Conclusions - Freshwater Ecology: Concepts and Environmental Applications - page 475

an appreciate what we have now because there may not be an opportu-
nity to do so later.
There is reason for hope. Many rivers and streams in developed areas
are cleaner than they were in the middle of the 20th century. Knowledge
of methods for lowering eutrophication, ways to avoid contamination by
sewage, techniques for mitigation of sources of acid precipitation, and
other technological advances have led to some improvements. These im-
provements occur mainly in developed countries. It remains to be seen if
developing countries will be able to afford to preserve their aquatic re-
sources. In addition, global ozone depletion will probably be reversed by
the phaseout of chemicals that destroy ozone in the upper atmosphere,
leading to future decreases in UV damage to aquatic life.
Unfortunately, some of the problems associated with human activities
are not reversible over a human life span. Extinction is clearly not re-
versible. Groundwater pollution can be mitigated, but there is no known
case of complete removal of a pollutant from groundwater. Unwanted
species introductions are the same; once they are established, eradication
is generally impossible. The effects of pollution are now global. There are
no completely pristine habitats left.
Much of the future job of aquatic ecologists may be in “damage con-
trol.” We will be asked what is necessary to maintain ecosystem function
and preserve desirable species. A more detailed knowledge of aquatic ecol-
ogy than we currently possess is necessary to provide this information. For
example, the link between diversity and ecosystem function is not well un-
derstood. The redundancy of ecosystem services by species (i.e., what is the
minimum assemblage of species necessary to maintain productivity and the
ability to neutralize pollutants in aquatic ecosystems) is not well docu-
mented. We simply cannot predict any but the most extreme effects of our
impacts on aquatic habitats. Likewise, detailed knowledge of the biology
of species is often required before they can be preserved. Such knowledge
is sorely lacking for all but the most popular game fishes.
Many aquatic ecologists enter the field because of a love of water and
the organisms living in it. This leads to high levels of satisfaction derived
from studying the aquatic environment. Many scientists with such moti-
vation never directly study environmental problems. However, their
contributions may increase our ability to understand aquatic habitats.
My graduate study centered on a spring-fed pool in which the cyano-
bacterium Nostoc grows unusually large. This study was motivated by
nothing beyond scientific curiosity. However, the research was eventually
used to develop a management plan to protect the Nostoc in this pool. It
can be difficult to predict what scientific information will ultimately be
useful.
Some information presented in this topic may seem marginally useful
to students taking a class as a requirement for a program specializing in
other aspects of aquatic sciences. For example, a fisheries student may have
difficulty motivating interest for nutrient cycling. However, experience has
shown that managers who do not take a holistic approach are doomed to
make mistakes. Such mistakes may lead to financial loss and permanent
damage to an ecosystem. Many aquatic species have been intentionally in-
troduced to provide benefits, only to later cause unintended problems that