FLORIDA SPRINGS

Case studies on impacts of nutrients on Florida springs ecosystems

Source: J. Stevenson, Michigan State Univ.

Florida SpringsKarst geology

Surface water & ground water are closely connected

Land uses readily impact ground-water quality; which is expressed in springs

Spring water quality affects downstream aquatic resources

Glossary

• “Nitrate” will be used as shorthand for “nitrate/nitrite-nitrogen” (NO3/NO2-N or “NOx-N”).

• Nitrate levels are usually expressed as “mg/L” or “parts per million” (ppm).

• Background nitrate levels in ground water and springs is reported as <0.05 mg/L. (Florida

Geological Survey)

Florida Springs

• Many Florida springs exhibit 5 to 10-fold increases in levels of nitrate compared to background and/or historic levels. (Scott & others 2004; Florida Springs Task Force 2006)

• This is associated with increased nitrate levels in the Floridan Aquifer System. (Sources: groundwater studies)

Wakulla Spring with Hydrilla, 1998

Florida Springs

• Both N and P influence algal growth in 27 major Florida springs. (Stevenson & others 2004)

• N and P were the major nutrient pollutants in the Wekiva River Pollutant Load Reduction Goal assessment. (Mattson & others 2006)

Filamentous macroalgae in Branford Spring (Suwannee River), 2000

Florida Springs

• Increases of nitrate in Silver, Wekiwa, and Rock Springs are associated with increased epiphytic and filamentous algae and disruption of ecosystem function. (Munch and others 2007; Mattson and others 2006)

• N and P are factors in the proliferation of epiphytic algae and loss of SAV in Springs Coast rivers. (SWFWMD studies)

Epiphytic algae growth on the Lower Santa Fe River, 2000

Florida SpringsOther Considerations

• Increased growth of algae and/or changes in algal communities may be impacting fauna of springs.

• Nitrate may be exhibiting toxicity to species of aquatic fauna at levels seen in a number of springs throughout the state.

• Growth of nuisance and toxic species of algae, linked to nutrient enrichment, has been implicated in outbreaks of rashes and allergic reactions in folks swimming in springs.

Sources of Nitrate in Florida Springs

Ground Water Source Studies

• Wekiva basin - nitrate in ground water and springs derived from mix of inorganic (fertilizer) and organic (wastewater, manure) sources. (Toth and Fortich 2002)

• Silver Springs basin - nitrate in ground water primarily indicate inorganic (fertilizer) source, with some organic contribution. (Phelps 2004)

• Suwannee basin springs - nitrate in springs derived from mixed sources (inorganic & organic), depending upon adjacent land uses. (Katz and others 1999)

• Rainbow Springs basin - main source of nitrate in the groundwater basin was inorganic fertilizer. (Jones and others 1996)

N inputs and loads to the Wekiva River Basin (Source: MACTEC

2007)

Silver/Rainbow SpringsNitrogen inputs from fertilizer

Source: Marion Co. WRAM Study

Water Quality Management Efforts in Springs

SJRWMD Pollutant Load Reduction Goals

FDEP Total Maximum Daily Loads

Pollutant Load Reduction GoalsWekiva River & Rock Springs Run

(Source: Mattson & others 2006)

Current Mean Current Mean Concentration Concentration

(mg/L)(mg/L)

Target Mean Target Mean Concentration Concentration

(mg/L)(mg/L)% Reduction to % Reduction to

Meet TargetMeet Target

Nitrate

Wekiwa Spring 1.20 0.22 82%

Upper Wekiva R. 0.70 0.22 69%

Lower Wekiva R. 0.34 0.22 36%

Rock Spring 1.43 0.22 85%

Rock Springs Run 0.46 0.22 52%

Total Phosphorus

Upper Wekiva River 0.119 0.059 50%

Lower Wekiva River 0.119 0.059 50%

Rock Springs Run 0.086 0.061 29%

Summary

• Elevated nitrate levels are seen in springs throughout the state, and in portions of the Floridan Aquifer which feeds these springs.

• These changes in nitrate levels (interacting with phosphorus) are being increasingly linked to changes in spring ecology, including increased algal growth, declines in native SAV, increases in exotic SAV, and potential impacts on aquatic fauna.

• Fertilizer from residential and agricultural sources has been identified as a source of nitrate to ground water and springs.

Nitrate levels are elevated relative to reference & background conditions

Wekiwa Spring 1924

Source: SJRWMD data

Silver Springs50 yr comparison

Source: Munch and others 2007

Source: Univ. of Florida study for SWFWMD

Pollution-sensitive benthic invertebrate taxa are lost with increasing amounts of “nuisance” algae

Source: FDEP Bioassessment Program data

Nitrate levels in selected Florida Springs & toxicity thresholds from the literature (SJRWMD literature review)