2011 REU
Allen Li (Boston University, Boston, Massachusetts)
Alongshore Variation in the Characteristics of Primary Dunes on a North Carolina Barrier Island Experiencing Heterogeneous Migration Rates
Abstract: Direct (construction and pedestrian trampling) and indirect (sea level rise) anthropogenic effects have led to losses of dunes at 70% of coastal beaches globally. Coastal sand dunes provide an array of ecosystem services that makes their preservation a significant concern. The most effective means of dune creation and preservation are unclear so I quantified several variables 
associated with dunes on Onslow Island, NC to determine what associations might exist. Eolian sediment flux was determined using settlement traps placed flush to the surface. Dune vegetation density and structure were determined using a line-intercept method. Morphology of dunes and adjacent back beach were measured using LIDAR. Fluxes of sediment were consistently higher on the north and south ends of the island. Vegetation density was fairly constant along the island on both the seaward and landward slopes of the dunes but relatively high amounts (20-40% cover) of exposed roots were found only in the middle of the island. Back beach width was greatest on the ends of the island (>15 m wide) and narrowest or absent in the middle of the island. The positive correlation of higher sediment fluxes (that builds dunes) and higher above-ground plant density (that retains sediments) with wider back beaches indicates that dune creation and preservation begins with establishing and maintaining back beaches.
worked with: Dr Stephen Fegley and Dr. Antonio Rodriguez
Justin Hilliard (Fairmont State University, Fairmont, West Virginia)
Estimating Habitat Quality for Shorebirds near a Barrier Island Inlet in North Carolina
Abstract: Coastal inlets separating barrier islands experience extensive engineering activity to maintain navigable channels. These activities alter the condition of landforms associated with the inlets including ebb-tide and flood tide deltas, intertidal and subtidal shoals, and beaches bordering the inlets. All of these landforms are frequently used for foraging by shorebirds, some of which are 
threatened or endangered. Identifying the features that make a given habitat useful for foraging by birds is useful for mitigating unintentional changes to inlet habitats that decrease their value to the birds. I quantified spatially-explicit shorebird foraging, infaunal composition, and sediment structure in a range of landforms in the New River Inlet, North Carolina. PERMANOVA revealed significant differences in the abundance and species diversity of shorebirds using different areas of the inlet. The lowest forager abundances, lowest shorebird diversity, and coarsest grain sizes were all associated with intertidal beach within the inlet itself compared to beaches and flats on either the ebb or flood sides of the inlet. Density of total infauna was not significant across all of the habitats but individual species showed specific patterns of distribution. For example, mole crabs (Emerita talpoida) were found only on the ebb tide areas and within the inlet. This distribution matched the distribution of willets. The highest infaunal diversity corresponded to the area of highest shorebird diversity: both occurred on the flood tide flats. These patterns of association suggest that changes induced by human activities that increase or decrease specific inlet landforms could alter the relative abundances of shorebird species.
worked with: Dr. Stephen Fegley and Beth VanDusen
Melana Horton (North Carolina State University, Raleigh, North Carolina)
Juvenile Ghost Crab (Ocypode quadrata) Abundances in Multi-use and Military Training Beaches of Onslow Island
Abstract: Ghost crabs (Ocypode quadrata) serve multiple ecological roles in beach and dune communities. Their demonstrated sensitivity to anthropogenic activities in the beach habitat has made them useful bioindicators of impending environmental damage. Sampling studies on Onslow Beach, NC have documented a persistent (over 4 years) depression of adult ghost crab abundances within the military training zone. Previous experimental studies testing hypotheses that might explain this pattern have not revealed a compelling explanation. I studied the along island abundances and 
behavior of juvenile ghost crabs. On two occasions I conducted walking surveys of active adult and ghost crabs in beaches with high and low abundances of burrows. I measured the depths of juvenile crab burrows by making, and then excavating, plaster casts. I also conducted laboratory trials testing for preferences for sediment moisture for constructing burrows by juvenile crabs. The nighttime surveys demonstrated that both juvenile and adult ghost crabs were less abundant in the training zone than elsewhere but the relative abundances of juvenile to adult crabs was much higher within the training zone. Mean (±1 SE) juvenile crab burrow depth was 23.9 (2.4) cm, well within the depth range that has been demonstrated in previous studies to be compacted by vehicular traffic. Juvenile ghost crabs preferred to burrow in moist over dry sand by 3:1. Apparently ghost crabs recruit to beaches along the length of Onslow Island, but the training zone, where vehicular traffic can be frequent and intense may induce higher juvenile crab mortality rates, especially given that the majority of beach traffic travels in the moist, more compact sand of the lower beach which is the preferred location for juvenile crabs to burrow.
worked with: Dr. Stephen Fegley and Beth VanDusen
Jeremy Pivor (Washington University in Saint Louis, Saint Louis, Missouri)
Scope and scale of ecosystem services provided by feeding activities of oysters on an intertidal reef
Abstract: Oyster reefs are capable of providing several important ecosystem services. However, the spatial extent of some of these services, for example water filtration, is unclear. I conducted a study to determine how well an oyster reef filtered water and how far from the reef this filtering effect persisted. I studied a 476 m2 area oyster reef located near Hoop Pole Creek, NC. Flow 
patterns (direction and magnitude) across the reef were measured using an acoustic current profiler. During an ebbing tide we established flow normal and flow parallel transect centered over the middle of the reef. Separate water samples (125 mL) were taken from kayaks near the water surface and near the sediment surface at several locations along both transects and placed on ice. Benthic cores were also collected at each location. Chlorophyll a concentrations were determined using flourometric methods in the laboratory. Benthic organic matter was estimated via combustion. No significant differences in concentrations of water chlorophyll, benthic chlorophyll, or benthic organic matter across the flow normal transect. Significant decreases in water chlorophyll concentration accompanied by significant increases in benthic chlorophyll concentration and organic matter were found on the flow parallel transect from the upstream to downstream direction. However, these affects were largely restricted to areas close to the reef. No effects of reef presence on water or benthic concentrations of chlorophyll could be detected several m downstream. The landscape effects of this small reef were localized.
worked with: Dr. Charles Peterson and Dr. Jon Grabowski
W. Chris Berner (North Carolina State University, Raleigh, North Carolina)
Diel cycles of phytoplankton biomass and ammonium in the lower Neuse River
Abstract: Ammonium, the most common form of nitrogen available to sustain primary production in many estuaries has not been demonstrated to induce changes in phytoplankton biomass over short time intervals. I conducted an intensive, 24-hour sampling in the lower Neuse River to determine 
whether diel patterns of chlorophyll a in the water column correlated to in situ NH4+ concentrations. Water samples (1 L) were collected every 3 hours from 1 m below the water surface in a single location and preserved in the field. In the laboratory separate subsamples of each sample were used to determine chlorophyll a concentrations using HPLC, ammonium concentrations by fluorometry, and phytoplankton composition by microscopy. Ammonium showed a small magnitude, distinct diel pattern with lowest concentrations of ammonium in the late afternoon and early evening. Both chlorophyll a and direct counts of phytoplankton exhibited the same diel pattern but the magnitude of the changes were greater than for ammonium. Although these results suggest increased ammonium concentration increased phytoplankton abundance the greatest contributor to changes in water column phytoplankton biomass was caused by vertical migration of some abundance species.
worked with: Dr. Hans Paerl and Dr. Nathan Hall
Noel Anderson (Oberlin College, Oberlin, Ohio)
Blowin’ in the Wind: The Contribution of Aeolian Sand to Back-Barrier Marsh Accretion
Abstract: As sea level rises salt marshes, which must occur within a relatively narrow range of the intertidal to persist, must accumulate sediments to avoid drowning. To predict which salt marshes may be threatened by rapid sea level rise we much identify and quantify all sources of material that contributes to elevation of the marsh platform. The morphology of the southern third of Onslow Island, NC is dominated by no or low (<1 m) dunes and numerous overwash fans while the northern third of the island has high (>5 m) dunes backed by dense maritime forest suggesting that eolian 
transport of sediment to the back barrier salt marshes may be important in the southern, but not the northern, portion of the island. Along a shore-normal transect established behind the southern and northern portions of the island cores were collected at increasing distances into the marsh. In the laboratory sediment grain size (using a CILAS) and percent organic matter (via loss on ignition) were determined in the top 25 cm of each core at 1 cm intervals. Cores taken in locations closer to the dunes on the southern end of the island had greater proportions of well-sorted, coarser sand grains (characteristic of eolian transport) . Cores taken in the same relative locations in the northern end of the island did possess coarse sand grains. Percent organic matter showed an inverse relationship with coarse sand abundance in all cores. Island morphology can be used as a predictor of the rates of eolian transport and, at least on Onslow Island, such transport is an important source of sediment to some of the back barrier salt marshes.
worked with: Dr. Antonio Rodriguez
Chelsea E. Berg (Wheaton College, Wheaton, Illinois)
Wrack and sand as reservoirs of allochthonous and autochthonous bacteria on Onslow Beach, Camp Lejeune, North Carolina
Abstract: Public health concerns regarding recreational water quality do not generally consider pathogens found in sand or algae. At beaches along the Great Lakes and in the state of California, fecal indicator bacteria (FIB), such as E. coli and Enterococcus sp., have been quantified in algae and sand. We hypothesized that algae along the coast of NC would also harbor FIB populations.
After surveying the total biomass of algae present per beach, we collected wet and dry samples of the dominant Sargassum sp. and Codium sp. in addition to the sand located immediately below each. Bacterial concentrations of FIB and Vibrio spp. were enumerated per gram of sample using IDEXX and membrane filtration. Both Enterococcus (FIB) and Vibrio spp. were present in high concentrations per gram of algae and sand. Algal wrack was found to harbor statistically more Enterococcus and Vibrio spp. than sand. A student’s t-test indicated that the differences between wet and dry samples were not significant. Wrack was shown to be a more significant reservoir and a more hospitable environment for FIB and Vibrio per gram than sand. When algal concentrations are high, the wrack could be a potential contributor to contaminated water and beaches. Future investigations should be made into the public health implications of this study for bacterial transference from algae to beachgoers. Members of the FIB studied are typically non-pathogenic, so high concentrations of FIB in the absence of fecal pathogens do not necessarily translate to an increase in public health risk.
worked with: Dr. Rachel Noble
Nicole A. Poletto (Villanova University, Villanova, Pennsylvania)
An assessment of coastal stream sediment supply to marshes in a North Carolina estuary
Abstract: Coastal communities are becoming overpopulated and heavily developed. Land use change of coastal ecosystems can affect the ability of wetlands to accrete sediment at a rate to 
avoid submergence from sea level rise. To assess the potential for coastal streams to supply sediment to marshes affected by varied land use, seven sites were monitored by ISCOs in the New River Estuary in Camp Lejeune, North Carolina. The purpose of this study is to assess sediment supply of coastal streams to marshes in different land use situations. The sediment load was analyzed through annual patterns and through individual storms at each site. A significant correlation was found between the amount of impervious surface and sediment load to the streams annually. Flow vs. concentration figures for each storm showed hysteresis patterns that indicated the source of the sediment loaded into the stream, which showed more uniform patterns in less developed watersheds. Analysis of sediment load to streams compared to downstream wetland accretion showed that streams provide only a very small percentage of sediment required for accretion under a range of sea level rise estimates. This suggests that stream supply of sediment will not be crucial in wetland accretion.
worked with: Dr. Michael Piehler and Suzanne Thompson
2010 REU
Amelia M. Smith (Maine Maritime Academy)
Landscape Effects on Sediments, Macrophytes, and Macrofauna in Onslow Island Salt Marshes
Abstract: Often salt marshes are assumed to have limited spatial variation in sediment and biotic composition. This study sampled two different marshes located on Onslow Island, NC that have different adjacent landscape features. One marsh abuts a 15-year old hurricane overwash while the
other neighbors well-developed maritime forest. The greater availability of sand for transport into the marsh from the overwash could influence the marsh sediment character and consequently alter the biological characteristics of the marss. We collected quantitative data on above- and below-ground plant biomass, fiddler crab (Uca spp.) and march periwinkle (Littorina irrorata) population densities, and sediment composition from replicate plots in different saltmarsh habitats (medium Spartina alterniflora, short S. alterniflora, and S. alterniflora – Salicornia spp. mix) in each marsh. Percent organic composition of the sediments and fiddler crab densities showed no differences. In the marsh adjacent to the maritime forest sediments were significantly finer in composition, periwinkles were more abundant, and amounts of above- and below-ground plant biomass differed depending on habitat (Spartina showed significantly higher above-ground biomass and lower below-ground biomass in mix stands in the maritime-fronted marsh). Although not all sediment and biological characteristics changed, landscape effects appear to contribute to salt marsh structure.
worked with: Dr. Stephen Fegley and Beth VanDusen
Diana Rypkema (Cornell University)
The standard method overestimates ammonium in N-limited estuarine systems
Abstract: Ammonium (NH4+) is essential to our understanding of nitrogen cycling in the Neuse River Estuary. However, accurately measuring low NH4+ concentrations is challenging. Samples are 
extremely easy to contaminate, through contact with the air, which contains volatile nitrogenous compounds. The automated indophenol blue (IPB) method is used to determine NH4+ concentrations for the Neuse River Estuary Modeling and Monitoring (ModMon) Program and the New River Estuary Defense Coastal/Estuarine Research Program (DCERP). To avoid the contamination problem an alternative fluorometric ammonium method (FAM) can be used to measure NH4+ concentrations. The FAM is based on the reaction of NH4+ and o-pthalaldehyde (OPA), which produces a fluorescent compound. This method is sensitive to small variations in NH4+ concentrations and produces accurate results with high repeatability. We compared the IPB method and the FAM to determine potential variation in NH4+ concentration estimates. In general, the IPB method used in the ModMon and New River DCERP overestimates NH4+ concentrations in these two estuaries. We also investigated potential sources for differences in NH4+ concentrations determined by both methods. Results indicate that the observed discrepancy is likely due to a combination of filtration effects, sample storage and failure to subtract background absorbance caused by colored dissolved organic matter (CDOM) from sample absorbance in the IPB method.
worked with: Dr. Hans Paerl and Nathan Hall
Kathleen Walsh (The University of Virginia)
Land use affects in-stream temperature and thermal loading from coastal streams
Abstract: Temperature is a critical parameter in aquatic ecosystems because it controls rates of many important processes and transformations. Estuarine temperature is a topic of interest because of rising global temperatures and the ecological importance of these systems. Temperature and flow
measurements were taken every 30 minutes over a 1-year period in ten coastal subwatersheds that lead directly into the New River Estuary in Camp Lejeune, NC. Our study streams had differences in land cover which were characterized using measures of forested area and developed land. We hypothesized that these two characteristics would affect stream temperature and thermal loading. Steam temperatures were generally higher at sites with higher development and lower forest cover. Correlation analysis revealed decreased forest cover was associated with increased thermal loading during base flow conditions, while increased developed land was associated with increased thermal loading during storm events. Increased in-stream temperatures and excess thermal loading can affect estuarine ecosystem function. These impacts must be considered in decisions regarding coastal development.
worked with: Dr. Michael Piehler, Rebecca Schwartz, and Suzanne Thompson
Octavia Sola (Warren Wilson College)
The Effects of Human Activities on Shorebird Behavior on Onslow Beach, Camp Lejeune
Abstract: Recent estimates indicate that populations of many species of shorebirds are declining. Human disturbance has generally been suggested as one of the leading reasons for declines of many species. This study tested whether human activities on a multiple use beach affected shorebird 
behavior. The focal observation method was used to quantify shorebird behavior on Onslow Beach, a barrier island located on Marine Corps Base Camp Lejeune. Overall, fewer birds used the area where military training occurred than in either a beach recreational zone or a zone with no human activities. The main disturbances during the observation period on Onslow Beach were caused by helicopters. In addition the amount of time willets (Catoptrophorus semipalmatus) spent foraging was significantly less when many people were present compared to areas where there were few people. Potential food for the shorebirds was present in all of the zones. These patterns are consistent with the hypothesis that human activities alter resource utilization by local shorebird populations.
worked with: Dr. Stephen Fegley and Beth VanDusen
Richard G. Browne (University of North Carolina) & Daniel T. Hood (Arizona State University)
A New Method for the Quantitative Measurement of Aeolian Transport of Sediment
Abstract: Aeolian transport is a large contributor to the movement of sand onto, off, and along beaches, which makes quantifying the magnitude of this process important to predicting how a coastal zone will evolve. Flux measurements of wind-blown sediment are usually based on data 
derived from sand traps that capture and hold sand for analysis. These traps are deployed for short periods (~1 day) and cannot capture multiple wind events. Existing sand trap designs cannot be employed for periods of time exceeding several days without a loss of information about the temporal pattern of aeolian sediment flux. We designed a sediment trap to have this capability. Each trap consists of a below-ground section containing a water-filled reservoir and a water-level logger combined with an above-ground, wedge-shaped section that collects suspended or bedload sediment from a single, preselected direction. Although some design and methodological challenges remain, using the data recorded from the logger (and comparing it to “control” traps) we were able to quantify sediment flux in detail over an extended period of time.
AND
Variations in Underlying Lithology along Onslow Beach, NC
Abstract: Sea-level rise commonly influences alongshore barrier island morphology and evolution by forcing a shoreline to transgress over different lithologic units. Previous studies of Onslow Beach, NC shoreline evolution show the island’s northern end has been marked by modest beach erosion and accretion of large dunes while the southern end experiences higher rates of erosion and is frequently overwashed. Our objective was to determine whether (1) modern along-beach variations in erosion rates at Onslow Beach reflect the variable underlying geology and (2) how the underlying geology impacts the barrier’s evolution. Four to seven vibracores were obtained along transects at each of five sites selected to represent the spatial variability in island morphology and erosion rates. Examination of cores, combined with topographical information, indicates that the island is composed of several distinct depositional layers (beach layer, dune layer, washover fan, back-barrier marsh, and estuarine layer) as well as underlaying discontinuous strata deposited prior to modern island development (pre-barrier sand and clay). Consideration of the relative thickness of the layers and placement of the contacts suggests that the rhythmic shape of the shoreline and the variable rates of beach erosion have been influenced by the underlying geology; specifically, the elevation of the pre-barrier contact. Where the contact is high, there are higher rates of erosion and where the contact is low, there are lower rates of erosion and even accretion. We hypothesize that when the contact was originally exposed and sea level rose, the difference in elevation between the north and the south caused a headland to form in the south and an embayment to form in the north. Headlands are often spatially correlated with high erosion, while embayments are often spatially correlated with low erosion. Spatial variations in the rate of shoreline movement created the modern island morphology we see today.
worked with: Dr. Tony Rodriguez, Dr. C. Robin Mattheus, and Ethan Theuerkauf
Stephanie Yin (Brown University) and Ben Riffe (Davidson College)
Distribution and Abundances of Ghost Crabs (Ocypode quadrata) Across Mixed Use and Military Training Beaches
Abstract:
Ghost crab, Ocypode quadrata, population abundances are persistently depressed in the military training zone of Onslow Beach. Using a combination of field studies and laboratory experiments we
tested four hypotheses that may explain this spatial pattern: (i) Vehicles compact sediment in the military training zone, making it more difficult for ghost crabs to burrow; (ii) Varying depths of shell hash layers across Onslow Beach influences ghost crab distribution because shallow shell hash inhibits ghost crab burrowing; (iii) Sediment moisture differences across Onslow Beach shape ghost crab distribution; and (iv) Ghost crabs prefer vegetated areas because vegetation retains moisture, holds sand structures, and provides shelter. The depth of the shell hash layer appeared most 
important. Data from our sandbox experiments showed that shell hash affects ghost crab burrowing preferences. Shallow shell hash can significantly change the distribution of final burrowing locations, suggesting that impenetrable layers of shell hash might actually change ghost crab locations on Onslow Beach, particularly for larger crabs that tend to dig deeper burrows. In the military training zone, layers of shell hash occur around 20 cm in depth and might drive off the larger crabs, leaving small or juvenile crabs that are satisfied with shallow burrows above the shell hash. These shallow burrows leave the crabs susceptible to mortality by vehicle passes.
worked with: Dr. Pete Peterson and Beth VanDusen
