Martí B.
Fannin
21 May 2002
Natural and Cultural History of Piney Z/ Lake
Lafayette
The Piney Z area was so named because of an area
with pines growing in a Z-shape when viewed arially. The lake
and its western and eastern bordering lakes, (both called the
same thing, Lafayette) form the watershed for southeastern Tallahassee.
A watershed is the area where the water from rains and runoff
drains to. Piney Z as such would not exist naturally, it is maintained
by man, and would drain on its own as a natural part of the karst
topography of the Big Bend area. Karst land is a topographic structure
consisting of a porous limestone ground, with sinkholes leading
to underground lakes of water such as the Floridian aquifer. The
following is a diagram showing the basic structure of the sinkhole
area:
(http://dhr.dos.state.fl.us/bar/hist_contexts/karst.html). A sinkhole
is formed when there is not enough earth above an underground
lake to support itself, and it caves in; hence the name.
Lake Piney Z itself is an artificial lake, kept in existence by
damming up access to the sinkhole in western lake Lafayette, and
making dikes on either side where Piney Z meets western and eastern
lake Lafayette. Naturally a flood plain, the land was used by
farmers as grazing land in the early 20th century until the lake
was created and maintained. This area was not meant to remain
a lake so long, and soon became very dirty, with a thick layer
of organic muck. This muck would ordinarily be dealt with naturally
as the lake rose and fell, but its artificially maintained water
level has kept this from happening. The muck itself is made up
of dead plants and phytoplankton, which were spurred into growth
that far exceeded the natural rate by the addition of phosphate
runoff from fertilizers used in crops and lawns. Eutrophication
is a natural process as lakes age, but the addition of phosphates
greatly increases the rate of algal bloom, as evidenced by the
experiment where a lake was separated by a plastic divider curtain.
One side was given nitrogen, the other side nitrogen and phosphorus.
The following is the result after time for the algae to grow had
passed:
(http://www.umanitoba.ca/institutes/fisheries/eutro.html. The
top is with nitrogen only, bottom has phosphorus. With such a
large amount of dead material in the water, obscurinthe sandy
bottom and clouding the water, fish began to die.
Lake Piney Z was purchased by the government in the early 1990s
with plans to convert it to a commercial fishery. The first thing
that was done was that the lake was drained to expose the muck
to the open air. Then portions of it were scraped to the sandy
bottom. The muck was used to build finger dikes to extend the
amount of fishable shoreline. The sandy bottom is used by fish
in spawning. Although there was not enough money to fully scrape
the lake, around half of it was done.
In the future, the government plans to stock the lake with fish
to make it a well known fishery along the lines of lake Jackson.
Water Quality Parameters
Several water quality parameters are used to judge
the health of lakes like Piney Z. Six will be described here.
One is temperature. Basically, human interaction with lakes and
streams should not change the temperature beyond its normal range
for whatever season it is. High temperatures can also impede water’s
ability to hold oxygen and other essential substances (http://www.state.ky.us/nrepc/water/wcptmp.htm).
At piney Z, this was measured with a simple thermometer linked
to a TI-83+. The thermometer was lowered into the water at the
end of a meter stick, and when the temperature read stably it
was recorded.
Which leads us to dissolved oxygen. Extremely important, all aerobic
life forms need it to survive, as separating the oxygen from water
is considerably more difficult. Low dissolved oxygen is bad for
fish. Alternately, extremely high dissolved oxygen can cause something
akin to the bends in humans. Oxygen bubbles block blood flow and
cause death. Also harmful are external bubbles, known as emphysema,
which is visible on the fish’s scales and fins (http://www.state.ky.us/nrepc/water/wcpdo.htm).
The next water quality parameter is pH. The “p” in
“pH” represents “-log.” Thus, pH is -log
(H+), where H+ is the concentration of hydrogen ions. This measures
the alkaline or acidic nature of a solution, in this case our
lake water. Too acidic or too basic water kills fish and other
life. In general, a pH of 6.0 to 9.0 is conducive to fish life
(http://www.state.ky.us/nrepc/water/wcpph.htm). This was measured
at lake Piney Z through a probe, again attached to the end of
a meter stick.
Turbidity is the measurement of the clearness of the water, or
the amount of suspended particles or life forms in it. Water that
is cloudy cannot bring light to the lower depths, and thus plants
die and fish have more trouble breathing. We did not make a quantified
measurement of this parameter at the lake; however, the water
can be described as very tannic and obscured by floating dirt
and algae, as well as surface floating aquatic plants like lilies.
Phosphates are compounds containing the element phosphorus, normally
extremely toxic but not so when an ion. Phosphorus from fertilizer
runoff causes massive algal blooms by providing extremely high
amounts of nutrients to the free floating phytoplankton, as well
as to larger rooted underwater plants (http://www.state.ky.us/nrepc/water/wcptp.htm).
Nitrates are are the last of the water quality parameters discussed
here. Nitrates are NO3(-1) ions which come from nitrite (NO2)
ions converted by bacteria into nitrates. Monitoring nitrate levels
is important because as nitrates deplete dissolved oxygen, high
levels will cause aerobic aquatic life - as well as humans - to
have serious diseases. In very high levels, nitrates kill aquatic
life.
