| The combination of warm water
and nutrient deposition is the primary causal
factor of unsightly algal blooms. As time
progresses, sedimentation increases, depth
decreases, and the lake environment grows
warmer still. The algal blooms cause increases
in algal predators and detritovores (organisms
that break down dead organic material).
In extreme cases, the amplification of these
populations results in low levels of dissolved
oxygen in the water. Possible consequences
of low dissolved oxygen levels include fish
kills. Native fish inhabitation is also
impacted by the changes associated with
warmer temperatures and habitat fragmentation
(dams).
Why Watershed
Management?
Much of the origin of poor lake water
quality is from the contributing watershed.
The eroded sediments and nutrients generated
by upstream sources are washed into the
river and trapped in the lake causing
decreases in depth and turbidity. Few
substantial efforts have been made to
curb such pollution. In 1977, the Federal
Water Pollution Control Act (FWPCA) was
substantially amended and renamed the
Clean Water Act (CWA). The 1972 and 1977
amendments implemented an extensive permit
system that focused on control of pollutants
from individual sources. While this "end
of the pipeline" method has met with
some success, it noticeably left the control
of pollutants from runoff (non-point source
pollution) residing in the States or other
authorities. Without upstream controls
in place, downstream water quality has
deteriorated and management attempts have
been transient in nature.
Wetlands serve as a source of groundwater
recharge and discharge, flood storage,
erosion and shoreline anchoring, sediment
trapping, food chain support, and nutrient
retention and removal. One of the most
important hydrologic functions of wetland
is this provision of water retention and
prevention of flooding and sedimentation.
Studies have shown that increased proportions
of wetlands in a watershed reduce flood
flows and improve water quality downstream
(Johnston, Detenbeck, and Niemi 1990).
Given the cost of dredging, I wonder if
filling those wetlands and farming to
the edge of the riverbank really made
money?
Cristen, algae are protists and fish
are vertebrates, and why are you using
environmental law acronyms?
I know algae are protists and I know
that this is the Native Plant Society
Newsletter. Remember Clements' interactive
theory of ecology! Disturbance can have
all kinds of effects throughout an ecosystem
as evidenced by the prominence of invasive
species in highly disturbed areas. Minimization
of disturbance via control of non-point
source pollution, reestablishment of wetland
zones, and establishment of buffer strips
around lakeshores and river edges can
work wonders in the preservation and restoration
of native species. That's why this newsletter
is about watersheds.
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