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 useFishingAquacultureIndustrial useEnergetic usesTransport

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 - MetazooplkantonCopepods

• 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

Phytoplankto

n

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 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

mixed function oxidasesregulatory enzymesbehavioural effects

Main type of biomarkers:biomarkers of the nervous systembiomarkers of the reproductive

systembiomarkers of the immunity systembiomarkers 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 considerationmust be widely distributed and readily available in high

numbers throughout the yearshould have economic, recreational or ecological importance should be easily cultured in the laboratory

fish, invertebrates and planktonic organismsHigh 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

AlgaeInvertebrates (planktonic, benthic and sediment dwelling organisms)FishMicro-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

Phys

ico-c

hem

ical p

rope

rties 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.

PECsWhen 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 femaleMictic egg n

Male nfecondation

Illustrations adapted from Pourriot & Francez 1986

Amictic egg 2n

Stimulus

(bad conditions)

Resting egg 2NVitellogenous

Gland

Lorica

Stomach

Bladder

EggFoot

Mastax

Ciliated corona

PenisToes

Brachyonus calyciflorus Keratela cochlearis Brachyonus leydigi Tricotria sp. Polyarthra sp.