Tripod Deployment: YR160825 to YR160913, PC-ADP and LISST, Clay Bank, York River Virginia

Dataset consists of burst data collected as part of a tripod deployment. The tripod included the following instruments: Pulse-coherent Acoustic Doppler Profiler (PCADP), Sequoia LISST, two HOBOs

Resistivity, Magnetic Susceptibility and Sediment Characterization of the York River Estuary in Support of the Empirical Investigation of the Factors Influencing Marine Applications of EMI (Year 2 of SERDP Project MR-2409) Final Report.

Vessel and personnel support was provided for a series of cruises to three salinity regimes along the York River. Data and samples from a standard suite of hydrographic and sedimentological measurements, as well as electrical resistivity and magnetic susceptibility, were collected and analyzed for each location. These cruises provided opportunities to obtain information that is being used to quantify the unique marine contributions to the early time TEM noise, including conductivity variations in the water and variability in bottom sediment properties in real marine environments, for use in the parallel modeling and electromagnetic-induction sensor work ongoing in the same project. Data collected during Year 1 of this project were used to select the appropriate locations to provide a range of conductivity and sediment conditions

Suspended Particulate Matter Longitudinal Survey – Currituck Sound, NC; Oct 13-15, 2015, Cruise: CS151013-15, CHSD Stations: S5566-5587

Dataset consists of water column and bottom burst data, PICS, and light attenuation data collected as part of a 21 station longitudinal survey of the Currituck Sound, NC along a ~60 km transect northward from the Wright Memorial Bridge

2016 Data collected for Resistivity, Magnetic Susceptibility and Sediment Characterization of the York River Estuary, VA in Support of the Empirical Investigation of the Factors Influencing Marine Applications of EMI (Year 2 of SERDP Project MR-2409)

The objective of this component of the Strategic Environmental Research and Development Program (SERDP) Project MR-2409 was to conduct field measurements to aid in the determination of the electromagnetic induction (EMI) response to the water column and underlying sediments in the York River estuary, which includes water column and sediment properties similar to many underwater environments of interest to unexploded ordinance detection. Data and samples from a standard suite of hydrographic and sedimentological measurements, as well as electrical resistivity and magnetic susceptibility, were collected and analyzed for each location. These cruises provided opportunities to obtain information that is being used to quantify the unique marine contributions to the early time TEM noise, including conductivity variations in the water and variability in bottom sediment properties in real marine environments, for use in the parallel modeling and electromagnetic-induction sensor work ongoing in the same project. Data collected during Year 1 (2014) of this project were used to select the appropriate locations to provide a range of conductivity and sediment conditions. This work was used to choose appropriate locations during Year 2 (2016) of this project, described in this report, to field-test the EMI sensor arrays. (Note that there was a delay of several months between the end of Year 1 work and the start of Year 2 work. Thus the Year 2 final report is dated more than 12 months after the Year 1 final report.

Laser In-situ Scattering and Transmissometer (LISST) Observations in Support of the Sensor Insertion System Duck, NC October, 1997

The objective of this portion of the study was to collect LIS ST time series at times corresponding to collection of pumped samples of suspended sediment across the width of the surf zone during a major field experiment called SandyDuck \u2797. The pumped samples were analyzed for total percent sand (\u3e60 micron), total percent mud (0.8 - 60 micron), organic content and sand size distribution. The LISST measures the particle size distribution from 5-500 microns. The purpose was to provide a high quality data set of pumped samples with which to later test the sensitivity of indirect measurements of suspended sand concentration to the presence of suspended mud. The response of OBSs is known to be particularly sensitive to the presence of suspended mud (turbidity) due to the inverse response of OBS output to grain size. Better constraints on the proper interpretation of OBS time series will improve confidence in conclusions with regards to net along-shelf transport of sand during storms. Standard analysis of the pumped samples does not provide the size distribution of the mud portion of the suspended particles. The LISST time series help fill this ga

Role of Sediment Resuspension on Estuarine Suspended Particulate Mercury Dynamics

Coastal sediments are an important site for transient and long-term mercury (Hg) storage, and they foster a geochemical environment optimal for Hg methylation. Therefore, efforts have been taken to constrain the role of sediments as a source of methylmercury (MeHg) to the estuarine water column. This study employed the Gust Microcosm Erosion Core system capable of quantifying particle removal from undisturbed cores under measurable shear stress conditions to assess particulate Hg and MeHg exchange between sediments and the water column. Samples were collected from organic-rich and organic-poor sediment types from the mid- and lower Delaware Bay. It was found that bulk sediment samples from organic-rich systems overpredict total Hg and MeHg release to the water column, whereas organic-poor sediments underpredict the exchange. In general, organic-rich sediments in shallow environments have the most impact on surface particle dynamics. There is little evidence to suggest that MeHg formed in the sediments is released to the water column via particulate exchange, and therefore, nonsedimentary sources likely control MeHg levels in this estuarine water column

Effects of Shell Hash on Friction Angles of Surficial Seafloor Sediments near Oysters

Oysters are hypothesized to affect the shear strength of nearby surficial seafloor sediment as fragments of oyster shells (shell hash) are typically more angular relative to sand particles alone, among other differences. Resistance to shearing is well characterized by the friction angle, which is estimated in this study from vacuum triaxial laboratory and portable free-fall penetrometer field tests. Friction angles of sediment with shell hash were higher relative to those of sediment without shell hash (via hydrochloric acid treatment) on average by about 19% (36.0°–30.2°, respectively). Triaxial confining pressures ranged between 2.1 and 49.0 kPa to simulate subtidal and intertidal aquatic conditions. Regularity (average of particle roundness and sphericity) values of sediment samples with shell hash were found to be less than those of samples without by about 6% (0.66 and 0.70, respectively), which indicates the particle shapes of the former are, overall, more angular and less spherical. Further study and methodology improvements are needed to decrease the approximate 9° friction angle discrepancy estimated from field- and laboratory-based tests. Knowing oysters have the potential to increase sediment shearing resistance helps establish a pathway of how shellfish colonies may contribute to mitigating surficial erosion around coastal infrastructure

Minimal effects of oyster aquaculture on local water quality: Examples from southern Chesapeake Bay

As the oyster aquaculture industry grows and becomes incorporated into management practices, it is important to understand its effects on local environments. This study investigated how water quality and hydrodynamics varied among farms as well as inside versus outside the extent of caged grow-out areas located in southern Chesapeake Bay. Current speed and water quality variables (chlorophyll-a fluorescence, turbidity, and dissolved oxygen) were measured along multiple transects within and adjacent to four oyster farms during two seasons. At the scale of individual aquaculture sites, we were able to detect statistically significant differences in current speed and water quality variables between the areas inside and outside the farms. However, the magnitudes of the water quality differences were minor. Differences between sites and between seasons for water quality variables were typically an order of magnitude greater than those observed within each site (i.e. inside and outside the farm footprint). The relatively small effect of the presence of oysters on water quality is likely attributable to a combination of high background variability, relatively high flushing rates, relatively low oyster density, and small farm footprints. Minimal impacts overall suggest that low-density oyster farms located in adequately-flushed areas are unlikely to negatively impact local water quality. Associated datafiles available at: https://doi.org/10.25773/wwva-tz1

Environmental and Ecological Benefits and Impacts of Oyster Aquaculture Chesapeake Bay, Virginia, USA

To better quantify the ecological benefits and impacts of oyster aquaculture, we sampled water quality, sediment quality, benthic macrofaunal communities and oysters at four oyster aquaculture sites located on the western shore of Chesapeake Bay in Virginia, USA. At each site, we collected samples from within the footprint of the aquaculture cages and from nearby areas with similar physical and environmental conditions but far enough away to be minimally influenced by aquaculture operations. Data collected from the water column included chlorophyll concentrations, turbidity, pH, dissolved oxygen concentrations, light attenuation, particle concentration, median particle size, total suspended solids and their organic content, and dissolved nutrient concentrations. Sediment and macrofauna community data collected included sediment grain size and organic content and macrofauna identity, abundance, biomass and species richness. In addition to assessing the potential impacts of oyster aquaculture on the water column and benthos, we also assessed differences in the oysters harvested Environmental and ecological benefits and impacts of oyster aquaculture at each site and estimated the total amount of nitrogen and phosphorus harvested at each site. Differences in water quality, sediment quality, and macrofauna community structure between areas within and outside the farm footprint were rare and of small magnitude and varying direction (i.e. negative versus positive impact) when they did occur. Aquaculture sites varied by an order of magnitude in size, annual harvest and harvest per unit area. They also varied by an order of magnitude in the total amount of nitrogen (N) and phosphorus (P) harvested per unit area. In contrast to the negative environmental impacts associated with other forms of animal protein production for human consumption, oyster harvest from aquaculture sites studied here resulted in the removal of 21-372 lbs. of N and 3-49lbs of P per farm per year