CITY OF LAKELAND LAKES WATER QUALITY REPORT 1988-2000

Written By: City of Lakeland Public Works Department Lakes & Stormwater Division August 2001

TABLE OF CONTENTS

I. II. III. IV. V.

Introduction Geographical Settings Named Lakes The Lake Life Cycle Pollutants and Lakes Are the Fish Safe to Eat? Is it Safe to Swim in the Lakes? Nutrients Chlorophyll Secchi TSI Water Levels Metals VI. Fish & Wildlife VII. Role of Plants Plant Management Programs VIII. Comprehensive Lakes Plan IX. Lake by Lake Information Glossary

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TABLES AND FIGURES Figure 1 - Map of Named Lakes Figure 2 - Hydrologic Cycle Map Table 1 - Lake Trophic States Table 2 - Average Annual Water Quality Data for 2000 Table 3 - Average Annual Water Quality Data for 1988-2000 Table 4 - Average Metal Concentrations for 2000 Table 5 - Average Metal Concentrations for 1988-2000 Table 6 - List of 38 named lakes

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I.

INTRODUCTION This Lakeland Lakes Water Quality Report summarizes information collected by the City of Lakeland Lakes Program during its first ten years of lakes monitoring. In this report, we provide some useful information for lake users including boat ramp locations and depth soundings for the major lakes in the City. In addition, information on water quality pollution levels and trends is presented to provide the reader with a feel for the health of our lakes. In these cases, we have tried to explain the significance of the data. It should be noted that the science of lakes and rivers (limnology) is still relatively new, and there is much that is still not understood. As with all ecosystems, lakes are incredibly complex. The City of Lakeland encompasses an area of approximately 28,000 acres and contains 38 named lakes and numerous smaller lakes. Among the 38 named lakes, sizes range from 2.5 acres (Lake Blanton) to 2272 acres (Lake Parker). Water discharged from these lakes flow through creeks, ditches and pipes to tributaries of three major river systems - the Peace River, the Alafia River, and the Hillsborough River. Our lakes are invaluable to the citizens of Lakeland as they provide opportunities for recreation, sanctuaries for wildlife, and natural beauty. The importance of the lakes has long been recognized by Lakeland's citizens and civic leaders and was the primary reason for the creation of Lakeland's Lakes Program in 1987. All lakes have an economic value and contribute to a community's quality of life. Prior to the establishment of the City of Lakeland Lakes Program, little information was available on our lakes. Some lakes had no documented water quality data. In 1988, a program was started to monitor water quality on 16 of the major lake systems in the City. This report summarizes the results of this effort. It is our hope that the report will provide information useful to the citizens that are interested in the ecology of these resources as well as those that use them for recreational activities.

II.

GEOGRAPHICAL SETTING The City of Lakeland is located in west central Florida. The soils in this region are naturally rich in phosphorus, a major element needed for growth by plants. The rich phosphorus deposits in the soil have been mined since the turn of the century. It is important to note that soils in Lakeland differ significantly with those found in other parts of Polk County. Three ridges run through the County in a north-south direction. The Lakeland Ridge runs along the West side of the County, the Winter Haven Ridge through the center, and the Lake Wales Ridge along the East. The City of Lakeland is located on the top and eastern slope of the Lakeland Ridge. In the eastern part of the County on the Lake Wales Ridge, the sandy, well-drained soils are typically nutrient poor. Lakes in this region generally have low concentrations of nutrients. These conditions support fewer plants and animals which result is clearer water. The rich, green-water lakes (as found in the Lakeland area) support a greater abundance of fish, and are therefore preferred by many fishermen. Clear water lakes are more aesthetically appealing, and are the choice of boaters, skiers and swimmers. The combination of drainage basins that contain naturally rich soils, abundant rainfall (approximately 52 inches/year) that carries nutrients to the lakes, and a warm sub-tropical climate create the ideal environment for plant growth. Consequently, the lakes in Lakeland are naturally productive. This characteristic is discussed in more detail in Section V.

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III.

NAMED LAKES Figure 1 shows the location of the 38 named lakes in Lakeland. Some of these lakes are located partially in the City and partially in the County. The official authority for naming lakes is the U.S. Board on Geographic Names. The Board is composed of representatives from Federal departments and independent agencies concerned with the use of geographic names. The nine downtown lakes in Lakeland received their names in various ways. Lakes Hunter, Parker and Hollingsworth were named after settlers living adjacent to the lakes. Mr. Munn (Lakeland’s founder) named Lake Morton after his brother-in-law. There is a discrepancy as to whether Lake Bonny (originally Boney) was named after an Indian fighter or after fish in the lake, which were bony. Lake Wire was named after the telegraph line poles that stood in its waters. Lake Bonnet was named after the water lilies growing in a narrow band along its shore. Lake Mirror was originally known as Deep Lake because of its depth, although others called it Lake Bushy because of the trees and heavy undergrowth that covered its shore. The current name was given to the lake because of the reflections seen at night around the lighted promenade.

IV.

THE LAKE LIFE CYCLE Lakes undergo a life cycle that includes various stages from their formation to their eventual filling and return to terrestrial landscapes. In Florida, the vast majority of lakes are formed from sinkhole activity. Limestone, Florida's bedrock, is slowly dissolved by weakly acidic rainwater that percolates through the overlaying sand, clay and organic topsoils. In time, cavities in the limestone are formed, then collapse due to the Swiss cheese like bedrock that results in depressions on the land surface. Water from rainfall, groundwater seepage and in some cases surface sources (creeks and rivers) fill the depressions. In most cases, newly formed lakes are nutrient poor and have clear water. As lakes age, nutrients, sediments and pollutants from the surrounding watershed migrate to the basin. Lake productivity increases with increased nutrient loading resulting in a reduction in water clarity. Basins slowly fill with soil and the remains of plants and animals. The rate at which a lake basin fills typically increases with age. The process of lake aging through increasing productivity is termed eutrophication. An index to measure the degree of lake eutrophication (Trophic State Index – TSI) has been developed and has been calculate for sixteen of Lakeland's lakes. Lakes with a trophic state index value exceeding 70 are highly productive and have persistent algae blooms and poor water clarity (See Section V).

V.

POLLUTANTS AND LAKES The alteration of land by development for residential, agricultural or other uses changes the way water flows through the watershed to a lake or river. The replacement of vegetation with concrete and asphalt reduces the capacity of the land to cleanse or remove pollutants from water as it travels through the watershed to a lake. Figure 2 illustrates the hydrologic cycle and the movement of water through the environment. Pollutants that are released into the environment are carried by stormwater runoff, groundwater and the atmosphere to our lakes. As a result, our lakes are reservoirs for a variety of naturally occurring and man-made contaminants. The most common pollutant problem in Lakeland and in many lakes throughout the world is overenrichment. The discharge of nutrients from fertilizers and eroding soils has resulted in nutrient concentrations in lakes high enough to cause imbalances in plant and animal communities. The construction of stormwater systems that transport this enriched water directly to our lakes and streams has hastened the rate that lakes age. Without the benefit of treatment that comes with the natural sheetflow of water over native soils and vegetation, the pollutants contained in the

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Figure 1. Map of Named Lakes

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Figure 2. The Hydrologic Cycle This cycle has no beginning and no end. The water that collects in oceans, lakes, rivers and reservoirs is continually evaporating under the heat of the sun. It rises into the air as vapor and floats silently into the atmosphere. When vapor cools, it condenses and returns to the earth as precipitation. In Florida, this usually takes the form of rainfall, which becomes runoff and again collects in large water bodies. A small amount percolates through the ground into the aquifers where it is stored as groundwater or moves underground toward the ocean. Even more is absorbed by plants and trees, to be released later through evapotranspiration and resume its looping journey upward in the form of vapor.

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runoff are discharged into our lakes. Stormwater runoff is now considered the greatest source of pollutant loading to Florida's lakes, rivers and estuaries. Since the early 1980's, developments have been required to provide some degree of stormwater treatment prior to discharge offsite. Most of the City of Lakeland's stormwater system was constructed prior to any treatment requirements. These older systems will need to be outfitted with pollutant removal systems if long term water quality improvements are to be expected. When nutrients are discharged into a lake at unnaturally high rates, lakes age faster. Nutrient concentrations in untreated urban runoff are typically ten to one hundred times higher than in runoff from similar undeveloped land. The rapid enrichment fuels algae blooms that cloud the water, cause changes in water chemistry, increase the rate at which the lake fills in, and disrupt other wildlife in the lake. Reversing over-enrichment is difficult and expensive. In lakes where eutrophication is advanced, such as Lake Hollingsworth, the sediments may be an important source of nutrient loading and must be removed before any improvements can be expected.

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ARE THE FISH SAFE TO EAT?

Most of us who eat fish from urban lakes are concerned about their purity. The frequent news about fish consumption advisories issued by state and federal governments adds to the uncertainty. Fish from several lakes in Lakeland have been tested as part of special studies. Five species of fish were collected from the lakes representing a range of trophic groups from omnivorous (fish that eat both plant and animals) to top predators. The study determined that metals and organic concentration levels in the flesh of fish from Lake Hollingsworth are low and consumption does not appear to pose any threat to human health. The State of Florida’s Health Department has tested many of Florida’s water bodies for mercury contamination. In a 1994-1995 advisory from the Game and Freshwater Fish Commission, Lake Parker was listed as a lake where consumption of fish is unrestricted. A 1983 study of Lake Wire and Lake Morton analyzed lead levels in fish flesh from these lakes and found the levels low.

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IS IT SAFE TO SWIM IN THE LAKES

Standards for evaluating the safety of lakes for swimming involve the counting of Coliform bacteria. Coliform bacteria are a group of non-pathogenic bacteria that live in the digestive tracts of warm-blooded animals. The presence of these bacteria are thought to be indicative of contamination by pathogens. (See Tables 2 & 3) The following parameters are used to regularly monitor the conditions of our City lakes:

A.

NUTRIENTS Nutrients found in lakes, such as phosphorus and nitrogen, are critical for plant growth. Typically, nutrients are cycled in a lake through the process of plant production, decomposition of plant and animal matter through fungi and bacteria, and the ensuing release of nutrients. Some nutrients become part of the bottom sediments, some become available for plant growth, and some stay dissolved in the water column. Nutrient enrichment can accelerate eutrophication, although the exact process is not completely understood. Nutrients entering a lake not only “fertilize” algae, increasing its production, they will also fertilize floating, submersed, and shoreline aquatic plants. Often with extensive growth of rooted aquatic plant growth, the water becomes clearer, although nutrient input has increased. The plants grow and use the nutrients, binding them either in the sediments or in the plant itself. Nutrients can cause a lake to become shallower as increased algae and plant production, and ensuing decomposition, add silt to lake bottoms. Layers of sediment accumulate over the years making the lake shallower, eventually turning the lake into a wetland. A nutrient rich lake will fill in faster than a lake 7

with low nutrient levels. The process of natural eutrophication, the infilling of a basin as a lake ages, occurs over many thousands of years. Cultural eutrophication is the acceleration of a lake’s aging due to human activities and added nutrient inputs.

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The City of Lakeland lies in a nutrient rich region known as the Bone Valley Formation. The soils in this area contain high amounts of phosphorus. Phosphorus and nitrogen are the two limiting nutrients in area lakes. Through the dissolution by rain and groundwater, Lakeland’s lakes have higher phosphorus values occurring naturally than most Florida lakes. In addition to urban stormwater runoff, nutrients such as phosphorus and nitrogen can enter the lake from many sources: rainfall directly on lakes; runoff from watersheds; soils naturally containing phosphorus; fertilizers applied to crops and yards; treated waste from industrial processes, such as phosphate mining; effluent from sewage treatment plants; septic tanks; auto exhaust; bird and animal waste; lawn and tree debris; detergents containing phosphates. Typically, nutrients are transported from one place to another by water, usually rainwater. Rainwater is not pure water. Even unpolluted air contains compounds that are picked up by rain. Air pollution adds even more substances to rainwater. Often compounds found in rain contain the nutrients phosphorus and nitrogen, along with other compounds such as sulfides which contribute to lake acidification. Lakes receive nutrients from rain directly and indirectly. When rain falls into lakes, the nutrients are received directly with the rainfall. Lakes also receive nutrients from rain that has fallen on land and has picked up added nutrients on the way. Surface runoff is rain that falls on the ground and flows overland. This runoff then picks up nutrients from yards, woods, roadways and parking lots. Stormwater runoff is the rain which flows quickly from impervious areas such as roads, parking lots and buildings carrying with it particles, debris, and automobile waste products. Nutrient laden water can also reach the lakes by traveling underground. Subsurface runoff flows through rocks or soils which can have high nutrient concentrations, it can then seep into lakes or enter them as springs. In the case of Lakeland’s lakes lying in the phosphoric Bone Valley Region, the nutrient is phosphate. Nutrients can also seep out of septic tanks and flow underground to lakes. Treated sewage (effluent) which comes out of sewage treatment plants is extremely high in nutrients. As populations increase, some areas have resorted to disposing of their effluent in wetlands or other water bodies, or by pumping it into the ground or spraying it on fields. No matter how one disposes of the effluent, the nutrients can still flow overground or underground to a lake.

B.

CHLOROPHYLL Chlorophyll is the green pigment in plants that not only imparts color but makes it possible for photosynthesis to occur. Chlorophyll is possibly the most frequently used estimator of algal biomass in lakes and streams, at least in the United States. Algal production (biomass) is controlled by water temperature, light availability, nutrient availability, hydraulic residence time (the time required for the lake volume to replace itself), and consumption by animals. When enough light is available for photosynthesis, the availability of nutrients is often the controlling factor. Usually phosphorus and nitrogen are the least available nutrients, so they become the limiting factors in algal production. The by-products of modern living are high in these sources of nutrients. Wastewater, fertilizers, agricultural drainage, detergents, and municipal sewage contain high concentrations of phosphorus and nitrogen, and if they enter a lake, they will stimulate algal productivity.

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C.

SECCHI A Secchi Disk is a flat horizontal white or white with alternating black quadrants disk that is lowered from a rope into the water until it disappears from view. The standard Secchi disk used in fresh water systems is an eight-inch black and white disk. The depth of the water column where a Secchi Disk can no longer be seen is a measure of the transparency of the water. Transparency is affected by the color of the water and by suspended particles of silt, clay, or algae. Transparency can be a measure of some sorts of pollution. Limnologists (Lake Managers) tend to think of water quality in terms of the amount of algae, weeds (aquatic plants), silt and turbidity in a water body. Out of 114 Polk County lakes sampled in 1997 by Polk County Natural Resources staff, average Secchi disk values ranged from 0.2 m (8 inches) to 4.0 m (13 feet). Lakeland has 38 named lakes 16 of these lakes are routinely sampled for water quality. Average Secchi disk values in 1997 for Lakeland lakes ranged from 0.23 m (9 inches) to 3.7 m (12 feet). The lowest Secchi readings were in Lake Hollingsworth; the highest readings were in Lake Wire. Lake Wire’s extensive growths of submersed aquatic plants influence Secchi depth and water clarity.

D.

TSI TSI is an acronym for trophic state index or indices. Various indices are available to evaluate measured in-lake variables so that the extent of eutrophy (aging) or degradation can be compared to other lakes in the area. Trophic state indices provide a quantitative means of assessing lake changes by simplifying complex environmental measurements. The basis for using a trophic state index is that, in many lakes, the degree of eutrophication is related to increased nutrient concentrations in the lake. The assumption follows that an increase in lake phosphorus concentrations leads to an increase in algal biomass as measured by chlorophyll a, which would result in a decrease in water transparency as measured by Secchi disk. The Carlson (1977) Trophic State Index (TSI) is the most widely used and best known. Since 1977, several additional trophic state indices have been developed that rely on Carlson’s approach. However, while many of these indices have similar features, most of them were derived from data on temperate lakes. For this reason, Carlson’s Index or the other recent indices should not be applied directly to Florida Lakes. Studies on subtropical and warm-temperate Florida lakes argue that relationships among Secchi Depth (SD), Total Phosphorus (TP), and chlorophyll a are unique for Florida lakes. The development of a Florida TSI by the University of Florida in 1983, takes into account multiple variables and represents an average of the physical, chemical and biological components of the trophic state theory. Many Florida lakes are nitrogen limited, while the Carlson Index assumes that lakes are phosphorus limited. The Florida trophic state index uses sub-indices for Secchi Depth, Total Phosphorus, Total Nitrogen, and chlorophyll a. Average TSI’s were developed depending on whether a lake is phosphorus limited, nitrogen limited, or relatively nutrient balanced. Since an increase in plant biomass is a measure of eutrophication (enrichment), plant biomass indicators were selected as components of the sub-indices. To determine algal biomass, an index based on chlorophyll was developed. The Florida TSI uses percent macrophyte (large aquatic plants) coverage as the index for macrophyte biomass. There are subjective problems in dealing with percent macrophyte cover, since the index does not qualify submergent vs. floating or native vs. exotic plants. The primary problem with using macrophyte coverage as an index is that macrophyte abundance and chlorophyll a appear to be independent of each other in Florida lakes. The main point of using a TSI to classify Florida lakes for management purposes, is the selection of a critical value for the TSI. That is, deciding the value above which a lake is likely to exhibit eutrophication or enrichment problems. Huber et. al. (1983) in a comparison of 573 Florida lakes discovered that 411 of the lakes had TSI’s of 60 or below. These 411 lakes seemed to have less urgent problems. Of the remaining 162 9

lakes compared, 90 problem lakes were identified with TSI’s greater than 60. Of the 90 problem lakes, several lakes are well known as enriched or “troubled” lakes: such as Apopka, Hancock, Thonotosassa and Okeechobee. In conclusion, Huber et. al., assumed that a TSI of 60 is the cut-off for Florida lakes, above which enrichment becomes a problem. The formula to calculate TSI was adopted by the State of Florida and is outlined in the State’s 1996 305(b) report: ChlA TSI = 16.8 +(14.4 x LN (CHLA)) TN TSI = 56 + (19.8 x LN (TN)) TN2TSI = 10 x (5.96 + 2.15 x LN (TN + .0001)) TP TSI = (18.6 x LN (TP x 1000)) – 18.4 TP2 TSI = 10 x (2.36 x LN (TP x 1000) – 2.38) Limiting nutrient considerations for calculating NUTR TSI: If TN/TP>30 then NUTR TSI = TP2 TSI If TN/TP