Plankton in large rivers ecological and ecotoxicological importance

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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
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Water quality definition
Reference system system where human influence is
minimal (historic data)
sustainable and self regulated systems
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
Main surface water uses
Agricultural use Fishing Aquaculture Industrial
use Energetic uses Transport
Most demanding uses in terms of water
quality. Compliance of a water body to criteria
defined for these uses allow all other uses.
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
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Plankton in large rivers
Bacteria Phytoplankton
Small species (0,5 - 20 ?m) with high growth
rates adapted to important light variations
Diatoms Chlorophytes
Dictyosphaerium sp.
Scenedesmus sp.

• Many pigments
• Broad absorption spectrum
• Significant growth rates even in dim light

( Cyanobacteria )
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Plankton in large rivers - Metazooplkanton
Cladocerans
Daphniidae
Bosminidae
From Amoros 1984
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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 span

Molluscs larvae
Dreissena veliger
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Plankton in large rivers
Protozooplankton

• High numbers of biomass up to 30 of total
  zooplankton
• High turn-over rates

Ciliates (Heterotrophs and mixotrophs)
Flagellates
Ingestion of Paramecium by Didinium nasutum
Hetero
Mixo
Vorticella sp.
Amoebozoa, Heliozoa, ...
Black White illustrations adapted from Hausmann
and Hülsmann 1996
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Foodwebs in aquatic ecosystems
Planktivores (Fish, macroinvertebrates, )
!
Metazooplankton
Protozooplankton
Microbial loop

Phytoplankton
Bacteria
Autotrophic Mixotrophic protozoans
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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

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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 biomarkers of the reproductive
system biomarkers of the immunity
system biomarkers relative to genetic material
mixed function oxidases regulatory
enzymes behavioural effects
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
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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
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Risk characterisation of toxic pollutants
Effect assessment
Predicted No Effect Concentrations (PNECs)
Exposure assessment
Predicted Environmental Concentrations (PECs)
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Risk characterisation of toxic pollutants
Risk characterisation ratio PEC / PNEC If
PEC/PNEC lt1 No hazard for the
environment If 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
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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)
Physico-chemical properties
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Risk characterisation of toxic pollutants
Default values overriden Number of days of
emission Receiving water body characteristics
Measurements in effluent and/or air exhausts
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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 not occur.
Use of ecotoxicological data and safety factors
most likely not occur.
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)
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Rotifers as indicators of water
quality Saprobic indice of Sládecek
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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)
• Anions (cyanides, fluorides, sulphides and
  sulphites)
• Acids and alkalis

• Lists issued by EEC
• For most dangerous toxic compounds
• On the basis of toxicity, persistence and
  potential for bioaccumulation.

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Plankton in large rivers
Metazooplankton
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)

Ciliated corona
Amictic egg 2n
Lorica
Mastax
Resting egg 2N
Stimulus (bad conditions)
Stomach
Amictic female
fecondation
Vitellogenous Gland
Male n
Bladder
Penis
Mictic egg n
Egg
Toes
Mictic female
Foot
Illustrations adapted from Pourriot Francez 1986