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Tidal cuts aim to restore water flow
BY JULIEN GORBACH
keysnews.com
ISLAMORADA --
Everglades restoration officials will hold a public hearing Tuesday
about a pilot project to restore natural water flow from Florida Bay to
the Atlantic Ocean.
For nearly 100 years,
the changes wrought by Henry Flagler's Overseas Railroad project have
impeded the natural circulation. Project proponents say "tidal cuts"
slicing through the islands will clear up stagnant water significantly,
revive sea bottom plant and animal communities and foster the larval
distribution of such species as the spiny lobster.
But controversy has
continued over the quality of the water streaming into the bay through
the Everglades. Some scientists and environmentalists warn that
nitrogen-laden water, continuing through the cuts, would further punish
the already trouble-plagued coral reefs out in the ocean.
The meeting will be
from 7-9 p.m. Tuesday at the Marathon Government Center.
The proposed Florida
Keys Tidal Restoration project would consist of three cuts that range
from 150 feet to 450 feet across, between Mile Markers 54 and 56.5 near
Curry Hammock State Park. A fourth cut, at Mile Marker 57, would stretch
2,400 feet across.
South Florida Water
Management District project manager Dewey Worth said the pilot project
will remove 450 feet of fill from the site between Little Crawl Key and
Big Crawl Key, replacing it with either culverts or a bridge. The spot
has become a large accumulation of organic sediments, from decomposing
seaweed, seagrass and other debris.
"There is an area we
call a dead zone around the causeway," he said. "There is not much
living in there."
Worth said officials
do not expect the project to have a measurable effect on Florida Bay. It
is a pilot study that will help determine the costs and benefits of
doing tidal restoration throughout the Keys.
Worth added Tuesday's
hearing is not about the wisdom of this plan or tidal cuts in general.
Rather, he said, "it is more about performance measures we are using to
analyze the project benefits, and the site selection process."
He explained, "That is
somewhat technical, but this is part of our disclosure as to what it is
we are doing and how we are arriving at recommendations."
Public comment about
the cuts was already collected as part of the hearings in South Florida
for the Comprehensive Everglades Restoration Plan, he said.
Nevertheless,
scientists have questioned whether the cuts could cause further damage
to the coral reefs, which some say already have suffered a 90 percent
loss since the 1970s.
Freshwater impacts?
There is broad
scientific consensus that freshwater flows from the Everglades and bay
into the Atlantic have not fostered reef development. That is understood
to be the reason why there has been poor reef development over thousands
of years in the Long Key area, where there are large passes for water
flow. The best reef growth has been off Key Largo and Big Pine Key.
"It's been called a
shot in the back by your own lagoon," explained Jim Porter, a professor
of ecology and marine sciences at the University of Georgia and a
longtime researcher of coral in the Keys. "[The bay] is a shallow-water
environment. Even historically, the water was hot, saline and richer in
nutrients than water over the offshore reefs. So areas near the
historical cuts do not show the best coral reef developments."
A more controversial
position, held by some scientists, is that freshwater coming into
Florida Bay carries nitrogen from the sugar farms of the Everglades
Agricultural Area, south of Lake Okeechobee. Brian Lapointe, a
researcher with the Harbor Branch Oceanographic Institute, has long
argued that this nitrogen is responsible for the rapid deterioration of
the reefs in the last couple of decades.
He points to the fact
that between 1990 and 1995, the amount of freshwater flowing into the
bay doubled through Taylor Slough and tripled through Shark River
Slough. And from 1996 to 2000, there was a 38 percent loss of corals
Keyswide, as well as an over 400 percent increase in coral disease,
according to an assessment by Phil Dustan, a biology professor with the
College of Charleston in South Carolina.
Lapointe has been
arguing for years against Everglades restoration plans to increase
freshwater flow into the bay, and the tidal cuts project adds to his
concern.
"It seems to me that
every step of their plan involves increased nutrient levels to the
downstream reefs," he said. "And it's kind of a no-brainer that this is
not what you want to do if you have the health of these reefs in mind."
Benefits of cuts
Porter and Dustan,
however, are more equivocal. They argue the cuts could have some
benefits. A study of annual growth bands in the corals of Lignum Vitae
Basin indicates that coral growth slowed in the years that have followed
the construction of Flagler's railroad, Porter said. The corals have
growth rings like trees that show this, he explained.
Dustan said he
believes a return of historical water flows in general is a good thing,
as long as the water quality is high.
"I think you have to
look at it on a case-by-case basis, but one of the biggest disruptions
was Flagler's railroad," he said. "That really changed the flow of water
in Florida Bay."
Porter said he would
want to have before-and-after monitoring of any cuts to see if nutrients
are moving from the bay toward the reef.
"The other question I
want to know is will the overall water quality on the ocean side of the
Keys deteriorate," he said, referring to suspended sediment, water
clarity and chlorophyll content.
Worth said scientists
will be looking at water quality and taking results into consideration
before making a recommendation on the pilot study. But the volume of
water through the proposed cut will be minuscule compared to Vaca Cut,
which is just to the south.
The Florida Marine
Research Institute has already started baseline monitoring, Worth said,
but in any case, "the reefs are pretty far away."
A computer model will
be used to project the water flow and determine whether reefs need to be
a part of the monitoring that follows, he said.
The pilot project,
however, is not officially linked with a $6 million Florida Keys
Feasibility Study that is required by the CERP and scheduled for
completion in 2006. While the data from the pilot project will be useful
to the feasibility study, the study itself -- which will examine the
water quality and circulation in the bay -- will determine what happens
with the cuts.
Upstream concerns
Regardless, Lapointe
is opposed to the cuts, and he rejects South Florida Water Management
District promises that they will address water quality issues upstream
as the Everglades restoration plan proceeds.
"They are going to
increase the nutrient loading to the most sensitive parts of the Keys,
to the corals, through those cuts," Lapointe said. "I think the idea
they can restore the natural flow from the Everglades is kind of a myth,
because there is nothing natural left of up there. The oxidized topsoil
is bleeding nitrogen and phosphorus and mercury. So the idea that they
can bring water down that is clean, that is another myth."
Scientists agree high
levels of nutrients cause algae to overgrow the reefs and cut off light
and water circulation, essentially smothering them. Nutrients and
turbidity also promote the growth of bacteria and coral diseases.
Porter concedes that
because nutrient concentrations correlate with freshwater and salinity
levels, it is clear nutrients are being carried off the land and into
the bay.
But he says key pieces
of information are missing when it comes to assessing the damage they
are inflicting to the reefs: How often the water from the land reaches
the reef, and how long it stays on the reef.
Porter said there are
multiple causes for the coral destruction. The sea-urchin die-off, and
global warming are also major factors.
"Think of it like a
pie diagram," he said. "But I am not going to tell you what percentage
is each one. That's the problem. We don't know."
But some might argue
that no matter how one slices the pie, nutrient levels are going to be a
major slice.
"That's what Brian [Lapointe]
would say," Porter said. "Me, I would like to see the numbers."
This
story published on Sun, Oct 19, 2003
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