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Status and Trends   175information derived from the photography was subsequentlytransferred by using a zoom transfer scope onto a stable mediumoverlaying USGS 1:24,000-scale quadrangle base maps. Inthose cases in which the data were inadequate or incomplete,contemporary supplemental data were acquired from othersources and used to complete the photographic coverage.The seagrass classification system that was developedconsisted of two classes of open water—RIV (riverine, freshwater) and EST (estuarine or marine open water)—andfive classes of seagrass habitats. One seagrass habitat classdesignated continuous seagrass, CSG, for which no densitydistinction was made, and the other four classes designatedpatchy seagrass based on percent ground cover of patchesin 5% increments: PSG1 (0%–10%, very sparse), PSG2(15%–40%, sparse), PSG3 (45%–70%, moderate), and PSG4(75%–95%, dense). For purposes of this vignette, we reportthe data only as continuous or patchy.The groundtruthing phase included the participation offield staff from Gulf Islands National Seashore, U.S. Fish andWildlife Service, Dauphin Island Sea Lab, Mississippi StateUniversity, Alabama Department of Conservation and NaturalResources, and FDEP. Water conditions during this time werenot optimal (F. Sargent, Florida Marine Research Institute,oral commun.); therefore, the usefulness of the photographywas limited. In addition, because of personnel and resourcelimitations, groundtruthing of this photography was alsolimited. Draft maps were sent out to the aforementionedagencies for review and comments. All comments receivedwere incorporated into the final maps.A more recent effort to map seagrass cover in the SpringsCoast segment was completed in 1999 by the Department ofFisheries and Aquatic Sciences at the University of Floridaunder contract to the Southwest Florida Water ManagementDistrict (SWFWMD) (Frazer and Hale, 2001). Naturalcolor aerial photography at a scale of 1:24,000 was flownin December 1999 and was groundtruthed and scanned intodigital format for analysis by using a combination of imageprocessing and traditional photointerpretation techniques.After adapting the original maps to the results of an accuracyassessment protocol that was conducted by personnel fromSWFWMD and FDEP, the maps were estimated to beapproximately 80% accurate in describing seagrass abundanceand distribution along the Springs Coast.Methodology Employed To AnalyzeHistorical TrendsTo date, there has been no comprehensive study oftrends in seagrass cover over time in the Big Bend region.Current and previous seagrass mapping efforts suffer froma lack of consistency in approach (summarized in Mattson,2000) that makes determination of trends difficult. In additionto the 1992 mapping effort (U.S. Geological Survey, 1992)described above, the only other regionwide mapping surveywas conducted by a private contractor for the MineralsManagement Service (MMS) in 1984. Natural color aerialphotography at a 1:40,000 scale was flown in October andNovember 1984 and interpreted stereoscopically (ContinentalShelf Associates, Inc., and Martel Laboratories, Inc., 1985).Groundtruthing efforts (both by divers and by using remotevideo cameras) concentrated mainly on deepwater areasbecause of the focus of the study and the lack of data ondeepwater seagrass beds (Continental Shelf Associates, Inc.,and Martel Laboratories, Inc., 1985; D. Deis, oral commun.,October 1998). The results of the 1984 survey for MMS andthe later 1992 survey by USGS are not considered comparable,and no trend analysis using these two datasets is conducted inthis report.In an effort to create comparable datasets of seagrassabundance and distribution for the Springs Coast, researchersat the University of Florida reclassified the aerial photographsacquired in 1992 and used the same combination of traditionalphotointerpretation and image processing developed for theaerial photography taken in 1999 (Frazer and Hale, 2001).The product was the first estimate of changes in seagrassabundance and distribution occurring in the 1990s, but aerialphotographic coverage was restricted to the nearshore watersalong the Springs Coast.An additional effort to assess historical changes wasrecently conducted by the University of Florida, SWFWMDand the Florida Marine Research Institute (FMRI) in 2000.This project was an attempt to locate and revisit sites assessedby Iverson and Bittaker in the late 1970s in their Floridaseagrass study (Iverson and Bittaker, 1986). This effortincluded much of the northern Big Bend Proper, as well asthe Springs Coast. The effort was hampered by the lack ofaccurate geographic reference coordinates on the sites visitedby the earlier investigators. The sites were located as bestas possible, and latitude/longitude was obtained by using ahandheld Global Positioning System unit. Upon location of asite, the revisit entailed qualitative inspections of the bottomto assess seagrass species present for comparison with the pasteffort. Acquisition of coordinates on these sites now permitsrevisits to be made reliably in future years. The main goalof this revisit was to see if broad-scale changes in seagrassspecies composition or distribution had occurred over the past25 yr by comparing the species of seagrass seen historically ata site with those observed at the time of the study. The mainlimitation of this effort was that it could not be assured that theexact sites visited by Iverson and Bittaker in the 1970s werebeing revisited in 1999.Status and TrendsThree regionwide mapping studies of seagrass coveragewere conducted in the last two decades of the 20th century(Continental Shelf Associates and Martel Laboratories, 1985;U.S. Geological Survey, 1992; Sargent and others, 1995).

176   Seagrass Status and Trends in the Northern Gulf of Mexico: 1940–2002Table 1. Estimates of seagrass cover in the Big Bend region.[Area is given in hectares (acres)]ContinuousCoverPatchyCoverTotalMinerals Management Service (1984)Big Bend 28)Springs 85,642)U.S. Geological Survey (1992)Big Bend ProperSprings da Marine Research Institute (1995)Big Bend Proper1181,000(447,251)Springs ity of Florida (2001)39,714(98,133)281,742(201,985)3Springs Coast199946,545(115,013)292,028(227,401)31For this study, Big Bend Proper was defined as the five counties fromApalachicola River to the Withlacoochee River. Springs Coast was thethree counties from Withlacoochee River to the Anclote River.Interpreted as 25% cover/m2.3Represents total area surveyed.Regionwide Mapping StudiesMinerals Management ServiceThe MMS effort in 1984 (Continental Shelf Associatesand Martel Laboratories, 1985) mapped 520,292 ha (1,285,642acres) of seagrass habitat (fig. 3; table 1) in the Big Bendregion. Differences in the scale and quality of the photographyused and the focus of this earlier effort on offshore seagrassresources mean that the 1984 data cannot be directly comparedto subsequent mapping data; therefore caution should be usedin comparing figures 3 and 4 and the data in table 1. It shouldbe noted that the MMS effort in 1984 is the only attempt todate to map the extent of the offshore, deepwater seagrass bedsof the Big Bend.USGSSprings Coast19922The results of these studies as well as a subregional mappingstudy conducted by the University of Florida in 2001 areshown in table 1. In spite of different project goals, methods,and scales of source data, estimates of seagrass abundancefor the region have generally arrived at the same basic area ofseagrass coverage. The MMS mapping project (ContinentalShelf Associates and Martel Laboratories, 1985) used aerialphotographs and underwater video transects to sample depthsto 20 m (66 ft). The USGS (1992) and Sargent and others(1995) collected and interpreted aerial photographs of theregion. All of these projects estimated seagrass coveragealong the Big Bend as roughly 300,000 ha (741,300 acres).A few subregional mapping studies of smaller extent havebeen conducted; however, their study areas were confined tonearshore areas, e.g., within 3 km (2 mi) of shore (McNultyand others, 1972), or did not cover the entire region (e.g.,Livingston, 1993, covered only Apalachee Bay).The 1992 seagrass mapping study by the USGS yieldedan estimate of 250,487 ha (618,953 acres) of total seagrasscover in the entire Big Bend region (fig. 4; table 1). Thisestimate somewhat corresponds with Iverson and Bittaker’s(1986) estimate of 300,000 ha (741,300 acres) and less so withthe FMRI 1995 estimate (Sargent and others, 1995) of 335,000ha (827,785 acres). Of the total acreage mapped in 1992,23% was mapped as continuous seagrass cover, and 77% waspatchy cover. Of this total Big Bend seagrass cover reported in1992, more than half (57%) occurred in the southern portionof the region, the Springs Coast; the remainder (43%) was inBig Bend Proper.Florida Marine Research InstituteThis effort by Sargent and others (1995) mapped 335,000ha (827,785 acres) of seagrass habitat (fig. 4; table 1). Sources

Status and Trends   177of photography varied depending upon which area of the Statethe study was in. It appears that the photography they usedfrom the Big Bend region was the 1992 USGS photography,which they remapped. This study observed an opposite trendin seagrass cover between the two major segments than did theUSGS study: the majority of the seagrass mapped (54%) wasin the Big Bend Proper, with less (46%) in the Springs Coast.Table 2. Records of seagrass species occurrence made byIverson and Bittaker (1986) and later by researchers at theUniversity of Florida, Southwest Florida Water ManagementDistrict, and Florida Marine Research Institue in 2000 (unpublisheddata). The number of sites at which a species was observed ineach geographic subregion for each sampling period is listed.1974–80Other Subregional Mapping StudiesSprings CoastThe mapping study conducted by the University ofFlorida in 1999 and 2000 (Frazer and Hale, 2001) identified92,028 ha (227,401 acres) in 1999. Comparing their estimateto the 81,742 ha (201,985 acres) found in 1992 (U.S.Geological Survey, 1992), their study suggested an increasein seagrass coverage in this subarea. The analysis of change(Frazer and Hale, 2001) in seagrass abundance and distributionalong the Springs Coast produced several interesting results.The area in which seagrass density increased was twice thearea in which seagrass density decreased. Seagrasses in theSt. Martins Keys and the Homosassa River estuarine areasappear to have increased in coverage; however, some declinesin coverage appear to have occurred near the mouth of CrystalRiver and in the Anclote Key and Tarpon Springs region.Apalachee BayA subregional study not listed in table 1 was conductedin the region of the Fenholloway River estuary. Livingston(1993) compared seagrass cover off the Fenholloway River,which was affected by highly colored wastewater from a pulpmill discharge upstream, with cover in adjacent, unimpacteddrainages (Econfina River, Aucilla River, Spring WarriorCreek). From this comparison, he estimated that about 2,330ha (5,757 acres) of historical seagrass coverage had been lostsince 1954 (when the mill began operation) as a consequenceof light reductions from the mill’s wastewater (Livingston,1993; Livingston and others, 1998).The resurvey of the sites sampled by Iverson andBittaker (1986) in the 1970s suggests that changes in speciescomposition may have occurred over the past 25 yr (Haleand others, 2004). Although some seagrasses were observedat more sites in the 1999 survey than in the earlier survey(table 2), the distribution of particular species seems to havechanged. Turtle grass (Thalassia testudinum) decreasedin occurrence from deeper areas of the region, while otherspecies seem to have disappeared from areas near the mouthsof several coastal rivers. In addition, some species which wererecorded during the Iverson and Bittaker (1986) survey werenot observed at all during the recent survey (Hale andothers, 2004).2000Big Bend ProperTurtle grass(Thalassia testudinum)1715Manatee grass(Syringodium filiforme)1818Shoal grass(Halodule wrightii)1623Star grass(Halophila engelmannii)144Springs CoastTurtle grass(Thalassia testudinum)4639Manatee grass(Syringodium filiforme)2533Shoal grass(Halodule wrightii)2730Star grass(Halophila engelmannii)97

178   Seagrass Status and Trends in the Northern Gulf of Mexico: 1940–2002LandSeagrass, continuousSeagrass, patchyWaterGulf of MexicoNkm 0mi 010520103015204025Figure 3. Distribution of seagrasses in the Florida Big Bend region, 1984.

Status and Trends   179LandSeagrass, continuousSeagrass, patchyWaterGulf of MexicoNkm 0mi 010520103015204025Figure 4. Distribution of seagrasses in the Florida Big Bend region, 1992.

180   Seagrass Status and Trends in the Northern Gulf of Mexico: 1940–2002Although several seagrass mapping projects havebeen conducted in the Big Bend region over the past 20–25yr, differences in the actual area mapped, methodology,and quality of base data quality make trend analyses andcomparisons impossible. There are anecdotal accounts ofchanges in seagrass cover in portions of the region; thisanecdotal evidence suggests that there should be future effortsto conduct trend analyses. Moore (1963) and Grinnel (1971)both provided credible observations which suggest thatinshore areas off the Suwannee River that are now unvegetatedwere historically vegetated with seagrasses. In a study inWaccasassa Bay in the early 1960s, Putnam (1967) indicatedthat seagrass cover may have been more extensive historicallythan is currently seen in this estuary.Causes of ChangeAs noted previously, documented trends in seagrass coveralong the Big Bend are lacking. Consequently, the causes ofchange cannot be discussed in great detail at this time. Twomajor issues of concern, however, can be identified as possiblyhaving an effect on seagrass resources in the Big Bend region.Hydrologic Alteration of WatershedsInvestigations in the Steinhatchee River subbasin havesuggested that historical drainage activities associated withcommercial forestry may have affected river flow regimes(KBN Engineering and Applied Sciences, 1990). The maineffect of this alteration was shown to be an increase in riverpeak flows during wet seasons (KBN Engineering and AppliedSciences, 1990). Drainage activities were mainly conductedin headwater wetland areas, such as San Pedro Bay (TaylorCounty) and Mallory Swamp (Lafayette and Dixie Counties),and involved increased flow of highly colored surface-waterrunoff into the estuary of the river, with possible effectson seagrass communities. Therefore, it is possible that thechanges in flow regimes in the Steinhatchee River subbasinhave resulted in increased organic load to the river andnearshore coastal area with a concomitant increase in colorand a resultant decrease in light available to seagrasses inthe area.In a nearshore area adjacent to the Fenholloway River,Livingston and others (1998) found that higher color as aresult of industrial discharges was associated with changesin the absolute quantity and quality of light penetrating thewater column and that these changes had measurable negativeeffects on seagrass biology and community characteristics.These findings suggested that there are similar effectsfrom hydrologic alteration in these coastal watersheds (i.e.,increased discharge of highly colored runoff, with resultingnegative effects on seagrasses because of changes in waterclarity). They also suggested that forestry practices havethe potential to cause changes in estuaries and nearshoreareas along the Big Bend and merit the attention of seagrassecologists and water resource managers. Unfortunately, thereare few historical data that can be used to determine whetheror not changes in water clarity or seagrass cover as a result offorestry-related activities have occurred in the Steinhatcheeestuary (or other watersheds where forestry activities inthe headwater wetland areas may have resulted in similaralterations of flow regimes and chemical characteristics, e.g.,the Suwannee and Waccasassa Rivers). Currently, many of theheadwater wetland areas are being purchased by governmentagencies outright, or conservation easements are beingacquired, and efforts are underway to restore more natural,historical drainage patterns and river flow regimes.Nutrient Enrichment of Estuaries and NearshoreCoastal WatersBecause of the karst geology of the land which drains tothe Big Bend coastal waters, many regions are moderately tohighly prone to groundwater contamination (Katz and others,1997; Hornsby and Ceryak, 1999). Land-use activities canrapidly and profoundly affect water quality in the underlyingFloridan aquifer system (Katz and others, 1997). Elevatedlevels of nitrate-nitrogen have been found in portions of theFloridan aquifer throughout the Big Bend (Jones and others1997, 1998; Hornsby and Ceryak, 1999) and have manifestedas increasing levels of nitrate-nitrogen in some river systems(Ham and Hatzell, 1996) and in the individual springs whichfeed the rivers (Jones and others, 1997, 1998; Hornsby andothers, 2000). Nitrogen sources include agricultural landuses, fertilizer from golf courses, and urban development(residential and commercial).Increased nutrient concentrations in the coastal riversystems and subsequent nutrient delivery to the Gulf ofMexico have led to concerns about algal blooms affectinglight penetration to seagrasses. Phytoplankton blooms inthe water column, increased epiphyte loads on seagrassblades, or macroalgal blooms covering seagrass beds all mayproduce undesirable effects on seagrass cover and communitycharacteristics. Increased water column nitrogen has beenshown to affect phytoplankton production and standing cropin the Suwannee estuary (Bledsoe and Phlips, 2000; Phlipsand Bledsoe, 2002), and increased nitrate-nitrite concentrationappears to be associated with higher periphyton standing cropsin the Suwannee River and tributaries (Hornsby and others,2000). In contrast, algal production along much of the Sp

Gulf of Mexico. Big Bend Watershed boundary City Interstate highway River Gulf Intracoastal Waterway County line . N km 0 20 40 60 . 80 mi 0 10 20 30 40 50 . R i v e r o c k o n e e O c h A n c l o t e R i v e r. Figure 1. Watershed for the Florida Big Bend region. 172 Seagrass Status and Trends in the Northern Gulf of Mexico: 1940-2002