Restoration of Aquatic Systems - Chapter 3 potx

55 chapter 3 Industrial Pollution: Pulp Mills The manufacture of pulp and paper represents a major industry in the southern United States. Because of the high volume of the effluent from pulp mills (20 to 50 million gallons per day) and the discharge of various agents that have an impact on water and sediment quality, the paper industry represents a formidable challenge in terms of restoration. The discharge of various components leads to varying levels of impacts, depending on the level of treatment and the assimilative capacity of the receiving system. These factors include high concentrations of total dissolved solids (mainly sodium, chloride, and sulfide) that contribute to the high specific conductance of the effluent. Conductivity contributes to the elimination of primary freshwater species due to osmotic imbalances. Enhanced loading of dissolved organic carbon (DOC) increases Biochemical Oxygen Demand (BOD) in the receiving areas that, in turn, causes hypoxic and even anoxic conditions. Various organic compounds that include tannins, lignins, and fulvates are components of the DOC. These compounds also contribute to the high levels of color in pulp effluents that, in turn, adversely affect light penetration in receiving water bodies. Pulp effluents contain high levels of nutrients (mainly ammonia and orthophosphate) that contribute to adverse impacts on microphyte and macrophyte assemblages in receiv- ing areas. Toxic agents in pulp effluents include ammonia, certain metals, and chlorinated compounds (that can include dioxin). Various methods are available to mitigate many of the toxic components of pulp effluents. Publications of the impacts of pulp effluents in the study areas are available (Livingston, 1975a, 1980a, 1981, 1982a, 1984a, 1985a,b, 1987a,b, 1993b, 1997a, 1999b, 2000, 2002; Livingston et al., 1998a). 3.1 Study Area The Gulf coastal zone of north Florida extends from the alluvial Perdido River–Bay system in eastern Alabama and the western Florida Panhandle to the black water rivers of have been part of the long-term studies of our research group (Livingston, 2000, 2002). The panhandle landscape is the result of stream and river flows and wave action that has acted on the land surface over the past 10 to 15 million years. Beach ridges, spits, cliffs, barrier islands, swales, sloughs, dunes, lagoons, and estuaries along a relatively flat upland configuration characterize the northeast Gulf region. Western bay systems are associated with alluvial rivers having relatively restricted coastal plain areas. The Apalachicola and Apalachee Bay basins (Figure 3.1) are part of broad coastal plains that include extensive marsh areas. Barrier islands start in Apalachicola Bay, extending west to the Pensacola and Perdido Bay systems. On the eastern end of the Panhandle coast (Apalachee Bay), there is no barrier island development, and coastal swamps and marshlands dominate 1966_book.fm Page 55 Friday, June 3, 2005 9:20 AM © 2006 by Taylor & Francis Group, LLC Apalachee Bay in the Big Bend area (Figure 3.1A). The drainage systems in this region 56 Restoration of Aquatic Systems the coast. This area is characterized by shallow, sloping margins, the lack of wave action, and an inadequate supply of sand (Tanner, 1960) for barrier island development. Upland watersheds for coastal regions of the northeast Gulf are located in Alabama, Florida, and Georgia, in an area approximating 135,000 km 2 (Figure 3.1a). Associated estuarine/coastal systems are characterized by habitats that are mainly controlled by the upland freshwater drainage basins. Intersecting habitats of the coastal zone include salt- water marshes, sandy beaches, tidal creeks, intertidal flats, oyster reefs, seagrass beds, sub-tidal unvegetated soft bottoms, and various transitional areas. The salinity regimes of these areas are variously affected by major river systems or, as is the case in Apalachee Bay, by a series of small rivers and groundwater flows. Nine of the twelve major rivers and five of the seven major tributaries of Florida occur in this region. The major alluvial rivers of the northwest Florida Panhandle (Perdido, Escambia, Choctawhatchee, Apalach- icola) have their headwaters in Georgia and Alabama (Figure 3.1a). A series of smaller streams along the panhandle coast include the Blackwater and Yellow Rivers of the Pensacola Bay system, the Chipola River (part of the Apalachicola drainage), and the Ochlockonee River on Apalachee Bay. Farther down the coast, a series of small streams (St. Marks, Aucilla, Econfina, and Fenholloway) with drainage basins in Florida, flow into Apalachee Bay. The Florida Panhandle has a range of human populations from low densities in the and Apalachee Bay drainage basins are among the least populated coastal areas in the United States. Coastal urban areas include Pensacola (Escambia Bay–Pensacola Bay), Figure 3.1a The Florida Panhandle, showing the primary river basins and distribution of associated river–estuaries and coastal systems. This figure is a composite of information provided by the National Oceanic and Atmospheric Administration, the Florida Department of Environmental Pro- tection, and the ESRI Corporation. Elevenmile Creek Perdido River Perdido Bay Escambia River Escambia Bay Blackwater River Yellow River Choctawhatchee River Apalachicola River Econfina River Fenholloway River Apalachee Bay Apalachicola Bay Choctawhatchee Bay Blackwater Bay Gulf of Mexico N 100 0 100 Kilometers Alabama Georgia Florida Northeast Gulf of Mexico (a) 1966_book.fm Page 56 Friday, June 3, 2005 9:20 AM © 2006 by Taylor & Francis Group, LLC eastern drainages to the more populous areas to the west (Figure 3.1b). The Apalachicola Chapter 3: Industrial Pollution: Pulp Mills 57 FIGURE 3.1b Population density in the Northwest Florida area of study. This figure is a composite of information provided by the National Oceanic and Atmospheric Administration (NOAA), the Florida Department of Environmental Pr otection (FDEP), and the ESRI Corporation. Elevenmile Creek Perdido River Escambia River Blackwater River Yellow River Choctawhatchee River Apalachicola River Econfina River Fenholloway River Apalachicola N 100 0 100 Kilometers Ft. Walton Beach Destin Niceville Blountstown Tallahassee Perry Panama City Pensacola Population density (number of people per square mile) 0–100 100–200 200–400 400–800 800–1600 1600–3200 >3200 (Data not included) Milton (b) 1966_book.fm Page 57 Friday, June 3, 2005 9:20 AM © 2006 by Taylor & Francis Group, LLC 58 Restoration of Aquatic Systems FIGURE 3.1c Distribution of point sources of discharges to coastal waters in the northwest Florida study area. This figur e is a composite of information provided by the National Oceanic and Atmospheric Administration (NOAA), the Florida Department of Environmental Protection (FDEP), and the ESRI Corporation. Elevenmile Creek Pensacola Escambia River Blackwater River Yellow River Choctawhatchee River Apalachicola River Econfina River Fenholloway River Apalachicola N 100 0 100 Kilometers Ft. Walton Beach Destin Niceville Blountstown Tallahassee Panama City Milton Point Sources of Pollution Hazardous materials sites, 1997 Sewage treatment facilities NPDES permit sites (data not included) (c) Perry Perdido River 1966_book.fm Page 58 Friday, June 3, 2005 9:20 AM © 2006 by Taylor & Francis Group, LLC Chapter 3: Industrial Pollution: Pulp Mills 59 Destin/Fort Walton Beach/Niceville (western Choctawhatchee Bay), and Panama City The distribution of sewage treatment facilities, hazardous waste sites, and NPDES permit sites follows closely the distribution of human populations along the northeast system include a pulp mill in the upper bay, and agricultural and urban runoff in the lower bay. The highest concentration of point and non-point sources of pollution occurs in the Pensacola Bay system. In recent years, there have been major increases in urban storm water runoff in western Choctawhatchee Bay. Apalachicola Bay and Apalachee Bay remain relatively free of such discharges, and are among the least polluted coastal systems in the conterminous United States. In the Apalachicola system, the single most important pollution source is a sewage treatment plant in Apalachicola that discharges into a creek north of the city. In Apalachee Bay, the primary source of pollution is a pulp mill on the Fenholloway River, with discharges near the inland city of Perry, Florida. There are significant differences in the development of emergent and submergent vegetation in the subject coastal systems of the northeast Gulf. Perdido Bay and the Pensacola system have moderate concentrations of marshes, whereas the Choctawhatchee system is practically devoid of emergent vegetation (EV). The Apalachicola and Apalachee Bay systems have extensive and well-developed marsh systems. The big alluvial river- bay systems have limited development of submerged aquatic vegetation (SAV), whereas Apalachee Bay is characterized by one of the highest concentrations of seagrass beds in the Northern Hemisphere. The Econfina and Fenholloway estuaries are distinguished from the alluvial river–bay systems to the west by the relatively low flow/watershed and flow/open water ratios, and by the well-developed marsh areas relative to the flow rates of the contributing rivers to Apalachee Bay. The shallowness of Apalachee Bay, together with the relatively low freshwater flows and considerable development of fringing coastal wetlands, contribute to the seagrass beds as the dominant offshore habitat along the Big Bend area of north Florida. of the active Gulf Coast geosyncline, and is a shallow to moderately deep (average depth; 2.2 m) inshore water body oriented along a northeast–southwest axis. A study outline is (1) lower Perdido River, (2) upper Perdido Bay (north of the Route 98 bridge), (3) lower Perdido Bay, and (4) the Perdido Pass complex. The bay system has a length of 53.4 km and an average width of 4.2 km. The primary source of freshwater input to the estuary is the Perdido River system that flows southward about 96.5 km, draining an area of about 2937 km 2 (Livingston, 1998b, 2000, 2002). The Elevenmile Creek system (including Elev- enmile Creek; Figure 3.2) is a small drainage basin (about 70 km 2 ) that receives input from a small municipal waste system and a paper mill. The Bayou Marcus Creek drains a residential area of western Pensacola with input from urban storm water runoff. A sewage treatment plant (STP) (recently diverted to adjoining marshes) occupies the area north of the Bayou Marcus Creek. The Gulf Intracoastal Waterway (GIWW) runs through the lower end of Perdido Bay about 5.6 km northeast of Perdido Pass. The U.S. Army Corps of Engineers maintains the Perdido Pass channel at about 4 m as part of the GIWW (U.S. Army Corps of Engineers, 1976). As in the Choctawhatchee Bay system, there is a shelf that can extend up to 400 m in width around the periphery of the Perdido estuary. This shelf usually does not exceed 1 m in depth. The upper bay is shallow, and depth tends to increase southward. The deepest parts of the estuary are located at the mouth of the Perdido River and in the lower bay. Prior to the opening of Perdido Pass in the early 1900s, Perdido Bay was a largely freshwater system, covered with freshwater plants (Brush, 1991). Access to the Gulf was 1966_book.fm Page 59 Friday, June 3, 2005 9:20 AM © 2006 by Taylor & Francis Group, LLC (St. Andrews Bay) (Figure 3.1b). Gulf coast (Figure 3.1c). Outstanding sources of pollution loading in the Perdido Bay The Perdido Bay system (Figure 3.2) lies in an area of submergence on the north flank given in Appendix I. The bay can be divided into four distinct geographic regions: 60 Restoration of Aquatic Systems Figure 3.2 Perdido drainage systems and near-shore parts of the Gulf of Mexico with distributions of permanent sampling stations used in the long-term studies of the area. The Florida Geographic Data Library (FGDL) pr ovided geographic data. N S WE Agricultural Runoff Wolf Bay U.S. 98 Bridge Perdido Bay ECUA STP Mill Outfall Perdido Key Perdido Pass Ono Island Urban Runoff 46 47 45 48 43 44 40 41 42 42A 42C 42B 37 SC1 SC2 33 31 29 25 26 23 22 21 18 09 Perdido River Elevenmile Creek GULF OF MEXICO 1966_book.fm Page 60 Friday, June 3, 2005 9:20 AM © 2006 by Taylor & Francis Group, LLC Chapter 3: Industrial Pollution: Pulp Mills 61 restricted by the shallow, shifting body of freshwater. At the time of an early survey (1767), the pass had a depth of approximately 2 m. During an outbreak of malaria in the early 1900s, the mouth of the bay was opened to the Gulf. This transformed the bay into the saltwater system it is today. This action resulted in the creation of the Ono Island/Old River complex. The history of Perdido Bay is thus comparable to that of the Choc- tawhatchee Bay system (Livingston, 1986a,b, 1989b) that was also opened at the mouth by another group of citizens with shovels in 1929. Since the turn of the century, there has been a steady increase in the human population in the Perdido basin. Problems of sewage treatment and urban storm water runoff remain unresolved in various residential areas around the bay to the present day. Agricultural runoff, based largely in Alabama, contrib- Detailed, long-term analyses of the Perdido drainage system have been carried out for the past 16 years (Livingston, 1992b, 1994, 1995d, 1997b, 1998b, 2000, 2002; Livingston et al., 1998a) that include long-term, bay-wide synoptic analyses at fixed stations (Figure 3.2). According to a U.S. Fish and Wildlife Service Report (1990), SAV was largely concentrated in the lower bay. Historically, SAV has decreased by more than half from 1940–1941 to 1979. Dredging of the Gulf Intracoastal Waterway (GIWW) in the 1930s and continuous pass enlargement and open water spoil disposal have been postulated as factors in the decline of SAV in the lower bay (Bortone, 1991). SAV development has been restricted to the dominant species. Field/laboratory experiments (Livingston, 1992b) indicated light as the chief limiting factor with grass development not extending deeper than 0.8 to 1.0 m. Based on the success of previous grass bed transplant experiments, Davis et al. (1999) concluded that V. americana beds in upper Perdido Bay were recruitment-limited rather than constrained by water quality, toxic substances, light inhibition, or unsuitable sub- strate. The Perdido Bay system has been adversely affected by pulp mill effluents and overloads from the sewage treatment plant in the upper bay, the dredged opening to the Gulf, and urbanization, and agricultural runoff in the lower bay. The region along the upper Gulf coast of peninsular Florida from the Ochlockonee River to the Suwannee River has a series of drainage basins that include the Aucilla, which occupies a broad, shallow shelf along the Gulf coast. The smaller basins are wholly within the coastal plain as part of a poorly drained region that is composed of springs, lakes, ponds, freshwater swamps, and coastal marshes. The Econfina and Fenholloway river estuaries both originate in the San Pedro Swamp (Figure 3.3). A study outline is long-term physical modifications through forestry activities. However, most of Apalachee Bay remains in a relatively natural state due to the almost complete lack of human development in the primary drainage basins. The dominant habitat feature of Apalachee Bay is an extensive series of seagrass beds that extends from Florida Bay in the south to Ochlockonee Bay in the north (Iverson and Bittaker, 1986). The one area of significant anthropogenous effect in an otherwise pristine system is the Fenholloway River estuary where pulp mill discharges have caused adverse effects due to high DOC and water color, high BOD, low dissolved oxygen (DO), and high nutrient loading (ammonia and orthophosphate) (Livingston 1980a, 1982a, 1985a,b, 1988a; Livingston et al., 1998b). The Econfina River remains one of the most natural black water streams along the coast, and has been used as a reference area for studies in the Fenholloway mon meteorological regime. River flow characteristics in the two drainages are comparable in rate and seasonal variation. 1966_book.fm Page 61 Friday, June 3, 2005 9:20 AM © 2006 by Taylor & Francis Group, LLC utes to nutrient loading in Wolf Bay at the lower end of the basin (Figure 3.2). Grassy Point on the west side of the upper bay (Figure 3.4) with Vallisneria americana as Econfina, and Fenholloway Rivers (Figure 3.3). These streams drain into Apalachee Bay, system since 1971. Both the Econfina and Fenholloway drainages (Figure 3.5) share a com- given in Appendix I. This basin has been affected, in terms of water flow characteristics, by 62 Restoration of Aquatic Systems Figure 3.3 Econfina-Fenholloway drainage systems and near-shore parts of the Gulf of Mexico with distributions of permanent sampling stations used in the long-term studies of the area. The Florida Geographic Data Library (FGDL) provided geographic data. E12 E09 E26 E25 E10 E08 E13 T21 T17 T19 T22 T23 T20 F12 F11 P25 P26 P14 P15 P16 E11 N S EW GULF OF MEXICO Mill Outfall 1966_book.fm Page 62 Friday, June 3, 2005 9:20 AM © 2006 by Taylor & Francis Group, LLC Chapter 3: Industrial Pollution: Pulp Mills 63 Figure 3.4 River flows of the Econfina and Fenholloway Rivers and Elevenmile Creek (monthly, January 1990–December 1991). Figure 3.5 Ammonia loading in the Econfina and Fenholloway Rivers and Elevenmile Creek (monthly, January–December 1999).† 1 10 100 Jan Feb March April May June July Aug Sept Oct Nov Dec Jan Feb March April May June July Aug Sept Oct Nov Dec month 11-mile Creek-90/01 Econ. Riv 90/91 Fen. Riv 90/91 1 10 100 1000 10000 Jan Feb March April May June July Aug Sept Oct Nov Dec month Econ. NH 3 load-99 Fen. NH 3 load-99 11-Mile NH 3 load-99 1966_book.fm Page 63 Friday, June 3, 2005 9:20 AM © 2006 by Taylor & Francis Group, LLC 64 Restoration of Aquatic Systems Comparative analyses were conducted of various features of the rivers affected by kraft pulp mills (Fenholloway River, Elevenmile Creek) and the reference blackwater stream, the Econfina River. Methods used for the comparison of monthly data (river flows, nutrient loading, water quality) were developed to determine significant differences between matching Amelia and Nassau sites (polluted and unpolluted) over the 12-month study periods (Livingston, 2001a). A detailed explanation of the statistics used is given in the parametric t -test was used to compare the sample means. For cases where one or both of the data sets violated the assumption of normality, a data transformation was made to bring the data into normality. Tests were also developed to compare two serially correlated populations of numbers taken at subject stations by calculating differences of the obser- vations and plotting the autocorrelations (months) of the differences. If differences were not serially correlated, we applied the Wilcoxon sign-rank test to compare (0.05 confidence level) the two sets of numbers. 3.2 River Flows, Nutrient Loading, and Water Quality Changes (P < 0.05) higher than that in the Econfina River. Ammonia loading was higher in the Fenholloway River than that in Elevenmile Creek. In both streams affected by pulp mill effluents, ammonia loading was generally high throughout the season, whereas loading in the reference stream generally followed seasonal changes in river flow. Orthophosphate loading (Figure 3.6) was also significantly (P < 0.05) higher in the rivers affected by pulp effluents compared to the Econfina system. However, such loading was significantly Figure 3.6 Orthophosphate loading in the Econfina and Fenholloway Rivers and Elevenmile Creek (monthly, January–December 1999). 1 10 100 1000 Jan Feb March April May June July Aug Sept Oct Nov Dec month Econ. PO4 load-99 Fen. PO4 load-99 11-Mile PO4 load-99 1966_book.fm Page 64 Friday, June 3, 2005 9:20 AM © 2006 by Taylor & Francis Group, LLC River flow rates of the three rivers were comparable (Figure 3.4). However, ammonia loading in the Fenholloway River and Elevenmile Creek (Figure 3.5) were significantly Appendix II. For independent, random samples from normally distributed populations, [...]... 92/08 92/09 92/10 92/11 92/12 93/ 01 93/ 02 93/ 03 0 19 7 5 0 9 7 2 2 0 3 2 1 0 5 2 1 1 0 6 0 0 0 1 2 2 2 0 31 .5 0 0 0 11.1 28.5 100 100 0 0 50 31 .5 17.6 77.7 33 .3 44.4 50 100 0 40.1 F 03 F 03 F 03 F 03 F 03 F 03 F 03 F 03 F 03 F 03 F 03 92/04 92/05 92/06 92/08 92/09 92/10 92/11 92/12 93/ 01 93/ 02 93/ 03 Average nd 2 4 0 1 nd 12 31 32 nd nd 8.2 nd 2 1 0 1 nd 1 1 6 nd nd 1.5 nd 0 4 0 1 nd 12 31 25 nd nd 6.1 nd 0 100 0... 100 nd 8 2 133 24 89.8 88.8 F02 F02 92/04 92/05 7 0 1 0 7 0 100 0 Restoration of Aquatic Systems Station 1966_book.fm Page 70 Friday, June 3, 2005 9:20 AM 70 Table 3. 1 Fishes Taken in the Econfina and Fenholloway Rivers (monthly from 1992 to 19 93) 0 4 4 38 17 9 9 9 10 8 1 37 .9 2 8 5 3 3 3 3 6 4 0 1 3 5 3 3 4 3 4 1 1 2.9 68 54 2 30 13 1 5 67 124 0 0 2 12 3 7 3 4 5 8 0 20.8 97.1 30 .6 6.4 83. 3 76.4 16.6... 2002/10 20 03/ 02 20 03/ 06 20 03/ 10 2004/02 2004/06 1966_book.fm Page 76 Friday, June 3, 2005 9:20 AM 76 Restoration of Aquatic Systems 100 Inftaxa-22 © 2006 by Taylor & Francis Group, LLC Inftaxa- 23 10 1 0.1 year/month Figure 3. 14 Species richness of infaunal macroinvertebrates at Stations P22 and P 23 taken monthly over the study period 1966_book.fm Page 77 Friday, June 3, 2005 9:20 AM Chapter 3: Industrial... 15 229 36 nd 11 21 26 11 nd 15 82 0 56 nd 5 46 36 7 32 10 3 41 nd 1 nd 6 10 3 nd 2 4 6 2 nd 3 7 0 4 nd 2 5 8 2 3 3 3 4 nd 1 nd 74/01 74/02 74/ 03 74/04 74/05 74/06 74/07 74/08 74/09 74/10 74/11 74/12 75/01 75/02 75/ 03 75/04 75/05 75/06 75/07 75/08 75/09 75/10 75/11 75/12 76/01 0 0 1 5 8 8 0 6 4 11 3 6 nd nd nd 1 21 5 4 4 nd 4 1 2 0 0 0 1 3 2 1 0 3 2 1 2 4 nd nd nd 1 6 2 2 3 nd 2 1 2 0 6 6 5 3 nd 4 2... F01D F01D 92/09 92/10 93/ 02 92/08 92/11 92/12 93/ 02 0 1 0 nd nd nd nd 0 1 0 nd nd nd nd 0 1 0 nd nd nd nd 0 100 0 nd nd nd nd 0 1 0 2 2 0 0 0 1 2 4 0 1 0 2 1 0 0 0 0 48 0 0 100 0 15 .3 50 0 0 0 0 97.9 0 F01F F01F F01F F01F F01F F01F F01F F01F F01F F01F F01F 92/04 92/05 92/06 92/08 92/09 92/10 92/11 92/12 93/ 01 93/ 02 93/ 03 0 24 38 6 2 7 3 3 25 22 nd 0 3 3 3 1 3 1 1 4 1 nd 0 19 36 4 0 5 0 0 22 22 nd 0... 1966_book.fm Page 66 Friday, June 3, 2005 9:20 AM 66 Restoration of Aquatic Systems Econ Cond-99 Fen Cond-99 11-Mile Cond .-9 9 2501 2001 1501 1001 Dec Nov Oct Sept Aug July June May April March Feb 1 Jan 501 month Figure 3. 8 Specific conductance in the Econfina and Fenholloway Rivers and Elevenmile Creek (monthly, January–December 1999) Econ Color-99 Fen Color-99 11-Mile Color-99 1401 1201 1001 801 601 401... Industrial Pollution: Pulp Mills Date Note: nd = no data 73 © 2006 by Taylor & Francis Group, LLC 1966_book.fm Page 73 Friday, June 3, 2005 9:20 AM Chapter 3: Table 3. 2 Fishes Taken in the Econfina and Fenholloway Saltwater Marshes (monthly from 1974 to 1976) 1966_book.fm Page 74 Friday, June 3, 2005 9:20 AM 74 Restoration of Aquatic Systems MERTENn-22 MERTENn- 23 1000000000 100000000 10000000 1000000 100000 10000... 100 100 78.1 nd nd 43. 9 Note: nd = no data 71 © 2006 by Taylor & Francis Group, LLC 1966_book.fm Page 71 Friday, June 3, 2005 9:20 AM 92/04 92/05 92/06 92/08 92/09 92/10 92/11 92/12 93/ 01 93/ 02 93/ 03 Average 70 176 31 36 17 6 7 74 127 Industrial Pollution: Pulp Mills E01A E01A E01A E01A E01A E01A E01A E01A E01A E01A E01A 92/06 92/08 92/09 92/10 92/11 92/12 93/ 01 93/ 02 93/ 03 Chapter 3: E01 E01 E01 E01... 1966_book.fm Page 67 Friday, June 3, 2005 9:20 AM Chapter 3: Industrial Pollution: Pulp Mills Econ NH 3- 9 9 67 Fen NH 3- 9 9 11-Mile NH 3- 9 9 6 5 4 3 2 Dec Nov Oct Sept Aug July June May April March Feb 0 Jan 1 month Figure 3. 10 Ammonia concentrations in the Econfina and Fenholloway Rivers and Elevenmile Creek (monthly, January–December 1999) Ammonia concentrations in both of the rivers affected by mill effluents... 1993b) The highest cumulative © 2006 by Taylor & Francis Group, LLC 1966_book.fm Page 68 Friday, June 3, 2005 9:20 AM 68 Restoration of Aquatic Systems Econ PO 4-9 9 Fen PO 4-9 9 11-Mile PO 4-9 9 3 2 1 Dec Nov Oct Sept Aug July June May April March Feb Jan 0 month Figure 3. 11 Orthophosphate concentrations in the Econfina and Fenholloway Rivers and Elevenmile Creek (monthly, January–December 1999) numbers of . 100 E01A 92/12 9 3 4 44.4 F 03 92/12 31 1 31 100 E01A 93/ 01 10 4 5 50 F 03 93/ 01 32 6 25 78.1 E01A 93/ 02 8 1 8 100 F 03 93/ 02 nd nd nd nd E01A 93/ 03 1 1 0 0 F 03 93/ 03 nd nd nd nd Average 37 .9 2.9 20.8. 92/06 4 3 2 50 F 03 92/06 4 1 4 100 E01A 92/08 38 5 12 31 .5 F 03 92/08 0 0 0 0 E01A 92/09 17 3 3 17.6 F 03 92/09 1 1 1 100 E01A 92/10 9 3 7 77.7 F 03 92/10 nd nd nd nd E01A 92/11 9 4 3 33. 3 F 03 92/11. 19 3 6 31 .5 E01 92/09 31 5 2 6.4 F02 92/09 7 2 0 0 E01 92/10 36 3 30 83. 3 F02 92/10 5 1 0 0 E01 92/11 17 3 13 76.4 F02 92/11 0 0 0 0 E01 92/12 6 3 1 16.6 F02 92/12 9 5 1 11.1 E01 93/ 01 7 3 5 71.4