Environmental Assessment and Sustainability CIV913

BIOLOGICAL ASSESSMENT

of

River Water Quality

Assessing the biological quality of fresh waters : Wright, J. F., Water Pollution Biology - Abel PD Water Quality Monitoring - Bartram J & Ballance RFreshwater Ecology - Jeffries M & Mills DEcology of Freshwaters - Moss B

BIOLOGICAL ASSESSMENT

Biological Methods• Macroinvertebrate community status

• Macroinvertebrates - specific taxa

• Macrophyte community assessment

• Diatom community status

• Sewage fungus

• Bioaccumulation

• Moss bags

• In-situ and ex-situ Bioassays

• combinations of the above

BIOLOGICAL ASSESSMENT

• INDICATOR ORGANISMS

Those which by their presence and abundance, provide some indication, either qualitatively or quantitatively or both, of the prevailing environmental conditions.

BIOLOGICAL ASSESSMENTMacroinvertabrates

• Advantages

– Diverse

– Sedentary

– Long-lived

– Well characterised

• Disadvantages

– Aggregated distribution

– Seasonal variation

– River drift

– Difficult to get reliable quantitative samples.

BIOLOGICAL ASSESSMENT

CHEMICAL AND BIOLOGICAL ASSESSMENT

• Overall should show a similar picture.

• There are local differences:

– England and Wales > 20% river length (8500Km) chem and biological assessments > 2 grades diff.

– Schemes are independent, and measure different features.

CHEMICAL vs. BIOLOGICAL ASSESSMENT

Biological Assessment better than Chemical.– longer term picture (community structure)

– can show periodic pollution

– also responds to a wide range of chemical contaminants

– contaminants at low levels may bioaccumulate (gives a response)

• Drawbacks to Biological Assessment– Discontinuous (seasonal) method

– dependent on habitat

– labour intensive and requires taxonomical skills

– invasive (potentially disruptive to riverbed)

– errors (drift of organisms)

– Sampling technique critical

BIOLOGICAL ASSESSMENT

• Qualitative Sampling.The number of taxa recovered depends on:

– sampling effort (taxon accretion curve)– operator and technique,

• 5 Surber samples or 10-20 min kick sampling yields 80% of taxa,• 3 min kick sampling by experienced operators yields 40 to 50%

of taxa

• Identification– level of taxonomic skill (ie determination of species

versus families)

• Data Processing

BIOLOGICAL ASSESSMENT

STATISTICAL CONSIDERATIONS

• Quantitative Sampling.

– More demanding.

– Used to determine relative population density.

– High levels of confidence within narrow limits requires large numbers of samples.

– Number of samples required to estimate population density is approx:

BIOLOGICAL ASSESSMENT

n = (st/Dx)2

x: mean number of taxa per sample,

n: number of samples,

s: standard deviation,

D: index of precision,

t: Student`s t for the required level f confidence.

eg

if x = 10, s = 5, to obtain estimate of pop density within 10% of true value with 95% confidence, require 100 samples.

BUT BEWARE OF LIMITATIONS.

BIOLOGICAL ASSESSMENT

DATA ANALYSIS AND INTERPRETATION

• Series of comparisons.

• Spatial, or

• Temporal, or

• Both

BIOLOGICAL ASSESSMENT

DATA ANALYSIS AND INTERPRETATION

• Can we distinguish between an anthropogenic impact and one from coincidental factors?

• To determine the effects of pollution, need a good understanding of the conditions in unpolluted waters.

• Must consider both numbers of species and their relative abundance.

• Complexity - hence use of Indexes.

BIOLOGICAL ASSESSMENT

BIOTIC Indexes - Diversity Indexes

• Developed to study stability versus diversity in ecosystems.

• Many approaches, differ in weighting given to the number of species and to the distribution of individuals between species.

• Many are not independent of sample size.

• Practical advantage is the low taxonomical skill requirement.

BIOLOGICAL ASSESSMENT

BIOTIC Indexes.

All Indexes are empirical.

• Saprobien Indexes (Knopp 1954)

– Central and Eastern Europe.

– Recognise 4 sabrobic zones and relative abundance (eg rare, frequent, abundant)

– Organism allocation to pollution zones.

• Trent Biotic Index (Woodiwiss 1964)

– allocate macrofauna to groups

– low taxonomic skill requirement

– abundance not considered

Biotic Indexes

Lothians Index (Graham 1964)– similar to Trent, different scales

Chandler Biotic Index (Chandler 1970)– 5 levels of abundance considered (weighting of scores)

Biological Monitoring Working Party, BMWP (1979)– each family is scored, scores summed– no account taken of abundance of individuals

Average Score per Taxon (ASPT)– is BMWP score divided by number of Taxa (families)– better when sampling technique varies

BIOLOGICAL ASSESSMENT

River Invertebrate Prediction and Classification Scheme• RIVPACS (Multivariate analysis)

– Input a minimum of 8 physical parameters:• latitude• longitude• altitude• distance from source• discharge• width• depth• substratum composition.

General Quality Assessment (GQA)- Biological -

• Environment Agency– Ecological Quality Index (EQI)

• uses the predicted diversity (BMWP, ASPT) for the river as a baseline (calculated by RIVPACS)

• numerical ratio between observed and predicted values gives index.

• River stretch graded “a ----- f” based on EQI value

Actual BMWP

RIVPACS BMWPEQI =