The Effect of Sewage Effluent Removal on the Water Quality of Lake Howell, Florida

Retrospective Theses and Dissertations

1986

Patricia L. Smith University of Central Florida

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STARS Citation Smith, Patricia L., "The Effect of Sewage Effluent Removal on the Water Quality of Lake Howell, Florida" (1986). Retrospective Theses and Dissertations. 4943. https://stars.library.ucf.edu/rtd/4943 THE EFFECT OF SEWAGE EFFLUENT REMOVAL ON THE WATER QUALITY OF LAKE HOWELL, FLORIDA

BY PATRICIA LYNN SMITH B.A., Florida Technological University, 1973 B.S., University of Central Florida, 1982

THESIS Submitted in partial fulfillment of the requirements for the degree of Master of Science in Biology in the Graduate Studies Program of the College of Arts and Sciences University of Central Florida Orlando, Florida

Spring Term 1986 ABSTRACT

In April, 1983, sewage effluent discharge from the Maitland and Winter Park sewage treatment plants was diverted from Lake Howell to the Iron Bridge Regional Sewage Treatment Plant. The sewage treatment plants of the cities of Winter Park and Maitland had been discharging into Lake Howell since 1927 and 1962, respectively . . These point sources had contributed 95% of the total phosphorous and 69% of the total nitrogen budgets for Lake Howell. Physico- chemical parameters were monitored monthly for two years from January, 1983 through December, 1984. Annual mean values fro chlorophyll , pH, Secchi disc transparency, and a water temperature were found to be higher during the second year (1984). Annual mean values for alkalinity, dissolved oxygen, and pheophytin (non-functional chlorophyll ) were a a higher during 1983. Chemical parameters were monitored quarterly for 1983 and 1984 for comparison with data obtained prior to the sewage diversion from Lake Howell. Biological oxygen demand, nitrate nitrogen, total kjeldahl nitrogen, orthophosphate, and total phosphate were found to decrease · over all years compared, from 1978 through 1984. TABLE OF CONTENTS

Introduction ...... 1 Methods and Materials 12 Results and Discussion 17 Summary 27 Literature Cited 52

iii LIST OF TABLES

TABLE 1. Monthly mean values for random sample station physical parameters data determined for Lake Howell for January, 1983, through December, 1984...... 29 TABLE 2. Monthly mean values for random sample sta tion chemical parameter data for Lake Howell for January, 1983 through December, 1984...... 30 TABLE 3. Annual mean values for chemical parameters in Lake Howell, from 1978 through 1984. 31 TABLE 4. Monthly mean values for random sample sta tion biological parameter data determined for Lake Howell, for January, 1983 through December, 1984...... 32 TABLE 5. Annual mean values and standard deviations for random sample station parameters sampled in 1983 and 1984 for Lake Howell, Florida...... 33

iv LIST OF FIGURES

FIGURE 1. Vicinity map of Lake Howell, Florida with tributaries and fixed site sample stations. • ...... •.. 34 FIGURE 2. Map of Lake Howell, Florida with grid overlay. • .....•...... •...... 36 FIGURE 3. Monthly means and confidence intervals for surface water temperatures .....•..... 38 FIGURE 4. Monthly means and confidence intervals for Secchi disc transparency ...... 40 FIGURE 5. Monthly means and confidence intervals for surface water dissolved oxygen ...... 42 FIGURE 6. Monthly means and confidence intervals for pH...... 44 FIGURE 7. Monthly means and confidence intervals for surface water alkalinity (bicarbonate, carbonate, total) ...... 46 FIGURE 8. Monthly means and confidence intervals for surface water chlorophylla ...... 48 FIGURE 9. Pheophytin and active (functional) chlorophyli ...... ••...... a so

v INTRODUCTION

Eutrophication is the process of adding nutrients to an aquatic system and the effect of those nutrients on its productivity. The natural process of nutrient addition to a lake occurs from various sources such as animal waste, decaying vegetation, precipitation, stormwater runoll, and nitrogen fixation by algae (Boyd, 1971). Cultural eutrophi cation occurs when man's activities within the watershed of a lake increase the lake's productivity (Ocum, 1971). Excess nutrients from agricultural runoff, sewage, and industrial wastes can acc~lerate the natural process. In certain activities, such as aquaculture, cultural eutrophi cation via fertilization is beneficial in increasing crop yield (Juday and Schloemer, 1938; Smith, 1948; Hepher, 1958, 1962). However in a natural system, cultural eutrophication can have a negative impact. Adverse effects of excess nutrients include changes in trophic levels within an aquatic system, as well as physical changes within a lake basin. The primary indicator of an eutrophic system is increased productivity at the producer t~ophic ·level, evidenced by overabundant growth of phyto plankton or macrophytes (Edmondson, 1969). Concomitant with increased phytoplankton levels is a potential increase in the hypolimn~tic oxyge~ deficit and decreased water clarity. 2

Bluegreen algal (Cyanophyta) species typically associated with eutrophic conditions can produce algal blooms and surface water scums. During calm weather -periods, decompo sition of these algal scums can result in depletiom of dis solved oxygen, fish kills, toxic conditions, and foul odors (Boyd, Davis, and Johnston, 1978; Boyd, Preacher, and Justice, 1978; Paerl and Ustach, 1982). At the consumer trophic level, typical responses to eutrophication include increased productiviy, accompanied by decreased species diversity and changes in species composition. Invertebrate populations exhibit decreased in species diversity in nutrient enriched lakes. Langford (1948) found increases in rotifer population number?, compared to other zooplankton present, in fertilization experiments of Canadian lakes. Benthic invertebrate species diversity decreased in Michigan lakes fertilized with a high-nitrogen, high-phosphorous fertilizer. Larvae of Chironomus plumosis (midge) replaced a community composed of damselflies, caddisflies, scuds, dragonflies, and beetles (Ball, 1948). Fish populations within eutrophic lakes change from harvestable game and food fishes to rough fish species (Hasler, 1948; Wetzel, 1975; Environmental Protection Agency, 1978). Changes in the lake basin include increased sedimentation rates and changes in bottom composition as a result of decomposition of excessive plant materials which settle to the bottom of a lake basin. Typical sediments of eutrophic lakes, i.e., gytta, sapropel, 3 and muck, are composed of fibrous or unconsolidated material, rather than sand (Ruttner, 1968; Cole, 1975). The history of the term "eutrophic: is outlined by Hutchinson (1971). Initial definitions centered on the con cept of eutrophic as "well-nourished" (Weber, 1907). As classification schemes for lake trophic states were devised, the traditional definition and typology of the eutrophic lake evolved. The eutrophic lake came to be defined as one with a shallow basin, being nutrient enriched,- and as a seral stage in the ecological succession of community types. Identification of the major nutrients involved in eutrophication and the sources and effects of these nutrients was a lengthy process. E.arly studies by Birge and Juday (1922) identified nitrogen and phosphorous as major constit uents of various algal species. Other studies that had been done in the 1930s and 1940s of the nutritional requirements of phytoplankton were reviewed by Ketchum (1954). Nitrogen,· phosphorous, and carbon .were listed as three of a host of essential nutrients. · As the nutrient requirements for phyto plankton were established, other sutdies centered on the manipulation of the major nutrients within a lake system to determine effects on the productivity levels of the system. Studies of lake fertilization for the enhancement of fish productivity indicated that increased nutrient levels directly increased phytoplankton and fish population numbers (Swingle and Smith, 1942). 4

Even though it was recognized early in limnological history that adding nutrients to a lake caused eutrophi cation, the consequences of nutrient addition and deter mination of which nutrients were the causative agents and/or limiting factors for algae growth did not become apparent until the middle of this century. Circumstantial evidence for the cultural eutrophication of lakes was provided by Hasler (1948). His summary included lakes that appeared to have been inadvertently fertilized by domestic sources such as sewage effluent and agricultural and industrial drainage. Sawyer (1954) outlined factors that contributed natural fertilizers to lakes and acknowledged the existence of nutrients in sewage effluent. Sawyer (1954) indicated the importance of determining natural sources of nutrient loading to lakes, prior to estimating a safe loading rate for sewage effluent. By the 1960s, recognition of the role of cultural influences in eutrophication was realized. Pollu tion problems of the Laurentian Great Lakes and other lakes · affected by domestic wastes were serious enough for the National Academy of Sciences to appoint a committee to study eutrophication. An international symposium was held to discuss the causes and possible cures for eutrophic lakes (National Academy of Sciences, 1971). Further delineation of the causes of eutrophication ensued. Vollenweider (1968) had established the relationship between the loading rates of nitrogen and phosphorous into 5

lakes and the degree of eutrophication. The importance of nitrogen and phosphorous as limiting nutrients for phyto plankton was dete.rmined later (Shelske, et al., _1972; Barlow, et al., 1973; Boyd, et al., 1981). Schindler's (1974) experiments with nitrogen and phosphorous compounds on Lake 226 near Ontario, Canada, indicated that both of these nutrients could act solely and together to create eutrophic conditions. Reduction of phosphorous input alone was expected to significantly reduce phytoplankton levels. With the role of nitrogen and phosphorous established, determination of the amounts of nutrients necessary to create adverse conditions followed. Models for predicting chloro phylla values from known phosphorous concentrations were developed by Dillon and Rigler (1974), Vollenweider (1974, 1975), and Jones and Bachmann (1976). Recently, Smith (1982) and Canfield (1983) established the importance of nitrogen, as well as phosphorous, for predicting chlorophylla values. With the role of nutrient input in the eutrophication of lake systems established, the problem of restoring the affected lakes remained. Lake restoration techniques have focused on the reduction of nutrient loads by control or removal of phosphorous and nitrogen sources. The methods used for lake restorations include chemical, mechanical, and biological techniques. The most utilized lake restoration technique has been the dredging and removal of nutrient laden lake sediments. Removal of highly organic sediments 6 can lower a lake's trophic level by decreasing nutrients available for plant productivity and reducing oxygen demand. Fifty-nine percent of the lake restoration projects funded by the United States Environmental Protection Agency's Clean Lakes Program have used this technique (Wedepohl, et al., 1983). Another successful technique has been nutrient inacti vation using chemical compounds to precipitate phosphorous from lake waters. Aluminum sulfate has been the most used chemical compound. The efficacy of this method was demon strated in Medical Lake, Washington (Gasperino, et al., 1979). Following application of aluminum sulfate, the soluble reactive phosphorous concentration within the lake was reduced by 90%. Consequent improvements in water quality were the chlorophyll a concentrations decreasing from 60 mg m-3 to le~s than 10 mg m- 3 , and the Secchi disc visibility increasing form 1 m to 7 m. In Liberty Lake, Washington, the soluble phosphorous concentration decreased from 0.04 mg 1-l to ·0.005 mg 1-l, after the addition of aluminum sulfate (Funk and Gibbons, 1979). The nitrogen and phosphorous removal by the diversion and filtration of stormwater runoff within an urban area reduced by 90% the nutrient loading to Lake Eola, Florida. The application of aluminum sulfate further precipitated phosphorous compounds as well as inactivating phosphorous release from the lake sediments (Harper, et ai., 1983). 7

Biological restoration techniques generally involve the removal of nutrients by filtering the stormwater runoff through a biological wetland system. Stormwater was cleansed near Clear Lake, Minnesota, by channeling it through a Phalaris arundinacea (reed canary grass) marsh. After filtration through the marsh, total phosphorous in water discharged into the lake was reduced by 40% (Barten, 1983). The addition of nutrient-poor water into a lake to dilute the existing concentrations of nutrients was effective in restoring Green Lake, Washington. Green Lake, a naturally eutrophic system with a principal nutrient source from sub surface seepage, had nutrient-poor water from the Seattle city water supply added to the lake. Nitrate nitrogen, orthophosphate, and total phosphorous concentrations were reduced by 75%. Improved water quality was evidenced by an increase in the mean Secchi disc visibility from 1.3 m to 3.5 m over a six year period (Oglesby, 1969). Dilution water from the Columbia River was added to eutrophic Moses Lake, Washington, and resulted in more than a 50% improvement in phosphorous, chlorophylla, and Secchi visibility values (Welch, 1979). The diversion of point source sewage effluent discharge from a lake has been utilized in many lake restorations (Horwitz, 1980; Cooke, 1982). Nitrogen and phosphorous compounds found in sewage treatment plant effluent have been 8 documented as a causative factor in the cultural eutrophica tion process (Hasler, 1947; Sawyer, 1954; Dean, 1963; Miller and Maloney, 1971). The responses of lake . systems to sewage effluent diversion have been varied; some lakes exhibit improvements in water quality while others maintain their eutrophic characteristics. Uttormark and Hutchins (1980) analyzed data collected from 23 lake studies. All of the lakes experienced decreased ·phosphorous levels _following . the - diversion of sewage effluent. An improvement in trophic conditions was visible in only 10 of the 23 lakes. Two lakes which exhibited significant and rapid signs of recovery were Lake Washington, near Seattle, Washington, and Lake Norrviken, Sweden. Lake Washington showed signs of recovery within two years after the complete removal of sewage effluent. The sewage effluent had contributed 56% .of the phosphorous load and 12% of the nitrogen load to the lake. After sewage effluent diversion, a 72% reduction in phosphorous and a 20% reduction in nitrate nitrogen occurred. The Secchi disc visibility increased from 1.2 m to 3.5 m. Chlorophylla concentration within the epilimnion decreased by 80%, and phytoplankton cell volumes decreased by 70% (Edmondson, 1970; 1972). In Lake Norrviken a 74% decrease in nitrogen loading and a 48% decrease _in phosphorous loading occurred after sewage effluent diversion. Within two years, nitrogen concentration within the lake was reduced by 50% and phosphorous concentration by 30% (Ahlgren, 1972). Secchi 9 disc visibility increases ranged from 20% to 50% when compared to pre-diversion values. Chlorophyll values decreased by 50% as Lake Norrviken changed from an eutrophic to a mesotrophic state. The trophic state of many other lakes did not signifi cantly improve following the diversion of sewage effluent . For example, Lake Trummen in Sweden did not recover after sewage was diverted in 1958. In 1970 a second restoration attempt was made on the lake using sediment removal. This resulted in the reduction of nutrients and phytoplanktop biomass (Cronberg,

1982). Lake Sammamish, Washingto~ showed no signs of recovery four years after the diversion of 22% of the nitrate nitrogen and 38% of the phosphorous loads (Emery,: _et al., 1973). When sewage discharge was diverted from Lake Vesijarvi, Finland, in 1976, Keto (1982) found a 60% reduction in total phosphorous content and a 30% reduction in total nitrogen content after two years. Interestingly, phytoplankton bio mass initially decreased, then doubled three years later. Bluegreen algae increased, with algal blooms occurring in August for subsequent years following the diversion. In Lake Ramsjon, Sweden, 85% of the phosphorous load was removed from the sewage effluent discharge. Within one year, total phosphorous and chlorophylla concentrations were reduced by 47% and 20% respectively. However, it was concluded that the trophic state of the lake had remained unchanged (Forsberg, et al. , 19 7 5) . 10

Sewage effluent discharge was completely diverted from

Lake Howell, Florid~ in April of 1983. Prior to this date, Lake Howell had received,discharge from two sewage treatment plants. The City of Maitland began discharging treated sewage effluent from a trickling filter plant into Lake Howell in 1962. The plant was expanded to a 3.0 million gallon per day (mgd) output in 1972. Further secondary treatment was provided by phosphorous removal using alum compounds (Grant, pers. comm.). Between January, 1982, April, 1983, the average daily discharge from the sewage treatment plant was 1.9 mgd (Magley, 1984). In 1927, the City of Winter Park's sewage treatment plant began discharg ing primary treated effluent into Howell Branch Creek, up stream from Lake Howell. This sewage treatment plant was upgraded to a trickling filter plant in 1947. Between 1966 and 1967 the plant was expanded to a capacity of 4.5 mgd, and additional secondary treatment was added (McClintock, pers. comm.; Florida Department of Environmental Regulation, 1982). The average daily flow rate was 2.93 mgd between January, 1982 and April, 1983. Twenty-two percent of the average - annual flow of Howell Branch Creek was derived from the Winter Park sewage treatment plant. Total phosphorous and total nitrogen budgets for Lake Howell were · calculated in 1984 (Magley, 1984). The point source contribution of Maitland's sewage effluent was 6% of the total phosphorous and 29% of the total nitrogen budgets. 11

Winter Park's sewage effluent contributed 89% of the total phosphorous and 40% of the total nitrogen budgets. The combined input of these point sources provided 95% of the total phosphorous and 69% of the total ni~rogen budgets for Lake Howell. The remaining nutrient contributions were derived from nonpoint sources (Magley, 1984). The sewage effluent discharge from the Maitland and Winter Park sewage treatment plants was diverted to the Iron Bridge Regional Sewage Treatment Plant located near Oveido, Florida, with the hope that the removal of the phosphorous and nitrogen loading into Lake Howell would improve water quality and reduce nutrient loading downstream in Lake Jesup. The objectives of this study were to determine the significant changes in water quality within Lake Howell following sewage effluent diversion and to compare data collected during the post-diversion study with prior data. Data collected prior to the sewage effluent diversion in 1983 were obtained from Seminole County's Deparment of Environmental Services. METHODS AND MATERIALS Description of the Study Area Lake Howell is a 164 ha lake located in south Seminole County (28° 38' 33" N lat., 81° 18' 46" W long.). Its shallow, irregularly shaped basin is a remnant depression of the ocean floor, and is . typical of the coastal lowlands of eastern Florida (Cooke, 1945; Lichtler, 1972). The lake has a uniform bottom composed of white sand mixed with sapropel. The mean depth of the lake is 2.8 m, and the maximum depth is 4.7 m. Algae blooms within Lake Howell have occurred during spring and late summer for many years. Littoral vegetation is absent from the north, south, and west shores, except for scattered stands of Typha latifolia (cattails). A Taxodium spp. (cypress) wetland borders the east shore. The surface of Lake Howell was completely covered by Eichornia crassipes

(water hyacinth) during the 1940s. Herbicides were used to ~ control this plant. At present, sporadic mats of water hya cinth float near the shoreline (Jane, pers. comm.). Lake Howell has a 7200 ha drainage basin that is part of the 7650 ha Howell Branch Creek subbasin of the St. Johns River basin. Howell Branch Creek, the primary drainage system of the lake, flows northeasterly toward Lake Howell from its headwaters at Spring Lake and Lake Dot in north central Orange County. Lakes Concord, Adair, and Ivanhoe

12 13 contribute flow to the creek. As Howell Branch Creek flows through the cities of Winter Park and Maitland, it widens and forms the Winter Park chain of lakes: Lakes Sue, Virginia, Osceola, and Maitland. Howell Brarich Creek discharges from Lake Maitland and enters on the western shore of Lake Howell. The creek leaves Lake Howell and flows northeasterly into Lake Jessup (East Central Florida Regional Planning Council, 1980). The Lake Howell . drainage basin has two subbasins, characterized by soil type. The upper subbasin, located within Orange County, has soils primarily of the Lakeland Eustis-Blanton-Orlando association; these soils are common in Florida's central highlands. These sandy soils are moder ately to somewhat excessively well drained (Leighty, et al., 1960). The soils of the lower subbasin, located within Seminole County, are of the Blanton-Leon-Plummer association. These soils are nearly level, moderately drained, and inter spersed with wetlands, ponds, and lakes (Furman and White, 1966). Land use within the Lake Howell drainage basin varies from urban to commercial. Most of the drainage basin is urban and includes commercial districts within the cities of Orlando, Winter Park, Maitland, and Casselberry. A small part of the watershed is agricultural (orange groves). The lakes within the Lake Howell drainage basin receive direct stormwater runoff from surrounding urban areas. The State 14

Road 436 corridor is a major feature. Stormwater runoff from this corridor drains into Howell Branch Creek. Lake Howell, as the penultimate lake along the creek's ~ourse, is impacted by the cumulative effect of nutrients from upstream. Howell Branch Creek provides 74% of the tributary flow to the lake, with an average annual flow of 20.37 cubic feet per second (cfs). In addition, surface water enters Lake Howell from storm drains, overland flow of stormwater, Cassel Creek, the Deer Run canal, and the Lake Ann canal. Cassel Creek contri butes 11%, ·with an average annual flow of 3.19 cfs. An average annual flow of 2.36 cfs (9%) enters by way of the Deer Run canal. The Lake Ann canal has an average annual flow of 1.57 cfs, and provides 6% of the surface water flow to the lake (Figure 1). The water level in Lake Howell ·is regulated upstream by a weir at Howell Branch Creek. During drought conditions, water does not flow over the weir downstream into Lake Howell. Groundwater seepage and the remaining surface water sources maintain Lake Howell's water level during drought conditions, in addition to other sources.

Physicochemical Parameters

Six random sampling stations were s~mpled _for two years at monthly intervals from January, 1983 through December, 1984. Random sampling stations were chosen from a numbered grid overlay on a map of the lake. A station was deemed the 15 midpoint of a 7.45 ha grid square (Figure 2). The sampling stations were chosen using a computerized random number generator program. Water samples were collected at the surface (0.5 m depth) using a 1.2 1 Kemmerer water sampler. All samples were col lected between the hours of 0900 and 1000 during midmonth. Alkalinity (bicarbonate, carbonate, total) and pH were deter mined using the methods outlined in Standard Methods (American Public Health Association (APHA), 1980).

Chlorophyll and pheophytin concentrations were obt~iried a a colorimetrically (APHA, 1980) using a Model 26 Beckman Spectrophotometer. A 20 cm black and white Secchi disc was used to determine Secchi disc transparency. Water temperature and dissolved' oxygen were measured in the field (0.5 m depth) using a Model 57 YSI meter. Water depth was determined from soundings with a weighted line. Two permanent sampling stations were sampled quarterly in Lake Howell from January, 1983, through December, 1984 (Figure 1). Biochemical oxygen demand (BOD) was determined at these stations using a 5-day incubation period for the membrane electrode method (APHA, 1980). A Model 54 YSI meter was used for dissolved oxygen determinations. Nitrate nitrogen concentrations were determined colorimetrically using the brucine method (APHA, 1975). Total kjeldahl nitrogen (ammonia and organic nitrogen) was measured colori metrically after digestion by the macrokjeldahl method 16

(APHA, 1980). Orthophosphate concentrations were determined using the ascorbic acid-ammonium molybdate method (APHA, 1980). Preliminary treatment of samples by sulfuric acid nitric acid digestion was followed by the ascorbic acid ammonium molybdate method to determine total phosphate concentrations (APHA, 1980). A Bausch and Lomb Spectronic 710 Spectrophotometer was used in these determinations. -1 Total Alkalinity (mg 1 Caco3 ) was determined using methods outlined in Standard Methods (APHA, 1980). Statistical Analyses The data .collected at the random sampling stations were analyzed using an Apple Ile computer. Monthly and annual population means and confidence intervals for the means were calculated at a 95% (p = 0.05) confidence level. Statistical differences between annual means were based upon using the large-sample test for the standard error of the difference between two means and z-table values at a 95% confidence level (McClave and Dietrich, 1979). The data collected at the permanent sampling stations for 1983 and 1984 were used to calculate annual means. Additional data for 1978 through 1982, obtained from the Seminole County Department of Environmental Services, were used to calculate the annual means used in determining trends prior to the diversion of sewage effluent from Lake Howell. RESULTS AND DISCUSSION The monthly mean surf ace water temperature in Lake Howell ranged from 12.0 C in January, 1984, to 30.4 C in July, 1983 (Table 1). The lowest surface water temperatures recorded for 1983 occurred in the months of January through March. The monthly mean surface water temperatures during these months were very similar, averaging 15.6 C. The monthly mean surf ace water temperature rose steadily each month from April, 1983, through July, 1983, reaching 30.4 C, then declined each month, reaching 12.0 C in January, 1984. The monthly mean surf ace water temperatures then increased monthly, reaching 28.6 C ih August, 1984, and declined steadily each month thereafter, reaching 20.6 C in December, 1984. Trends for both years were similar with the lowest temperatures recorded in January through March, and the highest temperatures recorded in July and August of each year (Figure 3). The annual mean surface water temperatures for 1983 and 1984 were 23.1 C. and 23.3 C respectively. ·The application of the large-sample test for the standard error of the difference between two means (p = 0.05) (McClave and Dietrich, 1979) revealed no signiftcant difference between the annual means of the surface water temperatures for 1983

and 1984.

17 18

The monthly mean Secchi disc transparency flucturated from 47.5 cm in January, 1983, to the maximum recorded value of 82.3 cm in September, 1983. Monthly mean Secchi disc transparency ihen declined to 53.7 cm in Oct6ber, 1983, and increased afterward by approximately 4 cm per month to 65.7 cm in January, 1984. The monthly mean Secchi disc trans parency decreased to the minimum recorded value of 33.8 cm in March, 1984. Each month thereafter Secchi disc trans parency increased through July, 1984, reaching 78.7 cm and remained steady for the remainder of 1984. The annual mean Secchi disc transparency was higher for 1984 (61.2 cm) than 1983 (58.2 cm), indicating a slight increase in water clarity. However there was no significant difference between the two annual means (p 0.05) (McClave and Dietrich, 1979). No pattern emerged for the two years of the study (Figure 4). Lake Howell's range of Secchi disc transparency falls within those determined for eutrophic north and central Florida _lakes (Shannon and Brezonik, 1972). Lake Howell was an eutrophic lake throughout the two years of the study. Lake Howell's monthly mean surface water dissolved oxygen concentrations ranged from 4.0 ppm in July, 1983, to 12.8 ppm in February, 1984 (Table 2). The lowest monthly mean dissolved oxygen concentrations occurred in July of each year. The highest monthly mean surface water dissolved oxygen concentrations were in the months of January through March of each year, when surface water temperatures were the 19 coldest. The monthly mean surface water dissolved oxygen concentrations fluctuated from January, 1983, until September, _ 1983, then increased each month to reach 12.8 ppm in February, 1984. The monthly mean surface water dissolved oxygen concen trations decreased to 6.5 ppm in April, 1984, and remained fairly constant, reaching 8.0 ppm in August, 1984. In September, 1984, the monthly mean surface water dissolved oxygen concentrations decreased to 6.5 ppm, then increased slightly each successive month until reaching 7.1 ppm in December, 1984. Dissimilar trends were apparent for the two years of the study (Figure 5). The monthly mean surface water dissolved oxygen concentrations were temperature dependent during: January· through April, 1983, September through December, 1983, February through April, 1984, and September through December, 1984. During the remaining warmer months of each year, the monthly mean surface water dissolved oxygen concentrations were not correlated with temperature (figures 3 and 5). The annual mean surface water dissolved oxygen concentrations were essentially the same for 1983 and 1984 (7.75 ppm and 7.73 ppm respectively), with no significant difference (p = 0.05) (McClave and Dietrich, 1979). The monthly mean pH values in Lake Howell ranged from 7.18 in September, 1983, to 9.28 in March, 1984 (Table 2). Generally pH was greater than 8.2 for the months of January through June, 1983, and February through July, 1984 (Table 20

2, Figure 6). There was no significant difference between the annual mean pH values of 8.17 for 1983, and 8.29 for

1984, at the p = 0.05 confidence level (McClave and Dietrich, 1979). The monthly mean total alkalinity ranged from 24.08 -1 -1 mg 1 Caco in July, 1983, to 60.66 mg 1 Caco in 3 3 February, 1983 (Table 2). In general, the monthly mean

total alkalinity was ~ highest during February through -June, 1983, then decreased to its lowest value in July, 1983. The monthly mean total alkalinity increased up to 39.17 mg 1-l

Caco3 in August, 1983, and remained near this value until May, 1984, when an increase to 52.00 mg 1-l occurred. Monthly mean total alkalinity remained high for June, 1984, -1 then decreased to approximately 44.80 mg 1 Caco3 in July and August, 1984. Another decrease in monthly mean total alkalinity, to 40.33 mg 1-l occurred in September, 1984; this value was maintained for the remainder of 1984 (Figure 7). The annual mean total alkalinity was higher for 1983, -1 ' -1 at 48.30 mg 1 Caco , than for 1984, at 42.94 mg 1 Caco . 3 3 However, there was no significant difference (p = 0.05) between the annual mean total alkalinity for 1983 and 1984. The total alkalinity in Lake Howell was due primarily to bicarbonate ions (Figure 7). The monthly mean bicarbonate alkalinity values ranged 1 -1 from 17.3 mg 1- Caco3 in March, 1984, to 56.8 mg 1 Caco3 in May, 1983 (Table 2). Bicarbonate alkalinity fluctuated 21 from January through July, 1983, then leveled off at approxi- -1 mately 39.0 mg 1 Caco3 through January~ 1984. The monthly mean bicarbonate alkalinity decreased to 20.8 mg 1-l Caco 3 in February, 1984,· and then to 17.3 mg 1-l Cac63 in M~rch, 1984. A value near 40.0 mg 1-l was maintained from April, 1984, through the remainder of the year (Figure 7). Although the annual mean bicarbonate alkalinity values were ·44.09 -1 1 mg 1 Caco3 in 1983, and 37.68 mg 1- Caco3 in 1984, the application or the large-sample test for the standard error of the difference between two means (McClave and

Dietrich, 1979) revealed no significant difference (p = 0.05). No monthly mean carbonate alkalinity was found from July, 1983, through January, 1984, in April, 1984, and again between August and December, 1984. The maximum monthly mean -1 carbonate alkalinity, 24.3 mg 1 Caco3 , was recorded for February, 1984 (Table 2). In general, the monthly mean carbonate alkalinity peaked in March of each year, to disappear in June (Figure 7). The annual mean carbonate

alkalinity for 1983 was 6.12 mg 1-l Caco3 and for 1984 was 5.38 mg 1 -1 Caco . The annual mean carbonate alkalinity 3 for 1983 and 1984 were not statistically significantly different (p = 0.05) (McClave and Dietrich, 1979). Each of the nutrient parameters monitored quarterly during the study exhibited definite decreases in concentrations between 1983 and 1984 (Table 3). 22

When comparing the annual mean BOD values of pre-sewage diversion years (1978 through 1982) with. annual mean values obtained for 1983 and 1984, BOD had increased annually from

1978 through 1983. The annual mean BOD value then decre~sed 37% from 6.94 ppm in 1983, to 4.34 ppm in 1984. The annual mean nitrate nitrogen values fluctuated during the pre-sewage years, 1978 through 1982. Nitrate nitrogen increased 63% from 0.07 ppm in 1982 to 0.19 ppm in 1983, then decreased 68% from 1983 to 1984, at 0.06 ppm. The lowest annual mean nitrate nitrogen value for all years compared occurred in 1984. The total kjeldahl (TKN) annual means fluctuated from year to year, with the lowest annual mean value occurring in 1984. TKN decreased 49% between 1982 (3.50 ppm), and 1983 (1.78 ppm), and again by 33% between 1983 and 1984 (1.19 ppm). The annual mean orthophosphate values fluctuated during the pre-sewage diversion years. Orthophosphate decreased 76% from 0.73 ppm in 1982 to 0.26 ppm in 1983; it decreased by 64% from 1983 to 0.06 ppm in 1984. The 1984 annual mean orthophosphate value was the lowest for each of the years

compared. The annual mean total phosphate values fluctuated yearly with a 63% decrease from 0.79 ppm in 1982, to 0.38 ppm in 1983, and 52% decrease in 1984 to 0.14 ppm. The lowest. overall annual mean total phosphate value was in 1984. 23

According to Shannon and Brezonik (1972), total phosphate values ranging from 0.055 ppm to 0.557 ppm indicate an eutrophic lake in central Florida. Lake Howell's range of total phosphate values places it into the eutrophic cate gory from 1978 through 1984 (Table 3). The monthly mean chlorophyll concentrations fluctuated a over the study period, never falling below 21.50 mg m- 3 (May, _ 1983). The peak monthly mean chlorophyll concen- a trations occurred in March, 198~ (128.08 mg m- 3 ) and March,

1984, (256.72 mg m- 3 ). A secondary peak occurred in October,

1983 (89.32 mg m- 3 ) (Figure 8, Table 4). The peak monthly mean chlorophyll concentration values were evidence of a excessive algal blooms. Lakes with low water clarity, due to overabundant algae, are considered to be of poorer water quality than clear water lakes. Lake studies predicting water clarity, indicated by Secchi disc transparency, as a function of algal biomass, indicated by chlorophylla concen tration, have demonstrated a significant hyperbolic relation ship between the two water qnality measurements (Bachmann and Jones, 1974; Carlson~ 1977; Canfield and Hodgson, 1981). A slight increase in chlorophyll concentration results in a a rapid decrease in Secchi disc transp~rency, when chlorophylla concentrations are less than 10 mg m- 3 • Above this value little difference in Secchi disc transparency occurs, indi- eating no apparent improvement in water quality. Canfield and Hodgson (1981) found that Florida lakes with chlorophylla 24 concentrations less than 10 mg m- 3 reflected sensitive changes in water clarity as measured by Secchi disc trans parency, while lakes with concentrations greater than 50 mg m- 3 exhibited only slight differences in Secchi disc transparency. Within Lake Howell's range of chlorophyll a values (21.50 mg m- 3 to 256.73 mg m- 3 ) no improvement in water clarity would be predicted using Secchi disc transparency. Lake Howell's range of chlorophyll concentrations a were within and above the range for eutrophic lakes (13.2 mg m- 3 to 65.8 mg m- 3 ) determined for north and central Florida by Shannon and Brezonik (1972). The monthly mean chlorophyll concentrations were inversely correlated with a . bicarbonate alkalinity, and positively correlated with carbonate alkalinity, indicating the possible use of the bicarbonate ion (Hco3-) as a carbon source for photosyn thesis by algae, with carbonate (C0 - 2 ) as a by-product 3 (Whittingham, 1952; Steeman Nielsen and Jensen, 1958; Briggs, 1959). The annual mean chlorophylla concentration of 77.05 mg m- 3 for 1984 was greater than the annual mean for 1983 of

6 8.02 mg m-3 • There was no significant difference (p = 0.05) between the annual means for 1983 and 1984 (McClave and Dietrich, 1979). The plant pigment pheophytina is a degradation product of chlorophyll and as such this derivative compound is not a photosynthetically active (Lewin 1962; Lorenzen, 1967; Moss, 25

1967). The presence of high concentrations of pheophytin a within an algal population indicates disintegration of algal cells (Wetzel, 1975). Monthly mean pheophytin concentra a tions ranged from 0.96 mg m- 3 for February and March, 1984, to 70.23 mg m- 3 for February, 1983 (Table 4). The monthly mean pheophytin concentrations fluctuated monthly during 1983 and 1984 (Figure 9); no trends were evident. There were more fluctuations in the monthly mean pheophytin a concentra tions for 1983. The annual mean pheophytin a concentration.

for 1983 (27.90 mg m- 3 ) was significantly (p = 0.05) greater than that for 1984 (14.69 mg m- 3 ). The greater annual mean pheophytin concentration for 1983 indicated an a . older algal population with senescent cells. The fluctuations in the monthly mean active chlorophylla (chlorophylla - pheophytina) concentrations did not follow the monthly mean chlorophyll concentrations (Figure 9). a Fifty percent (66.09 mg m- 3 ) of the March, 1983, monthly mean chlorophyll value was due ·to the presence of active a chlorophyll , indicating that during 1983 the peak algal a 3 bloom occurred in October, not March, when 89% (79.81 mg m- ) of the monthly mean chlorophylla value was due to active chlorophylla. Of the March, 1984 monthly mean chlorophylla value, 99% (256.52 mg m- 3 ) was viable active chlorophylla. Since results of pievious lake restoration efforts using sewage effluent diversion as the nutrient abatement technique 26 revealed water quality improvements following the removal of total phosphorous and total nitrogen loading, one would suspect similar occurrences in Lake Howell. Although the concentrations of chemical parameters monitored decreased, the remaining physical and biological indicators of water quality did not significantly improve.· As it was not deter mined statistically if the percentage decrease measured was was significantly different, one could not definitely state that the lake had improved using 'the chemical parameters as measures of water quality. Although large percentages of the external nutrient load were removed, these may be small percentages of the total loading when both autochthonous and allochthonous nutrient sources are considered. Most nutrient models neglect input from internal sources. Internal nutrient loading has undermined other lake restoration attempts when external nutrient sources were removed (Bjork, 1972; Larsen, 1981). Factors not calculated in the determination of the nutrient budget for Lake Howell included internal loading rates from sediments and the recycling of algal biomass com ponents. Phosphorous release from sediments into the water column has been determined for other lakes (Hayes, 1958;

Lean, 1973; Larsen, 1976). The removal of the sewage effl~ ent~s nutrient contribution may not have been adequate to effect a change in Lake Howell's water quality. It is recom mended that further monitoring of the lake's condition be considered to determine future water quality changes. SUMMARY

1. Alkalinity (bicaybonate, carbonate, total), dissolved

oxygen, and pheophytin a had lower annual mean values for 1984 than for 1983. 2. Water temperature, Secchi disc transparency, pH, and chlorophylla had higher annual mean values for 1984 than for 1983. 3. Although the annual mean values of the random sample station parameters differed for each year of the study, the application of _the large-sample test for the standard error of the difference between two means (McClave and Dietrich, 1979), revealed no significant difference

(p = 0.05) between the annual means of the parameters for 1983 and 1984, with the exception of pheophytina. 4. Of the fixed sample station parameters, BOD and nitrate nitrogen increased between the pre-sewage diversion year 1982 and the post-sewage diversion year 1983, and TKN, orthophosphate, and total phosphate decreased between 1982 and 1983. 5. Of the fixed sample station parameters, all exhibited decreased between 1983 and 1984 in the following percen tages: BOD by 37%, nitrate nitrogen by 68%, TKN by 33%, orthophosphate by 64%, and total phosphate by 52%.

27 28

6. Total phosphate, Secchi disc transparency, and chloro

phylla in Lake Howell, before and after sewage diversion, indicate an eutrophic system when compared to other

north and central Florida lakes (Shannon and Brezonik,

1972).

7. Chlorophylla concentrations did not decrease, as measured Secchi disc transparency, after the sewage diversion and

the bicarbonate alkalinity was inversely related to

chlorophyll concentrations in Lake Howell. a TABLE 1. Monthly mean values (n = 6) for random sample station physical parameter data determined for Lake Howell for January, 1983, through December, 1984.

YEAR MONTH WATER TEMPERATURE SECCHI DISC TRANSPARENCY (oC) (cm)

1983 J 14.7 47.5 F 16.3 51.3 M 15.8 42.7 A 22.1 49.8 M 26.0 66.8 J 28.1 47.0 J 30.4 70.5 A 30.0 68.0 s 27.5 82.3 0 26.0 53.7 N 22.0 57.5 D 18.1 61.0

1984 J 12.0 65.7 F 18.0 59.8 M 19.9 33.8 A 20.8 49.7 M 25.3 60.5 J 26.2 68.0 J 28.4 78.7 A 28.6 71.3 s 28.1 65.3 0 26.1 60.1 N 24.1 62.2 D 20.6 62.2

N \.0 TABLE 2. Monthly mean values (n = 6) for random sample station chemical parameter data determined for Lake Howell for January, 1983, through December, 1084.

YEAR MONTH DISSOLVED OXYGEN pH ALK~tINITY (ppm) (mg 1 CaC0 1 ) Bicarbonate Carbonate Total

- 1983 J 11. 98 8.28 31.58 1. 83 33.41 F 11.25 8.97 49.33 11. 33 60.66 M 11.50 9.05 38.62 20.38 59.00 A 6.58 8.79 40.33 17.33 57.66 M 6.37 8.79 56.83 3.33 60.16 J 8.15 9.21 34.33 19.17 53.50 J 4.00 7.73 24.08 0.00 24.08 A 7.82 7.66 39.17 0.00 39.17 s 5.28 7.18 38.67 0.00 38.67 0 . 5. 88 7.24 39.50 0.00 39.50 N 7.10 7.74 38.83 0.00 38.83 D 7.92 7.51 39.33 0.00 39.33 1984 J 9.78 7.47 39.33 0.00 39.33 F 12.83 9.15 20.75 18.83 39.58 M 9.12 9.28 17.33 24.33 41. 66 A 6.50 8.77 41. 50 0.00 41.50 M 6.52 8.56 41.17 10.83 52.00 J 6.50 8.52 42.00 9.83 51.83 J 6.32 8.15 44.17 0.67 44.84 A 8.00 7.83 44.78 0.00 44.78 s 6.50 1 7.91 40.33 0.00 40.33 0 6.70 7.95 40.33 0.00 40.33 N 6.87 7.96 40.33 0.00 40.33 D 7.13 7.98 40.17 0.00 40.17

v.) 0 TABLE 3. Annual mean values for chemical parameters in Lake Howell, Seminole County, Florida, from 1978 through 1984. Data for years 1978 through 1982 obtained from Seminole County's Department of Environmental Services.

PARAMETER 1978 1979 1980 1981 1982 1983 1984

Biological oxygen demand 5.741 4.55 5.02 6.25 6.80 6.94 4.34 (ppm) ( 8) 2 (2) (5) (2) (4) (8) (8) Nitrate nitrogen 3 0.09 0.45 0.31 0.07 0.19 0.06 (ppm) (10) (3) (5) (4) (8) (8) Total kjeldahl nitrogen 1.53 2 .-05 9.20 3.50 1.78 1.19 (ppm) (10) (3) ( 5) (4) (8) (8) Orthophosphate 0.50 0.58 1.09 0.47 0.73 0.26 0.06 (ppm) (8) (10) (6) (5) (4) (8) (8)

Total phosphate 0.64 0.46 1.21 0.62 ·O. 79 0.38 0.14 (ppm) (8) (8) (6) (5) . (4) (8) (8)

1. Annual mean value 2. Number of samples 3. No data available for that year TABLE 4. Monthly mean values (n = 6) for random sample station biological parameter data determined for Lake Howell, for January, 1983, through December, 1984.

YEAR MONTH CHLOROPHYLL 1FUNCTIONAL CHLOROPHYLL -3 a (mg m ' (mg m- 3) a

1983 J 89.43 27.01 62.42 F 92.14 70.23 21.91 M 128.08 61.99 66.09 A 55.69 31.29 24.40 M 21. 50 12.50 9.00 J 60.48 11.48 49.00 J 43.88 19.50 24.38 A 58.70 17.47 41.23 s 48.34 16.37 31.97 0 89.32 9. 51 ' 79.81 N 73.06 18.68 54.38 D 46.78 38.59 8.19 1984 J 47.45 30.54 16.91 F 75.67 0.96 74.71 M 256.72 0.96 256.52 A 80.97 5.75 75.22 M 72.39 17.65 54.74 J 59.04 16.47 54.74 J 40.99 ' 12.44 28.55 A 63.26 3.33 59.93 s 50.01 21. 37 28.64 0 54.80 13.11 41.69 N 55.53 22.49 33.04 D 48.23 30.08 18.15

w 1 Fu~ction.al chlorophylla = chlorophylla values N - pheophytin a values 33

TABLE 5. Annual mean values and standard deviations for random sample station physicochemical and biological parameters sampled in 1983 and 1984 for Lake Howell, Florida.

PARAMETER YEAR ANNUAL MEAN STANDARD DEVIATION

Alkalin!fY, total 1983 48.30 15.13 (mg 1 CaC03) 1984 .-42. 94 4.39

Alkalin~fY, bicarbonate 1983 44.09 42.04 (mg 1 Caco3) 1984 37.68 8.76 Alkalin!fY, carbonate 1983 6.12 8.48 8.47 · (mg 1 Caco3) 1984 5.38 Chloropb-jlla 1983 68.02 39.85 (mg m ) 1984 77.05 55.75 Dissolved oxygen 1983 7.75 2.72 (pµn) 1984 7.73 1.98 pH 1983 8.17 0.73 1984 8.29 0.57

Pheophyt-ina 1983 27.90 19.59 (mg m 3 ) 1984 14.69 12.96 Secchi disc transparency 1983 58.17 12.19 (cm) 1984 61.22 11.17 Water temperature 1983 23.08 5.57 (oC) 1984 23.31 5.08 34

FIGURE 1. Vicinity map of Lake Howell, Florida, with tribu taries. Numbers identify fixed site sample stations. Letters identify tributaries: A)

Howell Branch Creek, B) Cassel C~eek, C) Deer Run Canal, D) Lake Ann Canal, E) Lake Ann. Red Bu Road

) ~ NTS 36

FIGURE 2. Map of Lake Howell, Florida, with- grid overlay used to obtain random sample stations. 17

34 35 36 N I

I I I w 0 122 244m -...... ) LAKE HOWELL 38

FIGURE 3. Monthly means and 95% confidence -intervals for

surface (0.5 rn depth) water ternperatures · in Lake

Howell, Florida, January, 1983 through December,

1984. The arrow indicates the month that 100%

of the sewage effluent was diverted from the

lake. 35 Lake Howell

25 0

Q) ... 20 ..:I ...0 Q) a. E 15 t! ... Q) ... 10 ~

0------.------_.. __ ..._ ___ ...... __ ~------_..--...__._...... __ ~ F A J A 0 D F A J A 0 D 1983 • 1984 40

FIGURE 4. Secchi disc transparency monthly means and 95% confidence intervals for Lake Howell, Florida, January, 1983 through December, 1984. The arrow indicates the month that sewage effluent was completely diverted from the lake. 100 Lake Howell

E 0 60

~ 0 c CD.... 50 0 Q. fl) c 0 40 ~

0 .!? 0 30

.i::. 0 0 CD (/) 20

10 0------....______...______. ______

F A J A 0 D F A J A 0 D 1983 • 1984 42

FIGURE 5. Surface (0.5 m depth) water dissolved oxygen concentration monthly means and 95% confidence intervals for Lake Howell, Florida, January, 1983 through December, 1984. The arrow indicates the month that the sewage effluent was completely diverted from Lake Howell. Lake Howell 14.0

12.0

E Q. Q. 10.0

c Q) D 8.0 ~ )( 0 -a Q) 6.0 > -0 IA IA c 4.0

2.0

F A J A 0 D F A J A 0 D 1983 • 1984 44

FIGURE 6. Hydrogen ion (pH) concentration monthly means and 95% confidence intervals for Lake Howell, Florida, January, 1983 through December, 1984. The arrow

indicates the month that 100% of the sewage effluent was diverted from Lake Howell. 14 Lake Howell

o...__.__....__,__...... _--...... _..._...______.__,___. ______..._ ....

F A J A 0 D F A J A 0 D 1983 • 1984 46

FIGURE 7. Monthly means and 95% confidence -intervals for

stirface (0.5 m depth) water .alkalinity (bicar bonate, carbonate, total) for Lake Howell, Florida, January, 1983 through December, 1984. The arrow indicates the month that sewage effluent was completely diverted from Lake Howell. Lake Howell Total HC03 70 co=3

rt) 0 u 50 c u l I \ I \ I 40 I CJ' '-J~l . E \ I \ I \ I ~ 30 .... L I c \ I \ c I .¥- ,' <( 20 ,, ', \ I ,l \ \ I 10 \ I \ \ J \ I I J--\ ~ \ \ I \ 0 +> F A J A 0 D F A J A 0 D -....j 1983 • 1984 48

FIGURE 8. Monthly means and confidence intervals for surface (0 ! 5 m depth) water chlorophylla concentrations for Lake Howell, Florida from January, 1983 through December, 1984. The arrow indicates the month that 100% of the sewage effluent was diverted from the lake. 300

Lake Howell 270

240

210 ,,, e 180 0e

0 150 ~ .I:. Q. 0 ~ 120 ~ 0

o ...... _.__.. __ ..._ __ _._ ...... ______..__...._...... _... __ .__..__...... __ ..._...... F A J A 0 D F A J A 0 D 1983 • 1984 50

FIGURE 9. Functional chlorophylla (chlorophylla - pheophytina} monthly mean values for Lake Howell, Florida for January, 1983 through December, 1984. The arrow indicates the month that 100% of the sewage effluent was diverted from Lake Howell. 300 Lake ·Howell .__. Chlorophyll 0 270 A-A Active Chlorophyll 0 filU Pheophytin0 240

210 ro I E 180 Cl E

c 150 ~ ..c. Q. 0._ :c0 120 (.J

1983 • 1984 LITERATURE CITED

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