The Effect of Major Industrial Spills upon
Stream Organisms
JOHN CAIRNS, JR., Professor
JOHN S. CROSSMAN, Research Assistant
KENNETH L. DICKSON, Assistant Professor
EDWIN E. HERRICKS, Research Assistant
Department of Biology
and
Center for Environmental Studies
Virginia Polytechnic Institute and State University
Blacksburg, Virginia
INTRODUCTION
Aquatic ecosystems have the ability to assimilate a certain amount of waste
material and maintain near normal function. With the constant use and reuse of
water from our natural aquatic systems by industries, agriculture, and municipalities
the function may be altered or disrupted if the assimilative capacity is exceeded. The
ability of a stream or river to assimilate wastes is governed by the capacity of the
system to transform them before they reach deleterious levels. If an overload occurs
the system is disrupted, and the transforming capacity may be substantially reduced.
Recovery may be rapid or slow depending upon a number of factors including 1)
severity and duration of the stress; 2) number and kinds of associated stresses; 3)
recolonization of the area by useful aquatic organisms; and 4) residual effects upon
non-biological units (e.g., substrate, etc.).
Industrial spills typically involve an abrupt release of a waste into a river. The
waste usually passes downstream in a slug which lengthens as it proceeds due to
mixing characteristics of the river and channel water. Exposure to peak concentration is usually short and will vary depending on velocity and other factors. This
usually produces an acute stress which may eliminate most of the least tolerant
organisms, but has considerably less effect upon the populations of moderately
tolerant and tolerant organisms. Once the stress is removed or reduced the
community will become reestablished through processes such as downstream drift
and other methods of recolonization, although many of the species may be different
from those originally present.
The assessment of biological damage caused by spills is in the early stages of
development, and has been little more than cursory. It is usually restricted to
observations of fish mortality and rarely includes detailed observations of the effects
upon lower organisms. Observations may not begin until hours or even days after the
spill, and are often carried out by untrained people. Interpretation of this
information is difficult for many reasons, primary among these is the lack of
information about conditions which existed before the spill and the rather random
and unplanned gathering of data by untrained observers after the spill.
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