20000008 Ver 1_Monitoring Report_20090904

LMG
LAND MANAGEMENT GROUP INC.
Environmental Consultants
August 31, 2009
TO: Mr. John Domey
NC Division of Water Quality
1617 Mail Service Center
Raleigh, NC 27699
zoooA
RE: Mason Inlet Relocation Project - Biological Monitoring Report: August 2008 (Year 7)
Dear Mr. Dorney:
Enclosed is a copy of the August 2008 (Year 7) Annual Biological Monitoring Report for the Mason Inlet
Relocation Project. The report summarizes conditions of the intertidal marsh adjacent to Mason Creek as
documented during the August 2008 monitoring event. It includes comparative analyses from pre-project (Year
0) through December 2008 (Year 7). Copies of this document have been furnished to the US Army Corps of
Engineers (Wilmington Regulatory Field Office). Note that the enclosed document includes the benthic summary
report recently received from UNC-Wilmington.
Please contact our office if you need additional hard-copies and/or digital copies. Should you have any
questions or comments regarding the findings of this report, please feel free to contact me either by phone (910-
452-0001) or by email at cpreziosi(a)lmgroup.net.
Sincerely,
Land Management Group, Inc.
encl.
Christian Prezios'
Section Manager
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4 2009
DENR • WATER QUALITY
WETLANDS AND STCr?A1y!S4TSR 9RNVGI f
www.lmgroup.net • [e-mail] • Phone: [phone] • Fax: [phone]
3805 Wrightsville Ave., Suite 15, Wilmington, NC 28403 • P.O. Box 2522, Wilmington,
NC 28402
0
MASON INLET RELOCATION PROJECT
NEW HANOVER COUNTY, NC
•
BIOLOGICAL MONITORING REPORT:
YEAR 7 (2008) POST CONTRUCTION MONITORING
Prepared for.
New Hanover County (NC), Permittee
Prepared by.
Land Management Group, Inc.
Environmental Consultants
Wilmington, NC
•
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TABLE OF CONTENTS
1. INTRODUCTION ..............................................................................................................1
II. METHODOLOGY ............................................................................................................2
A. MONITORING PARAMETERS ..................................................................................2
B. FIELD SAMPLING PROTOCOL ................................................................................3
C. DATA ANALYSIS .......................................................................................................5
III. RESULTS ...........................................................................................................................5
A. STEM DENSITY ..........................................................................................................5
B. STEM HEIGHT ............................................................................................................6
C. SEDIMENTS ....................6
.............................................................................................
D. BENTHIC 1NFAUNA ..................................................................................................7
IV. DISCUSSION ....................................................................................................................8
A. VEGETATION (Spartina alterniflora) ........................................................................8
B. SEDIMENTS ................................................................................................................9
C. BENTHIC INVERTEBRATES (BACKBARRIER INFAUNA) ...............................10
D. PHYSICAL MONITORING AND HABITAT TYPES .............................................10
V. CONCLUSION ................................................................................................................10
List of Tables, Figures and Appendices
Figure 1 ..........................................................................................Original Transect Location Map,
Figure 2 .........................................................................................Updated Transect Location Map
Figure 3-18 ................................................................................................................. Data Analysis
Appendix A. Benthic Infaunal Summary of Findings
• Appendix B. August 2008 Site Photographs
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MASON INLET RELOCATION PROJECT
ANNUAL BIOLOGICAL MONITORING REPORT (YEAR 7)
I. INTRODUCTION
The goal of the biological monitoring program is to determine if there is a significant
difference between pre-construction (Year 0) and post-construction conditions (Year 1,
• Year 2, Year 3, etc.) for specific parameters sampled annually in tidal marsh, intertidal
sand flat, and barrier island beachfront (i.e. intertidal surf zone) habitats located within
and adjacent to the project area. These data, in conjunction with data collected from
supplemental monitoring programs, will help to document any potential impact to
habitats resulting from project activities.
Pre- and post-construction monitoring provides data related to primary productivity,
benthic infaunal abundance and composition, substrate texture/organic content, and
macroinvertebrate densities (beachfront only). Quantitative and qualitative sampling
yields information to be used to determine if any deleterious effects may be attributable
to the inlet relocation project. The extent to which monitoring parameters will be
affected depends on various physical conditions (e.g. the character of the dredged
material, tidal and current regimes, etc.). Therefore, concurrent physical monitoring is
referenced in annual biological monitoring reports.
•
Additional monitoring is conducted by UNC Wilmington and Audubon North Carolina.
At the onset of the project, the Mason Inlet Waterbird Management Plan was developed
to help protect critical nesting habitat along the north end of Wrightsville Beach.
Audubon North Carolina manages currently manages this area through the installation
informational signage, patrols, and visitor education programs. In addition, Audubon
assists UNC-Wilmington with monitoring of bird usage and nest success. Analysis of the
benthic infaunal communities is conducted by UNCW Center for Marine Science each
monitoring year. The summary of findings for the benthic analysis is included as an
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appendix to this document (refer to Appendix A). The hydrographic monitoring report
and the waterbird monitoring report are submitted annually as independent documents to
reviewing regulatory agencies.
Reports for post-construction monitoring Year I to Year 6 were based on data collected
during the late fall/early winter season. The timing of the sampling during these years
was intended to coincide with the original pre-construction monitoring event conducted
in early December 2001. During an interagency meeting in April 2008, the U.S. Army
Corps of Engineers (USACE) requested that biological monitoring be shifted to the
growing season. In addition, the USACE modified the monitoring plan to discontinue
macro-invertebrate sampling of the beachfront and benthic infaunal sampling of intertidal
flats. As a result of the meeting, Year 7 monitoring was conducted in August 2008
(approximately ten months after the Year 6 event). Subsequent analysis of inter-year
trends in data (winter sampling in Year 0 through Year 6 and summer sampling in Year
7) must take into consideration variability due to seasonality. The following report
summarizes the methodology and results for Year 7 (August 2008) post-construction
monitoring.
II. METHODOLOGY
Sampling for Year I post-construction conditions was conducted in December 2002
approximately seven (7) months after project completion. Annual monitoring is to
•
continue for the life of the permit or until such time deemed necessary by relevant federal
and/or state agencies. Note that based upon the April 2008 interagency meeting,
sampling of macro-invertebrates of the beachfront and benthic infauna of intertidal flats
has been discontinued. Six years of post-construction data for these biological indices
has been provided in earlier reports.
A. Monitoring Parameters
Selection of monitoring parameters has been based upon those factors potentially
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impacted by project activities and those readily sampled and evaluated. The following
monitoring parameters are included in the assessment:
(1) Spartina stem density
(2) Mature (>30 cm height) Spartina stem height
(3) Percent sand, silt, and clay of surface substrate
(4) Percent organic content of surface substrate
(5) Distance (ft) loss or gain of intertidal marsh habitat at transect locations.
• These parameters, while traditionally viewed as representative indicators of marsh habitat
structure and function, require less intensive and less frequent sampling than other biotic
or chemical indices. In addition to the identified quantitative sampling, qualitative
observations of marsh and/or intertidal habitat may be noted. Photographic
documentation of Year 7 sampling is provided in Appendix B.
B. Field Sampling Protocol
Sampling efforts focused on the area of potential impact where biota and physical
conditions (e.g. soil texture) are most likely affected by project activities and associated
perturbations such as altered flooding regime and sedimentation. Any perturbations to
tidal marsh will manifest in system responses distributed linearly from Mason Creek.
Therefore, three permanent 300-foot monitoring transects were established along a
roughly perpendicular axis on each side of Mason Creek (totaling six transects). These
transects are labeled NIT I, MT2, MT3, MT4, MT5, and MT6, respectively). Five
permanent stations along each transect (located 5, 50, 100, 150 and 300 feet away from
the marsh edge along Mason Creek) were established prior to the initiation of the project.
The station located furthest from Mason Creek (300 ft) serves as the control plot for each
transect.
Any stations affected by post-project erosion/sloughing near the creek bank were re-
established at prescribed distances from the new creek edge. Due to the level of erosion
observed along the southern section of the marsh, all stations in transects MT4-MT6 were
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re-established in 2008. These stations were re-established in areas containing stable low
marsh habitat and transition into areas of slightly higher topography. Figure 1 depicts the
location of each monitoring transect established in the marsh and changes in the marsh
boundary along the creek from Year 0 to Year 7. Figure 2 provides additional
information on the re-established transect locations and updated aerial photography.
One-meter square quadrats at each station were sampled for stem density and height
range of S. alterniflora. Stem heights were grouped in categories based upon pre-
determined ranges (30-60 cm, 60-90 cm, 90-120 em, >120 cm). Each height range was
assigned a value (1, 2, 3, and 4, respectively). The number of stems in each category
were then multiplied by the corresponding height value to obtain a height index.
Cumulative height indices for each quadrat were calculated and recorded.
Sediments were characterized according to percent sand/silt/clay and percent organic
matter (OM). One sample was collected at each of the fixed stations (5, 50, 100, and 150,
and 300-ft plots). Sediment samples were transferred to A&L Agricultural Labs
(Richmond, VA) for particle size analysis and OM by combustion.
Metal rebar installed flush with the sediment surface prior to project construction will be
used to evaluate sediment deposition and/or loss over time for each plot. Notched PVC
pipe will be used as a supplemental method of evaluating sediment accretion and/or loss.
Note that the loss of stations throughout post-construction monitoring has limited the
scope of this assessment.
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Biological monitoring included a benthic infaunal survey. Three replicates of 15 cm-
deep cores (10 cm diameter) were sampled at three observation points (i.e. at 5', 150',
and 300' from creek edge) along three of the six transects (MT2, MT4, and MT6)
(N=27). Replicates were collected 10 ft from the permanent vegetative quadrat at a
randomly-generated bearing. Individual core samples were transferred to sample bags
and labeled. All samples were transferred to LNCW-Center for Marine Science benthic
laboratory for processing and identification. Samples were fixed using a 10% formalin
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solution and sieved through a 0.5 mm screen mesh to separate infauna from sediment and
vegetative material. Benthic infaunal organisms were enumerated and identified to the
lowest reliable taxonomic level. Species richness and abundance were calculated from
these data.
C. Data Analysis
Mean values of each parameter were statistically compared using Analysis of Variance
(ANOVA)/paired t-tests for data normally distributed. Ninety-five percent confidence
intervals were used to determine statistically significant differences of means (means are
• significantly different if confidence intervals do not overlap; p< 0.05). Outliers (values
+/- 2 times the standard deviation) were removed from all statistical operations.
III. RESULTS
A. Stem Density
(1) Post-Construction (Year 7)
Mean Spartina stem density for all quadrats sampled was 26.4 +/- 6.3 stems/m2 (N=30).
There was no significant difference observed between mean stem density on the north
and south sides of Mason Creek. Mean stem densities of quadrats located on the north
and south sides of Mason Creek were 27+/- 6.8 stems/ m2 and 26.3 +/- 5.9 stems/ m2,
respectively (refer to Figure 3). There was no observed significant difference in stem
• density related to distance from creek (refer to Figure 4). Of the six transects sampled,
stem densities were greatest in Transect 5 (mean stem density of 29.2 stems/m) (refer to
Figure 5).
(2) Pre-Construction (Year 0) vs. Post-Construction (Year I through Year 7)
Mean stem density of Year 7 (26.4 stems/m2) was not significantly different from Year 3, Year
5, and Year 6. However, stem densities were significantly lower than in Year 0 (pre-
construction) and Year 4 (post-construction) (refer to Figure 6).
5
E

B. Stem Height
(1) Post-Construction (Year 7)
Height indices were significantly higher on the north side of Mason Creek than those
indices calculated for plants on the south side of the creek (refer to Figure 7). There was
no significant difference in height indices as a function of distance from creek bank (refer
to Figure 8). Of the six transects sampled, stem heights were greatest in Transect 3
(mean height index of 99.4) (refer to Figure 9).
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(2) Pre-Construction (Year 0) vs. Post-Construction (Year 1 through Year 7)
The observed mean stem height index for Year 7 was 68.6 +/- 30.4. Observed stem
heights during Year 7 were not significantly different than those observed during Year 1,
Year 5, and Year 6 (post-construction) (refer to Figure 10). Stem heights were
significantly higher in Year 7 than in Year 2 and Year 3. Of the seven years of
monitoring (including pre-construction), the mean stem height index was greatest during
Year 4 (post-construction). The mean steam height index of Year 7 was significantly
lower than in Year 0 (pre-construction) and Year 4 (post-construction).
C. Sediments
(1) Post-Construction (Year 7)
Relative deposition or loss of material from the marsh surface was measured from
notched PVC installed prior to project construction in December 2001. As previously
noted, changes in channel location have necessitated the installation of new markers at all
stations within the MT4, MT5, and MT6 transects limiting the scope of the sediment
deposition data.
Sediments collected from the south side of Mason Creek exhibited significantly higher
percent sand than sediments collected from the north side of Mason Creek (89.6 +/- 4.3%
sand and 78.4 +/- 11.8% sand, respectively) (refer to Figure 11). There was no
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significant difference in percent sand as a function of distance from the creek bank (refer
to Figure 12). However, samples collected 300 ft from Mason Creek consistently
exhibited the highest percent sand (90.7 +/- 4.7% sand).
Sediments collected from the north side of Mason Creek exhibited significantly higher
percent organic matter than sediments collected from the south side of Mason Creek (5.7
+/- 4.8% OM and 2.1 +/- 2.0% OM, respectively) (refer to Figure 13). There was no
significant difference in percent OM as a function of distance from the creek bank (refer
to Figure 14). However, samples collected 300-ft. from Mason Creek consistently
exhibited slightly higher percent OM (6.0 +/- 7.2% OM).
(2) Pre-Construction (Year 0) vs. Post-Construction (Year I through Year 7)
There was no statistical difference observed between mean percent sand for pre-
construction (December 2001, 88.5%) and post-construction Year 1 through 7 samples
(84.0%, 84.3%, 87.6%, 87.7%, 86.7%, 86.0%, and 84% respectively) (refer to Figure 15).
Similarly, there was no statistical difference observed between mean percent OM for pre-
construction (December 2001, 2.0%) and post-construction Year 1 through 7 samples
(3.7%, 3.5%, 3.1%, 1.9%, 1.9%, 1.9%, and 3.5% respectively) (refer to Figure 16).
D. Benthic Infauna
Benthic infaunal identification and data analysis was conducted by Troy Alphin,
Research Associate at the Center for Marine Science (University of North Carolina at
Wilmington). A summary report of findings with supporting tables and figures is
included as Appendix A.
7

IV. DISCUSSION
A. Vegetation (Spartina alternflora)
As identified above, Year 7 annual monitoring was conducted in August 2008. During
prior years (Year 0 through Year 6) monitoring was conducted during late November or
early December of each year. As a result of the temporal shift, seasonality is introduced
as a confounding variable when evaluating inter-year (i.e. Year 7 vs. Year 0 through Year
6) data trends. Inter-year patterns inferred through data collected in future monitoring
• events will not be influenced by seasonality since future monitoring is to occur during
August or early September of each year.
Recognizing seasonality as a confounding variable, one may still compare data sets
between years. It should be noted that the mean stem density of Spartina alterniflora
during Year 7 monitoring was higher than (but not significantly different from) Year 6.
However, overall stem densities for Year 7 remain significantly lower than those
documented during pre-construction monitoring. Of all the monitoring events (including
pre-project), Year 4 exhibited the greatest mean stem density. These same trends are
evident in the control plots (Figure 17). In consideration of this, inter-year variation
(rather than project-related factors) appears to have a greater influence on observed stem
densities.
In general, no significant differences in Spartina stem densities were observed between
• transect position (north vs. south) nor quadrat location (5', 50', 150', and 300').
Increased sediment deposition along the original MT6 transect continued to stress
volunteering stands, as continued decline and/or loss of new Spartina growth was
observed in August 2008. Sedimentation processes of the inlet throat and flood tide
shoals have resulted in adjustments to the channel pattern of Mason Creek. As a result,
there are sediment losses and/or gains along the length of the creek. This has necessitated
the re-establishment of transects MT4, MT5, and MT6 (on the southern side of the
creek).
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Stem height indices were significantly greater on the north side of Mason Creek than on
the south side in Year 7. While Year 0 data did not yield a statistical difference in stern
height indices between the north and south sides of the creek, it has been noted that the
north side of the creek is a more mature marsh system with generally taller Spartina
stems. For all years of monitoring (including pre-construction), stem height indices were
highest during Year 4 monitoring. However, a decline has been observed in subsequent
monitoring events following Year 4. This decline was also observed in the control sites
until the re-alignment of transects MT4, MTS, and MT6 prior to the Year 7 monitoring
0 event (Figure 18). In light of the results for Year 4 and the observed pattern for control
sites, it appears as though inter-year variation has a more prominent effect on stem
heights than project-related factors.
B. Sediments
Sediments collected from the south side of Mason Creek exhibited significantly higher
percent sand than sediments collected from the north side of Mason Creek. Conversely,
sediments from the north side of Mason Creek exhibited significantly higher percent OM.
This same pattern was observed during the pre-project monitoring conducted in
December 2001. As stated in the Pre-Construction Biological Monitoring Report,
sediment data suggest that the south side of Mason Creek is a relatively new, accreting
marsh system compared to the marsh located north of the creek.
w As was reported in Year 0, there was no significant difference in percent sand as a
function of distance from the creek bank. However, samples collected near the edge of
Mason Creek consistently exhibited the highest percent sand. Likewise, there was no
significant difference in percent OM as a function of distance from the creek bank.
However, samples collected near the edge of Mason Creek exhibited the lowest percent
OM. During Year 1 and Year 2 percent OM was highest at stations furthest from Mason
Creek (i.e. 300-ft). Results from Year 7 closely resemble those from pre-construction
monitoring (Year 0).
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C. Benthie Invertebrates (Backbarrier Infauna)
A summary of findings for the benthic infaunal sampling and characterization is provided
as Appendix A of this report. Overall, mean abundances were reduced in 2008 sampling
compared to previous years. Reduction in overall abundances and total abundances of
the dominant taxa may be indicative of predation pressure by finfish accessing the marsh
habitat during this time of year. However, reduced abundances could also be attributed to
changes in tidal flow regimes and sediment deposition patterns. Please refer to Appendix
A for more detailed characterization of the benthic community sampled during Year 7.
0
D. Physical Monitoring and Habitat Types
Physical (i.e. hydrographic) monitoring is conducted on an annual basis to document
sedimentation processes in the inlet area over time. As part of this monitoring effort,
Gahagan & Bryant Associates, Inc. (GBA) produce annual monitoring reports that
include detailed shoreline/channel profiles and bathymetric maps. Based upon the data
collected, observed trends in sediment deposition and loss are evaluated. As evidenced
through physical survey and aerial imagery, adjustments occurring within the inlet
interior include increased shoaling of the flood-tidal delta and slight adjustments of the
channel thalweg connecting Mason Creek to the inlet throat. Intertidal sand flats and
volunteer marsh continues to accrete behind Wrightsville Beach via increased sand
deposition in these areas. Please refer to the hydrographic reports submitted under
separate cover by GBA for more detailed information regarding bathymetric conditions
within and adjacent to the relocated inlet.
V. CONCLUSION
Pre-construction monitoring data demonstrate some observed patterns related to station
location (i.e. distance and position relative to creek). Year 7 monitoring demonstrated an
increase in both stem height and density relative to Year 6. These increases (while not
significant) may be attributed to the August sampling period. However, the observed
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40
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totals remain lower than Year 0 (pre-construction) and lower than Year 4 (post-
construction). Both stem density and stem height indices are consistent with those
metrics observed in Year 3 and Year 5 post-construction monitoring. Given the range of
recorded data and temporal variation in sampling it appears that inter-annual variation
may play a strong role in determining plant growth, rather than project-related
interference. In addition, observed stem densities and stem heights during Year 4 were
not significantly different from pre-construction data. This is also indicative of the role
of inter-year variation relative to project-related trends.
It is important to note that increased sediment deposition (at MT6) and erosion along the
southern edge of Mason Creek (near MT4 and MT5) appeared to affect the growth and
survivorship of Spartina stems during the Year 6 and Year 7 monitoring events. Inlet and
channel morphology demonstrate patterns of shoaling with the inlet interior (particularly
the flood shoal complex). Channel adjustments of Mason Creek (sediment loss or gain)
has necessitated the reestablishment of three transects (MT4, MT5, and MT6). Near
MT4 and MT5 over 150 If of marsh has been converted to open water. In comparison,
increased sediment deposition within the back-barrier areas of Wrightsville Beach has
resulted in increased marsh habitat. Overall, the re-establishment of transects has
resulted in some stations being located in areas of slightly higher microtopography
(potentially influencing findings related to stem density and height). As such,
comparative analyses between years beginning in 2008 (Year 7) may not accurately
reflect patterns in stem densities or height indices over the course of post-project
monitoring.
C
Year 7 monitoring represents the first year that data collection has occurred in the late
summer. Future monitoring will provide additional data, allowing for a more accurate
characterization of conditions during the growing season.
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a I
• 0 0 0
•
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Figure 3. Analysis of Stern Density vs. Position Relative to Mason Creek (Year 7)
11-? 50
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Figure 4. Stern Density vs. Distance from Mason Creek
i
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p = 0.5431
10
5
50 100 150
Distance from Mason Creek (ft)
r
300
•
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10
Figure 5. Analysis of Stem Density vs. Transect Number (bear 7)

N
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90
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figure 6. Analysis of Stern Density (Pre-Project vs. Post-Project)
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0 Figure 7. Analysis of Height Index vs. Position Relative to Mason Creek (Year 7)

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201
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North
South
Position Relative to Mason Creek
Figure 8e Analysis of Stem Height Index vs. Distance from Mason Creek (Year 7)
--120
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Figure 9e Analysis of Height Index vs. Transect Number (Year 7)
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Figure 11. Analysis of % Sand of Sediments vs. Position Relative to Mason Creek
100-T--
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Figure 12. Analysis of % Sand of Sediments vs. Distance from Mason Creek
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50 100 150 300
Distance from Creek (ft)
•
North South
Position Relative to !Mason Creek
9 Figure 13. Analysis of % Organic Matter of Sediments vs. Position Relative to Mason Creek
1•
2
1
0
Figure 14. Analysis of % Organic Matter of Sediments vs. Distance from Mason Creek
•
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Position Relative to Mason Creek

i
Figure 15. Analysis of % Sand by Year (Pre-Project vs. Post-Project)
100 7---
90
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p = .69®3
50
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- - - - - - - - - - - - F_ ? _F_
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Figure 16. Analysis of % Organic Matter by Year (Pre-Project vs. Post-Project)
N = 265
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Figure 17. Stem Densities at Control Locations (300' away from marsh edge) by Year
1
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Figure 18. Stem Heights at Control Locations (300' away from marsh edge) by Year
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-
5 6 7
0
0 1 2 3 4 5 6 7
Year
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APPENDIX A.
BENTHIC INFAUNAL SUMMARY OF FINDINGS
•
[1
Monitoring of Benthic Faunal Communities associated with the
Mason Inlet Relocation Project - 2008 Sampling
Prepared by Troy Alphin
Research Associate, Center for Marine Science
University of North Carolina at Wilmington
Benthic Faunal Communities
The health of estuarine habitats is often based on the provision of certain ecosystem
functions. Marshes habitats act as nursery because they provide both refuge for early
juveniles of many species and because they provide areas for them to forage. In most
cases these species forage (or prey) upon small organisms (mostly macro-invertebrates)
that live in or on the substrate surface or closely associated with the plant structures. The
investigation of these organisms and the communities they form is often difficult because
of their small size and highly variable abundance based on small scale spatial changes,
temporal fluctuation, and response to predators. The development of these macro-
invertebrate communities is closely tied to the proper ecosystem function provided by
marsh systems. If there are not sufficient organisms to allow juvenile fishes to forage
they will leave the relative safety of the marsh habitat, potentially increasing the risk
predation. It is possible that large scale changes in Benthic macro-invertebrate
communities could lead to shift in class strength of some species. Benthic infaunal and
epibenthic macrofauna are often studied to help evaluate the function of various
estuarine, marine, and aquatic habitats. Many of these organisms comprise a significant
portion of the diet of estuarine fishes and are critical to the maintenance of healthy fish
populations. In many cases benthic organisms are the critical food resource for larval
and juvenile fishes. Since the life history stages of both predator (fish) and prey (infauna
and epifauna) are closely link temporally, it is vital that benthic communities thrive
during periods that precede the recruitment of juvenile fish. In essence if the benthic
organisms are not present when juvenile fish move into the river, bay or sound, the
possibility of recruitment failure for certain fish increases.
•
Benthic infauna are those organisms that live within the sedimentary environment or on
the sediment surface, although organisms that primarily on the sediment surface are
referred to as "epibenthic". In general when we refer to epifauna in the soft substrate
community, we are referring to the more motile crustaceans and fishes, especially
juvenile finfish that may derive a significant portion of their diet from the benthos. The
organisms that comprise the majority of the benthic community are annelids (both
polychaete and oligochaete), bivalves, amphipods, isopods, and insects. Although other
taxonomic groups are often present, these groups tend to represent the numerical
dominants for most estuarine sites. These organisms demonstrate a variety of life history
strategies, based on feeding type and living position. While surface oriented species may
be readily available to bottom foraging fishes, deep burrowing forms are less likely to be
preyed upon.
1

This study focuses on the subgroup of benthic fauna considered macrofauna within the
size class of 500 microns (1000 microns= 1 millimeter) or greater. Most benthic
organisms in this size class are heavily preyed upon by larger finish and crustaceans.
These organisms tend to live 6 months to 1 year (although there are some groups such as
bivalves that can live for a number of years). These organisms also tend to have
relatively low motility and once settled tend to move less than 5 meters over the course of
their lives. The benthic community provides a critical ecosystem role in transferring
energy to higher trophic levels because this group feeds primarily on algae and detritus
(although there are some predatory forms as well). The other main reason for studying
this group is based on their close relationship with the sediment and different taxa will
respond to acute and chronic disturbances of this habitat in different ways. Monitoring of
benthic fauna is an important component of many environmental studies, including beach
dredge and fill operations (e.g. beach nourishment projects) and marsh restoration
projects since they tend to provide a good indicator of both short and long term impacts
and recovery. While year to year changes (inter-annual variation) are natural, acute and
chronic impacts to the habitat are better evaluated on a mulit-year basis when annual
variation can be accounted for.
Sampling Design
This report covers the 2008 sampling period of the post construction phase of the Mason
Inlet Relocation Project. This project was initiated in 2001 with a set of preliminary
samples collected in December, prior to construction. The Mason Inlet relocation was
completed in 2002, with post construction sampling being conducted annually since
2002. The infaunal sampling reported here focuses mainly on the 2008 sampling year
although key parameters of community composition are presented over the five years
post construction. All samples collected in 2004-2007 were collected in late November
and early December to coincide with the sampling period of the pre-construction
monitoring. In 2008, however, the sampling regime was changed and samples were
collected in August near the end of the period of high predation pressure on the benthic
community. It should be noted that this change in timing could affect comparison among
years. Additionally, some station locations have been re-established due to erosion
occurring over the previous years. In general, sampling stations are positioned 5 ft, 150
ft, and 300 ft from the marsh edge.
Infaunal samples were collected using standard benthic cores, 10 cm diameter x 15 cm
deep. The sites sampled in the 2008 sampling periods included a series of marsh transect
locations (MT2, MT4 and MT6). The MT transects consisted of three replicate core
samples taken at each of three distances from the marsh edge (5, 150, and 300 feet into
the marsh) on each transect (though the exact edge location varied somewhat over time
with erosion or accretion). Sand sites previously evaluated for benthic communities near
the inlet throat were not included during the 2008 sampling.
2
r?
All samples were fixed in 10% buffered formalin (formaldehyde derivative) solution with
rose Bengal dye added and later transferred to a 70% isoproponol preservative for storage
and processing. Samples were sieved through a 500 micron screen to remove fine
sediments and aid processing. All organisms retained were separated from the remaining
sediment and vegetative material using light microscopes and identified to the lowest
possible taxonomic level (generally species). As part of our standard quality control and
quality assurance procedures, identifications are subject to verification and a subset of
sorted samples are rechecked to ensure removal of all organisms. All newly identified
species and those that could not be identified to the species level are sent to authorities
for clarification. Diversity was calculated using the Shannon Diversity Index.
• Community Description
A total of 49 taxa (representing 14 major taxonomic groups) were collected during the
2008 sampling period. The species richness from the marsh transects MT2, MT4, and
MT6 were 27, 18, and 33 taxa respectively (Table 1 and 2). Among the marsh transect
sites Capitella capitata, Hargeria rapax, Neanthes succinea, Nematode sp. (this is taxa is
considered meiofauna, included here for informational purposes but should not be
considered as part of the community evlauation) and Tubificidae sp. were the dominant
taxa (Figure 4). Dominant taxa are defined as those species that make up greater than 3%
of the total number of individuals. Figure 5 shows the relative percentage breakdown for
all taxa greater than 3 % for each site.
Overall mean abundances were reduced in the 2008 sampling compared to previous
sampling years (Table 2). Mean total abundance among sites showed significant
differences with MT6-300 having significantly lower abundance than most other sites
and MT2-150 and MT4-150 showing greater abundances than MT6-5 and MT6-300
(Figure 1). Species richness showed no differences among sites (Figure 2). This is not
surprising since overall species richness was reduced during this sampling period (Table
2). The Shannon Diversity Index takes into account number of taxa as well as species
evenness. Comparison of mean diversity among sites showed, as in previous years,
diversity was low to moderate at most sites. However, only one difference was detected
* among sites with MT6-5 differing from MT6-150 (Figure 3). There was a high degree in
variation among the major taxonomic groups present at each site and the relative
abundance of these groups by site (Figure 6-Figure 14). The variation in taxonomic
groups present tends to reflect the general trends in species richness and diversity.
However many of these groups play critical roles in structuring the benthic habitat that
are not reflected in the abundance of individuals. Organisms or taxa that rework the
substrate may have a significant role in maintaining favorable conditions for other taxa.
The 2008 sampling season showed a clear reduction in abundance overall, as well as a
reduction in the total abundance of the dominant forms. Many benthic communities are
considered both resistant and resilient to perturbations. It is these characteristics that
make the benthic community such a critical measure of ecosystem function. While the
total abundance of organisms gives us an indication of the potential resource available for
3
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•
•
transfer to the upper trophic levels, these are not the only considerations. Interestingly
there was a downward shift in the mean abundance of tubificid oligochaetes. This is a
group of deep burrowing organisms that are generally not available as a food resource for
most juvenile fish. The reduction in abundance of this group may be an indication of
other factors (salinity, sediment characteristics, sediment chemistry, etc.) that may impact
this group. oligochaetes have direct development and are slow to disperse so major
impacts to this group may take years to recover. Shifts in abundance of keys groups may
be due in part to changes in sites characteristics such as erosion or possible changes in
local flow patterns. However, more detailed site information and longer-term sampling
would be needed prior to identifying specific causation for shifts in abundances.
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Figure 4. Dominant species for all sites sampled. Dorniance is based on the
percent of the total number of individuals collected.
0 20 40 60 80 100
- --
Capitella capitata
I
Hargeria rapax
Neanthes succinea
Nematoda sp
Tubificidae spp.
Fig ure S. Relative dominance of each species by site. Dominance is based
on the percent of the total number of individuals collected per site.
0 20 40 60 80 100
(MOdiOlus SP.)
Anurida mantima
Aphididae sp.
Bezzia/Palpomyia
Capitella capitata
Chthamalus fragilis
Coleoptera sp ®MT2 5
Cricotopus sp
?MT2 150
Dolichopodidae sp.
Gastropoda sp. ?MT2 300
Geukensia demissa DMT4 5
Hargeria rapax DMT4 150
Lepidactylus dytiscus
?MT4 300
Neanthes sucanea
Nematoda sp. 17MT6 5
Nemertea sp. ?MT6 150
Neohaustonus schmitzi ?
?MT6 300
Prionospio (heterobranchia)
Sphaeroma quadndentatum
Tubificidae spp.
Uca pugilator
Uca sp.
•
0
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oaa eaa ao5` e?`a oaa ° ?tia era
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Fiigure 6° Mean abundance by niajortaxonomicgroupfor samples
collected August 20M.
MT2150
10
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0.0 T z T T z _
oaa ?5\
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Fgure 7° Mean abundance by majort groupfor samplescollected
August 2008.
10
0
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1•
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re 90 Mean abundance by m4ortaxo °c pfor samplescollected
August 2008.
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Figure 9, Mean abundance by major taxonomic group for samples
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I0
is
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elO. Mean abundance by °®r t f®r sampiescolected
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PAT4
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Figmell. abundance by majw t group for sanVftcDlkxted
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S
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41 Iii
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Figure13° Mean abundwce by wort group for samplescolWed
August 2008°
10
IS

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8.0
6.0
4.0
2.0
0.0
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r\?oaa ???a\J\a \`?aps\ \?ya`?a `rae?a `rae,?a a\aa`ea
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Figure % Mean abundance by major t p for samples®olWed
August 2008,
I9
1s
10
APPENDIX B.
AUGUST 2008 SITE PHOTOGRAPHS
ar 7)
(1) View of beachfront dredging operation - Winter 2008
I•
•
•
Y ?y?y
1,4
s ? ae a k ,a 'T ? ? q a ? a +"'t '4
t a,*?yyg a?f:.S'? ry?yY AFB 'fit Y 5

T # e9pp
k
Mason Inlet Site Photographs
Relocation Project- August 2008
New Hanover County NC (Post-Construction Year 7)
r,
(3) Quadrat sampling (stem height and density) on north side of Mason Creek
I•
I•
0
(5) View of re-established MT6 transact on the south side of Mason Greek
Mason Inlet
Relocation Project
New Hanover County, NC
L.MG
Site Photographs
August 2008
(Post-Construction Year 7)
(6) View of re-established MT5 transact on the south side of Mason Greek
eve ??
1•
•

(7) Flood tidal shoal of inlet just south of Figure Eight Island

(8) View of sediment sampling conducted on the northern side of Mason Creek
¦
Mason Inlet
Relocation Project
New Hanover County, NC
I.,MG
Site Photographs
August 2008
(Post-Construction Year 7)