SpatialPatternsofPhosphorusConcentrationsinaWater
ConservationAreaoftheFloridaEverglades
KelleyYeomanandWilliam MitschPhD.
EvergladesWetlandResearchPark,FloridaGulfCoastUniversity
4940 Bayshore Drive,NaplesFL 34112-7336
RESULTS
ABSTRACT
One ofthefunctionsofwetlandsinan agricultural watershed is thewetlands’ ability tocycle
nutrientswithinthesystem and exchange chemicals tosurroundingwaters,landscapes, and the
atmosphere². The Florida Everglades is oneofthelargest wetlands intheworldandis limited by
bothannualhydroperiodsand nutrientloading³. The water received by thissystem flowssouth
fromLake Okeechobee. Excess nutrientsfromagricultural runoffandurbanizationarea major
threat tothelake. Inattempt toimprove waterquality, the SouthFlorida Water Management
District hasimplemented a series ofStormTreatment Areas (STAs)designed toremove excess
nutrientsbeforethey impact ournatural wetlands. Ten sampling locations were chosenin WCA-3A
starting ata publicboatramp offofinterstate-75(I-75)souththeTamiamiTrail (US-41),adistance
ofabout112.7kmformonthlysampling. In fieldmeasurements were taken forwaterdepth,
temperature, pH, salinity anddissolved oxygen. Phosphorousanalysiswas conductedbyusing The
Westco SmartChem 200discreteAnalyzer withEPAmethod 365.4.Thecorrelation between
decreasing dissolved oxygen concentration andan increasing water temperature was well defined
inthisstudy.As expected, thewetland was foundtobesinkofnutrientswithwelldefined inflows
andoutflowsoutnutrients.The ending of2015showedpromisingresultswithlowphosphorus
concentrations. However, the beginning of2016broughtanunexpectedhurdle, an El Niñothat
sweptacross thestate. The impact ofthisstormresultedin muchofthegreater Everglades being
shutdown,increased water levels thatlead towaterreleases fromLake Okeechobee intotheGulf
ofMexico, AtlanticOcean as well as the Florida Everglades andan overall change formanybiotic
andabiotic factors.As a resultfromtheLake Okeechobee water releases muchhigh phosphorus
concentrationswere measured thanexpected.
Figure 1. Dissolved oxygen and water temperature from April-June 2016
CONCLUSIONS
INTRODUCTION
Phosphorus(P)isoftenalimitingnutrientinagriculture andis addedtomany fertilizers toimprove
cropyield. Phosphorusisusuallypresent inbothorganic andinorganic forms.As thedissolved
inorganic Pincreases in awetland, insoluble mineral Pcan formwithiron,aluminumorcalcium
depending onhowacidic oralkaline themineral soilis withinthatparticular wetland. Asa sink
functionofwetlands,the increase ofmineral Psignificantly decreases theavailability ofPto
environment. Anexcess ofPhasalso showntocauseeutrophication inmany lakes andstreams. This
process occurswhentoomuchavailable P(ornitrogen)ispresent andpromotesalgal growth.Asthe
algae dies anddecomposes anaerobic organisms begin tothrive, depleting thedissolved oxygen in
thewater. This resultsin asignificant change in thebiota. Asa resultofthis,the SouthFlorida Water
Management District (SFWMD) hasdetermined a geometric mean of10parts-per-billion(ppb)of
phosphorusasthestandardfordetermining discharge limits¹. The objectives ofthisstudyare to
determine thecurrentphosphorusconcentrationinWater Conservation Area-3A northofthe
Everglades National Park andtocompare these findingstohistorical data providedby SFWMD and
othersandtodetermine ifthe Pconcentrationsare routinely below10ppb.The results fromthis
studyare hypothesized toshowadecreasing gradient ofphosphorusasthewater flowssouthtoThe
Everglades National Park.
Therelationshipbetweenofdissolvedoxygenandthetemperaturewasverywellillustratedwiththisstudy.
As thewatertemperatureincreasesthedissolvedoxygeninthewaterdecreases.Thisobservationcanbeseen
inbothfigures1and2.Thereisonelowspikerecordedatsite75-4whichmaybeexplainedbythelocationof
thesitewhichisin themiddleofahightrafficairboattrail.TotalPconcentrationsforthesamplingrecords
(Figure3)illustrateanoverallincreaseofPconcentrations.Theincreaseislikelyduetothewaterreleasesfrom
LakeOkeechobee.Anestimatedconcentrationof1ppbwasusedwhenthelaboratorylowthresholdof
<2.0ppbwasreported.BeforetheElNiñosweptoversouthFloridaandbeforethewaterreleasesofLake
Okeechobee,itisexpectedthatthePconcentrationsinWCA-3Awouldremainlow.Thereisaclearpattern
betweentheinflowatthe75-sidesamplesandtheoutflowatthe41-sidesamples.Asthewaterflowsthrough
thearea,thewetlandisactingasaPsinkanddecreasedconcentrationsofPareobservedattheendofthe
samplesites.SincethewaterreleasesthereisclearlyahigherconcentrationofPthroughouttheareaalthough
SFWMDclaimsmostoftheareahasremainedunimpacted.However,PconcentrationsneartheMiamicanal
(closesttositeM-2)containedPconcentrationsofupto20ppb.Otherareastowardsthe75-sideofthearea
arereportedtohavecloseto8-10ppmofPaswell⁵.TheeffectsofthehigherconcentrationsofPwillhaveto
becarefullyobservedovertime.
Figure 2. Dissolved oxygen and water temperature from October-December 2015
Figure 3. Phosphorus Concentrations in WCA-3A October-December 2015 and April-June 2016
METHODS
Tensampling locations were chosenin WCA-3Astartingat a publicboatramp offofinterstate-75
(I-75)souththeTamiami Trail (US-41),a distance ofabout112.7kmformonthlysampling (Figure
3).Infield measurements were taken forwaterdepth,temperature, pH, salinity and dissolved
oxygen. Sampling startedin Octoberin 2015andendedDecember 2015whenabanonairboat
trafficinthe WCAwas enacted. The ban waslifted inAprilof2016andsampling wasresumed until
June2016.The samples were collected in anacid washed 4ozpolyethylene bottlesjustbelow the
surface water. The samples were keptonice untilthey were preserved withacid toa pH2atthe
Everglades Wetland Research Park. The pH, salinity, dissolved oxygen andtemperature were
measured usingan YSI sonde.Water depthwasrecorded each time atthe sampling sites witha
meter stick. The water samples were broughtback toThe Everglades Wetland Research Parkfor
acid preservation, storage andanalysis. Samples were preserved within48hoursofcollectionand
storedforamaximum of20daysbeforeanalysis. Phosphorousanalysis wasconductedby using
The Westco SmartChem 200discrete Analyzer withEPA method365.4.Multiple samples were
analyzed by theCape CoralEnvironmental Resources Division asa secondary laboratoryand for
professional consistency. Bothlabshave adetection limit of2ppbP.
Wetlands around the world aredisappearing at analarming rate.Many policies in place today, do
not recognize wetlands the waythe rest of the world does. ForFlorida, muchof the wetlands have
been converted or lost over the decades with the exception ofa greaterportion of the Everglades.
Current efforts ofThe Everglades Restoration Project, which began in 1994⁴, to restore this system
are gaining some progress but at aslow rate and not without manyhurdles. The current discharge
of water fromLakeOkeechobee has already began to affectthebiota ofthe Everglades.
Phosphorus is often alimiting nutrient in agriculture and is added tomany fertilizers to improve
crop yield. Phosphorus is usually present in both organic and inorganic forms. Theabundance of
eachdepends ofmanydifferent factorssuch as vegetation, soil, and even the surrounding land
use. The objective of the STAsis toreduce the phosphorus load downstream to the WCAs’. This
study confirmed therelationship between dissolved oxygen relative towater temperature as well
as anunderstanding for spatial phosphorus concentrations. Conservation area-3ais proven tobe a
sink for nutrients as clear inflows and outflows aredefined in this study by adecreasing
phosphorous concentration across the wetland. Despite the increasing phosphorus load placed on
the WCAs’ fromLakeOkeechobee water releases, sampled areas were measuring at 10-12 ppb.
More recently, SFWMD has measured phosphorus concentrations as high as 20-23ppb. Sincethe
water releases haveceased, it is expected thatthe high phosphorus concentrations will soon
return to normal.
ACKNOWLEDGEMENTS
Iwould like to thank the entire Everglades Wetland Research Park, Dr.LiZhang and graduate
students Connor and Lauren for their guidance in the lab. This research receivedsupport on
behalf of the Undergraduate Student Scholarship Support Award (USSSA) jointly sponsored bythe
Officeof Undergraduate Scholarship (OUS)and the Officeof Research and Gradate Studies
(ORGS).
REFERENCES
1. Appendix 2C-1:Water Quality Standards forPhosphoruswithintheEverglades ProtectionArea (2004).
Retrieved February 24,2016,fromhttp://www.sfwmd.gov/portal/page/portal/pg_grp_
sfwmd_sfer/portlet_prevreport/2006_ sfer/volu me1/appendices/v1_app_2c-1.pdf
2. Mitsch, J.W., Gosselink, G. J.(2015).Wetlands.New Jersey: JohnWiley & Sons
3. Reddy, R.K., Wang, Y., DeBusk, F.W., Fisher, M. M., & Newman, S. (1998).FormsofSoilPhosphorousinSelected
Hydrologic Units oftheFlorida Everglades. SoilScience Society ofAmerica. 62,1134-1147.
4. SFWMD. Rain Gauge Data inWCA-3A. www.sfwmd.gov.Web. 03Feb. 2016.
5. VanHorn, Stuart."Water Quality intoShark River Slough duringHigh Water Emergency Operations." South
Florida Water Management District, 7Apr.2016.Web.
Picture 1. Airboat in WCA-3A