229 15 Using Seagrass Coverage as an Indicator of Ecosystem Condition Catherine A. Corbett, Peter H. Doering, Kevin A. Madley, Judith A. Ott, and David A. Tomasko CONTENTS Introduction 229 Charlotte Harbor, Florida 230 Methods 233 Historical Seagrass Coverage Estimates 233 Current Seagrass Mapping Efforts 233 Transects 234 Results 235 Seagrass Coverage 235 Deep Edge of Seagrass Beds 237 Discussion 240 Conclusions 241 Acknowledgments 242 References 243 Introduction Concern about the condition of natural resources faced with threats from human impacts have led to efforts to monitor and assess the effects of these impacts and the efficacy of the management regimes that attempt to mitigate them. Increasingly, the use of indicators that reflect biological, chemical, or physical attributes of the “health” of an ecosystem has been encouraged, and since the 1993 U.S. Government Performance and Results Act (GPRA), government agencies have been required to develop performance reports that measure management success using indicators and goals (U.S. EPA, 2000). The U.S. EPA has developed 15 evaluation guidelines for developing environmental indicators that includes, among others, the following: • Relevance to the assessment — The proposed indicator should be responsive to an identified question and provide information useful for management decisions. •Temporal variability across years — While indicator responses may show interannual variability even as environmental conditions remain stable, the indicator should reflect true trends in ecological condition for the assessment question. To determine variability across years, mon- itoring must proceed for several years at relatively ecologically stable sites. • Discriminatory ability — The indicator should reflect differences among sites along a known condition gradient. 2822_C015.fm Page 229 Monday, November 15, 2004 10:14 AM © 2005 by CRC Press 230 Estuarine Indicators • Linkage to management action — An indicator is useful only if it can provide adequate information to support management decisions or quantify the success of past decisions (U.S. EPA, 2000). Examples of indicators of ecological condition include direct measurements (e.g., total nitrogen con- centration), indices (e.g., macroinvertebrate condition index), and multimetrics (e.g., fish assemblage) (U.S. EPA, 2000). Evaluating seagrass coverage and condition has become one method of monitoring the condition of coastal regions worldwide. Monitoring and conserving seagrass is a global issue illustrated by the incidences of seagrass declines attributed to eutrophication that have been documented in Denmark, Australia, Bermuda, and the United States (Kemp, 2000). Within the United States, several federal agencies use aerial photography to map and monitor coastal wetlands (Dobson et al., 1995; Kiraly et al., 1990; Coyne et al., 2001; Kendall et al., 2001). In addition, federal, state, and local government part- nerships have resulted in seagrass monitoring programs in Chesapeake Bay (Chesapeake Executive Council, 1993), Florida (Virnstein and Morris, 1996; Kurz et al., 2000), North Carolina (Kiraly et al., 1990), Padilla Bay (Shull and Bulthuis, 2002), and Texas (Moulton et al., 1997). In Southwest Florida, including Tampa and Sarasota Bays, many research and restoration efforts have focused on seagrass meadows as indicators of estuarine condition. In Tampa Bay, where historical losses have been linked to both direct and indirect impacts, resource managers have set goals for restoring seagrass coverage to approximately 95% of the coverage present in 1950. The Nitrogen Management Consortium, a partnership among private and public entities, was formed to develop methods of reducing anthropogenic nitrogen loads to the bay to reduce algae blooms within the water column and epiphytes on the surface of seagrass blades, both of which reduce the supply of light available to the plants. Recent increases (1980s to 1996) in seagrass coverage in Tampa Bay (and also Sarasota Bay) are thought resultant from decreasing anthropogenic nitrogen loads to these estuaries (Kurz et al., 2000). Nonetheless, seagrass coverage in some areas of Tampa Bay may not be increasing as expected even though water clarity appears to be adequate to support seagrass growth in these areas (TBEP, 2000), and it appears that many factors other than nutrient loads may play an important role in driving seagrass coverage in some areas of the bay. In contrast to Tampa and Sarasota Bays, resource managers in Charlotte Harbor, located on the west coast of Florida south of Tampa and Sarasota Bays and contiguous with these estuaries, have not used seagrass coverage as an environmental indicator of the health of the estuary to date. Even with its close proximity to these other estuaries, Charlotte Harbor experiences disparate issues than its northern neighbors. Charlotte Harbor itself is approximately 700 km 2 of open water and has a watershed of well over 11,300 km 2 , a ratio of watershed to open water of over 16:1 (SWFWMD, 2000). The estuarine system is very dynamic due to the influence of the freshwater inflows from its major tributaries, and natural interannual variability in seagrass coverage mars the ability to ascribe changes in seagrass coverage to specific anthropogenic impacts within the watershed. This chapter reviews historical and current seagrass coverage information as well as 1999 to 2001 fixed transect monitoring data for the Charlotte Harbor region to examine some of the problems associated with using seagrass as an indicator of ecosystem condition. Although current seagrass monitoring efforts in Charlotte Harbor are extensive, insufficient data, natural variability, and confounding indirect and direct impacts within the region coalesce to create perplexing problems with the use of seagrass as an environmental indicator of ecosystem condition. Charlotte Harbor, Florida Charlotte Harbor is the second largest open water estuary in the state, and it is also generally considered includes numerous interconnected estuaries from Lemon Bay south to Estero Bay. The majority of the harbor is surrounded by an extensive conservation buffer system of well over 21,610 ha. Much of the shoreline in this buffer system is unaltered mangrove and salt marsh habitats, thereby providing abundant 2822_C015.fm Page 230 Monday, November 15, 2004 10:14 AM © 2005 by CRC Press one of Florida’s most productive and a relatively healthy estuary (Figure 15.1). The estuarine complex Using Seagrass Coverage as an Indicator of Ecosystem Condition 231 food and shelter for juveniles of many of the harbor’s estuarine species. The Charlotte Harbor watershed extends approximately 210 km (130 mi) from the northern-most headwaters of the Peace River to southern Estero Bay. Three large rivers, the Peace (a 6090 km 2 basin), the Myakka (a 1560 km 2 basin), and the Caloosahatchee River (3570 km 2 basin extending to Moore Haven), serve as the major sources of fresh water to the Charlotte Harbor estuary (Hammett, 1990). Six species of seagrass are found within the Charlotte Harbor region: Halodule wrightii, Thalassia testudinum, Syringodium filiforme, Halophila englemanni, H. decipiens, and Ruppia maritime. Halodule sp. is the most common species within the harbor, found in all the estuary segments, whereas Thalassia sp. and Syringodium sp . are more abundant in those estuary segments where they are found (Staugler and Ott, 2001) . Agriculture encompasses the major land use in the Charlotte Harbor watershed and is second only to tourism in economic impact. In 1995, a total of 114,520 ha within the watershed was dedicated to citrus crops, one third of all Florida citrus extent (CHNEP, 2000), while in 1990 more than 404,680 ha was devoted to rangeland or pasture for cattle (CHNEP, 1999). Simultaneously, Florida leads the United States in conversion of farmland to urban lands, and along the coast especially, residential and urban development is rapidly expanding. In 2020, the region is projected to have a population of almost 2 million residents, a 424% increase from the 1960s population of 363,200 (cited in CHNEP, 2000). Finally, there is an extensive phosphate mining industry within the middle and upper reaches of the northern watershed. The “Bone Valley” phosphate deposit of more than 202,342 ha (500,000 acres) lies primarily within the Peace River sub-basin. This phosphate deposit provides almost 75% of the nation’s phosphate supply and 25% of the world’s (CHNEP, 2000). Future mining is expected to move southward toward the harbor and last an additional 30 years. FIGURE 15.1 Map of Charlotte Harbor watershed. (Data provided by CHNEP, NOAA, and SWFWMD.) Charlotte Harbor, Florida Lemon Bay Myakka River Sarasota Bay Tampa Bay Lake Hancock Peace River Charlotte Harbor Pine Island Sound Estero Bay Caloosahatchee River 2822_C015.fm Page 231 Monday, November 15, 2004 10:14 AM © 2005 by CRC Press 232 Estuarine Indicators Within this rapidly changing region, the Charlotte Harbor ecosystem currently faces a number of considerable hydrologic and water quality challenges. In the southern region of the Charlotte Harbor system, the Caloosahatchee River, which contributes an annual average inflow to the lower harbor of approximately 57 m 3 /s (Hammett, 1990), was channelized and artificially connected to Lake Okeechobee in the late 1800s. A series of locks and dams were constructed along the river, one of which, the W. P. Franklin Locks and Dam, artificially truncates the river’s estuarine system by blocking the natural gradient of fresh to saltwater that historically extended upstream during the dry season. Currently, it is common that water immediately downstream of the locks has nearly one third the salinity of the Gulf of Mexico while water immediately upstream of the structure is fresh (SFWMD, 2000). Also, freshwater releases from Lake Okeechobee to the estuary for several weeks during late spring each year to lower lake levels before the summer rainy season exceed 71 to 85 m 3 /s (2500 to 3000 ft 3 /s), estimated as maximum high flows for estuarine resources (see Chamberlain and Doering, 1997). There are projects under way to restore a more natural variation in flows to the Caloosahatchee estuary stemming from the Comprehensive Everglades Restoration Plan (South Florida Ecosystem Task Force, 2002); nonetheless, the past hydro- logical alterations of the watershed have dramatically changed the natural quantity, quality, timing, and distribution of flows to the estuary with limited regard to maintaining the biological integrity of the ecosystem (SFWMD, 2000). In addition, the Caloosahatchee River is the major source of nutrients to the Caloosahatchee estuary (Environmental Research and Design, 2003), and more than a decade ago, the Florida Department of Environmental Regulation reported that the estuary had reached its nutrient loading limits as indicated by elevated chlorophyll a and depressed dissolved oxygen levels (DeGrove, 1981; DeGrove and Nearhoof, 1987; Baker, 1990). In the northern region of the watershed, the Upper Peace River has gone from a gaining stream with continuous flows throughout the year via groundwater contribution to a losing stream (i.e., predominantly groundwater recharge area) since the 1950s (SWFWMD, 2002). In contrast to historical conditions, flow measurements at the northern Bartow, Florida, USGS (U.S. Geological Survey) flow gauge now often exceed the flow measurements of the downstream Zolfo Springs gauge. The potentiometric surface of the Upper Floridan aquifer within the Upper Peace River basin has been lowered 6 to 12 m (20 to 40 ft) in the dry season (April–May), and areas of past artesian flow, such as Kissingen Spring, have ceased discharge. While the aquifer apparently is rebounding, the Upper Peace River now experiences periods of no or little flow for several weeks during the dry season (SWFWMD, 2002). The Peace River is also the major source of nutrient loads to northern Charlotte Harbor, and the entire stretch of the river is considered “fair” to “poor” water quality by Florida standards (FDEP, 2003). Three water bodies within the upper Peace River watershed, Lake Parker, Banana Lake, and Lake Hancock (along with their tributaries), consistently exhibit some of the poorest water quality within the state (FDEP, 2003). Lake Hancock, a 1840-ha lake within the headwaters of the Peace River, is a hyper- eutrophic lake that has accumulated a layer of flocculent organic sediments approximately 1.7 m thick or an estimated 13.8 million m 3 (Camp Dresser & McKee, Inc., 2001). It is considered one of the most degraded lakes within the State of Florida, and from 1985 to 1999 it had a mean chlorophyll value of 170 mg/m 3 (cited in Camp Dresser & McKee, Inc., 2001). The estimated yield of nitrogen from this lake is approximately 5700 kg/mi 2 /year (Tomasko, 2001) and represents roughly 19% of the total nitrogen loadings to the Peace River (cited in Camp Dresser & McKee, Inc., 2001). Also, the river has naturally high levels of phosphorus, and average total phosphorus concentrations from 1993 to 1995 exceeded 0.70 mg/L to place it within the poorest 20% of Florida streams (FDEP, 2003). Water quality data collected in the region indicate that algae blooms and chlorophyll a levels exceeding 60 to 80 µ g/L in the tidal Peace River region have occurred seasonally since monitoring began in 1976 (FDEP, 2003). Seasonal chlorophyll a levels of this magnitude are considered indicative of hypereutrophic conditions in some estuarine water quality classification systems (e.g., NOAA, 1996), and chlorophyll a concen- trations exceeding 20 µ g/L, considered “high” by classification systems (e.g., NOAA, 1996), were consistently observed in both the tidal Peace and Myakka Rivers during July through September from data collected in 1993–1996 (Morrison et al., 1997). 2822_C015.fm Page 232 Monday, November 15, 2004 10:14 AM © 2005 by CRC Press Using Seagrass Coverage as an Indicator of Ecosystem Condition 233 Methods Historical Seagrass Coverage Estimates To represent historical conditions, black-and-white photographs from 1946 to 1951 (referred to in the original document as the 1945 set) were acquired, and 1:24,000 scale positive false-color, infrared trans- parencies were produced from flights in April 1982 for current conditions. In 1983, the Florida Department of Natural Resources (FDNR) and the Florida Department of Transportation (FDOT) produced a document with associated maps that examined the historic and current land uses of Charlotte Harbor and Lake Worth Lagoon, Florida (Harris et al., 1983). The 1982 photographs were analyzed with stereoscopic visual equipment; the 1945 photographs did not have the requirements needed to perform stereoscopic analyses. For the 1945 and 1982 maps, seagrass beds were delineated onto Mylar ® overlays, and then the data were digitized into the FDOT proprietary point-vector database. Final maps were produced at 1:24,000 scale. Seagrass meadows, as determined from the 1945 aerial photography, were classified to only one category (submerged aquatic vegetation) because the quality of the photographs did not allow multiple category classification. The 1982 seagrass coverage was classified to three categories, but for the purposes of this report, coverages for all data sets, including subsequent mapping efforts, are reported as combi- nations of all seagrass classification categories employed (i.e., sparse, dense, patchy). Subsequently, Florida Marine Research Institute (FMRI) staff redigitized the seagrass polygons derived from the 1982 photographs to create a digital Arc/Info ® file. Because these 1982 data exist in digital format, calculations of seagrass coverage based on the harbor sub-basins were possible for this report and are used as historical data for comparison with more recent mapping results. However, lack of digital data for the 1945 effort has limited the examination of the 1945 seagrass coverage by sub-basin for this effort. Seagrass coverage for the 1945 maps was evaluated by USGS quadrangle areas rather than the 14 sub-basins that have been used to define coverage for subsequent mapping efforts. Also, the geographic boundaries for the 1945 study area do not match the boundaries of the 1982 and subsequent year analyses. Therefore, a comparison of total seagrass coverage from the 1945 to recent efforts is not possible. The 1983 study did not include Lemon Bay or southern Estero Bay. To fill a void in the aerial photographic coverage for 1982, FMRI interpreted Estero Bay coverage from photographs taken in 1990. Because of these issues, Estero and Lemon Bays are not included in the discussion of changes in seagrass coverages within this chapter. Finally, the black-and-white photographs used in the 1945 effort were of low quality for the purpose of delineating seagrass coverage, and the absence of ground verification during the year the photographs were produced is reason for caution when examining these data and resulting maps. Current Seagrass Mapping Efforts The Charlotte Harbor watershed falls within the jurisdiction of two water management districts, the South Florida Water Management District (SFWMD) and Southwest Florida Water Management District (SWFWMD), and these two agencies divide the responsibilities of mapping seagrass coverage within the Charlotte Harbor region. In northern Charlotte Harbor, the SWFWMD has conducted seagrass mapping efforts on a roughly biennial basis since 1988, while the SFWMD recently initiated the undertaking of biennial seagrass mapping efforts within their jurisdiction of southern Charlotte Harbor in 1999. In 1999, the most recent comprehensive mapping effort for the harbor, the two districts used somewhat dissimilar methodologies in their mapping efforts in that the minimum mapping units, map accuracy standards, and classification of “patchy” vs. “continuous” seagrass coverage (see below for explanation) varied slightly. Seagrass maps are produced through a multistep process. First, aerial photographs are obtained during times of good water clarity and moderately high seagrass biomass — usually November or December ( Note: The 2002 photographs were taken in January 2002) — after the summer rains have ceased. True color photographs at a scale of 1:24,000 are used. Appropriate environmental conditions, such as 2-m depth for water clarity, wave height less than 0.6 m, and wind speed less than 5 m/s (10 knots), are required on the day the photographs are obtained. 2822_C015.fm Page 233 Monday, November 15, 2004 10:14 AM © 2005 by CRC Press 234 Estuarine Indicators Next, investigators examine bottom cover in situ at various locations to allow identification of distinct photographic signatures and to investigate unusual signatures. In the office, the field classifications are matched to signatures on the photographs. Seagrass signatures are divided into two classes: continuous coverage (approximately <25% unvegetated bottom visible within a polygon) and patchy (approximately >25% unvegetated bottom visible within a polygon). However, mapping accuracy of these two polygon classifications could not be ground-truthed by site visits. For this effort, coverages for both polygon classes were combined. The minimum mapping unit is approximately 0.2 ha. It should be noted that in 1999 the SFWMD required a minimum mapping unit of 0.1 ha and defined “continuous” seagrass beds as polygons with approximately >85% cover. For earlier mapping efforts (1988, 1990, 1992, 1994, and 1996) the individual polygons were delineated on transparent Mylar ® sheets placed on top of the aerial photographs. A zoom transfer scope was used to transfer the delineated polygons to USGS quadrangles. Next, the polygons were digitally transferred to an ARC/Info database. The resulting seagrass maps meet USGS National Map Accuracy Standards for 1:24,000 scale maps. For the 1999 and 2002 Southwest Florida Water Management District seagrass maps, tighter ground control and more sophisticated mapping techniques were utilized to meet 1:12,000 National Map Accuracy Standards while still using 1:24,000 scale photographs. Analytical stereo-plotters were used for photointerpretation in lieu of stereoscopes. This method allowed for the production of a georeferenced digital file of the photo-interpreted images without the need for additional photographs to be transferred to maps. Instead of drawing complete polygons each year, effort and errors have been reduced by using the previous effort’s digital coverage as the baseline and delineating any changes to seagrass extent for the current effort. This method has provided a change analysis as well as current seagrass coverage. Hard-copy plots were produced and checked for errors. Finally, a number of randomly chosen points were identified and plotted for a post-map production classification accuracy assessment. The points were randomly selected using Arc/Info processes by first defining the coordinates of the study area, generally the BND coordinates of the Arc/Info coverage. The point selection then involved the random generation of numbers based on the minimum and maximum values of the X and Y coordinates of the study area. The numbers that were generated were stored as variables and a selection was made from the Arc/Info coverage to see if they fit the criteria specified (i.e., seagrass codes = “patchy” or “contin- uous”). A variable was also set up to be used as a counter, and set to a value of zero (0). If the area did not fit the selection criteria, the “counter” variable was not calculated and the loop ran itself again. If the area fit the selection criteria, a point was placed at the position, the coordinates were stored in the variable, and the “counter” variable was calculated with the next value. This process was repeated until approximately 10 to 20 points per estuary region were selected. Field staff then utilized the coordinates for the randomly chosen sites, a site map and a global positioning system (GPS) to visit the locations in the field and classify the bottom cover. These in situ inspections were compared to the map classifi- cations to develop an unbiased determination of the map’s classification accuracy. Transects As a supplement to the water management districts’ aerial photography mapping efforts to estimate seagrass extent, the Florida Department of Environmental Protection–Charlotte Harbor Aquatic Preserves Office established a series of 50 transects, distributed over the various sub-basins of the harbor, to quantify seagrass species composition, distribution, and abundance. Beginning in 1999, these 50 fixed transects seagrass conditions by detecting differences in seagrass depth distributions, abundance, epiphyte coverage, short-shoot densities, and species composition. Each transect consists of a fixed line, determined by a compass heading and marked with PVC (polyvinylchloride) stakes, extending from the shoreward seagrass edge out to the deep edge of the meadow. Program researchers collect depth measurements, seagrass species abundance (Braun-Blanquet Cover Scale), blade length, sediment type, and epiphyte coverage and type at 50-m intervals along each transect (or 10-m intervals for transects shorter than 50 m) from shore to edge of bed (Staugler and Ott, 2001). Depth measurements were adjusted to mean water depth by adjusting the tide level observed in the field to mean water based on the 12 National Oceanographic and Atmospheric Administration (NOAA) tide stations located throughout the study area. 2822_C015.fm Page 234 Monday, November 15, 2004 10:14 AM © 2005 by CRC Press (Figure 15.2) have been visited annually during September through November to determine changes in Using Seagrass Coverage as an Indicator of Ecosystem Condition 235 Results Seagrass Coverage The first comprehensive evaluation of seagrass coverage in the Charlotte Harbor region was completed in the 1983 FDNR and FDOT effort (Harris et al., 1983). The study compared seagrass coverage of Charlotte Harbor derived from black-and-white photographs from 1946 to 1951 (referred to in this report as 1945) to data derived from positive false-color infrared transparencies produced from flights in April The report documented a 29% decrease in seagrass, from 33,572 ha (82,959 acres) to 23,672 ha (58,495 acres) between 1945 and 1982 for the harbor, excluding Lemon and southern Estero Bays. All quadrangles within Charlotte Harbor demonstrated losses, ranging from 6 to 87%; however, the study determined that 40% of the total region-wide loss was located solely within the Captiva quadrangle region. When combined with the loss of Pine Island Center, Wulfert, and Sanibel quadrangles, this loss equaled 57% of the total Charlotte Harbor region-wide loss of 29%. The 1945 data exist neither in digital format nor are they reported with comparable geographic boundaries as the 1982 and subsequent coverage data. Also, the quality of the photographs used to obtain the 1945 seagrass coverage was questionable for the purpose of delineating seagrass. The absence of ground-verification during the years the photographs were produced is reason for caution when examining these data. Thus, the 1945 data will be discussed only briefly in the following analyses. FIGURE 15.2 Graphic of transect locations. (Data provided by CHNEP, FDEP, SFWMD, and SWFWMD.) Seagrass Transect Locations in 1999 Lemon Bay Myakka River Peace River Charlotte Harbor Placida Matlacha Pass Pine Island Sound San Carlos Bay 2822_C015.fm Page 235 Monday, November 15, 2004 10:14 AM © 2005 by CRC Press coverages have been converted to hectares (Table 15.1). 1982. The study reported the coverage in acres by USGS quadrangles (Figure 15.3); for this report, the 236 Estuarine Indicators Results of current mapping efforts in Charlotte Harbor from 1982 forward are reported according to water management district geopolitical regions (northern and southern Charlotte Harbor) and also further The first reliable seagrass interpretation work for Charlotte Harbor was created with the 1982 mapping for the Charlotte Harbor region. Apparent from this table is that there exists more data within the northern Charlotte Harbor region than in the southern region, and there exists only two harbor-wide data sets, the 1982 data set does not include seagrass coverage for the Lemon Bay sub-basin, and the data for the Estero Bay sub-basin incorporate data derived from photographs taken in 1990. Thus, for the following comparisons of seagrass extent in Charlotte Harbor, area calculations for the Lemon and Estero Bays sub-basins are not included. Interpretation of the 1982 photographs resulted in harbor-wide total of 23,127 ha of seagrass, excluding Lemon and Estero Bays. Combining both northern and southern Charlotte Harbor mapping efforts in 1999 produced seagrass estimates of 21,802 ha for the entire region, a 6% (1325 ha) decrease in coverage. Combined estimates for the seven sub-basins in Charlotte Harbor under the SWFWMD jurisdiction (Myakka River, Peace River, East Wall, West Wall, Middle Harbor, Placida Region, and South Harbor) demonstrate no trends in seagrass coverage between 1982 and 1999; however, the region does demon- strate interannual variability. Coverage for the seven sub-basins has fluctuated within a variance of less FIGURE 15.3 Graphic of USGS quads used for Harris et al. (1983). (Data provided by CHNEP, USGS, and NOAA.) 2822_C015.fm Page 236 Monday, November 15, 2004 10:14 AM © 2005 by CRC Press segmented into 14 sub-basins (Figure 15.4; Table 15.2). effort. Table 15.3 represents the seagrass coverage data collected to date with comparable methodologies 1982 and 1999. A change analysis by sub-basin of these two data sets is presented in Table 15.4. However, Using Seagrass Coverage as an Indicator of Ecosystem Condition 237 than 1000 ha since 1982. The 1999 extent is 10 ha less than the 1982 value, while the 2002 coverage The five Charlotte Harbor sub-basins within SFWMD jurisdiction (Pine Island Sound, Matlacha Pass, San Carlos Bay, Lower Caloosahatchee River, and Upper Caloosahatchee River) encompass the majority of the seagrass coverage in Charlotte Harbor — almost double that of the northern region in 1999. These five subsegments experienced an 8% (1315 ha) decrease in seagrass from 1982 to 1999. The Matlacha Pass, San Carlos Bay, and lower Caloosahatchee sub-basins alone account for approximately 77% of the overall 6% seagrass acreage decline in the entire Charlotte Harbor region from 1982 to 1999. It is interesting to note that between 1945 and 1982, there was a reported decrease of over 3944 ha in the Pine Island Sound region (approximately the Captiva quadrangle in the 1983 FDNR and FDOT effort), while between 1982 and 1999, the area (Pine Island Sound sub-basin) gained 631 ha in extent. Deep Edge of Seagrass Beds The seagrass transect data are analyzed using roughly the same sub-basin boundaries as the seagrass coverage data, except that there were no fixed transects within the Middle Harbor, Estero Bay, and Caloosahatchee sub-basins from 1999–2001. Also, data for the South Harbor sub-basin are incorporated which seagrass beds grew for each sub-basin in 1999, 2000, and 2001. As a result of the relatively short period of record, these transect data have not been analyzed for statistical significance. Also, observed changes may be within the realm of error due to sampling and/or conversion to tide-normalized values. Accordingly, caution must be used in drawing conclusions from the following analyses. Between 1999 and 2000, the average maximum depth for seagrass beds increased in every sub-basin, except the East Wall of Charlotte Harbor, in which the depth remained constant at 114 cm, and in Pine Island Sound, which experienced a decrease of 8 cm in average maximum depth. From 2000 to 2001 seagrass beds in every sub-basin receded to shallower depths, except in Lemon Bay, which experienced an increase of 3 cm in maximum depth. For the entire 3-year period of 1999 to 2001, seagrass receded in average maximum depth in the majority of sub-basins and increased in depth only in the West Wall, Matlacha Pass, and Lemon Bay sub-basins. These preliminary results indicate that the maximum depths to which seagrass grow within each sub-basin may demonstrate interannual variability. However, further information is needed to determine if these changes are significant or due to sampling and/or conversion errors. TABLE 15.1 Historical Seagrass Extent a (in ha) USGS Quad Name 1945 1982 Change % Change El Jobean 660 362 –299 –45 Punta Gorda SW 2,785 2,331 –454 –16 Placida 1,056 634 –422 –40 Bokeelia 4,919 4,600 –318 –6 Port Boca Grande 155 27 –128 –83 Captiva 8,056 4,112 –3,944 –49 Wulfert 1,112 677 –435 –39 Sanibel 2,143 1,594 –549 –26 Punta Gorda 361 312 –49 –13 Punta Gorda SE 1,718 1,441 –277 –16 Matlacha 2,339 1,999 –340 –15 Pine Island Center 4,639 3,919 –720 –16 Fort Myers Beach 1,451 1,063 –388 –27 Fort Myers SW 593 76 –516 –87 Estero 1,585 523 –1,062 –67 Total 33,572 23,672 –9,900 –29 a Data converted from acreages reported in Harris et al. (1983). Sub-basins repre- sent the reporting units for the northern and southern Charlotte Harbor region. 2822_C015.fm Page 237 Monday, November 15, 2004 10:14 AM © 2005 by CRC Press is 16 ha greater (Figure 15.5). into the Pine Island Sound and Placida sub-basins. Figure 15.6 shows the average maximum depths to 238 Estuarine Indicators FIGURE 15.4 Map of 14 seagrass sub-basins. (Data provided by CHNEP, SFWMD, SWFWMD, and NOAA.) TABLE 15.2 The 14 Sub-Basins Created for Analyses of Seagrass Coverage in the Greater Charlotte Harbor Region SWFWMD Region (northern Charlotte Harbor) SFWMD Region (southern Charlotte Harbor) Lemon Bay Charlotte Harbor: Peace River Pine Island Sound Myakka River Matlacha Pass Charlotte Harbor: San Carlos Bay Middle Harbor Lower Caloosahatchee River West Wall Upper Caloosahatchee River East Wall Estero Bay Placida Region South Harbor South Florida Water Management District Lemon Bay Myakka River Peace River West Wall Middle Harbor East Wall Placida South Harbor Pine Island Sound Matlacha Pass Upper Caloosahatchee Estuary Lower Caloosahatchee Estuary San Carlos Bay Estero Bay Southwest Florida Water Management District 2822_C015.fm Page 238 Monday, November 15, 2004 10:14 AM © 2005 by CRC Press [...]... Bay) 9,853 3, 245 2 ,42 0 0 242 2,5 04* 15,760 Total 25,631 * 10 ,48 4 2 ,45 6 1,5 04 0 1 1,008 14, 445 8,513 7,2 14 8,578 8,805 23,8 54 8 ,43 2 FMRI interpreted Estero Bay from 1990 photographs to fill a void in the 1982 maps TABLE 15 .4 Comparison of 1982 to 1999 Seagrass Coverage (in ha) by Sub-Basin Year 1982 1999 238 378 191 109 47 –269 –20 –71 1, 548 672 70 948 3,513 7,367 1 ,45 2 699 63 1,503 3, 340 7,357 –96 27... Harbor Subtotal (excluding Lemon Bay) 238 378 1,055 202 158 130 166 1,073 189 196 1,0 54 209 225 1, 044 191 109 1, 049 185 137 1, 548 672 70 948 3,513 7,367 1372 585 50 1 ,40 8 3,6 84 7 ,45 8 1,361 49 5 50 1,376 3,636 7,2 14 1 ,41 6 675 60 1,337 3,633 7,505 1,371 7 94 76 1 ,45 0 3,626 7,751 1 ,45 2 699 63 1,503 3, 340 7,357 1 ,45 4 699 64 1,531 3,313 7,383 Charlotte Harbor Pine Island Sound Matlacha Pass San Carlos Bay Upper... 1, 548 672 70 948 3,513 7,367 1 ,45 2 699 63 1,503 3, 340 7,357 –96 27 –7 555 –173 –10 –6 4 –10 59 –5 0 Charlotte Harbor Pine Island Sound Matlacha Pass San Carlos Bay Upper Caloosahatchee River Lower Caloosahatchee River Subtotal 9,853 3, 245 2 ,42 0 0 242 15,760 10 ,48 4 2 ,45 6 1,5 04 0 1 14, 445 631 –789 –916 0 – 241 –1315 6 – 24 –38 0 –100 –8 Total 23,127 21,802 –1325 –6 Subsegment Myakka River Peace River Charlotte... 14 St Johns River Water Management District, Palatka, FL © 2005 by CRC Press 2822_book.fm Page 247 Friday, November 12, 20 04 3:21 PM 16 Mangroves as an Indicator of Estuarine Conditions in Restoration Areas Kathy Worley CONTENTS Introduction 247 What Is a Mangrove? 247 Why Are Mangroves Important Indicators? 248 Die-Offs and Restoration 249 ... Natural Resources Available from Florida Fish and Wildlife Conservation Commission-Florida Marine Research Institute, St Petersburg, FL © 2005 by CRC Press 2822_C015.fm Page 244 Monday, November 15, 20 04 10: 14 AM 244 Estuarine Indicators Janicki Environmental, Inc 2003 Water Quality Data Analysis and Report for the Charlotte Harbor National Estuary Program, August 27, 2003 Available from the Charlotte... wetlands Wetlands Ecology and Management 4( 2):65–72 Twilley, R R 1998 Mangrove wetlands In Southern Forested Wetlands Ecology and Management M G Messina and W H Conner (eds.) CRC Press, Boca Raton, FL, pp 44 5 47 3 © 2005 by CRC Press 2822_book.fm Page 260 Friday, November 12, 20 04 3:21 PM 260 Estuarine Indicators U.S Fish and Wildlife Service 1999 South Florida Multi-Species Recovery Plan U.S Fish and Wildlife... that affect protein expression, and thus is complementary to Q-PCR, subtractive hybridizations, and gene arrays (Denslow et al., in press) Proteomics analysis requires separation of proteins by © 2005 by CRC Press 2822_C017.fm Page 2 64 Monday, November 15, 20 04 10:16 AM 2 64 Estuarine Indicators two-dimensional (2D) gel electrophoresis or ion-exchange chromatography followed by mass spectrometry of tryptic... found in warm humid climates usually between 25N and 25S latitude They exist as low shrubs in harsh conditions and can attain over 40 m in height under favorable conditions They are 247 © 2005 by CRC Press 2822_book.fm Page 248 Friday, November 12, 20 04 3:21 PM 248 Estuarine Indicators viviparous and possess a variety of adaptations that allow them to survive in “nasty” habitats, salty water, and reduced... detritus in association with fungi, bacteria, and protozoa form a large part of the foundation © 2005 by CRC Press 2822_book.fm Page 249 Friday, November 12, 20 04 3:21 PM Mangroves as an Indicator of Estuarine Conditions in Restoration Areas 249 of detritus-based food webs that support nearshore secondary production and primary and secondary estuarine consumers Thus, the condition and viability of mangroves... SPOIL BROADCAST AREA MIDDLE BOARDWALK CUT #4B 20 ft CHANNEL 100 ft LENGTH CLAM PASS CUT #4C 40 ft CHANNEL 1070 ft LENGTH CUT #4D 40 ft CHANNEL 200 ft LENGTH SPOIL AREA IV CLAM PASS GULF OF MEXICO GULF OF MEXICO CUT #3 20 ft CHANNEL 630 ft LENGTH SPOIL AREA I SPOIL AREA III CUT #4A 30 ft CHANNEL 2330 ft LENGTH SPOIL AREA II SOUTH BOARDWALK OUTER CLAM BAY FIGURE 16 .4 Excerpts from local government’s restoration . 8,056 4, 112 –3, 944 49 Wulfert 1,112 677 43 5 –39 Sanibel 2, 143 1,5 94 – 549 –26 Punta Gorda 361 312 49 –13 Punta Gorda SE 1,718 1 ,44 1 –277 –16 Matlacha 2,339 1,999 – 340 –15 Pine Island Center 4, 639. 9,853 10 ,48 4 631 6 Matlacha Pass 3, 245 2 ,45 6 –789 – 24 San Carlos Bay 2 ,42 0 1,5 04 –916 –38 Upper Caloosahatchee River 0 0 0 0 Lower Caloosahatchee River 242 1 – 241 –100 Subtotal 15,760 14, 445 –1315. 1,371 1 ,45 2 1 ,45 4 West Wall 672 585 49 5 675 7 94 699 699 Middle Harbor 70 50 50 60 76 63 64 Placida Region 948 1 ,40 8 1,376 1,337 1 ,45 0 1,503 1,531 South Harbor 3,513 3,6 84 3,636 3,633 3,626 3, 340 3,313 Subtotal