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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