St. Johns River Water Management District St. Johns River Water Management District

Dr. Dean R. Dobberfuhl Springs Lead Scientist St. Johns River Water Management District

St. Johns River Water Management District

• High nitrate concentrations • Less native aquatic vegetation • Blooms of attached algae • Lower fish abundance • Impaired ecosystem metabolism

The Problem Ecological structure and function have changed in

many springs.

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The springs are indicators of the state of the aquifer.

St. Johns River Water Management District

Springs Protection Initiative

Science Formulate cost-

effective solutions and support regulatory programs.

Outreach Projects

Design and help fund cost-effective

projects.

Regulation CUP ERP

MFLs

Water Supply Planning

The SJRMWD Springs Protection Initiative

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St. Johns River Water Management District

SPI Science ‒ The Approach • Assemble a scientific team organized into work groups. • Conduct an interdisciplinary study of one or more springs

systems using an approach similar to that used for the Water Supply Impact Study (WSIS). – Primary focus on Silver Springs system – Secondary focus on Alexander Springs system – Cross-system monitoring and analysis – Use restoration of primary producer community structure as a

unifying theme for integration of the work • Identify key drivers and interactions necessary to develop

effective management strategies.

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St. Johns River Water Management District

The Questions

• Which areas of the spring shed of Silver Springs contribute the highest N loads to the springs?

• What are the major drivers of PPCS and what is the relative influence and controllability of each?

• Will [NOx] reduction be sufficient to restore primary producer community structure?

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St. Johns River Water Management District

SPI Organization C. Fitzgerald, Initiative Leader D. Dobberfuhl, Lead Scientist

M. Brabham, Project Manager R. Reddy, Lead Scientist

L. Stahl, Project Manager

SW Hydrology A. Canion J. Jawitz

GW Hydrology D. Hearn J. Jawitz

M. Annable W. Graham

N Biogeochem D. Dobberfuhl

P. Inglett

Hydrodynamics P. Sucsy

D. Kaplan

Physicochemistry M. Coveney M. Cohen J. Martin

T. Osbourne

Biology R. Mattson

T. Frazer

Integrated Process

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Nitrogen Sources- Rates

and Types Nitrogen Transformation,

Loss, and Conveyance

Nitrogen Flux and

Concentration;

Primary Producer

Community Structure

Spring Ecosystem

Springshed and Groundwater System

Recharge Rate and Conveyance

Physicochemistry and Biological Interactions

Non-nitrate forcings

Cost-effective management of nitrate loads: Will focus on areas of the springshed with high N source rates, low N loss rates, and high N conveyance rates.

High Water Conveyance

Low N Loss Rate

High N Source Rate

Springshed

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Question: Which areas of the springshed of Silver Springs contribute the highest N loads to the springs?

Drivers: Nutrients

• Source tracking is difficult, well mixed aquifer • Aquifer mean nitrate removal 48% (± 14%) • Spring vent nitrate removal 17 - 43%

• Excess nitrate benefits algae, not SAV • Nitrate assimilation is 0th order while

denitrification is 1st order • Sediments may be important source of N

and P

Drivers: Nutrients

Trichoptera

Chironomidae

Drivers: Food Web

Primary Production

Primary Consumer

Tertiary Consumer

Secondary Consumer

Terrestrial Export

Primary Production

Primary Consumer

Tertiary Consumer

Secondary Consumer

Drivers: Food Web

http://news.nationalgeographic.com

Drivers: Velocity

Vcrit ≈ 0.25 m s-1

Kaplan, et al. 2016

floridaswater.com/springs

Thank you

St. Johns River Water Management District

St. Johns River Water Management District

Frazer, et al. 2016