Development and Application of DEP
Bioassessment Methods
Biological assessment provides a direct measure of
designated use attainment for the vast majority of Florida’s
surface waters, where the goal is propagation and
maintenance of a healthy, well balanced aquatic community.
Because accurate assessment requires that the methods be
customized for specific system types, Florida DEP has
developed biomonitoring tools for streams, lakes, and
wetlands. The methods for streams (Stream Condition Index
and BioRecon) and lakes (Lake Vegetation Index) have been
comprehensively validated and calibrated using the process
described below. While standardized sampling and
interpretation methods for wetlands have been developed,
they have not yet been fully calibrated. There exists a
“biological integrity” determination in marine waters
(measured as a 25% reduction in Shannon diversity); however,
development of more sophisticated marine bioassessment
methods is still in its infancy. Check this site
periodically for updates on the development of these tools.
In 1993, the Regionalization Project for Florida
delineated
13
sub-ecoregions from the 3 ecoregions originally determined in
the Ecoregions of the Conterminous United States (1987)
mapping project. Within 9 of the regions, stream reference
sites were identified to establish biological expectations.
The southernmost ecoregion, and its 4 sub-ecoregions, was
not included in stream biocriteria development because of
its unique ecological characteristics (typical streams are
extremely rare; generally only canals and occasionally
flowing wetland sloughs or strands are found in this area).
Using the recently developed 20 dip net sweep technique,
data was collected and analyzed from the ecoregions north of
Lake Okeechobee. After examining data from five years of
twice-yearly sampling, the 9 ecoregions were collapsed into
3 relatively homogeneous bioregions,
consisting of the panhandle, the peninsula (excluding the
Everglades Ecoregion) and northeast Florida.
The final products of Florida’s stream bioassessment
development include the current ten-metric Stream
Condition Index (SCI) and the six metric Bioreconnaissance (or BioRecon). The SCI is the primary
indicator of stream ecosystem health, identifying impairment
with respect to minimally disturbed condition. The BioRecon
is used as an initial watershed screening method to
determine whether or not additional resources should be
allocated to the area, such as sampling using the SCI
method. A major recalibration of the SCI, using the
Human
Disturbance Gradient (HDG) and
Biological Condition
Gradient (BCG) approaches, occurred in 2007. To provide
information for interpreting bioassessment results, a
standardized evaluation of habitat conditions
is performed concurrently with SCI and BioRecon sampling.
For additional technical information about the development
of the modern SCI and BioRecon tools, see Bioassessment
Publications page.
The SCI is a composite macroinvertebrate index for use in
flowing streams. Sampling consists of 20 dipnet sweeps of
the most productive habitats found in a 100-meter stretch of
a stream. DEP SOP FS 7420 outlines the
protocol to be used in calculating an SCI for a watercourse.
Organisms collected in these sweeps are preserved and
brought back to the laboratory for processing in accordance
with the DEP SOP LT 7200. Data generated on
the taxonomy and abundance of these organisms is used to
calculate ten biological metrics, each of which has been
shown to respond predictably to human disturbance. The
metrics are:
- Number of total taxa,
- Number of long lived taxa, those that require more than one
year to complete their life cycle,
- Number of Ephemeroptera (mayfly) taxa,
- Number of Tricoptera (caddisfly) taxa,
- Number of Florida sensitive taxa,
- Number of clinger taxa,
- Percent dominant taxon,
- Percent Tanytarsini,
- Percent very tolerant taxa,
- Percent filterers.
The majority of these metrics decrease in response to adverse human
influences, while two of the metrics (% dominant taxon and % very
tolerant taxa) increase in response to human disturbance. Once the
metrics are calculated, points are assigned for each metric based on
criteria which have been regionally calibrated
and are contained in DEP SOP LT7200. The points from each
of these 10 biological metrics are then summed to determine an overall
score of biological health, with scores of 64-100 considered
“exceptional,” scores from 40 to 63 considered “healthy,” and scores of
0-39 considered “impaired.”
BioRecon is the initial screening tool for streams,
intended to rapidly assess a site to prioritize it for more
intensive sampling. The SOP for Performing BioRecons (DEP
SOP FS 7410) differs from that for an SCI sample in
that only four dipnet sweeps of the most productive habitats
are performed. A Biorecon also differs from SCI sampling in
that the organisms are sorted in the field using the
BioRecon Field Sheet (FD 9000-01) to target
specific numbers of individuals for subsequent laboratory
identification. Regionally based thresholds specific to this
method have been established for each of 6 calculated
metrics (a subset of the 10 metrics used in the SCI). The
metrics in the BioRecon assessment, all of which decrease in
response to human disturbance, include:
- Number of total taxa,
- Number of long lived taxa, those that require more than one
year to complete their life cycle,
- Number of sensitive taxa,
- Number of clinger taxa,
- Number of Ephemeroptera (mayfly) taxa,
- Number of Tricoptera (caddisfly) taxa.
The final Biorecon score is regionally adjusted and normalized to a
range from 0 to 10 points. Scores of 6 to 10 are “exceptional,” scores
from 4 to 6 are considered “healthy,” while scores below 3 indicate
impairment.
Overall habitat quality is determined by measuring eight
attributes known to have potential effects on the stream
biota. FDEP bioassessment protocols require a field habitat
assessment at each stream site using DEP SOP FT 3100, which
involves a mapping exercise (using FD 9000-04, see sample)
and conducting a series of observations as specified in the
Physical/chemical characterization SOP (DEP SOP FT 3001).
Using all the information collected, each of the eight
habitat parameters on the Field Habitat Assessment Form (FD
9000-05) is given a score (ranging from 1 to 20, with 20
being the highest quality).
The primary habitat parameters are:
- Substrate Diversity - an indicator of the number of diverse,
productive habitats (snags, logs, tree roots, aquatic
vegetation, leaf packs [partially decayed], undercut banks,
rock, or other stable habitat) present in a stream
- Substrate Availability - an indicator of what percentage of
the area of the stream bed is composed of productive habitats
(as listed above)
- Water Velocity - a valuation based on the maximum observed
velocity of the stream at a typical transect, where higher
velocities typically receive higher scores
- Habitat Smothering - an indicator of the percentage of the
area of the stream bed which is covered or "smothered" by sand
or silt accumulation
The secondary habitat parameters are:
- Artificial Channelization - a visual interpretation of the
anthropogenic channelization of a stream based on its variance
from natural stream patterns (sinuosity) and the presence of
artificial bank structures
- Bank Stability - a visual interpretation of the stability of
a stream's banks based on evidence of erosion or bank failure
- Riparian Buffer Zone Width - a valuation based on the
estimated width of the riparian vegetative buffer on each side
of the stream
- Riparian Zone Vegetation Quality - a valuation based on: the
percentage of riparian zone surfaces which are vegetated by
native plant species; the presence of a variety of vegetative
classes (trees, understory shrubs, herbs); evidence of community
disruption (bare soil, mowing, vegetative harvesting)
The values assigned for each of these parameters are then averaged
and assigned a rating corresponding to one of four categories
(“optimal”: 120-160 points, “suboptimal”: 80 to 119 points, “marginal”:
40 to 79 points, and “poor”: 8 to 39 points).
Incorporation of Stream Assessment Tools into Program
Areas
Several program areas use these bioassessment tools.
Regulatory applications include:
- Fifth Year Inspection (FYI) Program—the permitting program
for domestic and industrial wastewater facilities
- Status and Trends Monitoring- a combined probabilistic and
fixed station monitoring program, where the data are analyzed
and compiled into the Integrated Report, a report to the U.S.
EPA on the status of Florida’s water resources.
- Total Maximum Daily Load (TMDL) Program—a program which
determines limits on pollutants for surface waters, and develops
plans to reduce pollutants and prioritize watersheds for
restoration
- NPDES Stormwater, and Municipal Separate Storm Sewer System
(MS4) Permits—programs which regulate industrial,
construction-related, and publicly owned stormwater discharges.
Non-regulatory applications include:
Algae Methods
Florida DEP has developed two methods to assess periphyton
communities, one for species composition and the other to estimate
attached algal coverage. Algae respond to a number of stressors, making
them potential early indicators of adverse aquatic change.
The Qualitative Periphyton Sampling SOP (DEP SOP FS 7220)
is a method for the collection of algal community composition
information from natural substrates. A total of 10 sample aliquots are
apportioned across available habitats (snags, roots, leaf packs,
vegetation and rock, excluding sediments) in a 100 m stream reach. To
perform the method, a seasoned substrate is chosen, and algae is removed
from a 9 cm diameter area and placed into a wide-mouth jar that was been
filled with 100 mL of site water. Water and algae are mixed and a 4 mL
aliquot is removed and placed into a centrifuge tube. Nine additional
aliquots are sampled in this manner for a final volume of 40 mL. FDEP
used periphyton data collected using this SOP to attempt to develop the
Stream Diatom Index.
Stream Diatom Index Development
In a process similar to that described for the SCI and LVI, DEP
attempted to develop a periphyton assessment tool, the Stream Diatom
Index (SDI), using a combination of the Human Disturbance Gradient (HDG)
and Biological Condition Gradient (BCG) approaches. Unfortunately, the
diatoms appear to be very strongly influenced by pH (as well as
conductivity and color), which confounds the periphyton community
response to human disturbance, including nutrient enrichment effects.
The SDI does not appear to clearly or predictably respond to objective
measures of human disturbance, currently making it an unreliable tool
for assessing adverse human effects on stream systems. FDEP has much
additional work before periphyton community composition may be used as a
reliable bioassessment tool. (Final SDI
Report)
Rapid Periphyton Survey
The Rapid Periphyton Survey (RPS) (conducted per DEP SOP FS
7230) quantifies the extent and abundance of algae in a 100 m
stream segment. Nine observations are made every 10 m for a total of 99
observations (11 transects, including 0 and 100 m marks). A canopy
measurement is made at the mid-point of each transect using a spherical
densiometer. A small handful of substrate is haphazardly collected at
each transect point and is visually examined for the presence/absence
and for the type of algae (filamentous, diatom, or other). The average
thickness is measured perpendicular to the substrate and this noted on
the Rapid Periphyton Survey field sheet (FD 9000-25). When
sufficient data are collected using the RPS method, DEP intends to
establish an RPS threshold that indicates where the algae interfere with
the designated use of a waterbody.
Florida DEP has developed lake bioassessment protocols to
monitor and assess the biological integrity of Florida
lakes. Initial geographic regionalization resulted in the
delineation of
47 lake
regions within Florida (Griffth et al. 1996. Florida
Lake Regions Report. US EPA, Corvallis, OR). Although an
early Lake Condition Index (LCI) was developed by comparing
reference lakes to non-reference lakes, subsequent efforts
in 2007 to recalibrate the LCI using the Human Disturbance
Gradient (HDG) concluded that the LCI was not well
correlated with adverse human effects because
macroinvertebrate response was overwhelmed by natural
factors (see
Evaluation of Benthic Macroinvertebrates
Assemblages as Indicators of Lake Condition.
Lake Vegetation Index
Because of the complications in assessing human disturbance in lakes
using the invertebrate community, DEP developed methods involving the
lake aquatic macrophyte community resulting in the Lake Vegetation Index
(LVI), a multi-metric tool which assesses lake health based on the plant
community structure. Four LVI metrics were chosen based on an HDG
evaluation, and the LVI was subsequently calibrated via the BCG process.
DEP currently uses the LVI as the primary method to assess biological
health in Florida lakes. The LVI is sampled per DEP SOP FS 7320
and calculated per DEP SOP LT 7500. The LVI method
involves dividing a lake into 12 units and identifying plants to the
lowest possible taxonomic level in 4 of the 12 units. Plants are
identified in each unit by a visual boat “drive by” and also via a
transect approach. A frodus is deployed a minimum of five times during
the transect to assess the presence of submersed aquatic plants. All
plants for a unit are recorded in a single column on the Lake Vegetation
Index Data Sheet (FD 9000-27) and a dominant or
co-dominant is assigned based on areal extent. Unknown plants are
brought back for expert identification and verification. The sampling
season for the LVI is May through October. Data generated on the
presence of species is used to calculate four biological metrics - each
of which has been shown to respond to human disturbance. The metrics
are:
- Native Taxa
- Invasive Taxa
- Sensitive Taxa
- Dominant Coefficient of Conservatism (C of C)
Florida DEP has concluded the initial development of
biological monitoring tools for wetland ecosystems. A
research team, led by Dr. Mark Brown of the University of
Florida's Center for Wetlands, investigated attributes from
multiple biological assemblages in wetlands for use in the
development of biocriteria for these systems. The wetland
biological assessment tools consists of vegetation
transects, 20 dipnet sweeps for macroinvertebrates, and a
qualitative periphyton sample collection. The University of
Florida research team developed a classification scheme for
Florida’s wetland types and also completed a wetlands
regionalization map. The Wetland Condition Index has three
components: a Wetland Vegetative Index, a Wetland
Macroinvertebrate Index and a Wetland Diatom Index. All
three indices are strongly correlated with the LDI. Wetland
indices were developed for isolated herbaceous wetlands,
isolated forested wetlands, and forested strands and
floodplain wetlands (see documents on
Bioassessment Publications page). DEP ultimately plans
to calibrate these indices using the BCG approach.
FDEP has conducted exploratory studies and workshops for
the development of estuarine and marine bioassesment tools (see
history of marine bioassessment activities).
While the previous attempts have not yielded practical
results, DEP is currently planning studies for further
development, potentially including an evaluation of epi-benthic
taxa and fish in a variety of habitat types.
For
more information please contact Devan Cobb at 850/245-8542 or
devan.r.cobb@dep.state.fl.us.
2012 State of Florida