Ingestion of Paramecium by Didinium nasutum Vorticella sp. Black & White illustrations adapted from Hausmann and Hülsmann 1996 Foodwebs in aquatic ecosystems Planktivores (Fish, macroinvertebrates, …) ! Metazooplankton Protozooplankton Microbial loop Phytoplankton Bacteria Autotrophic & Mixotrophic protozoans Chemical indices Provide, through measurements, situation at one moment in time Risk characterisation of toxic pollutants • Chemical-to-chemical process • Extrapolations based on laboratory tests, performed with very few species • Ecotoxicological data available for only very few existing chemicals despite Quantitative Structure - Activity Relationships. • Monitoring of only 10-20 substances in important aquatic ecosystems (expensive) • Do not consider synergistic, antagonistic and additive effects • Do not consider interactions among communities Biological monitoring Integration of perturbations based on monitoring of effects • Bioassessments : analysis of biological communities (observational approach) • Bioassays : early warning systems based on ecotoxicological tests Bioassays Biomarkers « Xenobiotically-induced variation in cellular or biochemical components or processes, structures, or functions that is measurable in a biological system or sample » (NRC, 1987). Main type of biomarkers: biomarkers of the nervous system mixed function oxidases biomarkers of the reproductive system regulatory enzymes biomarkers of the immunity system behavioural effects biomarkers relative to genetic material Suitable organisms for routine bioassays: must be sensitive to factors under consideration must be widely distributed and readily available in high numbers throughout the year should have economic, recreational or ecological importance should be easily cultured in the laboratory fish, invertebrates and planktonic organisms High sensitivity Early warning systems Prevention of damages to ecosystems Risk characterisation of toxic pollutants Selection of potentially dangerous substances (tonnage, persistance, accumulation properties, toxicity) out of the 100 000 substances of EINECS (European Inventory of Existing Chemical Substances) Priority lists issued by EEC Notification of new substances produced/imported in EU Risk characterisation of toxic pollutants Effect assessment Algae Predicted No Effect Concentrations (PNECs) Invertebrates (planktonic, benthic and sediment dwelling organisms) Fish Micro-organisms (Sewage Treatment Plant) Secondary poisoning Exposure assessment Predicted Environmental Concentrations (PECs) Risk characterisation of toxic pollutants Risk characterisation ratio: PEC / PNEC If PEC/PNEC <1 If PEC/PNEC 1 No hazard for the environment Hazard for the environment Conclusions: There is need for further information and/or testing There is at present no need for further information and/or testing or for risk reduction measures beyond those which are being applied already There is a need for limiting the risks Risk characterisation of toxic pollutants : Exposure assessment Determination of Predicted Environmental Concentration (PEC) of the substance Emissions are estimated for each life cycle stage of the substance: production, formulation, processing (industrial or domestic use), disposal. Emission can be measured by industry or calculated by models on the basis of physico-chemical properties and use categories of the substance. A Standard environment is defined on local, regional and continental scales. PECs When valid monitoring data are available, they are also used; otherways default values are used (worst case scenario) Risk characterisation of toxic pollutants Default values overriden: Number of days of emission Receiving water body characteristics Measurements in effluent and/or air exhausts Risk characterisation of toxic pollutants : effect assessment Determination of Predicted No Effect Concentration (PNEC) of the substance = concentration below which unacceptable effects on organisms will most likely occur. most likely notnot occur. Use of ecotoxicological data and safety factors Assessment factors to derive a PNEC Example: EC50 fish: 500 mg/l EC50 daphnid: 732 mg/l EC50 algae: 314 mg/l PNEC aqua: 314 = 314 µg/l 1000 NOEC : highest test concentration showing no effect (concentration-effect relationship) Rotifers as indicators of water quality: Saprobic indice of Sládecek Low organic pollution Oligosaprobes Oligotrophic waters Oligo--mesosaprobes -mesosaprobes Eutrophic waters -mesosaprobes High organic pollution Toxic pollutants Major types: • Metals arising from industrial and agricultural processes (lead, cadmium, copper, mercury) • Organic compounds: organochlorine pesticides, herbicides, polychlorobyphenyls (PCBs), chlorinated aliphatic hydrocarbons, solvents, straight-chain surfactants, petroleum hydrocarbons, polynuclear aromatics, chlorinated dibenzodioxins, organometallic compounds, phenols, formaldehyde. • Gases (chlorine and ammonia) • Anionsissued (cyanides,by fluorides, Lists EEC sulphides and sulphites) • Acids and dangerous alkalis For most toxic compounds • On the basis of toxicity, persistence and potential for bioaccumulation. « Black list » « Grey list » Plankton in large rivers Metazooplankton Brachyonus calyciflorus Rotifers Keratela cochlearis Brachyonus leydigi Tricotria sp. Polyarthra sp. • 100 - 800 m • Filter feeders on phytoplankton and bacterioplankton • Some species selective (size and taste) • Some species predators (protozooplankton or other rotifers) • Parthenogenesis high reproduction rates dominant (numbers) Amictic egg 2n Amictic female Stimulus Ciliated corona Lorica Resting egg 2N fecondation Male n (bad conditions) Mictic egg n Mictic female Illustrations adapted from Pourriot & Francez 1986 Mastax Stomach Vitellogenous Gland Bladder Penis Toes Egg Foot