Mapping and Monitoring Submerged Aquatic Vegetation in

163 Pages·2004·6.08 MB·English

Mapping and Monitoring
Submerged Aquatic Vegetation
in Ichetucknee Springs - 2004

Final Report

June 30, 2004

Prepared for:
Suwannee River Water Management District
9225 County Road 49
Rout 3, Box 64
Live Oak, FL 32060

Prepared by:
R. C. Kurz

2803 Fruitville Road
Suite 130
Sarasota, FL 34237
[phone]

and

D. C. Woithe
5115 Palmetto Point Drive
Palmetto, FL

and

S.K. Notestein, T. K. Frazer, J. A. Hale, and S.R. Keller
Department of Fisheries and Aquatic Sciences
University of Florida
7922 NW 71st Street
Gainesville, Florida 32653
[phone]
Executive Summary
In 2003, the SRWMD began collecting ecological data within the Ichetucknee Springs and River
to provide baseline information regarding the current health of this aquatic ecosystem. This
report describes the second year of data collection to further characterize the Ichetucknee River
and includes the mapping and monitoring of submerged aquatic vegetation (SAV) and collection
and analysis of water quality data.

The specific goals for this project were:

• To remap portions of the river which are exposed to intensive recreational use (e.g.,
docks used for entry and exit points by tubers, swimmers, and canoeists) and perform a
change analysis of these areas to compare SAV map data between 2003 and 2004;

• To develop spatial data for river depth, flow, reach and tree canopy shade, and assess
those data with respect to 2003 SAV mapping data; and

• To conduct sampling of SAV, periphyton, and water chemistry to continue to document
existing condition and to provide a basis for defining the relationship between water flow
and SAV abundance and biomass.

SAV coverage declined by approximately 454 m2 or 0.1 acres between 2003 and 2004. This
represents an approximate 2% loss within the remapped areas. The observed loss was a result of
changes in SAV to either bare bottom or emergent vegetation coverage. The greatest losses of
SAV occurred at the downstream take out area at US 27. A few small patches of Sagittaria and
Valisneria converted to bare bottom (approximately 110 m2), along with one patch of Chara
(140 m2). This loss in SAV appears to have been caused by disturbances resulting from
reconstruction of the floating dock structures and also changes in flow velocities caused by the
installation of a new floating barrier across the river at this location. Overall, changes in SAV
coverage were minimal between the two mapping periods and the majority of loss can be
explained by temporary impacts associated with the reconstruction of the take out area near US
27. Other losses were the result of conversion of former SAV polygons to emergent polygons,
likely due to lower river water levels observed during the drier 2004 mapping period.

Based on the spatial mapping analyses for the river, the vast majority of the river is less than 2 m
deep. Just over 50% of the river is less than 1 m deep (75,000 m2), with a slightly smaller area
(62,000 m2) between 1 and 2 m deep. The 2 to 3 meter interval is small (5,000 m2, less then 5%)
and occurs in Reach 3 (Rice Marsh) and the lower reaches. In general, flow follows the same
trends as the depth, with more rapid flow in areas with greater depth.

With respect to river reach, tree canopy shade decreases from reach 1 to 3, increases to reach 6,
then decreases again, although more gradually, to reach 9. The decrease in shade around reach 3
is due to the greater width of the river in this area, and the presence of Zizania beds beyond the
tree canopy. These two characteristics result in more open surface area away from the fringing
tree canopy. The decrease in shade in reaches 8 and 9 appear to be due in part to the more east-
west orientation of the river.

i Mapping and Monitoring SAV in Ichetucknee Springs 2004
Executive Summary
Analyses between nutrients and SAV cover, SAV biomass and periphyton were made among
samples collected from the main river. No significant relationships were observed (p > 0.05),
between nutrients and these parameters, suggesting that nutrient concentrations are not limiting
for SAV or periphyton in the main river. Specific analyses were also conducted to characterize
relationships between SAV coverage and depth, flow and terrestrial canopy cover. SAV
coverage and depth were positively correlated (r2 = 0.03), suggesting that depth was not limiting
SAV growth in this river. We did not observe a significant correlation between stream flow and
SAV coverage. When comparing SAV coverage to terrestrial canopy cover (%), a weak
negative correlation was observed (r2 = 0.02), suggesting that terrestrial canopy, in some cases,
may reduce potential SAV coverage.

As part of the 2004 sampling effort, six distinct springs (collectively referred to as “feeder
springs”) were individually investigated. Comparisons among feeder springs were also made for
temperature, specific conductivity, dissolved oxygen, pH, color, total nitrogen, nitrate,
ammonium, total phosphorus, soluble reactive phosphorus, and periphyton abundance.
Discharge values ranged from 1.5 m3/s for Singing Spring to 5.8 m3/s for Blue Spring. Based on
these discharge estimates these feeder springs were collectively discharging 18.3 m3/s (646.3
cubic feet per second) of ground water. At the time of sampling, mean specific conductivity
ranged from 291.0 µS/cm for Blue Spring to 352.0 µS/cm for Millpond Spring, with an average
of 312.4 µS/cm for all six springs. Mean total nitrogen concentrations ranged from 333 µg/L for
Millpond Spring to 1043 µg/L for Main Spring, with an average total nitrogen concentration of
663 µg/L for all six springs. Considerable variation in total nitrogen concentrations among the
feeder springs was observed with higher values in the Main and Blue Springs.

Mean periphyton abundance ranged from 0.025 mg chl/g host plant wet wt for Main Spring to
1.025 mg chl/g host plant wet wt for Singing Spring, with an average periphyton abundance of
0.371 mg chl/g host plant wet wt for all six springs. Several of the springs were significantly
different with respect to periphyton abundance on host macrophytes. Periphyton abundance in
the feeder springs was not significantly correlated with nitrate concentrations nor with total
nitrogen concentrations. However, there was a significant positive correlation between
periphyton abundance and soluble reactive phosphorus concentrations, as well as total
phosphorus. This relationship suggests that phosphorous may be the limiting nutrient for
periphyton in these feeder springs.

Based on the results of this study, the following recommendations are suggested to further
characterize and document SAV and water quality conditions within the river:

1. Although only a small change in SAV coverage was observed within the high use areas,
remapping should be conducted annually to maintain a historical record of coverage and
also to assess whether the losses which occurred at the US 27 take-out dock area has
recovered. A complete remapping effort of the entire river should be performed at least
once every five years.

2. Creation of a digital map from the 1979 Dutoit study should be performed to compare
historical SAV and current trends in SAV coverage.

ii Mapping and Monitoring SAV in Ichetucknee Springs 2004
Executive Summary

3. Water quality sampling should be continued to further assess the relationships between
groundwater flows and surface water quality in the river and associated relationships with
SAV coverage, biomass, and periphyton abundance.
iii Mapping and Monitoring SAV in Ichetucknee Springs 2004
Forward and Acknowledgments
Forward

This report was prepared for the Suwannee River Water Management District (SRWMD) by
Post, Buckley, Schuh & Jernigan (PBS&J) under Contract No. 02/03-180.

Acknowledgments

Mr. Rob Mattson of the SRWMD was instrumental in coordinating the administrative aspects of
the project with the various Park staff and provided direction and technical guidance throughout
the project. Mr. Sam Cole, Park Biologist for the Ichetucknee Springs State Park, provided
invaluable assistance in coordinating field mapping and sampling within the Ichetucknee Springs
and River. He also provided data used in the canopy and depth mapping.
iv Mapping and Monitoring SAV in Ichetucknee Springs 2004
Contents
Section Page
Executive Summary......................................................................................................................i
Forward ......................................................................................................................................iv
Acknowledgments.......................................................................................................................iv
1.0 Introduction.........................................................................................................................1-1
2.0 Methods and Materials........................................................................................................2-1
2.1 Project Area Description.........................................................................................2-1
2.2 SAV Re-mapping in 2004.......................................................................................2-3
2.2.1 SAV Mapping Methodology....................................................................2-3
2.2.2 Depth, Flow, and Tree Canopy Shade Mapping......................................2-5
2.2.3 River Reach..............................................................................................2-6
2.2.4 Tree Canopy Height and Shade...............................................................2-7
2.3 Preparation of Digital and Hard Copy Maps........................................................2-12
2.4 SAV Mapping Quality Control Process................................................................2-12
2.5 SAV and Water Chemistry Sampling...................................................................2-12
3.0 Results and Discussion.......................................................................................................3-1
3.1 SAV Mapping.........................................................................................................3-1
3.1.1 SAV Remapping......................................................................................3-2
3.1.2 Depth, Flow, and Tree Canopy Shade.....................................................3-2
3.2 SAV Monitoring.....................................................................................................3-4
3.2.1 Ichetucknee River....................................................................................3-4
3.2.2 Bivariate Analyses Between Parameters.................................................3-8
3.2.3 Selected Parameter Comparisons Between Years...................................3-9
3.2.4 Feeder Springs.......................................................................................3-11
4.0 References...........................................................................................................................4-1

Appendices
Appendix A - Metadata for Ichetucknee and Manatee Springs SAV Maps
Appendix B – Depth, Velocity, and Tree Height Measurement Data for Ichetucknee Springs
Appendix C - Graphs of Relationships between SAV and Depth, Velocity, and Tree Canopy
Appendix D - SAV Remap Areas in 2004 and Change Analysis Maps
Appendix E – SAV Depth, Flow, and Tree Canopy Shade Maps
Appendix F - Data and Statistical Summaries from SAV Transect Sampling

v Mapping and Monitoring SAV in Ichetucknee Springs 2004
1.0 Introduction
Ichetucknee Springs is a treasured natural resource and the 9th largest of 27 first magnitude
springs or spring groups in Florida. The springs and associated spring run/river provides a
significant source of freshwater, creates unique environmental conditions for rare aquatic
habitats and biota, and is an important recreational attraction for visitors from around the world.
However, the springs, its recharge basin, and downstream spring runs are fragile ecosystems and
have potentially been impacted by human development during the past century, particularly
through excess nutrient loading and groundwater withdrawals. Recognizing the importance of
these unique systems, the Florida Springs Task Force was formed by various state and local
agencies and private interest groups in 1999 to develop management strategies for preserving
and protecting the state’s springs.

The following study was managed by the Suwannee River Water Management District
(SRWMD) and funded by the Florida Department of Environmental Protection’s (FDEP) Florida
Springs Initiative to address the Task Force’s Information Strategy, which was developed to
implement monitoring programs to detect and document long-term trends in spring conditions.
This project involved a continuation of research begun in 2003 to evaluate SAV and water
quality conditions in the Ichetucknee Springs and River system as well as additional mapping
and analysis to characterize the river. This information is being used to evaluate trends in
ecological conditions in the springs and to provide better management tools for this aquatic
ecosystem.

The specific goals for this project were:

• To remap portions of the river which are exposed to intensive recreational use (e.g.,
docks used for entry and exit points by tubers, swimmers, and canoeists) and perform a
change analysis of these areas to compare SAV map data between 2003 and 2004;

• To develop spatial data for river depth, flow, reach and tree canopy shade, and assess
those data with respect to 2003 SAV mapping data; and

• To conduct sampling of SAV, periphyton, and water chemistry to continue to document
existing condition and to provide a basis for defining the relationship between water flow
and SAV abundance and biomass.

1-1 Mapping and Monitoring SAV in Ichetucknee Springs 2004
2.0 Methods and Materials
2.1 Project Area Description

The Ichetucknee Spring and River are
located approximately three miles west of
Fort White, Florida. The river crosses U.S.
27 and also defines a portion of the county
boundary between Suwannee and Columbia
County (Figure 2-1).

The Ichetucknee River is fed by nine named
springs located along the upper 2.5-miles of
the river. The northernmost spring forms
the head of the river and is known as
Ichetucknee Spring or Head Spring (Figure
2-2). Flow from this spring travels
southward and forms the Ichetucknee River
proper. The remaining eight named springs
of the group are, in downstream order,
Cedar Head Spring, Blue Hole Spring,
Roaring Springs, Singing Springs, Boiling
Spring, Grassy Hole Springs, Mill Pond
Spring, and Coffee Spring (Figure 2-3).
Flow characteristics for the Ichetucknee
Springs group are shown in Table 2-1.

The springs are within the confines of the
Ichetucknee Springs State Park, which
occupies 2,241 acres in Columbia and
Suwannee Counties and was established in
1970. Historically, the area was used by
Figure 2-1 (above). Aerial of Ichetucknee River.
local residents for swimming, watering of Figure 2-2 (below). Ichetucknee head spring.
livestock, and phosphate mining. The
average river width is 6 to 10 m and average depth is approximately 1 m in the upper reaches of
the river. At approximately 550 m downstream, the river meets the southward flow of Cedar
Head Spring and Blue Hole Spring. The river then flows about 4800 m south, then 6400 m
southwest and discharges into the Santa Fe River. Depth increases in the middle and lower
reaches of the river to approximately 2 to 4 m.

The Ichetucknee River lies within an ancient basin called the Ichetucknee Trace along the 50 ft
contour line of USGS topographic maps (Dutoit, 1979). The contributing basin or spring-shed of
the Ichetucknee Springs includes an area north toward Lake City and includes surface flows from
several sinkholes including Rose Sink near the city of Columbia. Local recharge occurs in the
vicinity of the headsprings through various sinkholes and percolation through limestone outcrops
and sandy soils. The SRWMD is currently evaluating the groundwater basin of the springs
through a separate Springs Initiative grant from the FDEP.

2-1 Mapping and Monitoring SAV in Ichetucknee Springs 2004
2.0 Methods and Materials

Table 2-1. Spring characteristics for Ichetucknee Springs.

Mean Max. Min. Length of
Discharge Discharge Discharge Spring Run
Spring/Run (ft3/sec)* (ft3/sec)* (ft3/sec)* Studied (ft.)
Ichetucknee** 360.0 578 241 17,388
*from: Florida Geological Survey (1977)
**period of record 1917-1974, n=375 measurements
***period of record 1932-1973, n=9 measurements

Figure 2-3. Map of Ichetucknee Springs System (from Florida Geological Survey, 1977).

2-2 Mapping and Monitoring SAV in Ichetucknee Springs 2004
2.0 Methods and Materials
2.2 SAV Re-mapping in 2004

Submerged aquatic vegetation (SAV) was mapped in the spring of 2003 in the Ichetucknee
Springs and River spring run (Kurz et al., 2003). This information was gathered to document the
existing spatial distribution and coverage of SAV in this important spring system. In 2004, SAV
was re-mapped in high recreational use areas to evaluate changes in coverage over the past 12
month period.

The mapping area in the Ichetucknee system was located entirely within Ichetucknee State Park
extending from the head spring downstream to the US 27 Bridge. Only high recreational use
areas were mapped within this boundary to evaluate changes between the 2003 and 2004
coverages during two consecutive spring seasons. The high use areas included the following
areas:

• Headspring reach (between the headspring and the “put-in” dock
• Mid point take-out dock
• Dampier’s Landing dock
• Downstream take-out dock at US 27

2.2.1 SAV Mapping Methodology

Field mapping methods for the 2004 remapping effort employed transect mapping with GPS
verification in select areas where a GPS signal was strong enough to meet FDEP mapping
standards. SAV was classified according to the percent coverage of each species present.
Following completion of field mapping, a seamless coverage of SAV bed polygons was created
for the Ichetucknee Springs and River. All coverages were prepared using ESRI’s ArcView GIS
software. All field mapping was performed during late April and early May 2003. Details
describing the GIS software, GPS equipment, field mapping methods, final map preparation, and
the quality control process follow.

2.2.1.1 GPS and GIS Specifications

The primary field mapping computer hardware was a Compaq iPAQ, model number 3850,
running Windows PocketPC. ESRI ArcPad Version 6.01.5 GIS software was used along with a
Teletype World NavigatorTM GPS, CF v2.0, Card #1651. The ArcPad mapping software
automatically retrieved positions from the GPS as the outline of the SAV bed (polygon) was
traced and produced mapped features in the field. The ArcPad graphical user interface was
customized with ArcPad Studio using VBScript and XML programing languages.

The custom interface provided data entry forms specifically designed for the previous 2003
mapping effort and was used in the remap effort in 2004. The final map was prepared in ESRI
ArcView 3.2. The Florida State Plane, North Zone, Datum HPGN (NAD 83/90) with units in
Feet projection was used. The minimum mapping unit was 30 square feet.

2-3 Mapping and Monitoring SAV in Ichetucknee Springs 2004