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TEMPORAL CHANGES IN SALINITY AND NUTRIENT REGIMES OF A TIDAL CREEK WITHIN THE GUANA TOLOMATO MATANZAS NATIONAL ESTUARINE RESEARCH
RESERVE, FL ASSOCIATED WITH THE 2004 HURRICANES
By
NICOLE DIX
A THESIS PRESENTED TO THE GRADUATE SCHOOL OF THE UNIVERSITY OF FLORIDA IN PARTIAL FULFILLMENT
OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF SCIENCE
UNIVERSITY OF FLORIDA
2006
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Copyright 2006
by
Nicole Dix
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To my new husband, Shane Pangle
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ACKNOWLEDGMENTS
I would like to acknowledge all of the past and present Phlips Lab employees who helped
with the sampling, processing, and chemistry needed to obtain the data for this project. In
particular, I would like to thank Jean Lockwood, Ken Black, and Katie O’Donnell. Of course,
this project would not have been possible without the foresight and persistence of Rick Gleeson
and NOAA’s National Estuarine Research Reserve to set up and manage the continuous
monitoring network. Finally, I thank my husband, Shane Pangle, for his love and support, and
for keeping me laughing.
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TABLE OF CONTENTS page
ACKNOWLEDGMENTS ...............................................................................................................4
LIST OF TABLES...........................................................................................................................6
LIST OF FIGURES .........................................................................................................................7
ABSTRACT.....................................................................................................................................8
CHAPTER
1 INTRODUCTION ....................................................................................................................9
2 METHODS.............................................................................................................................12
Site Description ......................................................................................................................12 Data Collection .......................................................................................................................12 Water Chemistry.....................................................................................................................13 Data Analysis..........................................................................................................................14
3 RESULTS...............................................................................................................................17
Salinity and Meteorological Conditions during Storm Events ...............................................17 Hurricane Charley ...........................................................................................................17 Hurricane Frances............................................................................................................18 Hurricane Ivan .................................................................................................................18 Hurricane Jeanne .............................................................................................................19
Seasonal Salinity Patterns.......................................................................................................19 Seasonal Water Quality Patterns ............................................................................................20
4 DISCUSSION.........................................................................................................................38
Sampling Scale and Ecosystem Variability............................................................................39 Potential Biological Community Impacts...............................................................................40 Long-Term Consequences ......................................................................................................41
LIST OF REFERENCES...............................................................................................................45
BIOGRAPHICAL SKETCH .........................................................................................................51
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LIST OF TABLES
Table page 3-1 Total rainfall and average wind speed for the 2004 hurricanes. ........................................22
3-2 Mean daily salinity (ppt) two weeks before and four weeks after the 2004 hurricanes. ...22
3-3 Summary statistics (based on daily averages) describing the distribution of salinity (ppt), daily rainfall totals (mm), wind speed (m/s), and water depth (m) for the 2003–2004 time series.. ...............................................................................................................23
3-4 Spearman’s correlation between mean monthly rainfall totals and salinity, and SRP, TSP, TP, NO2+3, NH4, TSN, TN, chlorophyll a, turbidity, color, and TSS. ......................24
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LIST OF FIGURES
Figure page 2-1 Location map of Pellicer Creek and Guana Tolomato Matanzas National Estuarine
Research Reserve monitoring stations. ..............................................................................16
3-1 A time series plot for 2–3 June, 2004 representative of times with little rain or wind. The solid line represents salinity. The dashed line represents water depth. Pearson’s ρ = 0.77 (p<0.0001) for salinity and depth. Readings were obtained from the Pellicer Creek water quality monitoring station at 0.5 hour intervals.............................................25
3-2 Short-term meteorological effects of Hurricane Charley, 13–15 August, 2004. A) Wind Speed. B) Wind Direction. C) Total Precipitation. D) Depth. E) Salinity...............26
3-3 Short-term meteorological effects of Hurricane Frances, 4–6 September, 2004. A) Wind Speed. B) Wind Direction. C) Total Precipitation. D) Depth. E) Salinity...............27
3-4 Short-term meteorological effects of Hurricane Ivan, 19–21 September, 2004. A) Wind Speed. B) Wind Direction. C) Total Precipitation. D) Depth. E) Salinity...............28
3-5 Short-term meteorological effects of Hurricane Jeanne, 25–27 September, 2004. A) Wind Speed. B) Wind Direction. C) Total Precipitation. D) Depth. E) Salinity...............29
3-6 Wind direction in relationship to orientation of Pellicer Creek.........................................30
3-7 2004 hurricane tracks. A) Charley. B) Frances. C) Ivan. D) Jeanne (Wikipedia 2006). ...31
3-8 Mean daily salinity (ppt) at the Pellicer Creek water quality station two weeks before Hurricane Charley and four weeks after Hurricane Jeanne. ..............................................31
3-9 Summer salinity (June-September) collected at 0.5 hour intervals from the Pellicer Creek water quality station. A) 2003. B) 2004. .................................................................32
3-10 Wind direction histograms. A) Summer 2003 and summer 2004 combined. B) Summer 2003. C) Summer 2004. D) Winter 2003–2004. ............................................33
3-11 2003–2004 mean monthly rainfall (represented by gray bars), collected from the Pellicer Creek weather station, plotted relative to maximum (top) and minimum (bottom) monthly nutrient concentrations, phytoplankton biomass, and water clarity parameters. A) Color. B) Salinity. C) TN. D) TP. E) chlorophyll a. F) NH4. G) NO2+3. H) SRP. I) POC. J) turbidity. .................................................................................34
4-1 Mean daily averages (2003–2004). A) Salinity. B) Total Precipitation. C) Water Depth. D) Wind Speed.......................................................................................................44
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Abstract of Thesis Presented to the Graduate School of the University of Florida in Partial Fulfillment of the
Requirements for the Master of Science
TEMPORAL CHANGES IN SALINITY AND NUTRIENT REGIMES OF A TIDAL CREEK WITHIN THE GUANA TOLOMATO MATANZAS NATIONAL ESTUARINE RESEARCH
RESERVE, FL ASSOCIATED WITH THE 2004 HURRICANES
By
Nicole Dix
December 2006
Chair: Edward Phlips Major Department: Fisheries and Aquatic Sciences
Hurricanes and the associated shifts in wind speed and water levels can impact the
integrity of near-shore aquatic ecosystems. Continuous data from Pellicer Creek within the
Guana Tolomato Matanzas National Estuarine Research Reserve, were combined with monthly
measures of nutrient and water clarity parameters to explore the effects of Hurricanes Charley,
Frances, Ivan, and Jeanne. In general, the four tropical systems of 2004 suppressed tidal salinity
variations. Although strong northeasterly winds associated with the hurricane events initially
prompted salinity spikes, high rainfall levels over the course of the event ultimately had the
opposite effect, causing strong declines in salinity for extended periods of time. Shortened
residence times during the hurricanes decreased phytoplankton standing crop, and freshwater
runoff was associated with increased nutrients. The number of intense storms striking the
southeastern coast of the United States was abnormally high in 2004 and 2005, and since the
pattern is expected to continue, associated impacts on Florida ecosystems may be accentuated
and prolonged. The results of these time intensive observations of water quality and
meteorological conditions in the Pellicer Creek ecosystem provide insight into the impacts of
multiple storm events on environmental variability.
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CHAPTER 1 INTRODUCTION
Hurricanes, and their effect on coastal ecosystems, have become a popular subject of
research in recent years due to the increasing availability of long-term datasets (Walker, Lodge,
Brokaw, and Waide 1991; Valiela et al. 1996; Wenner and Geist 2001; Kennish 2004) and
concern about potential ramifications of increases in the frequency of intense storms (Finkl and
Pilkey 1991; Landsea, Pielke, Mestas-Nuñez, and Knaff 1999; Elsner 2003; Bossak 2004; Paerl
et al. in press; Switzer, Winner, Dunham, Whittington, and Thomas in press). Rapid and large
shifts in wind speed and water levels can affect the integrity of near-shore aquatic ecosystems
(Hoese 1960; Geyer 1997; Michener, Blood, Bildstein, Brinson, and Gardner 1997; Valiela et al.
1996, 1998). Many studies have focused on the influence of hurricanes on estuarine water
quality and biological community structure, and common findings include spatial and temporal
changes in water level, light attenuation, sediment distribution, salinity regime, dissolved
oxygen, water temperature, nutrient concentrations, and macrobenthic community composition
(Boesch, Diaz, and Virnstein 1976; Simpson and Riehl 1981; Blood, Anderson, Smith, Nybro,
and Ginsberg 1991; Van Dolah and Anderson 1991; Tilmant et al. 1994; Mallin et al. 1999;
Proffitt 1999; Ward 2004; Hagy et al. 2006; Morrison, Sherwood, Boler, and Barron in press;
Stevens, Blewett, and Casey in press). The goal of this project was to explore the effects of
hurricanes on key physiochemical factors associated with the ecology of a tidal creek on the
northeast coast of Florida.
The 2004 hurricane season was one of the most active seasons on record for the North
Atlantic Basin. Florida experienced four intense hurricanes (Charley, Frances, Ivan, and Jeanne)
within a span of less than two months (August-September, 2004). The environmental
monitoring network of the National Estuarine Research Reserve (NERR) System-Wide
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Monitoring Program (SWMP) provided an opportunity to investigate temporal changes in
physiochemical and meteorological properties associated with the passage of these tropical
systems over Florida (NOAA 2004). Data from the Pellicer Creek weather and water quality
stations, managed by the Guana Tolomato Matanzas (GTM) NERR, were combined in this study
with monthly measures of nutrient and water clarity. The impacts of storm events were then
related to typical daily and seasonal variability to assess the relative magnitude and character of
deviations associated with storm events.
Although the GTMNERR network collects data on a variety of physical properties in
Pellicer Creek, including salinity, dissolved oxygen, temperature, and pH, the focus of this part
of the study was salinity because it is a key factor in the distribution of estuarine organisms
(Tabb and Jones 1962; McMillan and Moseley 1967; McMillan 1974; Hackney, Burbanck, and
Hackney 1976; Boesch et al. 1976; Mallin 1999, 2002; Walker 2001; Wenner, Sanger, Arendt,
Holland, and Chen 2004) and can be used to characterize hydrodynamics in estuaries (Imberger
et al. 1983, Orlando et al. 1994). Spatial and temporal patterns in salinity are also valuable
descriptors when developing management plans for estuaries (Orlando et al. 1994, Gibson and
Najjar 2000). For example, Montague and Ley (1993) assessed the potential impacts of sudden
changes in salinity on an estuary in northeast Florida Bay as part of a management plan to divert
freshwater flows in the Florida Everglades. They combined environmental measurements with
benthic vegetation/macrofauna sampling and found a negative correlation between the standard
deviation of salinity and biotic density/plant biomass. Therefore, environmental stress may not
only be caused by changes in the relative magnitudes of water quality parameters, but also by
their variability. Storm events can greatly accelerate rates and magnitudes of change.
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In addition to the GTMNERR monitoring data, nutrient concentrations, water clarity
indicators and phytoplankton standing crop (i.e., chlorophyll a concentrations) were used to
explore the impacts of storm events further. These parameters are linked to trophic status and
also influence biological community structure and function (Valiela et al. 1997, Grall and
Chauvaud 2002). Intertidal wetlands, such as those surrounding Pellicer Creek, are productive
ecosystems (Montague and Wiegert 1990) that can contribute nutrients to nearby coastal waters
(Heinle and Flemer 1976; Woodwell, Whitney, Hall, and Houghton 1977; Valiela, Teal,
Volkmann, Shafer, and Carpenter 1978; Nixon 1980). Potential nutrient sources for Pellicer
Creek include direct rainwater input, surface-water run-off, and groundwater seepage. All are
potentially affected by passing storms. Extreme rainfall can cause higher than average nutrient
concentrations in aquatic coastal ecosystems (Hama and Handa 1994, Valiela et al. 1996, 1998).
Two main research objectives were pursued in this study within the context of several
related hypotheses:
1. Describe relationships between salinity and several key morphometric and meteorological factors including water depth, wind speed and direction, and precipitation.
Hypothesis 1: Hurricanes will affect the typical diel cycle of salinity (two peaks and
troughs per day corresponding to high and low tide respectively) by resulting in accentuated levels during strong onshore winds and suppressed levels during offshore winds.
Hypothesis 2: Mean salinity will be higher and less variable during summer 2003 than summer 2004 due to absence of hurricanes in the former year.
2. Determine temporal changes in nutrient levels, water clarity, and phytoplankton biomass and
how they relate to wind speed and direction, and precipitation seasonally.
Hypothesis 3: Hurricanes will result in increased watershed runoff, which in turn will lead to an immediate increase in nutrient concentrations, particulate material, and dissolved organic matter (color) and an initial decline in chlorophyll a. Chlorophyll a concentrations will rise in the months following major storms, resulting in decreased bioavailable nutrients.
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CHAPTER 2 METHODS
Site Description
Pellicer Creek is a major tributary of the Matanzas River and the Guana Tolomato
Matanzas (GTM) estuary (Figure 2-1). It is the boundary between St. Johns and Flagler counties
in northeast Florida, an area of humid subtropical climate (Chen and Gerber 1990). The wet
season coincides occurs in summer (June to September), and the area has approximately 132 cm
of rainfall annually. Pellicer Creek experiences semi-diurnal tides with an average range of 0.6
m (NOAA 2004). The majority of the creek is surrounded by public conservation lands. The
sediment type is muddy sand (NOAA 2004), and the water is rich in dissolved organic matter
relative to the entire estuary. Salinity at the water quality station (Figure 2-1) ranges from
freshwater to almost seawater.
Data Collection
Weather and water quality data collection methods are standardized among the 26
established National Estuarine Research Reserve (NERR) sites (Kennish 2004), although station
locations vary depending on specific reserve interests. The GTMNERR manages a
meteorological station at the mouth of Pellicer Creek and four water quality monitoring stations
throughout the estuary. The Pellicer Creek water quality monitoring station, located
approximately 4 kilometers upstream from the weather station (Figure 2-1), was used in this
analysis to minimize spatial variability. Data were recorded at 15- and 30-minute intervals at the
weather and water quality stations, respectively. After quality assurance, data were published on
the Centralized Data Management Office website (http://cdmo.baruch.sc.edu). The continuous
time series of weather and water quality data was downloaded from the website, and the 15- and
45-minute observations were deleted from the weather dataset to match timestamps of the water
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quality series. Due to data logger malfunctions, the weather station did not record data for 32
days during portions of September, October, and November 2003. Malfunctions at the water
quality station resulted in missing salinity and depth data for 1 May to 12 May, 2004 and 27 June
to 7 July, 2004. These missing data may cause slightly biased averages, but should not affect
general interpretations.
In addition to continuous in situ monitoring data, water was collected at the same location
as the GTMNERR water quality station on a monthly basis. One integrated sample from the
entire column of water and two samples from 1 m above the bottom were collected with a PVC
pole (Venrick 1978). In addition, an ISCO automatic sampler was deployed to collect water
samples from 1 m above the bottom every 2.5 hours for one complete tidal cycle. Samples from
both collection methods were brought back to the lab on ice and processed in similar manner for
the determination of nutrient concentrations, including total nitrogen (TN), total soluble nitrogen
(TSN), total phosphorus (TP), total soluble phosphorus (TSP), nitrate (NO3), nitrite (NO2),
ammonium (NH4), and soluble reactive phosphorus (SRP), as well as water clarity parameters
such as chlorophyll a, total suspended solids (TSS), dissolved organic matter (color), and
turbidity.
Water Chemistry
Whole water samples were used to determine concentrations of TN, TP, TSS, chlorophyll
a, particulate organic carbon (POC), and turbidity. To determine TN and TP, samples were
digested and measured colorometrically on a Bran-Luebbe autoanalyzer (TN) and a dual-beam
scanning spectrophotometer (TP) (APHA 1998). Analysis methods for TSN and TSP were the
same as those for TN and TP, respectively, but samples were filtered first through PALL A/E
glass-fiber filters (1µm pore size) (APHA 1998). To measure TSS, aliquots of whole water were
filtered through pre-weighed glass-fiber filters (1.5 µm pore size). Filters were subsequently
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dried at 104oC, placed in a desiccator, and re-weighed (APHA 1998). Chlorophyll a was
processed using the Sartory and Grobbelaar (1984) ethanol extraction method. Absorbances
were determined using a dual-beam scanning spectrophotometer relative to a blank cuvette,
according to Standard Methods (APHA 1998). To determine POC concentrations, aliquots of
whole water were filtered through pre-burned (to eliminate any residual organic carbon) glass-
fiber filters (0.7 µm pore size). Filters were dried at 80oC, and organic carbon concentration was
determined using a coulometer (APHA 1998). Turbidity was measured in Nephelometric
Turbidity Units (NTU) using a LaMotte Model 2020 Turbidimeter.
Aliquots to be used for color and available nutrient analyses were filtered through glass-
fiber filters (1µm pore size), stored in a freezer (NH4, NO3, and NO2) or refrigerator (SRP and
color), and read within 48 hours of collection. Ammonium, nitrate, and nitrite concentrations
were determined colorometrically on a Bran-Luebbe autoanalyzer (Strickland and Parsons 1972,
APHA 1998). SRP concentrations were measured on a dual-beam scanning spectrophotometer
at 882nm following standard methods (APHA 1998). Color values were measured against a
platinum-cobalt standard using a dual-beam scanning spectrophotometer (APHA 1998).
Data Analysis
Continuous and monthly water quality data were combined with information from the
meteorological station in an attempt to determine relationships between salinity, water depth,
nutrient and chlorophyll a concentrations, and storm conditions (i.e., rainfall, wind speed, and
wind direction). Daily and seasonal averages were calculated to describe general physical
characteristics of Pellicer Creek and examine possible storm effects. Summer was defined as the
period between June and September. Winter was defined as January and February 2003,
November 2003 to February 2004, and November and December 2004.
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Sanger et al. (2002) and Wenner et al. (2004) measured storm effects by looking at the
time it took for a parameter to return to pre-storm conditions. They defined “pre-storm” as two
weeks before the storm and “post-storm” as four weeks after. Similarly, daily means and
coefficients of variance (CV) were calculated both for salinity values before and after storms and
for summer seasons of both years. Comparisons were limited for storms temporally close
together due to overlaps in pre- and post-storm timeframes. Descriptive statistics of the entire
time series were used to explore seasonal variability. The Wilcoxon sign-rank test was used to
test for differences between mean daily salinity during summer 2003 and summer 2004.
Spearman’s Rank Correlation was used to examine the association between salinity and depth for
a typical day with little rainfall or wind. The Spearman’s Rank Correlation was also used to
examine relationships between rainfall, salinity, and all other parameters. Non-parametric tests
were used after determining that most parameters were not normally distributed according to the
Kolmogorov-Smirnov test for goodness-of-fit. SAS statistical software (1999–2000) was used to
calculate all test statistics (α = 0.05).
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Figure 2-1. Location map of Pellicer Creek and Guana Tolomato Matanzas National Estuarine
Research Reserve monitoring stations.
Water Quality Station
Weather Station IC
W
Atlantic Ocean
N
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CHAPTER 3 RESULTS
Salinity and Meteorological Conditions during Storm Events
The nearly continuous salinity and weather time series for Pellicer Creek made it possible
to examine typical daily variations and immediate storm effects. In times of little wind and
rainfall activity, salinity variance followed oscillations typical of semidiurnal tides within the
region (Figure 3-1). Two slightly unequal peaks and two troughs per day corresponded to high
and low tides, respectively (ρ = 0.77).
A comparison of total rainfall and average wind speed for each of the 2004 hurricanes is
provided in Table 3-1. Each hurricane resulted in short-term changes in rainfall, wind speed,
wind direction, and salinity (Figure 3-2). Figure 3-3 puts wind direction in perspective with
respect to the orientation of the creek. The following summary illustrates the relationships
among salinity, wind speed, wind direction, and precipitation at the diel timescale:
Hurricane Charley
In the middle of August 2004, Hurricane Charley struck the southwest coast of Florida as a
Category 4 storm on the Saffir-Simpson Hurricane Scale. It traveled northeasterly across the
state and exited around Daytona Beach (Figure 3-4, Pasch, Brown, and Blake 2004). During
Charley, the Pellicer Creek weather station recorded a maximum wind speed of 17.9 meters per
second (m/s) and 9.1 cm of rainfall on 13 August (Figure 3-2a). The station was experiencing
southeasterly winds before passage of Charley; however, winds shifted to north-northeasterly
and increased in strength during the storm. The up-creek winds, and resulting increase of almost
20 cm above mean pre-storm water level, coincided with the observed increase in salinity. The
second smaller peak on 14 August coincided with a 19 cm drop in water depth. Two weeks
before passage of Charley, mean daily salinity was 12.2 ppt (Table 3-2, Figure 3-5).
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Immediately after the storm, salinities dropped to approximately 1 ppt, and water stayed fresh for
11 days. Salinities began to rise, showing typical tidal oscillations, on 25August, but they
remained below the pre-storm average for 20 days until salinity spiked on 5 September.
Hurricane Frances
Hurricane Frances made landfall on Florida’s southeast coast as a Category 2 on
September 5, 2004. The storm center traveled into the Gulf of Mexico and north through the Big
Bend region of the panhandle (Figure 3-4). Most of central and north Florida experienced more
than 25 cm of rain during Frances (Beven 2004). As evident in Figure 3-2b, rain and winds
lasted longer during Frances than during Charley. Maximum wind speed at the Pellicer Creek
weather station for the entire 2003–2004 time series (18.5 m/s) and highest daily total
precipitation (17.3 cm) were recorded during passage of Frances. Average salinity two weeks
before the storm was 1.8 ppt with a coefficient of variance (CV) of 96. On 5 September, salinity
peaked at 29.8 ppt, then steadily dropped to zero. Water remained fresh and exhibited much
smaller variability (CV = 9) until 20 September when salinities became elevated during passage
of Ivan.
Hurricane Ivan
While Frances was crossing Florida, another tropical storm, Ivan, was strengthening into a
hurricane about 1,600 kilometers east of Tobago. Hurricane Ivan traveled north through the Gulf
of Mexico, making landfall on the southern coast of Alabama on 16 September, 2004 (Figure 3-
4). The storm weakened over land, but continued tracking northeast over the southeastern U.S.
Ivan took a southern turn when it re-entered the Atlantic Ocean on 19 September and completed
its loop by crossing the southern tip of Florida and turning back north toward Louisiana (Stewart
2004). Ivan’s effect on the salinity and climate of Pellicer Creek can be seen in the time series
from 19-21 September, 2004 (Figure 3-2c). Waters were fresh before the storm due to the
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influence of Frances. However, salinity spiked to 19.5 ppt on 20 September as winds blew from
the northeast. Total rainfall on September 20 was 3.4 cm. Salinities fell after the initial spike
and remained low until 25 September.
Hurricane Jeanne
Hurricane Jeanne made landfall early 26 September, 2004 on Florida’s east coast near
Stuart as a Category 3 storm (Figure 3-4). It traveled west-northwest, weakening to a tropical
storm north of Tampa (Lawrence and Cobb 2004). Salinity increased to 8.9 ppt on 26 September
(Figure 3-2d), but levels dropped on 27 September and remained below 1ppt for 10 days. After
Jeanne, salinity remained below the pre-Charley average (12.2 ppt) for over three weeks (28
September-21 October, Table 3-2). Maximum water depth for the entire 2003–2004 time series,
2.4 m, was reached during the passage of Jeanne on 26 September.
Seasonal Salinity Patterns
Salinity variance patterns are evident in seasonal comparisons (Table 3-3). Mean daily
salinity during summer 2003 was significantly higher than that during summer 2004 (p <
0.0005). The CV was much lower in summer 2003 than in summer 2004. The histograms in
Figure 3-6 represent summer salinity distributions for 2003 and 2004 and demonstrate that the
Pellicer Creek water quality station experienced freshwater conditions about twice as often in
summer 2004 than in summer 2003.
The CV for both salinity and wind speed were much lower in winter than in summer
(Table 3-3). This may allude to the influence of wind on salinity. Prevailing winds were from
the northwest in winter and from the south in summer (Figure 3-7). Mean salinity for the two-
year time series was lower in summer than winter (Table 3-3).
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Seasonal Water Quality Patterns
Minimum and maximum monthly values for water quality parameters were plotted over
time relative to mean monthly rainfall (Figure 3-8). Because the rainfall time series from
September-November 2003 contained data gaps, monthly averages may have been low
estimates.
In general, color values increased with rainfall. One notable exception was in June 2004.
A large rain event on 26 June created a fairly high monthly average; however, since the pole and
ISCO samples were collected in the beginning of the month, they do not reflect the rain event.
Seasonally, there were bimodal peaks, one in late summer and another in the spring (Figure 3-
8a), coinciding with the rainfall pattern described for this region by Jordan (1984) and Chen and
Gerber (1990). Salinity was generally inversely related to rainfall patterns (Figure 3-8b).
Little diel variation existed in TN and TP concentrations, with a few exceptions (Figure
3-8c,d). On 26 March, 2003, salinity ranged from 3-14 ppt. Highest salinities corresponded with
lowest TN values and vice versa, suggesting that nitrogen followed freshwater flow of the creek.
A similar pattern occurred on 26 August, 2003. In general, TN and TP concentrations followed
rainfall patterns. TP did not, however, increase during the 2004 hurricane season.
Increased flushing in spring and summer 2004 (illustrated by high color concentrations)
resulted in low chlorophyll a concentrations and suppressed diel variability (Figure 3-8e).
Therefore, as hypothesized, shortened residence times during the hurricanes decreased
phytoplankton standing crop. As expected, maximum chlorophyll a levels began to rise in
October 2004 when average rainfall declined. However, the rise in phytoplankton levels did not
result in a decrease in bioavailable nutrients. In fact, NH4 and NO2+3 were elevated in November
2004 (Figure 3-8f,g). The large ammonium peak is likely due to low oxygen conditions causing
inorganic nitrogen to exist largely in reduced form. SRP ranges were fairly low after the
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hurricanes of 2004 (Figure 3-8h), suggesting that SRP was either diluted by fresh water runoff or
consumed by bacteria or phytoplankton. POC was more variable in 2004 than in 2003 (Figure 3-
8i).
Correlation analysis revealed no statistical relationship between rainfall and soluble
versus particulate material (Table 3-4). However, mean monthly rainfall totals were significantly
and positively correlated with NH4, TSN, TN, TSP, and turbidity. In addition, average monthly
salinity values were negatively correlated with NO2+3, TSN, TN, and color and positively
correlated with chlorophyll a.
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Table 3-1. Total rainfall and average wind speed for the 2004 hurricanes.
Hurricane Dates of Impact
on Pellicer Creek Total Rainfall
(mm) Average Wind
Speed (m/s) Charley August 11–15 129.6 1.92 Frances September 3–6 204.5 11.63 Ivan September 20 34.2 8.68 Jeanne September 25–26 61.2 13.63 Table 3-2. Mean daily salinity (ppt) two weeks before and four weeks after the 2004 hurricanes. Hurricane Timeframe Dates N Mean CV RangeCharley pre-storm 7/30/04–8/12/04 14 12.2 37 13.1 8/13/04–8/15/04 post-storm* 8/16/04–9/12/04 28 1.9 208 20 8/14/04–8/24/04 11 0.1 32 0.1 post-storm before Frances 8/16/04–9/3/04 19 1.4 122 5.5
Frances pre-storm 8/21/04–9/3/04 14 1.8 96 5.5 9/4/04–9/6/04 post-storm* 9/7/04–10/4/04 28 0.8 238 8.8 post-storm before Ivan 9/7/04–9/18/04 12 0.1 9 0.02
Ivan pre-storm* 9/5/04–9/18/04 14 1.6 338 20 9/19/04–9/21/04 post-storm* 9/22/04–10/19/04 28 2.6 107 8.9 post-storm before Jeanne 9/22/04–9/24/04 3 0.4 58 0.4
Jeanne pre-storm* 9/11/04–9/24/04 14 4.4 208 34 9/25/04–9/27/04 post-storm 9/28/04–10/25/04 28 0.6 239 5.3
*timeframe overlaps with one or more storms
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Table 3-3. Summary statistics (based on daily averages) describing the distribution of salinity (ppt), daily rainfall totals (mm), wind speed (m/s), and water depth (m) for the 2003–2004 time series. Summer includes June to September, while winter describes November through February. Statistics are also compared between the summers of 2003 and 2004.
Parameter Season Mean Median Std. Dev. CV Range Min. Max. salinity summer 03+04 10.9 13.0 8.2 76 25.6 0.1 25.7 winter 03+04 13.3 14.4 6.2 46 23.7 0.1 23.8 summer 03 12.3 14.8 7.3 59 21.8 0.1 21.8 summer 04 9.3 6.3 8.9 96 25.6 0.1 25.7 rainfall summer 03+04 5.7 0.0 15.7 276 173.2 0.0 173.2 winter 03+04 2.0 0.0 6.8 332 61.0 0.0 61.0 summer 03 4.0 0.0 7.9 196 39.9 0.0 39.9 summer 04 7.1 0.3 19.9 281 173.2 0.0 173.2 wind speed summer 03+04 2.3 1.8 1.7 74 13.4 1.0 14.4 winter 03+04 2.4 2.1 1.3 54 9.1 0.8 9.9 summer 03 1.9 1.8 0.6 31 3.6 1.0 4.6 summer 04 2.7 1.8 2.2 83 13.2 1.2 14.4 depth summer 03+04 1.3 1.3 0.2 13 1.1 1.0 2.1 winter 03+04 1.3 1.3 0.2 12 1.0 1.0 2.0 summer 03 1.3 1.3 0.2 12 0.8 1.0 1.8 summer 04 1.4 1.3 0.2 14 0.9 1.2 2.1
24
Table 3-4. Spearman’s ρ (N = 24) between mean monthly rainfall totals and salinity, and SRP, TSP, TP, NO2+3, NH4, TSN, TN, chlorophyll a, turbidity, color, and TSS (*significant values at the 95% confidence level).
Rainfall Salinity ρ (rho) p-value ρ p-value Salinity -0.36 0.0848 SRP 0.15 0.4812 0.37 0.0760 TSP 0.50 0.0136* -0.038 0.8591 TP 0.32 0.1318 0.23 0.2695 NO2+3 0.11 0.5933 -0.43 0.0383* NH4 0.42 0.0412* 0.019 0.9293 TSN 0.60 0.0019* -0.53 0.0078* TN 0.72 <0.0001* -0.47 0.0196* Chl a -0.056 0.7962 0.59 0.0023* Turb 0.51 0.0102* -0.13 0.5490 Color 0.39 0.0568* -0.88 <0.0001* TSS -0.003 0.9887 0.37 0.0773
25
0.0
5.0
10.0
15.0
20.0
25.0
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35.0
1 4 7 10 13 16 19 22 25 28 31 34 37 40 43 46 49 52 55 58 61 64 67 70 73 76 79 82 85 88 91 94
Time (hours)
Salin
ity (p
pt)
0.00.20.40.60.81.01.21.41.61.8
Dep
th (m
)
Figure 3-1. A time series plot for 2–3 June, 2004 representative of times with little rain or wind.
The solid line represents salinity. The dashed line represents water depth. Pearson’s ρ = 0.77 (p<0.0001) for salinity and depth. Readings were obtained from the Pellicer Creek water quality monitoring station at 0.5 hour intervals.
26
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004
Salin
ity (p
pt)
Figure 3-2. Short-term meteorological effects of Hurricane Charley, 13–15 August, 2004. A)
Wind Speed. B) Wind Direction. C) Total Precipitation. D) Depth. E) Salinity.
27
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2004
9/6/
2004
9/6/
2004
Salin
ity (p
pt)
Figure 3-3. Short-term meteorological effects of Hurricane Frances, 4–6 September, 2004. A)
Wind Speed. B) Wind Direction. C) Total Precipitation. D) Depth. E) Salinity.
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h (m
)
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4
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004
Salin
ity (p
pt)
Figure 3-4. Short-term meteorological effects of Hurricane Ivan, 19–21 September, 2004. A)
Wind Speed. B) Wind Direction. C) Total Precipitation. D) Depth. E) Salinity.
29
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)
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Salin
ity (p
pt)
Figure 3-5. Short-term meteorological effects of Hurricane Jeanne, 25–27 September, 2004. A)
Wind Speed. B) Wind Direction. C) Total Precipitation. D) Depth. E) Salinity.
30
Figure 3-6. Wind direction in relationship to orientation of Pellicer Creek.
360° / 0°
90°
180°
270°
N
31
A B
C D Figure 3-7. 2004 hurricane tracks. A) Charley. B) Frances. C) Ivan. D) Jeanne (Wikipedia
2006).
0
5
10
15
20
25
Dat
e
8/7/
2004
8/11
/200
4
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4
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4
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0/20
04
10/1
4/20
04
10/1
8/20
04
10/2
2/20
04
Salin
ity (p
pt)
Figure 3-8. Mean daily salinity (ppt) at the Pellicer Creek water quality station two weeks before
Hurricane Charley and four weeks after Hurricane Jeanne.
Charley Frances Ivan Jeanne
32
A 0 2.4 4.8 7.2 9.6 12 14.4 16.8 19.2 21.6 24 26.4 28.8
0
5
10
15
20
25
30
35
40
Percent
B 0 2.4 4.8 7.2 9.6 12 14.4 16.8 19.2 21.6 24 26.4 28.8 31.2
0
5
10
15
20
25
30
35
40
Percent
Figure 3-9. Summer salinity (June-September) collected at 0.5 hour intervals from the Pellicer
Creek water quality station. A) 2003. B) 2004.
33
A
40 40
40
40
30 30
30
30
20 20
20
20
10 10
10
10
N
E
S
W
20 20
20
20
15 15
15
15
10 10
10
10
5 5
5
5
N
E
S
W
B
C
20 20
20
20
15 15
15
15
10 10
10
10
5 5
5
5
N
E
S
W
40 40
40
40
30 30
30
30
20 20
20
20
10 10
10
10
N
E
S
W
D Figure 3-10. Wind direction histograms. A) Summer 2003 and summer 2004 combined.
B) Summer 2003. C) Summer 2004. D) Winter 2003–2004.
34
A
0100200300400500600700800
Jan-0
3
Mar-03
May-03
Jul-0
3
Sep-03
Nov-03
Jan-0
4
Mar-04
May-04
Jul-0
4
Sep-04
Nov-04
Col
or (P
CU
)
0
2
4
6
8
10
12
Rai
nfal
l (m
m)
B
0
5
10
15
20
25
30
35
Jan-0
3
Mar-03
May-03
Jul-0
3
Sep-03
Nov-03
Jan-0
4
Mar-04
May-04
Jul-0
4
Sep-04
Nov-04
Salin
ity (p
pt)
0
2
4
6
8
10
12
Rai
nfal
l (m
m)
C
0.000.200.400.600.801.001.201.401.60
Jan-0
3
Mar-03
May-03
Jul-0
3
Sep-03
Nov-03
Jan-0
4
Mar-04
May-04
Jul-0
4
Sep-04
Nov-04
TN (m
g/L)
0
2
4
6
8
10
12
Rai
nfal
l (m
m)
Figure 3-11. 2003–2004 mean monthly rainfall (represented by gray bars), collected from the
Pellicer Creek weather station, plotted relative to maximum (top) and minimum (bottom) monthly nutrient concentrations, phytoplankton biomass, and water clarity parameters. A) Color. B) Salinity. C) TN. D) TP. E) chlorophyll a. F) NH4. G) NO2+3. H) SRP. I) POC. J) turbidity.
35
D
0.000.020.040.060.080.100.120.140.160.180.20
Jan-0
3
Mar-03
May-03
Jul-0
3
Sep-03
Nov-03
Jan-0
4
Mar-04
May-04
Jul-0
4
Sep-04
Nov-04
TP (m
g/L)
0
2
4
6
8
10
12
Rai
nfal
l (m
m)
E
0
5
10
15
20
25
30
35
Jan-0
3
Mar-03
May-03
Jul-0
3
Sep-03
Nov-03
Jan-0
4
Mar-04
May-04
Jul-0
4
Sep-04
Nov-04
Chl
a (µ
g/L)
0
2
4
6
8
10
12
Rai
nfal
l (m
m)
F
0.000.050.100.150.200.250.300.350.400.450.50
Jan-0
3
Mar-03
May-03
Jul-0
3
Sep-03
Nov-03
Jan-0
4
Mar-04
May-04
Jul-0
4
Sep-04
Nov-04
NH
4 (m
g/L)
0
2
4
6
8
10
12
Rai
nfal
l (m
m)
Figure 3-11. Continued.
36
G
0.00
0.05
0.10
0.15
0.20
0.25
Jan-0
3
Mar-03
May-03
Jul-0
3
Sep-03
Nov-03
Jan-0
4
Mar-04
May-04
Jul-0
4
Sep-04
Nov-04
NO
2+3 (
mg/
L)
0
2
4
6
8
10
12
Rai
nfal
l (m
m)
H
0.000.010.020.030.040.050.060.070.080.090.10
Jan-0
3
Mar-03
May-0
3Ju
l-03
Sep-03
Nov-03
Jan-0
4
Mar-04
May-0
4Ju
l-04
Sep-04
Nov-04
SRP
(mg/
L)
0
2
4
6
8
10
12
Rai
nfal
l (m
m)
I
2003-2004 Monthly Max and Min POC and Mean Rainfall
0.01.02.03.04.05.06.07.08.0
Jan-0
3
Mar-03
May-03
Jul-0
3
Sep-03
Nov-03
Jan-0
4
Mar-04
May-04
Jul-0
4
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POC
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L)
02
46
810
12
Rai
nfal
l (m
m)
Figure 3-11. Continued.
37
J
0
5
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15
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25
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35
Jan-0
3
Mar-03
May-03
Jul-0
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Sep-03
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Turb
idity
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)
0
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Rai
nfal
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m)
Figure 3-11. Continued.
38
CHAPTER 4 DISCUSSION
The number of hurricanes striking the southeastern coast of the United States was
abnormally high in 2004 and 2005 (Bossak 2004). The frequency of “straight-moving” storms
emanating from western Africa has been rising (Bossak 2004), thus the southeastern United
States has experienced unusually heavy rainfall (Elsner 2003). Since the current trend of intense
hurricane activity is predicted to continue for the next 5 to 35 years (Goldenberg, Landsea,
Mestas-Nuñez, and Gray 2001), associated impacts on Florida ecosystems may be accentuated
and prolonged.
The results of these time intensive observations of water quality and meteorological
conditions in the Pellicer Creek ecosystem provide insight into the impacts of multiple storm
events on environmental variability. In general, the four tropical systems of 2004 suppressed
tidal salinity variations. Although strong northeasterly winds associated with hurricane events
initially promoted salinity spikes (Figure 3-2), high rainfall levels over the course of the event
ultimately had the opposite effect, causing strong declines in salinity for extended periods
(Figure 3-5). The severe drops in salinity associated with the four hurricanes are comparable to
the findings of Sanger et al. (2002) and Wenner et al. (2004) for National Estuarine Research
Rerserve (NERR) sites on the east coast of the United States. They found that storms that
approached the east coast generally caused short-term increases in salinity due to storm surge
and longer-term salinity decreases resulting from excess rainfall. Tropical systems moving up
the coast were associated with down-estuary winds and precipitation that caused reduced
salinity.
The hurricane effects described in this study were generally not outside the two-year
variability range. However, temporal salinity patterns were different in 2004 than 2003. Graphs
39
of daily averages put storms in perspective relative to the background variability of the two-year
time series (Figure 4-1). Typical Florida summer thunderstorms produce about 5–15 minutes of
heavy rain and little wind (Chen and Gerber 1990), while the 2004 hurricanes caused more
intense rainfall, sometimes of much longer duration (e.g., during Frances). Strong winds that
accompanied tropical storms may have been responsible for increasing variation in salinity
(Figure 4-1). This was unanticipated since fresh water influx was expected to keep salinities
low. In this sense, effects of wind and rainfall associated with hurricanes can have somewhat
independent impacts that act on separate timeframes.
Sampling Scale and Ecosystem Variability
Capturing small temporal variability in environmental factors is often essential in
understanding driving forces behind processes occurring at short timescales. Collection of
continuous data at Pellicer Creek provided invaluable evidence of hurricane effects. Data
collected at half-hour increments were examined to distinguish effects of different storm tracks,
intensities, and durations.
Hurricane Charley tracked closest to Pellicer Creek, but passed to the southeast. Only a
small salinity spike was observed (Figure 3-2a). Both Frances and Jeanne tracked from the south
and west of Pellicer Creek, meaning that the station was subjected to the most intense
northeastern quadrants of the storms. The largest salinity spikes resulted from those two storms,
with Hurricane Frances having had the greatest impact on water quality of Pellicer Creek.
Besides producing the most wind and rain, the one-day shift in salinity from 5-6 September
(-19.3 ppt) was the greatest of the entire time series. After Frances, conditions remained nearly
fresh for two weeks. It is unknown how long those conditions would have lasted because Ivan’s
impacts eventually masked them. Ivan and Jeanne delivered less rain than the first two
40
hurricanes, but possibly because the ground was saturated by then, they had the same freshening
effects as the first two storms (see Valiela et al. 1996, 1998).
Comparison of pre- versus post-storm salinities is limited for the storms due to their
proximity. Salinity magnitude and variance did decline as expected immediately after the
storms. Seasonally, however, salinity variance was higher during summer 2004 than summer
2003. This is attributed to the sharp salinity spikes and frequency of hurricanes. Unlike Wenner
et al. (2004) and Orlando et al. (1994), mean salinity during 2003–2004 was lower in summer
than in winter. This anomaly is attributed to seasonal effects of multiple hurricanes.
Potential Biological Community Impacts
Assessing storm effects is an important for understanding ecological processes shaping
coastal ecosystems. Hurricanes can change plant and animal community structure because
organisms can have difficulty adjusting to the associated extreme changes in the environment.
Montague and Ley (1993) found that stations in Florida Bay with large salinity fluctuations had
relatively low biomass and unstable species composition. After Cape Fear, North Carolina was
hit by six hurricanes in four years, Mallin et al. (1999) saw benthic infauna at one station shift
from marine to fresh water species dominated.
Timing of nutrient release may also play an important role in the community structure for
Pellicer Creek and the Guana Tolomato Matanzas NERR since Pellicer Creek may be a source of
nitrogen for the estuary. Negative correlations between salinity and both TN and color match
conclusions of Miller (2004) for water quality in northeast Florida. Miller hypothesized that
Pellicer Creek was a source of nitrogen to nearby intracoastal estuaries. Significant positive
correlations between rainfall and a number of water quality constituents, including NH4, TSN,
TN, TSP, and turbidity, support this hypothesis and indicate that hurricanes increase nutrient
load to nearby estuaries. Therefore, consideration of potential storm frequency is important in
41
assessing nutrient budgets and anthropogenic impacts (Kennish 2004). The positive correlation
between salinity and chlorophyll a may indicate that the estuary is a source of phytoplankton to
Pellicer Creek.
Long-term Consequences
In a 2006 Estuaries and Coasts Special Issue addressing hurricane effects, most authors
found impacts to be relatively short-lived (several weeks to months). The findings of this study
agree with this relative to water quality. However, since none of the storms were hurricane
strength as they passed Pellicer Creek, impacts were not as severe and potentially did not last as
long as they could have if a storm hit the area directly. Additive effects of four hurricanes in one
season, however, may have ecological implications (Tomasko et al. in press). For example,
Valiela et al. (1996) noted the potential importance of hurricane frequency for nitrogen retention.
The timing of hurricane season has important ecological implications (Michener et al.
1997). Typically, the ground is not saturated in early fall and soils are dry enough to absorb
initial rain events and recharge wetlands. However, excessive rainfall can alter the magnitude of
river discharge, thereby changing seasonal variability in salinity and nutrient loads.
Studies of hurricane effects are important, not only in the face of potential increases in
storm frequency, but also because the resulting freshwater inflow may mimic the impacts of
climate change. Since long-term increases in freshwater run-off affect estuarine community
structure (Hayward, Grenfell, Sabaa, Morley, and Horrocks 2006), greenhouse gases, increasing
sea surface temperatures, and rising sea levels are expected to directly and indirectly impact
intertidal wetlands and nearshore aquatic environments (Michener et al. 1997, Gibson and Najjar
2000). Ever-increasing development creates more impervious surfaces and alters hydrology
(Lerberg, Holland, and Sanger 2000, Wenner et al. 2004). Impacts from climate and
anthropogenic influences may last longer than those from hurricanes. Studying hurricane effects
42
can give an idea what might happen to systems given increases in freshwater due to climate
change. Hurricanes cannot be managed, but their impacts do need to be integrated into
management plans (Morrison et al. in press, Paerl et al. in press).
43
A
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)
Figure 4-1. Mean daily averages (2003–2004). A) Salinity. B) Total Precipitation. C) Water
Depth. D) Wind Speed.
45
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51
BIOGRAPHICAL SKETCH
Nicole Dix grew up in Longwood, FL, and graduated from Lake Mary High School. She
is a biologist with particular interests in estuarine ecology. She graduated from Florida State
University in December of 2002 with a B.S. in biology and a B.S. in science education. After
graduating, Nicole worked in Orlando, FL, for Glatting Jackson in the environmental consulting
department. Her responsibilities included performing endangered species surveys, writing
permitting reports, delineating and monitoring wetlands, and conducting a vegetative biomass
study along the Kissimmee River. Nicole started her master’s work at the University of Florida
in the fall of 2004 under the supervision of Dr. Edward Phlips. She was involved in a coastal
impact study of the Cayman Islands Turtle Farm, general chemical analyses and processing of
water samples in the lab, and monthly water quality monitoring in the estuarine environments
near St. Augustine, FL. Nicole obtained her M.S. in fisheries and aquatic sciences in the fall of
2006, and received a three-year Ph.D. fellowship from the National Estuarine Research Reserve
program to continue her research and education.
