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
The Problem
Ecological structure and function have changed in
many springs.
High nitrate concentrations
• Less native aquatic vegetation
• Blooms of attached algae
• Lower fish abundance
• Impaired ecosystem metabolism
•
The springs are indicators of the state of the aquifer.
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St. Johns River Water Management District
The SJRMWD Springs Protection Initiative
Science
Regulation
CUP
ERP
MFLs
Formulate costeffective solutions
and support
regulatory
programs.
Springs
Protection
Initiative
Outreach
Water Supply
Planning
Projects
Design and help
fund cost-effective
projects.
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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
Nitrogen
Sources- Rates
and Types
Recharge Rate
and Conveyance
Nitrogen
Transformation,
Loss, and
Conveyance
Springshed and
Groundwater
System
Nitrogen Flux
and
Concentration;
Primary
Producer
Community
Structure
Non-nitrate
forcings
Physicochemistry and
Biological Interactions
Spring Ecosystem
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Question: Which areas of the springshed of Silver Springs contribute the
highest N loads to the springs?
High Water
Conveyance
Low N
Loss Rate
Springshed
High N
Source Rate
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.
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Drivers: Nutrients
• Source tracking is difficult, well mixed aquifer
• Aquifer mean nitrate removal 48% (± 14%)
• Spring vent nitrate removal 17 - 43%
Drivers: Nutrients
• 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: Food Web
Trichoptera
Chironomidae
Terrestrial Export
Tertiary Consumer
Tertiary
Consumer
Secondary Consumer
Secondary
Consumer
Primary Consumer
Primary Production
Drivers: Food Web
http://news.nationalgeographic.com
Drivers: Velocity
Kaplan, et al. 2016
Vcrit ≈ 0.25 m s-1
Thank you
floridaswater.com/springs
St. Johns River Water Management District
St. Johns River Water Management District
Frazer, et al. 2016