Transcription
Lake Assessment Report forLake Ellenin Hillsborough County, FloridaDate Assessed: July 15, 2010Assessed by: David EilersReviewed by: Jim GriffinINTRODUCTIONThis assessment was conducted to update existing physical and ecological data for Lake Ellen onthe Hillsborough County & City of Tampa Water Atlas. The project is a collaborative effortbetween the University of South Florida’s Center for Community Design and Research andHillsborough County Stormwater Management Section. The project is funded by HillsboroughCounty and the Southwest Florida Water Management District’s Northwest Hillsborough,Hillsborough River and Alafia River Basin Boards. The project has, as its primary goal, the rapidassessing of up to 150 lakes in Hillsborough County during a five-year period. The product ofthese investigations will provide the County, lake property owners and the general public a betterunderstanding of the general health of Hillsborough County lakes, in terms of shorelinedevelopment, water quality, lake morphology (bottom contour, volume, area, etc.) and the plantbiomass and species diversity. These data are intended to assist the County and its citizens tobetter manage lakes and lake-centered watersheds.Figure 1. General photograph of Lake EllenPage 1Florida Center for Community Design and Research, University of South Florida
The first section of the report provides the results of the overall morphological assessment ofthe lake. Primary data products include: a contour (bathymetric) map of the lake, area, volumeand depth statistics, and the water level at the time of assessment. These data are useful forevaluating trends and for developing management actions such as plant management wheredepth and lake volume are needed.The second section provides the results of the vegetation assessment conducted on the lake.These results can be used to better understand and manage vegetation in the lake. A list isprovided with the different plant species found at various sites around the lake. Potentiallyinvasive, exotic (non-native) species are identified in a plant list and the percent of exotics ispresented in a summary table. Watershed values provide a means of reference.The third section provides the results of the water quality sampling of the lake. Both field dataiand laboratory data are presented. The trophic state index (TSI) is used to develop a generallake health statement, which is calculated for both the water column with vegetation and thewater column if vegetation were removed. These data are derived from the water chemistry andvegetative submerged biomass assessments and are useful in understanding the results ofcertain lake vegetation management practices.The intent of this assessment is to provide a starting point from which to track changes in thelake, and where previous comprehensive assessment data is available, to track changes in thelake’s general health. These data can provide the information needed to determine changes andto monitor trends in physical condition and ecological health of the lake.Section 1: Lake MorphologyiiBathymetric Map . Table 1 provides the lake’s morphologic parameters in various units. Thebottom of the lake was mapped using a Lowrance LCX 28C HD Wide Area Augmentation Systemiii(WAAS) enabled Global Positioning System (GPS) with fathometer (bottom sounder) todetermine the boat’s position, and bottom depth in a single measurement. The result is anestimate of the lake’s area, mean and maximum depths, and volume and the creation of a bottomcontour map (Figure 2). Besides pointing out the deeper fishing holes in the lake, the morphologicdata derived from this part of the assessment can be valuable to overall management of the lakevegetation as well as providing flood storage data for flood models.Table 1. Lake Morphologic Data (Area, Depth and Volume)ParameterFeetMetersAcresSurface Area (sq)2,254,666209,46551.76Mean Depth134Maximum Depth267.90Volume (cubic)27,257,610771,850Gauge 4iThe trophic state index is used by the Water Atlas to provide the public with an estimate of theirlake resource quality. For more information, see end note 1.iiA bathymetric map is a map that accurately depicts all of the various depths of a water body. Anaccurate bathymetric map is important for effective herbicide application and can be an importanttool when deciding which form of management is most appropriate for a water body. Lakevolumes, hydraulic retention time and carrying capacity are important parts of lake managementthat require the use of a bathymetric map.iiiWAAS is a form of differential GPS (DGPS) where data from 25 ground reference stationslocated in the United States receive GPS signals form GPS satellites in view and retransmit thesedata to a master control site and then to geostationary satellites. For more information, see endnote 2.Page 2Florida Center for Community Design and Research, University of South Florida
Figure 2. 2008 Bathymetric contour map for Lake EllenPage 3Florida Center for Community Design and Research, University of South Florida
Section 2: Lake Ecology (Vegetation)The lake’s apparent vegetative cover and shoreline detail are evaluated using the latest lakeaerial photograph as shown in and by use of WAAS-enabled GPS. Submerged vegetation isdetermined from the analysis of bottom returns from the Lowrance 28c HD combinedGPS/fathometer described earlier. As depicted in Figure 3, 10 vegetation assessment sites werechosen for intensive sampling based on the Lake Assessment Protocol (copy available onrequest) for a lake of this size. The site positions are set using GPS and then loaded into a GISmapping program (ArcGIS) for display. Each site is sampled in the three primary vegetativeivzones (emergent, submerged and floating) . The latest high resolution aerial photos are used toprovide shore details (docks, structures, vegetation zones) and to calculate the extent of surfacevegetation coverage. The primary indices of submerged vegetation cover and biomass for thelake, percent area coverage (PAC) and percent volume infestation (PVI), are determined bytransiting the lake by boat and employing a fathometer to collect ―hard and soft return‖ data.These data are later analyzed for presence and absence of vegetation and to determine theheight of vegetation if present. The PAC is determined from the presence and absence analysisof 100 sites in the lake and the PVI is determined by measuring the difference between hardreturns (lake bottom) and soft returns (top of vegetation) for sites (within the 100 analyzed sites)where plants are determined present.Beginning with the 2010 Lake Assessments, the Water Atlas Lake Assessment Team has addedvthe Florida Department of Environmental Protection (FDEP) Lake Vegetation Index (LVI) methodto the methods used to evaluate a lake. The LVI method was designed by DEP to be a rapidassessment of ecological condition, by determining how closely a lake’s flora resembles thatexpected from a minimally disturbed condition.The data collected during the site vegetation sampling include vegetation type, exotic vegetation,predominant plant species and submerged vegetation biomass. The total number of species fromall sites is used to approximate the total diversity of aquatic plants and the percent of invasiveexotic plants on the lake (Table 2). The Watershed value in Table 2 only includes lakes sampledduring the lake assessment project begun in May of 2006. These data will change as additionallakes are sampled. Table 3 through Table 5 detail the results from the 2010 aquatic plantassessment for the lake. These data are determined from the 10 sites used for intensivevegetation surveys. The tables are divided into Floating Leaf, Emergent and Submerged plantsand contain the plant code, species, common name and presence (indicated by a 1) or absence(indicated by a blank space) of species and the calculated percent occurrence (number sitesspecies is found/number of sites) and type of plant (Native, Non-Native, Invasive, Pest). In the―Type‖ category, the codes N and E0 denote species native to Florida. The code E1 denotesCategory I invasive species, as defined by the Florida Exotic Pest Plant Council (FLEPPC); theseare species ―that are altering native plant communities by displacing native species, changingcommunity structures or ecological functions, or hybridizing with natives.‖ The code E2 denotesCategory II invasive species, as defined by FLEPPC; these species ―have increased inabundance or frequency but have not yet altered Florida plant communities to the extent shownby Category I species.‖ Use of the term invasive indicates the plant is commonly consideredinvasive in this region of Florida. The term ―pest‖ indicates a plant (native or non-native) that hasa greater than 55% occurrence in the lake and is also considered a problem plant for this regionof Florida, or is a non-native invasive that is or has the potential to be a problem plant in the lakeand has at least 40% occurrence. These two terms are somewhat subjective; however, they areprovided to give lake property owners some guidance in the management of plants on theirproperty. Please remember that to remove or control plants in a wetland (lake shoreline) inHillsborough County the property owner must secure an Application To Perform MiscellaneousActivities In Wetlands permit from the Environmental Protection Commission of HillsboroughCounty and for management of in-lake vegetation outside the wetland fringe (for lakes with anivvSee end note 3.See end note 4.Page 4Florida Center for Community Design and Research, University of South Florida
area greater than ten acres), the property owner must secure a Florida Department ofEnvironmental Protection Aquatic Plant Removal Permit.Table 2. Total Diversity, Percent Exotics, and Number of Pest Plant SpeciesParameterLakeWatershedNumber of Vegetation Assessment Sites10138Total Plant Diversity (# of Taxa)61164% Non-Native Plants2621Total Pest Plant Species320Page 5Florida Center for Community Design and Research, University of South Florida
Figure 3. Map of vegetation assessment sites for Lake EllenPage 6Florida Center for Community Design and Research, University of South Florida
Table 3. List of Floating Leaf Zone Aquatic Plants FoundPlant Species CodeScientific NameCommon NameNuphar luteaNLMSpatterdock, Yellow PondlilyAlgal spp.ALGAlgal Mats, FloatingEichornia crassipesECSWater HyacinthIris virginicaIVASouthern Blue FlagNymphea odorataNOAAmerican White Water Lily, Fragrant Water LilyPage 7Florida Center for Community Design and Research, University of South FloridaPercent Occurrence80%50%20%10%10%TypeN, E0E1E0N, E0
Figure 4. Photograph of the floating vegetation zone on Lake Ellen featuring Nuphar lutea.Page 8Florida Center for Community Design and Research, University of South Florida
Table 4. List of Emergent Zone Aquatic Plants FoundPlant SpeciesScientific NameCodeACEAcer rubrumCommon NameSouthern Red MaplePercentOccurrence100%PGMTASPaspalidium geminatumTaxodium acendensEgyptian PaspalidiumPond Cypress100%100%PHNPanicum hemitomonMaidencane80%PCAPontederia cordataPickerel Weed70%BLSTYPBlechnum serrulatumTypha spp.Swamp fern, Toothed Midsorus FernCattails70%70%PRSBOCPanicum repensBoehmeria cylindricaTorpedo GrassBog Hemp, False Nettle60%60%MSSMikania scandensClimbing Hempvine60%LOSLudwigia octovalvis60%LPAVRALudwigia peruvianaVitis rotundifoliaMexican Primrosewillow, Long-stalkedLudwigiaPeruvian PrimrosewillowMuscandine GrapeWAXMyrica ceriferaWax Myrtle40%SAMSambucus canadensisElderberry40%SLASagittaria lancifoliaDuck Potato40%STSMELDBAQLASchinus terebinthifoliusMelaleuca quinquenerviaDioscorea bulbiferaQuercus laurifoliaBrazilian PepperPunk Tree, MelaleucaAir PotatoLaurel Oak; Diamond Oak30%30%30%30%SALSalix spp.Willow30%Page 9Florida Center for Community Design and Research, University of South Florida50%40%TypeN,E0E0N,E0N,E0N,E0NN,E0E1, PN,E0N,E0N,E0E0, PN,E0N,E0N,E0N,E0E1E1E1N,E0N,E0
Plant SpeciesCodeAPSBHAScientific NameCommon NameAlternanthera philoxeroidesBaccharis halimifoliaAlligator WeedSea MyrtlePercentOccurrence30%30%COMCommelina spp.Dayflower30%HYEHydrocotyl umbellataManyflower Marshpennywort, Water Pennywort30%ICEIlex cassineDahoon Holly20%COSCephalanthus occidentalisButtonbush20%CAACentella asiaticaAsian Pennywort, Coinwort20%POLPolygonum spp.Smartweed, Knotweed20%NEANephrolepis exaltataSword Fern, Wild Boston Fern20%ERHErechtites hieraciifoliaFireweed20%SSMSPOSapium sebiferumSabal palmettoChinese Tallow TreeSabal Palm, Cabbage Palm20%10%TDMTaxodium distichumBald Cypress10%TGAThalia geniculataFireflag, Arrowroot10%OCAOsmunda cinnamomeaCinnamon Fern10%DIMRFDesmodium incanumOsmunda regalisCreeping BeggarweedRoyal Fern10%10%PLUPluchea spp.Marsh Fleabane,Camphorweed10%PNAPhyla nodifloreaFrog-fruit, Carpetweed, Turkey Tangle Fogfruit10%CANCanna spp.Canna10%Page 10Florida Center for Community Design and Research, University of South 1N,E0N,E0N,E0N,E0E0N,E0N,E0N,E0E0
Plant SpeciesCodeCFLScientific NameCommon NameCoreopsis floridanaFlorida TickseedPercentOccurrence10%AVSBroomsedge Bluestem, Broom grass10%ALAAndropogon virginicus var.glaucusAsclepias lanceolataFewflower milkweed10%CYOCyperus odoratusFragrant Flatsedge10%BIDBidens spp.Bur Marigold10%JESJuncus effusus var solutusSoft Rush10%LIQLiquidamber styracifluaSweetgum10%Page 11Florida Center for Community Design and Research, University of South FloridaTypeN,E0N,E0N,E0N,E0N,E0N,E0N,E0
Figure 5. Photograph of Melaleuca quinquenervia, a non-native invasive tree, on Lake EllenPage 12Florida Center for Community Design and Research, University of South Florida
Table 5. List of Submerged Zone Aquatic Plants Found.Plant Species CodeScientific NameHydrilla verticillataHVANajas guadelupensisNGSUtricularia spp.UTANitella spp.NITCeratophyllum demersumCDMValisneria americanaVAAEleocharis baldwiniiEBIMicranthemum glomeratumMGMPage 13Common NameHydrilla, waterthymeSouthern NaiadBladderwortStonewortHornwort, CoontailTapegrassBaldwin's Spikerush, RoadgrassManatee Mudflower, Baby's TearsFlorida Center for Community Design and Research, University of South FloridaPercent Occurrence100%90%50%40%40%30%10%10%TypeE1, PN, E0N, E0N, E0N, E0N, E0N, E0N, E0
Figure 6. Photograph of Hydrilla verticillata, a non-native invasive species, on LakeEllenPage 14Florida Center for Community Design and Research, University of South Florida
Table 6. List of All Plants and Sample SitesPlant Common NameFound at Sample SitesEgyptian PaspalidiumHydrilla, waterthymePond CypressSouthern Red MapleSouthern NaiadMaidencaneSpatterdock, Yellow PondlilyCattailsPickerel WeedSwamp fern, Toothed Midsorus FernBog Hemp, False NettleClimbing HempvineMexican Primrosewillow, Long-stalked LudwigiaTorpedo GrassAlgal Mats, FloatingBladderwortPeruvian PrimrosewillowDuck PotatoElderberryHornwort, CoontailMuscandine GrapeStonewortWax MyrtleAir PotatoAlligator WeedBrazilian PepperDayflowerLaurel Oak; Diamond OakManyflower Marshpennywort, Water PennywortPunk Tree, MelaleucaSea Page 15Florida Center for Community Design and Research, University of South rgentSubmersed
Plant Common NameFound at Sample SitesWillowAsian Pennywort, CoinwortButtonbushChinese Tallow TreeDahoon HollyFireweedSmartweed, KnotweedSword Fern, Wild Boston FernWater HyacinthAmerican White Water Lily, Fragrant Water LilyBald CypressBaldwin's Spikerush, RoadgrassBroomsedge Bluestem, Broom grassBur MarigoldCannaCinnamon FernCreeping BeggarweedFewflower milkweedFireflag, ArrowrootFlorida TickseedFragrant FlatsedgeFrog-fruit, Carpetweed, Turkey Tangle FogfruitManatee Mudflower, Baby's TearsMarsh Fleabane,CamphorweedRoyal FernSabal Palm, Cabbage PalmSoft RushSouthern Blue 185614185859Page 16Florida Center for Community Design and Research, University of South TerrestrialEmergentFloatingEmergent
Section 3: Long-term Ambient Water ChemistryA critical element in any lake assessment is the long-term water chemistry data set. These dataare obtained from several data sources that are available to the Water Atlas and are managed inthe Water Atlas Data Download and graphically presented on the water quality page for lakes inHillsborough County. The Lake Ellen Water Quality Page can be viewed waterquality.asp?wbodyid 5182&wbodyatlas lake).A primary source of lake water chemistry in Hillsborough County is the Florida LAKEWATCHvolunteer lake monitor and the Florida LAKEWATCH laboratory at the University of Florida. LakeEllen does not have an active LAKEWATCH volunteer presently. The last LAKEWATCHvolunteer water chemistry data was collected on November 17, 2008, so only limited trendanalysis is possible. Other source data are used as available; however these data can onlyindicate conditions at time of sampling.These data are displayed and analyzed on the Water Atlas as shown in Figure 7Figure 7, Figurei8, and Figure 9 for Lake Ellen. The figures are graphs of: (1) the overall trophic state index (TSI) ,which is a method commonly used to characterize the productivity of a lake, and may be thoughtof as a lake’s ability to support plant growth and a healthy food source for aquatic life; (2) thechlorophyll a concentration, which indicates the lake’s algal concentration, and (3) the lake’sSecchi Disk depth which is a measure of water visibility and depth of light penetration. These dataare used to evaluate a lake’s ecological health and to provide a method of ranking lakes and areindicators used by the US Environmental Protection Agency (USEPA) and the FloridaDepartment of Environmental Protection (FDEP) to determine a lake’s level of impairment. Thechlorophyll a and Secchi Disk depth graphs include benchmarks which indicate the medianvalues for the various parameters for a large number of Lakes in Florida expressed aspercentiles.Based on best available data, Lake Ellen has a color value determined as a platinum cobalt unit(pcu) value of 22.7 and is considered a Clear lake (has a mean color in pcu equal to or below 40).The FDEP and USEPA may classify a lake as impaired if the lake is a dark lake (has a meancolor in pcu greater than 40) and has a TSI greater than 60, or is a clear lake and has a TSIgreater than 40. Lake Ellen has a TSI of 44 and meets the FDEP Impaired Waters Rule (IWR)criteria and could be classified as impaired. See also Table 7.Page 17Florida Center for Community Design and Research, University of South Florida
Figure 7. Recent Trophic State Index (TSI) graph for Lake EllenviviGraph source: Hillsborough County Water Atlas. For an explanation of the Good, Fair and Poorbenchmarks, please see the notes at the end of this report. For the latest data go hs20/graph it.aspx?wbodyid 5182&data TSI&datatype WQ&waterbodyatlas lake&ny 10&bench 1Page 18Florida Center for Community Design and Research, University of South Florida
Figure 8. Recent Chlorophyll a graph for Lake EllenviiviiGraph Source: Hillsborough County Water Atlas. For the latest data go s20/graph it.aspx?wbodyid 5182&data Chla ugl&datatype WQ&waterbodyatlas lake&ny 10&bench 1Page 19Florida Center for Community Design and Research, University of South Florida
Figure 9. Recent Secchi Disk graph for Lake EllenviiiAs part of the lake assessment the physical water quality and chemical water chemistry of a lakeare measured. These data only indicate a snapshot of the lake’s water quality; however they areuseful when compared to the trend data available from LAKEWATCH or other sources. Table 7contains the summary water quality data and index values and adjusted values calculated fromthese data. The total phosphorus (TP), total nitrogen (TN) and chlorophyll a water chemistrysample data are the results of chemical analysis of samples taken during the assessment andanalyzed by the Hillsborough County Environmental Protection Commission laboratory.The growth of plants (planktonic algae, macrophytic algae and rooted plants) is directlydependent on the available nutrients within the water column of a lake and to some extent thenutrients which are held in the sediment and the vegetation biomass of a lake. Additionally, algaeand other plant growth are limited by the nutrient in lowest concentration relative to that neededby a plant. Plant biomass contains less phosphorus by weight than nitrogen so phosphorus ismany times the limiting nutrient. When both nutrients are present at a concentration in the lakeso that either or both may restrict plant growth, the limiting factor is called ―balanced‖. The ratioof total nitrogen to total phosphorous, the ―N to P‖ ratio (N/P), is used to determine the limitingfactor. If N/P is greater than or equal to 30, the lake is considered phosphorus limited, when thisratio is less than or equal to 10, the lake is considered nitrogen limited and if between 10 and 30 itis considered balanced.viiiGraph Source: Hillsborough County Water Atlas. For the latest data go s20/graph it.aspx?wbodyid 5182&data secchift&datatype WQ&waterbodyatlas lake&ny 10&bench 1Page 20Florida Center for Community Design and Research, University of South Florida
Table 7. Water Quality Parameters (Laboratory) for Lake EllenParameterValueLake Area (Acres)51.76Lake Area (m2)209,465.00Lake Volume (m3)771,850.00Number of Vegetation Sites10Average Station SAV Weight2.21Wet Weight of Vegetation (g)185,167,314.86Dry Weight of Vegetation (g)14,813,385.19Total Phosphorus (ug/L)29.00Total Nitrogen (ug/L)551.00Chlorophyll a (ug/L)7.30TN/TP19.0Limiting NutrientBalancedChlorophyll TSI45Phosphorus TSI44Nitrogen TSI44TSI44Color (PCU)22.75Secchi disk depth (ft)8.90Impaired TSI for Lake40Lake Status (Water Column)ImpairedThe color of a lake is also important to the growth of algae. Dark, tannic lakes tend to suppressalgal growth and can tolerate a higher amount of nutrient in their water column; while clear lakestend to support higher algal growth with the same amount of nutrients. The color of a lake, whichis measured in a unit called the ―cobalt platinum unit (PCU)‖ because of the standard used todetermine color, is important because it is used by the State of Florida to determine lakeimpairment as explained earlier. A new rule which is being developed by USEPA and FDEP, willuse alkalinity in addition to color to determine a second set of ―clear-alkaline lakes‖ which will beallowed a higher TSI than a ―clear-acid‖ lake. This is because alkaline lakes have been found toexhibit higher nutrient and algal concentrations than acid lakes. Additionally, lakes connected toa river or other ―flow through‖ system tends to support lower algal growth for the same amount ofnutrient concentration. All these factors are important to the understanding of your lake’s overallcondition. Table 7 includes many of the factors that are typically used to determine the actualstate of plant growth in your lake. These data should be understood and reviewed whenestablishing a management plan for a lake; however, as stated above other factors must beconsidered when developing such a plan. Please contact the Water Atlas Program if you havequestions about this part or any other part of this report.Lake Ellen is in the ―Clear‖ category of lakes based on its mean color value of 22.7 pcu. Thismeans that to not be considered impaired, the TSI must be equal to or less than 40. The TSI forLake Ellen is 44 so the lake would be considered impaired by the FDEP criteria based on thissingle data set. Figure 7 also indicates that enough single occurrences of TSI greater than 40exist for the lake to be considered impaired.Table 8 provides data derived from the vegetation assessment which is used to determine anadjusted TSI. This is accomplished by calculating the amount of phosphorus and nitrogen thatcould be released by existing submerged vegetation (Adjusted Nutrient) if this vegetation weretreated with an herbicide or managed by the addition of Triploid Grass Carp (Ctenopharyngodonidella). The table also shows the result of a model that calculates the potential algae, aschlorophyll a (Adjusted Chlorophyll), which could develop due to the additional nutrients heldwithin the plant biomass. While it would not be expected that all the vegetation would be turnedinto available phosphorus by these management methods, the data is useful when planningPage 21Florida Center for Community Design and Research, University of South Florida
various management activities. Approximately 40.00 % of the lake has submerged vegetationpresent (PAC) and this vegetation represents about 10.05 % of the available lake volume (PVI).Please see additional parameters for adjusted values where appropriate in Table 8. Thevegetation holds enough nutrients to add about 56.06 g/L of phosphorus and 915.65 g/L ofnitrogen to the water column and increase the algal growth potential within the lake.Lake Ellen is a balanced lake, in terms of limiting nutrient, and an increase in either phosphorusor nitrogen could change the TSI and increase the potential for algal growth.Table 8. Field parameters and calculations used to determine nutrients held in SubmergedAquatic Vegetation (SAV) biomass.ParameterValue% Area Covered (PAC)40.0 %PVI10.1 %Total Phosphorus - Adjusted (ug/L)27.06Total Phosphorus - Combined (ug/L)56.06Total Nitrogen - Adjusted (ug/L)364.65Total Nitrogen - Combined (ug/L)915.65Chlorophyll - Adjusted from Total Nutrients (ug/L)10.65Chlorophyll - Combined (ug/L)17.95Adjusted Chlorophyll TSI58Adjusted Phosphorus TSI0Adjusted Nitrogen TSI0Adjusted TSI (for N, P, and CHLA)56Impaired TSI for Lake40Lake Ellen has significant coverage of submerged vegetation (PAC 40%) and vegetationrepresents 10.1 % of the volume of the lake. Vegetation, especially, submerged vegetation is areservoir for nutrients and for Lake Ellen, this reservoir represents a potential available nutrientconcentration of 27.06 µg/L total phosphorus, 364.65 µg/L total nitrogen with the potentialchlorophyll (produced from released nutrients) concentration of 10.65 µg/L. These data indicatethat the removal of submerged vegetation in Lake Ellen would result in a TSI increase from 44 to56 and would cause a larger level of impairment for the lake. Since the primary emergentspecies in the lake is now the invasive species Hydrilla, it will be necessary for vegetation to becontrolled in the lake, but this should be accomplished in a manner that does not cause animmediate loss of submerged vegetation which would cause the lake to move from a macrophytedominant system to a microphyte-dominated system.Table 9 contains the field data taken in the center of the lake using a multi-probe (we use either aYSI 6000 or a Eureka Manta) which has the ability to directly measure the temperature, pH,dissolved oxygen (DO), percent DO (calculated from DO, temperature and conductivity). Thesedata are listed for three levels in the lake and twice for the surface measurement. The duplicatesurface measurement is taken as a quality assurance check on measured data.Page 22Florida Center for Community Design and Research, University of South Florida
Table 9. Water Chemistry Data Based on Manta Water Chemistry Probe for Lake EllenSampleSampleTimeTemp 646.16Value9:30:00AMpH6.746.736.706.73Table 9 provides and indication of changes of the physical-chemical conditions of the watercolumn from surface to bottom. A lake that is well mixed like Lake Ellen will show little change invalues from top to bottom. The data also indicates a healthy system with adequate dissolvedoxygen concentrations at all levels and only moderate in temperature, conductivity or pH.To better understand many of the terms used in this report, we recommend that the reader visitthe Hillsborough County & City of Tampa Water Atlas and explore the ―Learn More‖ areas whichare found on the resource pages. Additional information can also be found using the DigitalLibrary on the Water Atlas website.Page 23Florida Center for Community Design and Research, University of South Florida
Section 4: ConclusionLake Ellen is a medium area (51.76-acre) lake that would be considered in the Mesotrophic toEutrophic category of lakes based on water chemistry. It has a plant diversity of 61 speciesrelative to the total watershed plant diversity of 164 species with about 40.00 % percent of theopen water areas containing submerged aquatic vegetation. Vegetation helps to maintain thenutrient balance in the
Page 2 Florida Center for Community Design and Research, University of South Florida The first section of the report provides the results of the overall morphological assessment of the lake. Primary data products include: a contour (bathymetric) map of the lake, area, volume and depth statistics, and the water level at the time of assessment.
