Download Susan Mullane

Rhizophora mangle
(Red Mangrove)
Kayla Tennant, Jessica Canas, Suzey Mullane & Raleigh
Clarke
Rhizophora mangle
Abstract
The northernmost range of Rhizophora mangle, commonly known as Red Mangrove, has
been previously documented at Fort Matanzas National Monument in St. Johns County, Florida
in 2006. Further research has shown that R.mangle has been growing north of that location in
northern parts of St. Johns County, and may have been for some time. The research was
designed to test the hypothesis that climate change affects the distribution of Rhizophora
mangle in northeastern parts of Florida. The point being that Rhizophora mangle provides a
habitat to many other species and plays an important ecological role in the environment.
Introduction
Rhizophora mangle can grow up to 5-20 m in deep organic soils and is commonly found
in salt water marshes or mangrove swamps. Red mangroves grow in salt marshes in low marsh
tidal zones similar to the habitats where we conducted field research (Tiner, 1193, p. 10-14).
Red mangroves populations are primarily located in southern parts of Florida with the
exception of extreme northern distributions in Cedar Key and St. Augustine. Along with the red
mangroves, there are two other species of mangroves that range along the southeastern coast
of the United States, black and white mangrove.
R.mangle have very distinct characteristics that distinguish them from other mangroves;
such as aerial prop roots and reddish bark. The leaves are evergreen, thick and leathery. The
tops are glossy and green and the underside is yellow-green with black dots and no visible
veination. The propped roots of the plant come from the stem and function in stabilizing the
plant. They also facilitate gas exchange for respiration when they are completely submerged in
water (Mehlig & Hill, 2007).
R. mangle is generally found in subtropical to tropical coastal regions: fringe, riverine,
over wash, basin and super tidal flats. The plants can live completely submerged in water or
where the tide fluctuates along the coasts. R. mangle live in salinity levels between 0-90ppt and
temperatures around 76 degrees Fahrenheit. The plants act as a natural barrier for coastlines,
acting as a storm buffer. Its surrounding vegetation includes Avicennia germinans (Black
Mangrove), Batis maritima (Salt Wart), Juncus roemerianus (Black Rush), Ditichlis spicata
(Seashore Salt grass), Iva frutescens (Marsh Elder), and Borrichia frutescens (Sea Oxeye)
(Florida Division of Forestry, 1979, p. 24-29). Together creating a unique environment and an
extremely diverse yet crucial habitat for marine and estuarine invertebrates and fish, as well as
a nesting site for wading birds.
We attempted to test whether climate change might influence changes in distribution
of R. mangle growth in the north eastern coast of Florida. Past documentation of the northern
most point of red mangrove last documented was located at Fort Matanzas National park,
However, we found additional individuals as much as 17.8 miles north of that location. We
document that range extension to Camachee Cove Yacht Harbor in St. Augustine.
Materials and Methods
The search for the northernmost point of R.mangle was centered in St John’s County, St.
Augustine, Florida. This work took place from January 2010 until April 2010. The starting point
was determined utilizing the location of the previously-documented northernmost point, 29°
42’N, 81° 14’W (Zomlefer, Judd & Giannasi, 2006, p.239-244). Eric Revuelta from St. Johns River
Water Management District assisted in identification of the surrounding vegetation: Batis
maritima (Saltwort), Avicennia germinans (Black Mangrove), Salicornia europaea (Glasswort),
Iva frutescens (Marsh Elder), Lycium carolinanum (Christmas Berry), Juncus roemerianus
(Needle Rush). GIS data waypoints were taken at this location with the use of a Garmin GPS,
and a measuring tape was used to document the heights of the specimens . The morphology of
the saplings were identified as R.mangle through the use of Peterson Field Guides (Petrides &
Wehr, 1998, p. 214-216), and photographs taken previously at Fort Matanzas. The access to
Google Earth and aerial maps donated by the St. John’s River Water Management facility
provided insight into potential areas with populations of R. mangle.
With the knowledge that red mangroves tend to develop in areas where black
mangroves grow rampant, these areas were targeted. They were the following: the site at East
side of Fort Matanzas National Monument Park, Camachee Cove Yacht Harbor, the Castillo de
San Marcos, the Fountain of Youth, the Guana Tolomato Matanzas Research Reserve, and
Fishers Island near the 312 Bridge. Fort Matanzas, the Guana Tolomato Matanzas Estuarine
Research Reserve, and the Fishers Island were explored by foot and kayak. The kayaks were
utilized to explore the Intracoastal waterway areas unreachable by foot.
Results
We documented that R.mangle has been growing further north of the previouslydocumented northernmost range at Fort Matanzas National Monument. Our search began at
Fort Matanzas National Monument, Rattlesnake Island, 29⁰42’N, 81⁰14’W, where previously
documented R.mangle still remains after four years. After making observations and analyzing
the morphology, the search continued along the eastern shoreline of the Matanzas River where
15 plants were discovered. The plants were found in different stages of growth; including a
propagule and a hypocotyl, several seedlings, (indicating recruitment) and several adult plants
ranging from .6096-1.8288 (m) were also found in the same area.
The red mangroves found along the eastern shoreline of the Matanzas River were green
and alive, with many signs of new growth. The red mangroves found at this point of interest
were growing along the muddy banks and shell beds along the Matanzas River, which was an
ideal place for R.mangle to propagate. Furthermore, the surrounding common vegetation was
evident that this was a suitable habitat for the mangroves. After exploring the area we other
potential sites by analyzing aerial photographs . By analyzing this imagery, we could identify the
locations of dense black mangroves and possibly the location of red mangroves. Therefore, the
next point of interest was North of the 312 Bridge at Fishers Island Marina (latitude?). After
hiking through thick black mangroves, we discovered three red mangroves that measured 2.19
(m), 2.96 (m), and 3.048 (m). It was clear that R.mangle had been growing for some time,
making Fishers Island the most northern point of red mangrove distribution at this point in our
explorations. Fish Island is an appropriate habitat due to its low energy shorelines accumulated
with organic mud and protected shell beds.
The goal was to observe and document the northernmost occurrence R.mangle during
the months of January, February, and March 2010 and compare the findings to climate factors.
Next, the exploration continued at Camachee Cove Yacht Harbor, north of the Vilano Bridge. At
(latitude longitude) we found one red mangrove measuring 1.25 (m). The tree was leafless;
however, the roots were moist and a new plumule was emerging, showing signs of new growth.
We determined that this plant was an outlier, because there was no evidence of R.mangle in
the surrounding areas. The propagation of this particular plant was located in dense Spartina
alterniflora (Smooth cordgrass);exposed to higher wave action and higher current velocities
when compared to the other documented location at Fisher Island. Higher wave energy
environements make it difficult for the R.mangle to propagate. Furthermore, this area was
more susceptible to harsh weather conditions; including high winds and frosts due to the lack
of protection from surrounding vegetation; such as, the Avicennia germinans (Black Mangrove).
.
Discussion
The historic range for red mangroves have been reported as far north as Cedar Key on the west
coast of Florida and north of the Ponce de Leon Inlet on the east coast of Florida: both of these
extremes lie at approximately 29⁰10’ N. The R.mangle species ranges have fluctuated over the past
several centuries due to short-term climate change (Odum, McIvor, & Smith, 1982, p.2). R.mangle is
most prevalent in south Florida, particularly the Florida Keys and in the Everglades (Alexander, 1954,
p.209)
Our attempts to document new, more northern locations of the red mangrove started
where it was last documented in 2006, Fort Matanzas. Starting where we knew R.mangle was
already present gave us insight to the living environment of R.mangle. R.mangle does not
develop adequately in regions where the annual average temperature is below 66 Degrees
Fahrenheit (Odum, McIvor, & Smith, 1982, p.1). The average temperature from 2006-2009 was
71.79 Degrees Fahrenheit, with the current average of January-March 2010 being 51.35
Degrees Fahrenheit in St. Augustine (www.srh.noaa.gov,2010). The average temperature
patterns for the last several years have allowed for R.mangle to grow in more northern parts of
Florida. On the other hand, recent freezes have a tremendous affect on the growth and
distribution of the mangroves by decreasing tree height and decreasing leaf size (Lugo and
Zucca, 1997). After first viewing the already documented R. mangle, we decided to make our
way up the east side of the Matanzas River, where we made our first extension of the northern
documentation of R.mangle.
Future research suggestions would entail the use of access permits to expand searches
into more potential areas, funding for kayaks, and current research on the species. Kayaks
would provide access to areas that traveling by foot would not allow. Kayaks serve as a means
of transportation to observe areas closer to the coast and the banks of rivers and the
Intercostals. With this knowledge a team may be able to have a better understanding of the
plants distribution.
Summary
The hypothesis at the beginning of our research stated: how climate change contributed
to the distribution of R.mangle growth on the north eastern coast of Florida. While we
documented a northern range extension by 17 miles, it is is impossible for us to assert that
climate change is the sole reason for the extended distribution of red mangrovesAny change in
overall climatic averages, including more frequent extremes in winter temperatures may limit
the growth and reproduction of R.mangle. However, our documented northern range extension
may contribute to the scientific body of information indicating any changes in species
distributions. The four major factors that appear to limit the growth of R.mangle and determine
the extent of mangrove ecosystem development; includes, (1) climate, (2)salt water, (3) tidal
fluctuation, and (4) wave energy (Odum, McIvor, & Smith, 1982, p.1). Therefore, climate
change , with its attendant increased warmer temperatures, longer summers and rising water
levels may also affect the distribution of R. mangle. Other factors that contribute to the range
of R. mangle include: Seeds travel north primarily through oceanic currents, river currents, and
wind. These three factors may provide an alternate explanation to climate change as the
primary cause of this range extension, although these factors may also be affected by climate
change
Acknowledgements
We thank Professor Barbara Blonder and Dr. Terri Seron for creating an intriguing
Environmental Science program and being environmental mentors. We also wish to thank
Guana Tolomato Matanzas Research Reserve for partnering and supporting research efforts
with Flagler College’s Science department. We thank Eric Revuelta from the St. Johns River
Water Management District, for guiding us in the field and providing expertise in botany
identification. We are greatful for Hugh for permitting us to conduct research at Fish Island
Marina, along the Matanzas River.
Literature Cited
Alexander, T. R. (2005). Trees Against The Sea. In T. E. Lodge, The Everglades Handbook:
Understanding The Ecosystem (pp. 207-209). Boca Raton: CRC Press LLC.
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Management (pp. 24-29). Tallahasse: Florida Dept. of Agriculture and Consumer Services,
Division of Forestry .
Mehlig, U, & Hill, K. (2007). Rhizophora mangle (aquatic plant, tree, shrub).
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Mangroves: http://www.twolittlefishies.com/images/mangrove_manual.pdf
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Tiner, R. W. (1993). Field Guide To Coastal Wetland Plants Of The Southeastern United States.
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www.srh.noaa.gov. (1973-2010). Retrieved March 13, 210, from ST AUGUSTINE WFOY,
FLORIDA : http://www.sercc.com/cgi-bin/sercc/cliMAIN.pl?fl7826
Zomlefer, W. B. (2006). Northernmost Limit of Rhizophora mangle (Red Mangrove;
Rhizophoraceae) in St. Johns County, Florida. Castenea , 239-244.This is the only primary
citation! You have no other primary and no secondary scientific sources. Fix this – you will
forfeit a large number of points otherwise…..