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A At no time should measured salinities exceed 30 ppt. This
will be particularly critical to achieve in the dry season,
from November to June.
A From March through August (late dry season - early wet
season), average monthly salinities should range between
15-25 ppt in the Western Bay Zone.
A In the late wet season (September-October), the Coastal
Mangrove Zone should be oligohaline (0-5 ppt), and the
Western Bay Zone should average less than 20 ppt.
A Salinity changes should be gradual and reflect changes in
coastal inflows that approximate those of an unregulated,
natural system.
Flows that achieve these salinity targets will produce stable
mesohaline conditions over the 10,000 acre nearshore bay
area of Biscayne National Park.
We used the methods described in draft CERP Guidance
Memorandum 4 to determine how much of the existing freshwater deliveries to Biscayne National Park are contributing
to the desired salinity regime. In the absence of operational
hydrodynamic models, several analytical and empirical methods were applied to arrive at a range of estimates of the flows
necessary to reach target salinities. It was determined that
approximately 1.1 million acre-feet/year of freshwater flows
would be required to meet the salinity targets described above
in the 10,000 acre area of seagrass habitat. Modeled stages and
flows from SFWMM Alt7r for the years 1965 to 2000 were used
to quantify existing freshwater deliveries to the Bay. Following
draft CERP Guidance Memorandum 4 methodology we produced a time-series comparison of the target with the existing
flows. While some peak-flow freshwater deliveries exceeded
the targets, the total quantity of current freshwater deliveries
to Biscayne National Park is about 40% of the total desired
freshwater quantity. The stable estuarine conditions desired in
Biscayne National Park are not achieved by current freshwater inflows because the total volume is too little and because
the timing and distribution are too unnatural. Therefore, the
total volume of current freshwater inflows is required for the
protection of fish and wildlife in Biscayne National Park. Improved timing of managed releases and increased total volume
would also benefit the estuarine ecosystem in the park.
South Florida Natural Resources Center Technical Series (2006:1)
TABLE OF CONTENTS
A C K N O W L E D G E M E N T S ................................................................................................................................................................ vi
F O R E W O R D .............................................................................................................................................................................................vu
IN T R O D U C T IO N ........................................................................................................................................................................................1
Conservation Designations............................... .... ..................................................... . . 1
Relationship to CERP Processes ................ 1
Area Description........................................................................................................ 3
E C O L O G IC A L T A R G E T S FO R B IS C A Y N E N A T IO N A L P A R K ................................................................................................... 7
Historical Conditions................................................................................................................... 7
Current Conditions.................................................................................................................................................................................8
Indicator Species: Benthic Community, Endangered Species, and Important Fishery Resources........................................ .8
Desired Conditions......................................................................................... .10
Summary of Ecological Targets. . 11
H Y D R O L O G IC T A R G E T S FO R B IS C A Y N E N A T IO N A L P A R K ................................................................................................. 12
Salinity................................................................................................................................................................................................. 12
From Salinity to Freshwater Flow Targets............................................... .............................................................. . . . 13
Estimates of Target Flows........................................................................... 13
Summary of Freshwater Flow Targets..................................................... 15
Estimation of Current Flows. ............................................ 16
Estimation of "Beneficial" Flow s.........................................................................................................................................................18
D IS C U S S IO N ............................................................................................................................................................................................20
LIT ER A TU R E C I T E D ...............................................................................................................................................................................22
Ecological and Hydrologic Targets for Western Biscayne National Park v
APPENDIX A: ADVECTION VERSUS DIFFUSION 25
VI South Florida Naturai Resources Center Technical Series (2006 1)
ACKNOW LEDGEM ENTS
This paper represents a joint effort by Biscayne National Park resource management staff and staff at the South Florida Natural
Resources Center at Everglades National Park. Tom Schmidt (NPS) provided important comments on the Biscayne Bay fishery.
During the evolution of this document, valuable comments and input were received from staff at the U.S. Fish and Wildlife Service
Office of Ecological Services in Vero Beach; in particular, Patrick Pitts provided valuable technical input to the initial stages of
the document. South Florida Water Management District staff provided technical comments on an earlier draft of the paper. We
would like to thank Dave Swift of the SFWMD for his persistent encouragement during the development of this document.
Contributors:
Sarah Bellmund, Biscayne National Park
Richard Curry, Biscayne National Park
Todd Kellison, Biscayne National Park
Amy Renshaw, Biscayne National Park
Edward Kearns, Everglades National Park
Kevin Kotun, Everglades National Park
William B. Perry, Everglades National Park
Editors:
Elizabeth Crisfield, Everglades National Park
Carol L. Mitchell, Everglades National Park
Please reference this report as follows:
SFNRC. 2006. Ecological & Hydrologic Targets for Western Biscayne National Park. South Florida Natural Resources Center, Everglades
National Park, Homestead, FL. SFNRC Technical Series 2006:1.25 pp.
Ecological and Hydrologic Targets for Western Biscayne National Park vii
FOREWORD
This report, “Ecological and Hydrologic Targets fo r Western Biscayne National Park,” represents the
culmination o f a process which involved the collaboration o f National Park Service staff and review by
the staff o f other agencies including the South Florida Water Management District (SFWMD) and the
U.S. Fish and Wildlife Service. The technical analyses in this paper support the National Park Service’s
broad responsibility fo r the preservation o f our nation’s natural and cultural resources. In the context o f
the ecosystem restoration efforts in south Florida, this translates into the responsibility fo r determining the
ecological and underlying physical conditions that represent the restored natural resources o f the south
Florida national parks. The description and quantification o f these desired restoration conditions sets the
goalposts fo r both ecosystem restoration projects and resources management projects that affect national
park natural resources.
This paper identifies an overarching goal in the form o f desired conditions fo r the western area of
Biscayne National Park, and develops ecological and physical (salinity and hydrology) performance
measures and targets fo r this area. The ecological analyses o f habitat value arise from the well-documented
relationships between salinity patterns and a healthy, diverse benthic community based on seagrass.
Hydrologic analyses are then based on the ways that freshwater and seawater mix in the bay to provide
desired nearshore estuarine salinities.