Funded External Research
in Support of Numeric Nutrient Criteria Development in Florida
Through receipt of EPA Region IV Nutrient Criteria Development funds, DEP
has been able to sponsor several research projects to aid in the
determination of appropriate numeric nutrient criteria for Florida's waters.
Descriptions of each of these efforts follow.
Water-Quality Trends
Associated with Algal Community Changes in Florida Lakes (5411KB)
Historical water-quality changes in Lakes Conine, Haines, and May in Polk
County, Florida were assessed using diatom assemblages in sediment cores.
Preliminary diatom evidence
suggested eutrophication but lacked the resolution to adequately define
pre-disturbance water-quality conditions or document trends. The present
study uses six diatom-based predictive models to infer past limnetic total
P, averaged trophic state index, and limnetic chlorophyll a values. All
indicators demonstrate that cultural eutrophication occurred in Lake Conine.
Pre-disturbance limnetic chlorophyll a concentrations of approximately 8-17
ug/L, TSIAVG values of 53-55, and limnetic total P concentrations of 35-40
ug/L. Productivity decreased somewhat during recent decades, probably
because of the removal of point-source nutrient supplies. In Lakes Haines
and May, limnetic total P was approximately 40-42 ug/L, TSIAVG was 58-59,
and limnetic chlorophyll a was approximately 16-19 ug/L. Data suggest that a
very slight recovery in trophic state might have occurred in both lakes
during recent decades. Paleolimnological evidence suggests that the lowest
practical restoration target for Lake Haines, and perhaps other lakes in
region 75-36, is approximately 42 ug/L limnetic total P. Attempts to manage
lakes at limnetic nutrient concentrations that are less than pre-disturbance
values are likely to prove ineffective because pre-disturbance water-quality
is determined by the natural edaphic supply of nutrients to lakes.
Developing and Testing
Algal Indicators of Nutrient Status in
Florida Streams (1819
KB)
Researchers at the Michigan State University Department of Zoology's
Ecology, Evolutionary Biology and Behavior Program (R. Jan Stevenson and
Bruce Wang, P.I.s) undertook analyses to develop algal indicators of trophic
status for Florida streams. Testing the hypothesis that nutrients affected
valued ecological attributes of streams (including algal biomass and algal
growth potential), MSU researchers evaluated FDEP datasets to determine the
significance of relationships between algal species indicators and nutrient
conditions. Species response measures were found to best correlate with a
multimetric index describing nutrient concentrations, incorporating values
for five water chemistry parameters (NH3, NOx, TN, PO4, and TP) and three
measures of algal biomass response (periphyton and plankton chlorophyll a
and assays of algal growth potential).
Sedimented Algal Pigment
Profiles in Florida Lakes (205
KB)
Sedimentary concentrations of algal pigments are considered proportional
to productivity of lakes at the time of their deposition. Total carotenoid
pigments are good indicators of primary production in freshwater. Thus total
carotenoids along with the cyanobacterial pigments oscillaxanthin and
myxoxanthophyll were extracted from sediment cores from Lakes Conine, Haines
and May in Polk County and Lake Wauberg in Alachua County. Percent native
chlorophylls were also analyzed to evaluate pigment preservation quality.
Algal pigment profiles were compared with
preliminary sedimented-diatom
analyses. Lake Conine showed abrupt increases in total carotenoid,
oscillaxanthin, and myxoxanthophyll pigments in upper sediments, which
indicates eutrophication. Diatoms and sedimented pigments suggest that
nutrient mitigation efforts, such as removal of the wastewater plant around
1990, might have reduced the lake’s trophic state somewhat during recent
decades. Pigment profiles in Lake Haines show clear evidence of recent
eutrophication that is consistent with cultural activities. Diatom and
algal-pigment data suggest that eutrophication has been pronounced and more
recent in Lake Haines than in the other study lakes. In Lake May, total
carotenoids and preliminary diatom data suggest that eutrophication began
after a period of shoreline disturbance in the lower 1/3 of the core. In
Lake Wauberg, algal pigments were high throughout the core. Algal pigments
and diatom evidence both support the conclusion that trophic state has been
high historically in Lake Wauberg and has fluctuated over time.
Paleolimnological
Characterization of Pre-Disturbance Water Quality Conditions in EPA-Defined
Florida Lake Regions (4268 KB)
DEP contracted with researchers at the University of Florida's Department
of Fisheries and Aquatic Sciences (Thomas Whitmore and Mark Brenner, P.I.s)
to determine pre-disturbance water quality conditions for eight Florida
lakes believed to have undergone cultural eutrophication. UF researchers
conducted simplified paleolimnological analyses of sediment cores to infer
historic limnetic water quality through the use of statistical models based
on sedimented diatoms, calibrated with data from a large set of Florida
lakes.
Nutrient Criteria for
Florida Lakes: A Comparison of Approaches (1.12 MB)
(Nutrient
Criteria for Florida Lakes: Document Summary - 163 KB)
Analyses were undertaken
to approach numeric nutrient criteria recommendations for five classes of
Florida lakes, defined by water color, pH, and geographic region - Acid
Clear Lakes in EPA Level II Ecoregion 65, Acid Clear Lakes in Ecoregion 75,
Acid Color Lakes, Alkaline Clear Lakes, and Alkaline Color Lakes. DEP
contractors (TetraTech, Inc., Jeroen Gerritsen, P.I.) identified six (6)
potential approaches to define numeric nutrient criteria for Florida lakes.
The first three approaches focused on methods to identify least impacted
background nutrient concentrations, whereas the second three were designed
to identify nutrient concentrations protective of biological condition. These analyses yielded
the several recommendations for provisional nutrient criteria, which
should be recognized to be only recommendations at this point.
Please contact
Jacob Brown if you are unable to download any of the documents from these
links or for directions to the meetings.
For questions about the development of the criteria or the TAC, please contact
Ken Weaver..
