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EFFECTS OF FRESHWATER DISCHARGE
FROM FINGER CANALS ON ESTUARINE
SEAGRASS AND MANGROVE ECOSYSTEMS
IN SOUTHWEST FLORIDA
Douglas Morrison
Jeff Malsi
Paul Renault
Philip Light
Cheryl Marx
Environmental Resources Division
City of Cape Coral
P.O. Box 150027
Cape Coral, Florida 33915
ABSTRACT
The Cape Coral canal system has altered the natural sheet flow of
freshwater into Matlacha Pass Aquatic Preserve (MPAP).       A "spreader"
waterway was constructed to re-establish sheet flow.     However, we have
found "breaks" in the Spreader which result in channelized flow
of fresh
to brackish water into MPAP.      This input affects the physiochemical
habitat of the saline wetlands and receiving waters of MPAP.
Salinity is an important factor affecting seagrass, Thalassia and
Halodule, distribution and abundance in Matlacha Pass.     The channelized
discharge from Cape Coral may inhibit or affect seagrass growth in MPAP.
Cattail (Typha) has invaded the mangrove ecosystem along channelized
flow paths which originate at breaks in the Spreader rim canal. Repair
of these breaks and elimination of channelized freshwater discharge would
inhibit Typha invasion and enhance re-establishment of saline wetland
vegetation.
INTRODUCTION
Matlacha Pass, in Lee County, is one of 40 State Aquatic Preserves
in Florida. Aquatic preserves are state-owned submerged lands of special
natural resource value which are intended to be maintained in an
essentially  natural  conditions.    Matlacha  Pass   is  identified  as
a
sensitive area of particular concern within the Charlotte Harbor estuarine
system because of its valuable natural resources, which include extensive
mangrove and seagrass ecosystems, and vulnerability to upland development
(Florida Department of Natural Resources, 1983).      These resources are
potentially threatened by, among other factors, channelized discharge of
fresh and brackish water from the adjacent Cape Coral waterway system.
The City of Cape Coral extends along the entire eastern border of
Matlacha Pass.   The City is transected by over 650 km of man-made fresh
and estuarine waterways. This extensive waterway system disrupted the
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