WSP10787

• File Number: 8170
• Description: Arkansas Basin Water Quality Issues
• State: CO
• Basin: Arkansas
• Water Division: 2
• Date: 9/1/1981
• Author: Bureau of Reclamati
• Title: Heavy Metals Pollution of the Upper Arkansas River - Colorado - and its Effects on the Distribution of the Aquatic Macrofauna
• Water Supply Pro - Doc Type: Report/Study

0010

be too infrequent to account for life history
variations of benthic organisms. However, in
this study most of the organisms collected had
1- to 2-year life cycles.

Sampling Apparatus for Fish Collection

Surveillance of fishes has been of great value in
studying the quality as well as the long-term
stability of an aquatic ecosystem. The collection
of fish involves removal by netting, electro-
fishing, trapping. or the use of poisons. Nets are
more easily used in slow-flowing reaches of a
river. In faster-moving water, the force of the
flow and of debris on a net may cause damage
as well as make sampling difficult. A review of
net types and their uses has been provided by
Lagler (1956) [951 and Everhart et al. 11975)
1561. Electrofishing with the use of alternating
or direct current may be used. Alternating
current stuns the fish and direct current induces
"galvanotaxis" which attracts the fish to a
negative probe. In both situations they can be
collected with a hand net (Everhart et al.. 1975
1561 I. Sharpe and Burkhard (19691 [137J
described the use of a Iightwei9ht, backpack
electrofishing unit for use in small streams and
remote areas. Trapping is used in waters that
may be too large or too deep for other methods.
and it requires very little labor (Hellawell, 1978
17211; however, the catching efficiency of trap
nets is low (Stott. 197011421). Poisons such
as rotenone have been successfully used in
flowing waters (Hocutt et al.. 1973 [75J I. but
it is generally destructive and should be used
only with extreme care or if elimination of the
fish population is required.

Physical Parameters and Field Measurements

The physical-chemical quality of habitats greatly
affects the composition and abundance of
macroinvertebrate and fish species. There is
usually an increase in species diversity with an
increase in stream size and stability of flow (Min-
shall and Minshall. 1966 111211. Other envir-
onmental parameters which influence the com-
position and abundance of aquatic macrofauna
include temperature, current velocity, substrate,
and water quality.

Temperature

Temperature is predominantly related to the size
of the stream. altitude. and season. Low

temperatures decrease the growth rates of many
animals (Hynes, 1970 1841 I. but according to
Pleskot (19701 [126J high temperatures also in-
hibit growth in some Baet;s mayfly species.

In a study of the life cycle of Baet;s spp.
mayflies. Humpesch (1979) 1801 reports that
mean temperature was clearly the major factor
affecting growth rates, and Elliott (1978) 1461
stated that temperature is probably the most im-
portant single factor responsible for the control
of events in the life history of aquatic insects.

Newell and Minshall (1978) 11211 showed that
a species of mayfly, rricorythodes m;nutus, had
a distinct change in life cycle depending on the
water temperature. In a constant-temperature
water source of 18 oC. 1. m;nutus was
multivoltine. but the normal seasonal fluctuation
of temperatures caused it to be bivoltine.

Armitage (1958) [41 found that. in general, and
within limits, positive correlations were found
between temperature and the abundance of in-
sects. If the temperature tolerance limits of the
organism are exceeded. then the population
levels will of course be reduced. This has been
shown by Obrdlik et al. (1979) [1221 in a study
of the reduction in abundance of the mayfly
Potananthus luteus in the cooling water, or ther-
mal discharge, of a power station.

Rehwoldt et al. (1972) (127) suggest that tem-
perature may be significant in the toxic effects
of some heavy metals, particularly if the toxic
mechanism is intercellular and involves a bio-
chemical reaction. An increase in water temper-
ature would probably increase toxicity.

Current

A stream. simply because of the current. is a
richer (increased diversity) habitat than a lake of
equal water quality (Hynes, 1970 1841). The
variability of general currents within a stream
provides little correlation with the distribution of
benthic fauna (Cummins. 1962 13111. as the
velocity near the bottom depends on the rough-
ness of the substrate (Hynes, 1970 184J).
Most devices used to measure currents are too
imprecise to measure all facets of currents and
thus are used primarily to provide discharge in-
formation. Currents are extremely important in
the life of aquatic organisms in that they bring in
food and dissolved substances and remove

7