Biological field and laboratory methods for measuring the quality of ...
Biological field and laboratory methods for measuring the quality of ...
Biological field and laboratory methods for measuring the quality of ...
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BIOLOGICAL METHODS<br />
Equitability "e," as calculated, may range<br />
from a to I except in <strong>the</strong> unusual situation<br />
where <strong>the</strong> distribution in <strong>the</strong> sample is more<br />
equitable than <strong>the</strong> distribution resulting from<br />
<strong>the</strong> MacArthur model. Such an eventuality will<br />
result in values <strong>of</strong> e greater than l, <strong>and</strong> this<br />
occasionally occurs in samples containing only a<br />
few specimens with several taxa represented.<br />
The estimate <strong>of</strong> d <strong>and</strong> e improves with increased<br />
sample size, <strong>and</strong> samples containing less than<br />
100 specimens should be evaluated with caution,<br />
if at all.<br />
When Wilhm (59) evaluated values calculated<br />
from data that numerous authors had collected<br />
from a variety <strong>of</strong> polluted <strong>and</strong> unpolluted<br />
waters, he found that in unpolluted waters d was<br />
generally between 3 <strong>and</strong> 4, whereas in polluted<br />
water, d was generally less than 1. However,<br />
collected data from sou<strong>the</strong>astern U. S. waters by<br />
EPA biologists has shown that where degradation<br />
is at slight to moderate levels, d lacks <strong>the</strong><br />
sensitivity to demonstrate differences. Equitability<br />
e, on <strong>the</strong> contrary, has been found to be<br />
very sensitive to even slight levels <strong>of</strong> degradation.<br />
Equitability levels below 0.5 have not been<br />
encountered in sou<strong>the</strong>astern streams known to<br />
be unaffected by oxygen-dem<strong>and</strong>ing wastes, <strong>and</strong><br />
in such streams, e generally ranges between 0.6<br />
<strong>and</strong> 0.8. Even slight levels <strong>of</strong> degradation have<br />
been found to reduce equitability below 0.5 <strong>and</strong><br />
generally to a range <strong>of</strong> 0.0 to 0.3.<br />
Agency biologists are encouraged to calculate<br />
both mean diversity d <strong>and</strong> equitability e <strong>for</strong><br />
samples collected in <strong>the</strong> course <strong>of</strong> macroinvertebrate<br />
studies. (If <strong>the</strong> mean <strong>and</strong> range <strong>of</strong> values<br />
found by different sampling <strong>methods</strong> <strong>and</strong> under<br />
varying levels <strong>and</strong> types <strong>of</strong> pollution are<br />
reported to <strong>the</strong> <strong>Biological</strong> Methods Branch,<br />
<strong>the</strong>se data will be included in tabular <strong>for</strong>m in<br />
future revisions <strong>of</strong> this Section.)<br />
5.2 Qualitative Data<br />
As previously defined, qualitative data result<br />
from samples collected in such a manner that no<br />
estimate <strong>of</strong> numerical abundance or biomass can<br />
be calculated. The output consists <strong>of</strong> a list <strong>of</strong><br />
taxa collected in <strong>the</strong> various habitats <strong>of</strong> <strong>the</strong><br />
environment being studied. The numerous<br />
18<br />
schemes advanced <strong>for</strong> <strong>the</strong> analysis <strong>of</strong> qualitative<br />
data may be grouped in two categories:<br />
5.2.1 Indicator-organism scheme<br />
For t his technique, individual taxa are<br />
classified on <strong>the</strong> basis <strong>of</strong> <strong>the</strong>ir tolerance or<br />
intolerance to various levels <strong>of</strong> putrescible<br />
wastes (4, 5, 30, 42, 48). Taxa are classified<br />
according to <strong>the</strong>ir presence or absence in different<br />
environments as determined by Held<br />
studies. Beck (6) reduced data based on <strong>the</strong><br />
presence or absence <strong>of</strong> indicator organisms to a<br />
simple numerical <strong>for</strong>m <strong>for</strong> ease in presentation.<br />
5.2.2 Reference station <strong>methods</strong><br />
Comparative or control station <strong>methods</strong><br />
compare <strong>the</strong> qualitative characteristics <strong>of</strong> <strong>the</strong><br />
fauna in clean water habitats with those <strong>of</strong><br />
fauna in habitats subject to stress. Patrick (46)<br />
compared stations on <strong>the</strong> basis <strong>of</strong> richness <strong>of</strong><br />
species <strong>and</strong> Wurtz (61) used indicator organisms<br />
in comparing stations.<br />
If adequate background data are available to<br />
an experienced investigator, both <strong>of</strong> <strong>the</strong>se techniques<br />
can prove quite useful-particularly <strong>for</strong><br />
<strong>the</strong> purpose <strong>of</strong> demonstrating <strong>the</strong> effects <strong>of</strong><br />
gross to moderate organic contamination on <strong>the</strong><br />
macroinvertebrate community. To detect more<br />
subtle changes in <strong>the</strong> macroinvertebrate community,<br />
collect quantitative data on numbers or<br />
biomass <strong>of</strong> organisms. Data on <strong>the</strong> presence <strong>of</strong><br />
tolerant <strong>and</strong> intolerant taxa <strong>and</strong> richness <strong>of</strong><br />
species may be effectively summarized <strong>for</strong> evaluation<br />
<strong>and</strong> presentation by means <strong>of</strong> line graphs,<br />
bar graphs, pie diagrams, histograms, or pictoral<br />
diagrams (27).<br />
The calssification by various authors <strong>of</strong> representative<br />
macroinvertebrates according to <strong>the</strong>ir<br />
tolerance <strong>of</strong> organic wastes is presented in Table<br />
7. In most cases, <strong>the</strong> taxonomic nomenclature<br />
used in <strong>the</strong> table is that <strong>of</strong> <strong>the</strong> original authors.<br />
The pollutional classifications <strong>of</strong> <strong>the</strong> authors<br />
were arbitrarily placed in three categories <br />
tolerant, facultative, <strong>and</strong> intolerant - defined as<br />
follows:<br />
• Tolerant: Organisms frequently associated<br />
with gross organic contamination <strong>and</strong> are<br />
generally capable <strong>of</strong> thriving under<br />
anaerobic conditions.