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Additional northern range extension of Rhizophora mangle (Red Mangrove) in Northeastern Florida, United States 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 (N29 54.897 W81 18.489). 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. Introduction Rhizophora mangle can grow up to 5-20 m in deep organic soils and are 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 (see figure 1) (Tiner, 1193, p. 10-14). Red mangrove populations are primarily located in southern parts of Florida with the exception of extreme northern distributions in Cedar Key and north of the Ponce de Leon Inlet (Sprung, 1999, p.2-3). Along with the red mangroves, there are two other species of mangroves that inhabit the southeastern coast range, black mangrove (Avencennia germinans) and white mangrove (Languncularia racemosa). R.mangle has 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 lives in salinity levels between 0-90ppt and temperatures that average 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). These associations create 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, creating an extremely diverse habitat. We attempted to test whether climate change might have contributed to the distribution of R. mangle growth in the north eastern coast of Florida. Before our fieldwork began we knew that the northern most point of red mangrove last documented was located at Fort Matanzas National park, although through the semester we have surpassed that last location by 17.8 miles north of that location. We documented the most recent, northern extent located at 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 29° (Zomlefer, Judd & Giannasi, 2006, p.239-244). The vegetation surrounding the original plant was identified as the Batis maritima (saltwort), Avicennia germinans (black mangrove), Salicornia europaea (glasswort), Iva frutescens (marsh elder), Lycium carolinanum (Christmas berry),and Juncus roemerianus (needle rush). GIS data waypoints were taken at this location with the use of a hand held Garmin GPS 76Cx. A measuring tape was used to document the heights of the saplings in SI units (m). The morphology of the saplings was 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 photographs obtained from the St. Johns River Water Management District provided insight into potential areas with populations of R.mangle. In order to narrow down the search for the distribution of R.mangle, the team targeted areas most populated with vegetation commonly found in R.mangle habitat. 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 Fishers Island were explored by foot and a kayak (see Figure 1). The kayak was utilized to explore the intracoastal waterway unreachable by foot. Results 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. We documented that R.mangle has been growing further north of the previously-documented 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 (See Figure 1). 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 indicated that this was a suitable habitat for the mangroves (Florida Division of Forestry, 1979, pg. 24-29). Next, we selected potential sites by analyzing aerial photographs (St. Johns River Water Management District, 2007-2010) . 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 (N29 52.227 W81 18.186). 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. Fishers Island is an appropriate habitat due to its low energy shorelines accumulated with organic mud and protected shell beds (Sprung, 1999, p.2). At Camachee Cove Yacht harbor (N29 54.897 W81 18.489) 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 environments make it difficult for the R.mangle to propagate. Furthermore, this area was more susceptible to temperature stress; including high winds and frosts due to the lack of protection from surrounding vegetation in comparison to other R.mangle habitats (Sprung, 1999, p.1). 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 in St. Augustine (www.srh.noaa.gov,2010) from 2006-2009 was 71.79 Degrees Fahrenheit, with the current average of January-March 2010 being 51.35 Degrees Fahrenheit. The higher than normal average temperature patterns for the last several years have likely allowed for R.mangle to grow in more northern parts of Florida. On the other hand, recent freezes (dates?)have a tremendous affect on the growth and distribution of the mangroves by decreasing tree height and decreasing leaf size (Lugo and Zucca, 1997). Future research suggestions would entail the use of access permits to expand searches into more potential areas, and of kayaksuse Kayaks would provide access to areas that traveling by foot would not allow and would serve as a means of transportation to observe areas closer to the coast and the banks of rivers and the Intracoastal waterway. 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. We documented a northern range extension by 17 miles, however it is impossible for us to assert that climate change is the sole reason for the extended distribution of red mangroves. Any 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 (Sprung, 1999, p.1-9). 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 weather patterns. 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 grateful for Hugh for permitting us to conduct research at Fishers Island Marina, along the Matanzas River. 1 R.mangle present/outlier Camachee Cove Yacht Harbor. Accessed by wading. 3 R.mangle present at Fisher Island. Accessed by kayak. 15 R.mangle present on the East side Matanzas River across from Fort Matanzas National Monument. Accessed by hiking. (Figure 1: Most southern point previously documented at Fort Matanzas National Monument. Northern point at Fisher Island is the most consistent documentation of R.mangle. The most northern point is a single plant, which is labeled an outlier, because there was no evidence of further R.mangle distribution. Two most northern points of R.mangle (Figure 2: Fort Matanzas Monument where previously documented R.mangle is shown, along with 15 new plants that were discovered along the east side of the Matanzas River) (Figure 3: 15 R.mangle discovered slightly north east of previous documentation in 2006) 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. Forestry, F. D. (1979). Marsh/Mangrove Zone. In Coastal Plants of Florida-A Key To Good Land Management (pp. 24-29). Tallahasse: Florida Dept. of Agriculture and Consumer Services, Division of Forestry . Mehlig, U, & Hill, K. (2007). Rizophora mangle (aquatic plant, tree, shrub). Sprung, J. (1999). Ecology and Care of Mangroves. Retrieved April 2010, from Magnificent Mangroves: http://www.twolittlefishies.com/images/mangrove_manual.pdf Tiner, R. W. (1993). Field Guide To Coastal Wetland Plants Of The Southeastern United States. In R. W. Tiner. Thomson-Shore, Inc. Wehr, G. A. (1998). Peterson Field Guides: Eastern Trees. New York City: Houghton Mifflin Company. 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. Castanea , 239-244.