plankton in large rivers ecological and ecotoxicological importance c. joaquim-justo laboratory of...
TRANSCRIPT
Plankton in large rivers ecological and ecotoxicological
importanceC. Joaquim-Justo
LABORATORY OF ANIMAL ECOLOGY AND ECOTOXICOLOGY Pr. J.P. Thomé UNIVERSITY OF LIÈGE
BELGIUM
Physical, chemical and biological characteristics defined as suitable for a certain use of a water resource
Domestic use (human consumption and hygienic purposes)
Recreational use (bathing, boating, aesthetic aspects of landscape, …)
Aquatic life
Reference systemsystem where human influence is minimal (historic data)
Agricultural use
Fishing
Aquaculture
Industrial use
Energetic uses
Transport
Main surface water uses:
Most demanding uses in terms of water quality.
Compliance of a water body to criteria defined forthese uses allow all other uses.
sustainable and self regulated systems
Water quality : definition
Aquatic life preservationNeed to determine what organisms found in ecosystemsNeed to understand ecosystem functionalityOrganisms at the base of food chains particularly important
Plankton in large riversBacteria
Phytoplankton
Diatoms Chlorophytes
Many pigments• Broad absorption spectrum• Significant growth rates even in dim light
Small species (0,5 - 20 m) with high growth rates adapted to important light variations
( Cyanobacteria )
Dictyosphaerium sp. Scenedesmus sp.
Cladocerans
Daphniidae BosminidaeFrom Amoros 1984
• Filter feeders (Daphniidae)• Selective predation (Bosminidae)• Parthenogenesis• Longer development time Development during summer (low flow, lowland reaches)
Bigger preys ingested compared to rotifers
Plankton in large rivers - Metazooplkanton
Plankton in large rivers - Metazooplkanton
Copepods
• 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 spanMolluscs larvae
Dreissena veliger
Nauplius larvae Copepodites & Adult
Plankton in large riversProtozooplankton
Ciliates (Heterotrophs and mixotrophs)
• High numbers of biomass up to 30 % of total zooplankton• High turn-over ratesFlagellates
Amoebozoa, Heliozoa, ...Vorticella sp.
Auto
HeteroIngestion of
Paramecium by Didinium nasutum
Black & White illustrations adapted from Hausmann and Hülsmann 1996
Mixo
Phytoplankton
Microbial loop
Bacteria
Metazooplankton Protozooplankton
Planktivores (Fish, macroinvertebrates, …)
Autotrophic & Mixotrophic protozoans
!
Foodwebs in aquatic ecosystems
Chemical indicesProvide, 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 communitiesBiological monitoringIntegration of perturbations based on monitoring of effects Bioassessments : analysis of biological communities (observational approach) Bioassays : early warning systems based on ecotoxicological tests
• •
Bioassays Biomarkers
mixed function oxidases
regulatory enzymes
behavioural effects
Main type of biomarkers:
biomarkers of the nervous system
biomarkers of the reproductive
system
biomarkers of the immunity system
biomarkers relative to genetic
material
« Xenobiotically-induced variation in cellular or biochemical components or processes, structures, or functions that is measurable in a biological system or sample » (NRC, 1987).
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 laboratoryfish, invertebrates and planktonic organisms
High sensitivity Early warning systems Prevention of damages to ecosystems
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
Exposure assessment
Predicted No Effect Concentrations
(PNECs)
Predicted Environmental
Concentrations (PECs)
Risk characterisation of toxic pollutants
Algae
Invertebrates (planktonic, benthic and sediment dwelling organisms)
Fish
Micro-organisms (Sewage Treatment Plant)
Secondary poisoning
Risk characterisation ratio: PEC / PNEC
If PEC/PNEC <1 No hazard for the environmentIf PEC/PNEC 1 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
Determination of Predicted Environmental Concentration (PEC) of the substance
Ph
ysi
co-c
hem
ical p
rop
ert
ies
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 :Exposure assessment
Default values overriden:
Number of days of emission
Receiving water body characteristics
Measurements in effluent and/or air exhausts
Risk characterisation of toxic pollutants
Risk characterisation of toxic pollutants : effect assessment
NOEC : highest test concentration showing no effect (concentration-effect relationship)
Example:
EC50 fish: 500 mg/l
EC50 daphnid: 732 mg/l EC50 algae: 314 mg/l
PNEC aqua: 314 = 314 µg/l1000
Assessment factors to derive a PNEC
= concentration below which unacceptable effects on organisms will most likely not occur.
Use of ecotoxicological data and safety factors
Determination of Predicted No Effect Concentration (PNEC) of the substance
most likely not occur.
Low organic pollution
High organic pollution
OligosaprobesOligo--mesosaprobes
-mesosaprobes-mesosaprobes
Oligotrophic waters
Eutrophic waters
Rotifers as indicators of water quality:Saprobic indice of Sládecek
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)• Anions (cyanides, fluorides, sulphides and sulphites)• Acids and alkalisLists issued by EEC • For most dangerous toxic compounds • On the basis of toxicity, persistence and potential for bioaccumulation.
Toxic pollutants
« Black list »
« Grey list »
Plankton in large riversMetazooplankton
Rotifers
• 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 female
Mictic female
Mictic egg n
Male n
fecondation
Illustrations adapted from Pourriot & Francez 1986
Amictic egg 2n
Stimulus
(bad conditions)
Resting egg 2N
VitellogenousGland
Lorica
Stomach
Bladder
Egg
Foot
Mastax
Ciliated corona
PenisToes
Brachyonus calyciflorus Keratela cochlearis Brachyonus leydigi Tricotria sp. Polyarthra sp.