HomeMy WebLinkAbout20080868 Ver 2_App G Methodology for Monitored Parameters_20190628A. Salinity Monitoring Methods
The YSI 600XLM multi -parameter water quality sondes were used for recording water
salinity and depth in earlier monitoring years (1999-2005) and re -installed from January 2007 to
August 2008, when they were replaced with In -Situ AquaTROLL 200 CTD loggers. The YSI
sondes automatically calculated salinity readings from conductivity and temperature. The
salinity sensor range is 0-70 parts per thousand (ppt), with an accuracy of +/- 1.0 percent of the
reading or 0.1 ppt, whichever is greater. The resolution is 0.01 ppt. The depth sensor is a
stainless steel strain gauge pressure sensor with a range of 0-30 feet, an accuracy of +/- 0.7 inch,
and a resolution of 0.01 inch.
The AquaTROLL 200 is manufactured by In -Situ, Inc. Like the YSI sondes, the
AquaTROLLs generate salinity readings from temperature and conductivity. The salinity sensor
range is 0-42 practical salinity units (psu), with an accuracy of +/- 0.5 percent of the reading.
The resolution is 0.001 psu. Practical salinity units (psu) are essentially equivalent to ppt;
however, psu is considered a more appropriate descriptor since it refers to the practical salinity
scale that is used to calculate salinity (Reid 2006). The depth sensor is a titanium/silicon strain
gauge pressure sensor with a range of 0-35 feet, an accuracy of +/- 0.003 inch, and a resolution
of 0.001 inch.
The AquaTROLLs are programmed to record a salinity and depth reading every 1.5 hours
(16 readings per day). Twice a month the TROLLS are downloaded and both conductivity and
depth calibrated as necessary. The probes are also cleaned and batteries checked and replaced as
necessary. Sensors are located near the bottom of the stream to ensure continuous data collection
during most low water conditions. Depth readings are compensated for the distance from the
sensor to the creek bottom. Occasional gaps in the continuous data in some years exist due to
dead batteries, equipment malfunctions, and low water levels not allowing sensors to be fully
submerged.
To aid in the interpretation of factors that may influence salinity fluctuations, continuous
salinity data from each AquaTROLL are displayed on graphs along with the continuous water
level data from that monitor, daily rainfall from the nearest rain gauge, and data from the Tar
River U.S. Geological Survey flow gauge at Greenville, NC
(http://waterdata.usgs.gov/nwis/uv?02084000). The Tar River becomes the Pamlico River at the
US Hwy 17 Bridge in Washington. These graphs are used for a qualitative assessment of the
relative effects of wind tides, local drainage basin input, and Tar River input on salinity
fluctuations in the subject creeks.
To compare factors that may influence salinity at the AquaTROLLs, a Spearman Rank
Order Correlation is employed. Variables used include monthly averages of Tar River discharge,
rainfall measured at nearest rain gauge or from NOAA station Aurora 6 N, and salinities at the
monitors. Significance is set at 0.05.
One-way analysis of variance (ANOVA) is used to test for differences between pre -
disturbance salinity and post -disturbance salinity using monthly averages due to the large amount
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Appendix G- Methodologies for Each Monitored Parameter
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February 2011-updated September 2012; Appendix G updated August 2018 for inclusion in 2018 Creeks Report
of data within each month. When variances are unequal, Kruskal-Wallis one-way ANOVA on
ranks was used.
NOTE: in early 2018, the downloader for the AquaTROLLs was switched to a Bluetooth device
and a tablet; the Rugged Readers continue to be carried to the field as a backup download device.
B. Wetland Hydrology Monitoring Methods
Each manual well consists of a 54-inch length of 1 1/4-inch diameter PVC well screen
(0.010-inch slots) and an 18-inch long riser made of solid -walled 1 1/4-inch diameter PVC pipe.
The well screen and riser are connected by a PVC coupler. The manual wells are installed to a
depth of 60 inches, with 12 inches of the riser extending above the ground. The top of the riser is
covered by a PVC cap, and a hole in the side of the riser provides air exchange during water
level fluctuations.
EcotoneTM WM80 water level monitors (manufactured by Remote Data Systems) were
used to provide semi -continuous data until 2011 when they were replaced by In Situ
Leve1TROLL 500s. The measurement probe is housed inside a 2-inch diameter PVC well screen
(0.010-inch slots) installed to a depth of approximately 50 inches. The current configuration of
cable and LeveITROLL records water levels over a range of about 5 feet. Installation varies
according to site conditions, but most units record water level within 2 feet above and 2 feet
below the ground surface. This installation method allows for the capture of both subsurface and
surface water level fluctuations. The units record the water level every 1.5 hours (16 times per
day). To prevent damage by bears, the aboveground portions of the monitors were surrounded
by an enclosure made of four metal T-posts connected with two or three strands of barbed wire.
All monitoring wells are checked and downloaded either once or twice a month. Using
rainfall data and well data, wetland hydroperiods are calculated for each monitoring well during
the growing season. A wetland hydroperiod is defined as the greatest number of consecutive
days during the growing season that the water table is within 12 inches of the surface or the
surface is inundated, and is expressed as a percentage of the growing season. For this project the
growing season is defined by the Beaufort County soil survey (Kirby 1995) as 14 March through
24 November (256 days). Growing season dates have recently been adjusted by the US Army
Corps of Engineers 2008 Interim Regional Supplement to the Corps of Engineers Wetland
Delineation Manual: Atlantic and Gulf Coastal Plain Region to match the WETS tables.
However, the previously established soil survey growing season dates will continue to be used
for this report in order to maintain consistency with baseline years in hydroperiod calculations.
Existing wells in Tooley Creek and Huddles Cut and new wells for expanded monitoring
have been and were installed in general accordance with the US Army Corps' ERDC TN-
WRAP-05-2 Technical Standard for Water -Table Monitoring of Potential Wetland Sites. In
2011, existing wells at Tooley Creek and Huddles Cut were semi -continuous WM80 Ecotone
monitors manufactured by Remote Data Systems. Each of the existing wells in Tooley and
Huddles Cut was paired with an In -Situ Leve1TROLL 500 (Leve1TROLL). Data collected with
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Appendix G- Methodologies for Each Monitored Parameter
PCS Phosphate Company, Inc.
February 2011-updated September 2012; Appendix G updated August 2018 for inclusion in 2018 Creeks Report
the Ecotones were compared to Leve1TROLL data and a choice was made to use the
Leve1TROLLs going forward to monitor wetland hydrology.
The casing for the Leve1TROLL unit was modified to allow for depth -to -water
measurements inside the well casing without removal of the probe (depth -to -water measurements
are not possible inside the Ecotone casing without probe removal). During each download at
each well, the depth to water is measured and this depth relative to ground surface is compared to
the real-time readings of the Leve1TROLLs to verify the accuracy of the instrument. If the
Leve1TROLL is reading >0.5 inch difference from the true reading, the Leve1TROLL is
calibrated according to manufacturer specifications. If a difference of >0.5 inch exists after
calibration, the Leve1TROLL is serviced or replaced. During each download, the download
time, manual water level measurement, real-time Leve1TROLL measurement, file name, and any
other pertinent information are recorded in the field. This information is transferred to a well
download sheet (Figure 5) kept in a binder at the CZR Wilmington office for reference. Wells
are downloaded once or twice a month to minimize data loss from faulty equipment.
NOTE: in early 2018, the downloader for the Leve1TROLLs was switched to a Bluetooth device
and a tablet; Rugged Readers continue to be carried to the field as a backup download device.
C. Water Quality Monitoring Methods
Twice a month field measurements include water depth, Secchi disk depth, temperature,
salinity, conductivity, turbidity, dissolved oxygen, and pH. Water depth is measured to the
nearest 0.25 inch in close proximity to the monitoring well where water samples are collected
and all other measurements taken. Samples are not collected if water depth is less than 1 inch;
QA/QC measures discussed in Appendix F are followed to reduce collection of substrate in such
extremely shallow water conditions. In previous years, water samples were collected from
nearby pools if conditions were dry or water depth was less than 1 inch at the normal collection
location. In late 2018, it was determined to not collect any future samples from isolated pools or
puddles. However, at the normal collection location, if it is dry or water depth is less than 1 inch,
a sample may be collected up to 20 feet upstream or downstream from the normal collection
location as long as the sample is collected in surface water in the channel that is visibly
connected to receiving waters. As usual, explanatory notes are added to the data form about
collection site conditions. Temperature, salinity, conductivity, and dissolved oxygen are
measured with a YSI Pro Plus multi -parameter water quality instrument. These measurements
are made in the middle of the water column when possible. Turbidity is measured with a
LaMotte 2020 turbidimeter. Turbidity water samples are collected in the field and turbidity is
measured at the time of collection. Care is taken to exclude detrital particles from the substrate
and surface in turbidity samples. A Hanna Instruments pHep 2 pH meter is used to measure pH
should the YSI pH probe fail.
The creek water samples are collected twice a month in polyethylene bottles and stored
inside an ice -filled cooler for daily shipment to the Central Environmental Laboratory at East
Carolina University. There, subsamples are taken for the various analyses. Precombusted
Whatman 934-AH (glass fiber) filters are used to separate particulate and dissolved fractions.
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Appendix G- Methodologies for Each Monitored Parameter
PCS Phosphate Company, Inc.
February 2011-updated September 2012; Appendix G updated August 2018 for inclusion in 2018 Creeks Report
The filtrate is stored frozen in a polyethylene bottle for later analyses of total dissolved
phosphorus (TDP), dissolved orthophosphate (PO4-P), ammonium nitrogen (NH4-N), nitrate
nitrogen (NO3-N), and dissolved Kjeldahl nitrogen. The filter pads are also stored frozen for
particulate nitrogen (PN), particulate phosphorus (PP), and chlorophyll a determinations. Total
fluoride analyses are carried out using unfiltered water samples. These methods are identical to
those used for the PCS Phosphate Pamlico River estuary water -quality monitoring program (see
Stanley 1997 for example).
With implementation of the new creeks monitoring plan in 2011, the samples are
also analyzed for dissolved organic carbon (DOC) and Total Dissolved Nitrogen (TDN).
The ECU geology lab provides CZR with previously ashed glass 50 mL vials covered with
aluminum foil and screw caps. Samples for carbon analysis are taken directly in the vials
at the same locations as the other water quality locations. With sterile gloves, a biologist
tilts the 50 mL vial into the water and slowly allows the vial to fill avoiding disturbance of
sediment or collection of any scum or sediment. The vial is recovered with the aluminum
foil and the screw cap, labeled, and put into the iced cooler. Samples are not collected if
shallow water depth prevents sample collection without sediment or scum.
The data for each hydrographic and water quality variable are summarized by means of
three standardized graphical formats, with the third format including a separate graph for each
sampling location. The first graph addresses INTRAANNUAL (i.e., seasonal) variability (the top
graph on the two -graph pages). Individual station values are plotted along with the mean value
(from the four stations) for each sample date. Raw data for the each year are contained in tabular
format in an appendix of each annual report.
The second graph format indicates INTERANNUAL variability and provides a look at
pre- versus post -impact sampling years (the bottom graph on the two -graph pages). The yearly
mean, and the range of values are indicated for each year and each sampling site (the top "error
bar" shows the maximum value recorded, and the bottom "error bar" indicates the minimum
value).
The third graphical format shows monthly means and 95 percent confidence intervals
(also called confidence limits) about the mean for the pre -impact and post -impact periods. A
conservative statistical evaluation is to look for the amount of overlap between the 95 percent
confidence limits- if the intervals do NOT overlap the two sampling periods (pre- and post -
impact) are hypothesized to be different. Each sampling location is represented on a different
graph. Station abbreviations H and HWQ are the same (e.g., station H1 is the same as station
HWQ1).
D. Metal Samples Collection Methods (Water Column and Sediments)
Prior to the collection of sediment samples, the water column sample is collected.
Leaning over the bow of the boat while it is slowly underway, using a 500 mL container
previously cleaned in the CZR lab with deionized water and alconox, a biologist wearing
sterile latex gloves rinses the container twice with creek water. The sample is then collected
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Appendix G- Methodologies for Each Monitored Parameter
PCS Phosphate Company, Inc.
February 2011-updated September 2012; Appendix G updated August 2018 for inclusion in 2018 Creeks Report
in the container and poured into the 250 mL bottle provided by the laboratory which
contains HNO3 preservative. The sample bottle is then sealed, labeled (location, date, and
time), and placed upright in a cooler packed with ice. The same collection container is used
for each creek although it is twice rinsed with the water from the creek to be sampled prior
to collection in each creek and new sterile latex gloves are worn during each creek
collection. As a back-up sample, the biologist also collects a 250 mL lab -provided bottle
using the same process. Samples are shipped or hand delivered at the laboratory using the
chain of custody form provided by the laboratory. The lab also provides a test bottle for
temperature fluctuation. The samples are analyzed for concentrations of silver (Ag),
arsenic (As), cadmium (Cd), chromium (Cr), copper (Cu), iron (Fe), and selenium (Se) by
Method 6020, and zinc (Zn) and molybdenum (Mo) by Method 6010 (aluminum is not
commonly analyzed in water samples).
The ponar device is deployed and retrieved from the boat and the collected sediment is
dumped into a plastic tray from which —0.5 gallon of sediment is scooped from the sample into a
Ziploc bag using a plastic or stainless steel scoop. As the sediment sample is scooped, sediment
that may have touched the metal of the ponar is avoided. Each bag is labeled with creek name
and date and, to minimize the potential for leaks, each sample is double bagged. The ponar
itself, plastic tray, and scoop/spoon are thoroughly rinsed with deionized water between each
sample to avoid cross -contamination. A second sample is collected from each station in case
there is a problem with the shipment to the laboratory or a problem encountered by the
laboratory during analyses. The backup samples are kept at CZR until results of the analyses are
completed at which time the samples are discarded. The sediment samples are shipped chilled to
the laboratory for analyses. The sediment samples are analyzed for concentrations of aluminum
(Al), silver (Ag), arsenic (As), cadmium (Cd), chromium (Cr), copper (Cu), iron (Fe),
molybdenum (Mo), selenium (Se), and zinc (Zn). Bulk density and Total Organic Carbon is also
measured for each sediment sample.
E. Vegetation Monitoring Methods
Drainage basin modifications are most likely to affect vegetation communities found
along the relatively narrow riparian wetlands upstream of the CAMA jurisdiction markers. For
this reason, vegetation assessments and monitoring sites were concentrated in these areas.
Vegetation sampling focuses on the shrub and herb layers. Compared to trees, shrubs and
herbs respond more quickly to changes in salinity and hydrology and therefore provide better
indicators of changes in the vegetation over time. At each vegetation monitoring site, 10
permanent sample quadrats were established along a 40-meter transect that proceeds on a
random compass azimuth from the monitoring well (the azimuth was adjusted to ensure all
quadrats were in the mapped bottomland hardwood wetland community, or riparian wetland, of
each creek). The quadrats are arranged on alternating sides of the transect axis, such that each
quadrat shares a corner with the quadrat behind it and the quadrat in front of it. However, no
quadrat shares a boundary with any other quadrat. Each sample quadrat consists of a 4-by-4
meter woody shrub vegetation plot with a 1-by-1 meter herb plot nested in the proximal corner.
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Appendix G- Methodologies for Each Monitored Parameter
PCs Phosphate Company, Inc.
February 2011-updated September 2012; Appendix G updated August 2018 for inclusion in 2018 Creeks Report
These will be used throughout the duration of the study to monitor density, coverage, and species
composition of the herb and shrub strata layers.
Shrubs and woody vines, defined as woody plants greater than 3.2 feet in height but less
than 3 inches in diameter at breast height (DBH), are inventoried in each of the ten 4-by-4 meter
plots located in the vicinity of each monitoring well in the riparian wetlands. For each species,
the number of stems present is counted and percent cover estimated. Herbs, defined as all
herbaceous vascular plants regardless of height and woody plants less than 3.2 feet in height, are
inventoried in each of the 1-by-1 meter plots nested within the 4-by-4 meter plots. For each
species, the number of stems present is counted and percent cover estimated. Qualitative
descriptions of the overstory are made in the vicinity of each monitoring well.
An importance value is calculated for each shrub and herb species present in each
transect. Relativized values of average percent cover, average stem count, and frequency of
occurrence in the 10 quadrats are used to calculate importance values. Dominant plants in each
transect are determined by applying the 50/20 rule to the importance values. The 50/20 rule was
described in the 1989 wetland delineation manual (Federal Interagency Committee for Wetland
Delineation 1989) and still is used in delineating wetlands (Williams 1992, USACOE 2008).
The 50/20 rule uses the quotient obtained from dividing each species' importance value by the
sum of all of the importance values for that transect (shrubs and herbs are treated separately).
This calculation expresses each species' importance value as a percentage of the cumulative
importance value of the entire transect. Beginning with the species having the highest
importance value and continuing in descending order, all species are listed until, cumulatively,
50 percent of the overall importance value has been reached. These species, along with any
additional species that individually comprise at least 20 percent of the overall importance value,
are considered to be dominant.
To further assist in determination of changes in the plant communities, the tolerance of
brackish conditions was assessed for each dominant species. The determination of each species'
tolerance was based on habitat descriptions provided in Radford et al. (1968), Beal (1977),
Godfrey and Wooten (1979, 1981), Odum et al. (1984), and Eleuterius (1990). A species was
considered tolerant of brackish conditions if any of the habitats listed in any of these references
were brackish, even if most of the habitats were fresh. The percentage of dominant species
intolerant of brackish conditions is calculated for each transect. Any significant changes in the
salinity of the creek should be reflected by a shift in this percentage.
A similar analysis is performed using the wetland indicator status (Reed 1988; replaced
by National Wetland Plant List annual updates) of the dominant plants. The percentage of
dominant species with a wetland indicator status of FAC (after years of consultation and review,
the ± status modifiers were discontinued in 2012) or drier is calculated for each transect. Any
major change toward drier conditions should be reflected by a change in this percentage.
NOTE: During the latter stages of development of the final PCS Plan of Study to monitor the
creeks, NCDWQ suggested that vegetation be monitored according the Carolina Vegetation
Survey (CVS) methodology. After consideration of this suggestion and discussion with the
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Appendix G- Methodologies for Each Monitored Parameter
PCS Phosphate Company, Inc.
February 2011-updated September 2012; Appendix G updated August 2018 for inclusion in 2018 Creeks Report
Corps and NCDWQ, PCS believes that in order to adequately compare available and future
monitoring data the existing vegetation survey methodology should be maintained in the new
plan. The purpose of the vegetation monitoring required by the PCS permit condition is not to
describe the complete biotic community at each creek, but to be able to document potential shifts
in the herbaceous and shrub community. While thorough and interesting, the CVS approach is
more complex than necessary to meet the purposes of the permit conditions and be congruent
and comparable with the past and future monitoring of the PCS subject creeks.
F. Fish Collection Methods
If a monitored stream is too shallow and narrow to sample using a trawl, fyke nets are
used to sample fish. Each fyke net sample occasion is conducted using two fyke nets (one net
fished upstream and one fished downstream) anchored for a set time of approximately 16 hours
(late afternoon until the following morning). Each fyke net is deployed across the entire width of
the sampled stream and consists of 0.25-inch mesh net with four 21-inch hoops, a 6-inch throat,
and a 22-foot wingspan.
For monitored stream large enough to trawl, each fish trawl sample is conducted using a
two -seam otter trawl. The trawl was constructed with a 10.5-foot head rope, 0.25-inch bar mesh
wings and body, and 0.12-inch bar mesh cod end. The trawl is towed for approximately one
minute, covering approximately 75 yards, from a beginning point marked in the field with
flagging (GPS coordinates also known) near the mouth of each monitored creek. Tow direction
is always toward the creek mouth.
All fish captured by either method are identified and counted. Those that are easily
identified in the field are released; others are preserved for later identification. Total length is
measured to the nearest millimeter for the first 30 specimens of each species. Representative
photographs of sample stations are taken during the first sample occasion and are on file with
CZR Incorporated.
To compare fish communities in each creek, CPUE, total abundance, species richness,
and species diversity are examined. Two standard diversity indices are used to measure species
diversity. The first, a modified Simpson's index (ds) (Simpson 1949; Brower and Zar 1984), is
defined as:
ds N(N-1)/Eni(ni-1), where
I ...i
n;= number of individuals of the ith species and
N= total number of individuals of all species.
Simpson's index is especially informative if a community is dominated by one or a few species.
The second diversity index used is the Shannon index (H') (Shannon 1948), defined as:
H'=- Epi lnpi, where
I ...i
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Appendix G- Methodologies for Each Monitored Parameter
PCS Phosphate Company, Inc.
February 2011-updated September 2012; Appendix G updated August 2018 for inclusion in 2018 Creeks Report
pi= ni/N and
ni and N are defined as for Simpson's index.
The Shannon index incorporates not only species richness, but also how evenly individuals are
distributed among the total number of species present in the community.
The above indices may be used to compare species diversity, but they tell nothing about
whether similar species are found at each site. To compare biotic communities in this manner,
the Jaccard coefficient and the Morisita-Horne index of community similarity are employed.
The Jaccard index (Q (Brower and Zar 1984) is defined as:
Cj=c/(s1+s2-c), where
c= number of species found at both sites and
sI, s2 are the total number of species in community 1 and 2, respectively.
The Morisita-Horne index (Gnh) (Li and Li 1996), while more complicated, has the
additional advantage of incorporating not just the presence of similar species but also the relative
abundance of species found at both sites. Consequently, it is a more comprehensive descriptor of
community similarity. It is defined as:
Cnh= 2 Exyi , where
(X1+ ),2)(NiN2)
xi and yi are the total number of the it' species at site land 2,
Ni and N2 represent the total number of individuals at site 1 and 2, respectively, and,
Xi= Exi xi-1 and X2 is similarly defined.
Ni(Ni-1)
Both the Jaccard and the Morisita-Horn indices of community similarity range from zero
to one; zero represents completely dissimilar populations and one represents identical
populations.
A two -sample t statistic (t-test) is used to compare CPUE, abundance, and diversity
between pre- and post -disturbance years. Significance is set at 0.05. When normality failed and
the data do not meet assumptions for a parametric test, a nonparametric test is used (Mann -
Whitney Rank Sum Test).
To compare CPUE, abundance, and diversity between years at each site, a one-way
analysis of variance (ANOVA) is used. Significance is set at 0.05. When normality fails and the
data do not meet assumptions for a parametric test, a nonparametric test is used (Kruskal-Wallis
ANOVA on Ranks). When significant differences (p< 0.05) occur between variables for each
year, a corresponding Tukey's or Dunn`s (post hoc) multiple pairwise comparison test is used to
display the relationship between the individual means.
Final Plan of Study for Potential Effects of Headwater Wetland Reduction on Downstream Aquatic Functions G-8
Appendix G- Methodologies for Each Monitored Parameter
PCs Phosphate Company, Inc.
February 2011-updated September 2012; Appendix G updated August 2018 for inclusion in 2018 Creeks Report
Water quality data are collected with a YSI Pro Plus multi -parameter instrument prior to
deployment and retrieval of fyke nets and/or before each at each creek. Parameters measured
include temperature, pH, salinity, conductivity, dissolved oxygen (DO), and Secchi depth. For
each parameter the deeper creeks, excluding pH and Secchi depth, a measurement is taken at
both surface and near bottom levels. Estimates of the percentage of the water surface covered by
submerged aquatic vegetation are also made. Water quality data are examined with regard to
how well each site provided habitat appropriate for the preservation of fish communities.
Particular attention is given to dissolved oxygen, as low DO levels are commonly implicated in
fish kills.
NOTE: per the 2014 data collection year report, Secchi depth continues to be measured but is no
longer included in statistical analyses.
G. Benthos Monitoring Methods
a. Timed Sweeps
Timed sweep methodology is used to sample benthic invertebrates along the
shoreline at each upstream and downstream location on subject creeks. The timed sweep
samples consist of 10-minute collections with a D-frame 0.5 mm net in representative shoreline
and near -shore habitats. Within each sampling station, three replicate samples are collected from
the same three locations from year to year. Basic hydrographic data also are collected during the
sweep sampling. The following data is recorded at each station:
• Depth
• Canopy cover
• Aufwuchs
• Bank erosion
• Substrate (% sand, silt, detritus)
• Water flow
• Water quality + pH
Organisms collected are preserved and returned to the laboratory for sorting,
enumeration, and identification to the lowest practical taxonomic level (usually species). Each
replicate is enumerated and the mean number of individuals per taxa and a 95 percent confidence
interval are calculated for the most abundant taxa (an average of at least 40 individuals per one
year) at each station. One replicate sample from a dedicated collection site in each sampling
station is used to calculate an Estuarine Biotic Index (EBI) in each creek (NCDENR 1997). An
EBI is an average of the water quality tolerance values for each taxon in the sample, weighted by
abundance values of the taxa. Only those taxa for which tolerance values are available can be
used to calculate an EBI. An EBI can be used at all salinities to make comparisons and assess
differences in site water quality (NCDENR 1997). All tolerance values for taxa encountered are
verified and assigned by Larry Eaton, Surface Water Protection, North Carolina Division of
Water Quality (NCDWQ) in an effort to standardize and evaluate benthic data from past study
years.
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Appendix G- Methodologies for Each Monitored Parameter
PCS Phosphate Company, Inc.
February 2011-updated September 2012; Appendix G updated August 2018 for inclusion in 2018 Creeks Report
NOTE: Larry Eaton retired in 2017 and no tolerance values have been assigned since his
retirement. There is no staff person within NC Division of Water Resources (formerly Division
of Water Quality or DWQ) with equivalent estuarine expertise to continue to make assignments.
b. Ponar Grab
Five ponar grabs are taken near mid -stream at each upstream and downstream
station on each subject creek. Basic hydrographic data are collected at each sample station.
Collected sediments are placed in 1 gallon plastic bags, with a full bag constituting a sample.
Samples are sieved in the field through a 0.5 min mesh screen. All organisms and material
retained on the screen are preserved and returned to the laboratory for sorting, enumeration, and
identification to the lowest practical taxonomic level (usually species). For each taxon, the
average number of individuals per grab and a 95 percent confidence interval are calculated. The
95 percent confidence intervals can be used as a rough gauge of the statistical significance of
differences between years. However, such comparisons must be made with care since very
abundant taxa are not fully enumerated, which may cause the width of the confidence intervals to
be underestimated for those taxa. An EBI is calculated for each sampling station based on total
individuals of each taxon collected from all five replicate grabs.
The Shannon -Wiener diversity index (H') (Shannon 1948), is used to detect
differences in species diversity in ponar samples. Ponar replicates are pooled for EBI and H'
calculations. The index is defined as:
H'=- Epi logpi, where
I ...i
n;= number of individuals of the ith species,
N= total number of individuals of all species, and
pi ni/N.
A two -sample t statistic (t-test) is used to compare Shannon -Wiener diversity
indices scores and total abundance between pre- and post -disturbance years. Significance is set
at 0.05. When normality fails and the data do not meet assumptions for a parametric test, a
nonparametric test is used (Mann -Whitney Rank Sum Test).
To compare Shannon -Wiener diversity indices scores and total abundance
between years at each site, a one-way analysis of variance (ANOVA) is used. Significance is set
at 0.05. When normality fails and the data do not meet assumptions for a parametric test, a
nonparametric test is used (Kruskal-Wallis ANOVA on Ranks). When significant differences
occur (p<0.05) between variables for each year, a Tukey's (post hoc) multiple pairwise
comparison test is used to display the relationship between the individual means.
Final Plan of Study for Potential Effects of Headwater Wetland Reduction on Downstream Aquatic Functions G-10
Appendix G- Methodologies for Each Monitored Parameter
PCs Phosphate Company, Inc.
February 2011-updated September 2012; Appendix G updated August 2018 for inclusion in 2018 Creeks Report