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- Cyanobacterial Contribution to Annual Cycles of Phytoplankton in Lake
Murray, SC
Authors: Haley Durbin et al.
Abstract: Freshwater lakes provide valuable recreational and tourism resources and are a major source of municipal drinking water for local communities. A primary management goal for lake systems is the maintenance of good water quality and a healthy aquatic ecosystem. Blooms of harmful or noxious species of cyanobacteria can result in severe water quality degradation. The purpose of this project was to provide baseline data on phytoplankton community composition, with special emphasis on cyanobacteria, and water quality parameters for Lake Murray, SC. The objective of this study was to determine the annual cyanobacterial contribution to total phytoplankton biomass in the lower reaches of Lake Murray. Measurements for this study were obtained at weekly to biweekly intervals from May 2021 to August 2022 on the northeast side of Lake Murray Dam, SC. Phytoplankton community composition was determined using a combination of high-performance liquid chromatography (HPLC) and ChemTax methods to measure the relative abundances of different algal groups. The phytoplankton community in Lake Murray is composed of a diverse assemblage of primarily green algae, diatoms, cyanobacteria, cryptophytes, and dinoflagellates. Community structure varied seasonally and annually. Total phytoplankton biomass remained below 7 μg of chl a l-1 and never reached “bloom” proportions (e.g.,> 40 μg of chl a l-1). Planktonic cyanobacteria were present year-round in the lower reaches of Lake Murray and comprised 5–40% of the total phytoplankton biomass. Peaks in cyanobacteria abundance occurred during the late summer months. Even at the peak in August 2021, concentrations of cyanobacteria were low (1.79 μg chl a l-1). Over annual cycles, cyanobacteria had a median chl a concentration of 0.63 μg l-1 and a median contribution of 14.9%. Although we were unable to identify any specific causal mechanisms for the fluctuations in cyanobacterial biomass, we demonstrated that cyanobacteria are a consistent component of the phytoplankton community in lower Lake Murray. Baseline measures of phytoplankton during “good” water quality conditions provide invaluable data essential for managers to establish criteria for early prediction of bloom events and evaluate the effectiveness of mitigation strategies. Departures from the norm, especially during the summer and early fall, may signal the beginning of a cyanobacterial (or other algal group) bloom and provide an early warning for recreational users and municipal water intakes.
PubDate: Tue, 05 Mar 2024 11:57:31 PST
- Detecting the Diatom HAB Genus Pseudo-nitzschia in the Public Shellfish
Harvesting Area of Huntington Beach State Park Using a Nanopore Sequencing
Approach
Authors: Megan Cevasco et al.
Abstract: Harmful algal blooms (HABs) cause detrimental economic, ecological, and human health impacts. A major group of HAB taxa of particular interest in coastal shellfish harvesting grounds consists of domoic-acid producing species within the cosmopolitan marine diatom genus Pseudo-nitzschia. Domoic acid (DA) is a neurotoxic amino acid that bioaccumulates in the tissue of filter-feeding shellfish and is responsible for amnesiac shellfish poisoning (ASP) in humans and other marine life. To minimize human health risks and economically damaging shellfish harvesting closures, there is a need to develop proactive monitoring efforts that focus on determining the environmental conditions likely to support Pseudo-nitzschia HABs. This project uses Nanopore sequence data from PCR amplicons using eDNA collected from the public shellfish harvesting area in Huntington Beach State Park. The aim of this research is to explore the use of ribosomal primers in providing baseline taxonomic data supporting effective management of shellfish harvesting areas along the South Carolina coast.
PubDate: Mon, 04 Mar 2024 12:46:58 PST
- Spatial and Temporal Variability in Water Quality and Phytoplankton
Community Composition in Charleston Harbor
Authors: Abigail Stephens et al.
Abstract: The Charleston Harbor estuary is a dynamic ecosystem draining three rivers that surround the rapidly urbanizing greater Charleston area. Projected climate change impacts include elevated sea surface temperature and local changes in water quality that will likely alter biogeochemical cycling as well as phytoplankton abundance and community composition. Partnering with the local non-profit organization Charleston Waterkeeper, surface water samples were collected from late April through October 2021 at 20 sites in the Charleston Harbor estuary system. Water quality parameters measured included sea surface temperature (SST), salinity, pH, dissolved inorganic carbon, chromophoric dissolved organic matter (CDOM), phytoplankton pigments and nitrate and phosphate concentrations. Relatively high (6—16 μM) nitrate values were observed throughout the year and the nitrate to phosphate (N:P) ratios were consistently elevated (50—200) relative to the Redfield ratio of 16. Analysis of variance indicated that the delivery of nitrate, phosphate, and CDOM into the estuary came from upriver of the Charleston Harbor. For instance, CDOM was significantly impacted by tidal stage (p < 0.05) and was negatively correlated with salinity at low salinity sites, but no correlation was observed at high salinity sites. Seasonal patterns in phytoplankton community abundance and composition were driven by changes in SST, as overall phytoplankton biomass increased with a community shift from diatoms during colder months to flagellated cells such as prasinophytes during the warmer summer months. Phytoplankton diversity was greatest during the early summer and lowest in October. This study provides a reference baseline for water quality parameters and phytoplankton community composition in an estuarine ecosystem that is changing rapidly due to dredging and climate change processes.
PubDate: Mon, 04 Mar 2024 12:46:52 PST
- Use of an Autonomous Surface Vehicle to Collect High Spatial Resolution
Water Quality Data at Lake Wateree, SC
Authors: Archana Venkatachari et al.
Abstract: Freshwater resources including lakes and reservoirs are increasingly threatened by harmful cyanobacterial blooms (HCBs). The scarcity of high spatial and temporal resolution data presents challenges for monitoring, predicting, and managing these blooms. Autonomous surface vehicles (ASVs) equipped with water quality sensors represent a powerful tool to obtain high-resolution spatial data at Lake Wateree (LW), South Carolina (SC). LW is a hydroelectric reservoir commonly covered with extensive blooms of the benthic cyanobacteria Microseira (Lyngbya) wollei and Phormium sp., with the thickest mats in shallow coves.The main objective of this study was to determine the best speed and duration of loiter (i.e., pauses) required to collect accurate quantitative data on a mobile platform. We present a low-cost motorized kayak (USD) designed to run autonomously equipped with a YSI EXO2 sonde measuring depth, temperature, conductivity, dissolved oxygen, pH, turbidity, and phycocyanin. The sonde was positioned horizontally on a rigid mount at 0.5 m below the surface to efficiently reduce the effect of turbulence. The data were compared to another YSI EXO2 sonde installed on the same ASV design, maintained stationary midway along the moving ASV’s path to assess the data accuracy obtained at different speeds and loiter periods. No statistically significant differences were observed for measurements collected on the stationary and moving ASVs for all water-quality sensors at a speed of up to 2.7 m/s (6 mph). Differences observed between the moving and stationary sondes for phycocyanin and turbidity sensors were within the reported factory accuracy at speeds up to 1.8 m/s (4 mph) and outside the expected factory accuracy at higher speed (2.7 m/s), showing the effects of motion and mixing on the collected data. Dissolved oxygen was outside of the reported factory accuracy for all tests. It is recommended to loiter periodically when moving at a faster speed to obtain more accurate data, as the differences between the sondes were alleviated during the loiter period. Overall, our ASV design has the potential to be employed to obtain robust spatial data at LW when deployed at optimal operating conditions.
PubDate: Mon, 04 Mar 2024 12:46:45 PST
- Impacts of Harmful Algal Blooms (HABs) on Agriculture: A Short
Communication
Authors: Debabrata Sahoo et al.
Abstract: agriculture, which requires clean water, healthy soil, and adequate nutrients, is crucial to meet the growing demand for food and fiber. Over application of nutrients to meet demand has degraded surface water quality, leading to accelerated eutrophication. Cultural eutrophication is a process by which aquatic ecosystems such as ponds, lakes, and estuaries become so enriched with nutrients—primarily nitrogen and phosphorus—as to become unusable for safe consumption and ecological purposes. Eutrophication has intensified due to climate change. Increased temperatures, intense storms, and drought can drive the formation of eutrophic and hypereutrophic conditions. Hypereutrophication results in the rapid proliferation of algae and phytoplankton, resulting in algal blooms. Harmful algal blooms (HABs), including the proliferation of cyanobacteria, which can produce cyanotoxins such as microcystins and cylindrospermopsin, can also grow in hypereutrophic conditions. These toxins can detrimentally impact humans, wildlife, and agricultural systems (e.g., fish, livestock, and crops). Fish that ingest algal toxins may suffer from liver damage and oxidative stress, with varying effects depending on the type of fish, the amount of exposure, and the duration of exposure to toxins. Additionally, a few studies report livestock death after drinking water contaminated with byproducts of HABs such as microcystin, nodularin, cylindrospermopsin, anatoxin-a, guanitoxin, and saxitoxin. The available research on the effects of microcystin on crops, vegetables, and fruits consistently demonstrates their negative impact. This short communication article summarizes the literature published between 2012 and 2022 documenting the impact of microcystins on agricultural commodities, particularly livestock and various crops. Although awareness has increased, few publications have discussed microcystin-related livestock deaths in recent years. However, numerous global studies have highlighted the harmful effects of microcystins on crops, fruits, and vegetables. The researchers suggest that in cases where the levels of microcystin exceed the standards established by the World Health Organization, careful monitoring is needed. Human exposure to microcystin may occur through the consumption of livestock, crops, and vegetables contaminated by microcystins through drinking or irrigation. More research is needed to understand the fate and transport mechanisms of microcystins in various agricultural settings, including controlled, simulated, and field experiments.
PubDate: Mon, 04 Mar 2024 12:46:39 PST
- Restoring Predevelopment Hydrology with Smart Stormwater Controls in
Aiken, South Carolina
Authors: Jason Hetrick et al.
Abstract: For decades, large quantities of stormwater runoff from the City of Aiken flowed at destructive velocities (exceeding 5 ft/s) into the Sand River, deeply eroding the channel in the downstream Hitchcock Woods. From 1990 to 2015, the City of Aiken commissioned several consultants to produce over a dozen studies to investigate viable solutions for the destructive erosion. Upon the recommendation from a collaborative Stormwater Task Force, the City of Aiken approved a stormwater implementation plan in 2018 which recommended 20 capital improvement projects sized to capture 58 ac-ft of stormwater in order to restore the river’s predevelopment hydrology, with a goal of reducing stormwater velocities in the Sand River to reflect design considerations in the National Engineering Handbook (between 2.0 ft/s for fine sand channels and 4.0 ft/s for coarse sand channels). In November 2023, the City of Aiken completed construction on two underground detention vaults with a total storage volume of 25 ac-ft. These vaults were designed to capture stormwater runoff before it enters Hitchcock Woods and infiltrate as much stormwater runoff as possible; any additional stormwater will be released at a reduced flow rate compared to existing conditions. The 10-year, 24-hour storm event was selected to size the vaults because it was an achievable metric given numerous constraints such as available land, impacts to existing infrastructure and environmental resources, and available funding. The 10-year event also corresponded to typical stormwater requirements for new development. The vaults utilized the largest height, 15 feet, available for precast underground storage vaults in the marketplace. In addition to providing stormwater management below ground, a new public park was constructed on top of the buried vaults to be used as a gateway between the Hitchcock Woods and the City of Aiken.
PubDate: Mon, 04 Mar 2024 12:46:33 PST
- Identifying Barriers Preventing Stormwater Pond Buffer Implementation in
Coastal South Carolina
Authors: Sean Cannon et al.
Abstract: Buffer zones are ecotones between upland areas and adjacent water bodies. They often consist of plant communities that stabilize shorelines, act as barriers reducing transport of fertilizer and lawn debris into water bodies, uptake nutrients and heavy metals, and provide habitat for wildlife. Few regulations exist that require vegetated buffers around stormwater ponds, and their widespread implementation has not occurred around ponds in coastal South Carolina. This lack of regulation on buffer requirements has potentially reduced the effectiveness of stormwater ponds and highlights the need to identify barriers preventing residents from implementing vegetated buffers. To investigate the barriers preventing the installation or support for stormwater buffer zones in coastal communities, an electronic survey was sent by e-mail through the South Carolina Department of Natural Resources and Ashley Cooper Stormwater Education Consortium listservs. Of the 646 respondents, 382 met the study criteria and identified owning a property with a pond or living in a neighborhood with one. Respondents were asked questions to determine their knowledge and perceptions of vegetated buffers, as well as their level of communication with landscape professionals. Results from this research indicate that residents are aware of the benefits vegetated buffer zones provide and prefer ponds with buffer zones over ponds with no buffer zones. This study reveals the following potential barriers preventing stormwater pond vegetated buffer zones: 1) limited knowledge of the costs associated with installation of vegetated buffer zones, 2) inadequate communication between residents and landscape professionals who maintain ponds, 3) respondents perceived lack of control over pond-related decisions, and 4) social norms within neighborhoods such as grass sod standards and an aversion to non-manicured vegetation. These findings can be used by stormwater professionals to help increase adoption of stormwater pond best management practices (BMPs) and improve water quality protection in South Carolina.
PubDate: Mon, 04 Mar 2024 12:46:26 PST
- Utilizing Watershed-Based Planning as a Tool to Protect Source Water: A
Case Study from the Lower Caw Caw Swamp
Authors: Kathryn Ellis et al.
Abstract: A watershed-based plan (WBP) is an example of a management tool that addresses nonpoint sources of pollution that affect surface water quality. We apply a simple spreadsheet tool to the Lower Caw Caw Swamp watershed in Orangeburg, South Carolina, to quantify the impact of modest management practices on water quality, and to examine how climate and land-use change could affect water quality in future decades. Three separate climate and land use scenarios are used to measure annual pollutant loads in the basin. Our analysis shows that E. coli loads in current conditions are largely attributed to anthropogenic sources of bacteria and have the potential to be reduced by about 15% with the implementation of structural stormwater best management practices (such as stormwater ponds and bioretention) and non-structural strategies (programmatic changes such as rooftop disconnection in residential areas and improving on-site sewage disposal systems). Modeled E. coli loads in future scenarios were almost twice the current loads as a result of a warmer climate and greater volumes of stormwater runoff generated by additional impervious surfaces and increased annual precipitation. These findings are consistent with others investigating water quality using future climate and land-use scenarios. We demonstrate that a simple watershed model can provide the basis for a watershed-based plan (WBP) to address nonpoint sources of pollution that affect surface water quality. This specific WBP analysis will be used to make recommendations to protect the City of Orangeburg’s source of drinking water along the North Fork of the Edisto River.
PubDate: Mon, 04 Mar 2024 12:46:19 PST
- South Carolina Beach Water Quality: Stakeholder Workshop Identifies
Challenges, Needs, and Recommendations
Authors: Angelos K. Hannides et al.
Abstract: Coastal water quality is often identified by diverse stakeholders as a major management challenge but can be difficult to define. South Carolina Beach Advocates (SCBA), a nonprofit organization formed in 2015 to educate the public, governmental authorities, and elected officials as to the environmental, economic, and societal impact of South Carolina's beaches and inlets, recognized this challenge and organized a virtual workshop in June 2022 to explore our beachfront communities' water quality management challenges, and discuss various perspectives on beach water quality. Thirty-eight participants from government agencies, local government, industry, academia, and civic society discussed this important topic and identified challenges and concerns, general requirements, needed new capabilities, and recommendations for next steps. Following the workshop, a Beach Water Quality Subcommittee was formed under the auspices of the SCBA to continue this important conversation.
PubDate: Mon, 04 Mar 2024 11:06:24 PST
- The South Carolina Water Monitoring Portal - A Hub for South Carolina
Water Quality Monitoring Data
Authors: Duncan R. Williamson et al.
Abstract: The South Carolina (SC) Water Monitoring Portal is an ArcGIS-based, geospatial application that incorporates water quality data from a variety of sources and projects them onto an interactive map. This application will provide those interested in accessing and retrieving South Carolina water quality data with a free and easyto- use tool that allows for spatial visualization, interaction with, and direct download of data. At the time of this publication, the application accesses roughly four million water quality data records collected by seventeen different organizations. To allow users to seamlessly find and access the data they need, filters are available to query the data to match the user's needs. Once users find the data applicable to them, they can download and export it into various formats. The application also allows groups and organizations to indirectly upload their own water quality data to have it incorporated into the application. With these capabilities in a spatial format, this application has the potential to provide many benefits. For example, in academia it could be utilized in both classroom and research settings, and regulatory agencies could use this application to communicate water quality from a spatial viewpoint, potentially fostering a better understanding of water quality to stakeholders. The management and protection of our state’s waters are difficult to achieve when the data pertaining to water quality isn’t easily accessible or available in a user-friendly format. The SC Water Monitoring Portal has the potential to aid in the protection and management of our state’s waters as it makes water quality data more accessible and the retrieval of data more user-friendly. The SC Water Monitoring Portal is hosted on the South Carolina (SC) Sea Grant Consortium and the College of Charleston’s Lowcountry Hazards Center websites, making it available to anyone interested in water quality data in the State of South Carolina (available online: www.scseagrant.org/SCWMP).
PubDate: Mon, 04 Mar 2024 10:41:27 PST
- Foreword
Authors: Brooke Saari et al.
Abstract: The JSCWR editorial committee is excited to introduce the Water Chats 2024 special issue (Volume 9, Issue 2), a spinoff inspired by the popular Water Chats webinar series launched in 2022 by the South Carolina Sea Grant Consortium, Clemson Extension, and Clemson’s South Carolina Water Resources Center. Water Chats aims to deliver timely water quality information to inspire conversations about protecting and restoring the quality of our state’s invaluable water resources. Providing opportunities for students, early career professionals, outreach professionals, and academic researchers to showcase their latest water quality research, we hope this special issue makes you think, and motivates all of us, as a community, to keep the discussion moving forward.
PubDate: Thu, 29 Feb 2024 12:31:31 PST
- Volume 9, Issue 2 - 2024 Special Issue
Abstract: none
PubDate: Thu, 29 Feb 2024 11:36:33 PST
- An Introduction to Consumptive Use of Water in South Carolina
Authors: Heather Bergerud Nix et al.
Abstract: Effective water resource management requires understanding the supply of and the demand for water. In South Carolina, as in other places, water demand is often determined using total withdrawal volumes. However, the volume of water that is withdrawn can be significantly different from the volume that is actually consumed, which becomes unavailable for downstream uses. Water used for energy generation is commonly excluded from evaluations of total withdrawal volume because it is often assumed to be no or low consumptive use, meaning much of the withdrawn water is returned to the source and remains available for downstream uses. Additionally, energy production withdrawal volumes may be significantly higher than other sectors’ usage and make it difficult to further compare water use of other sectors. Consumptive use volumes are not readily available for South Carolina and can be challenging to determine. However, estimates of consumptive use could allow more meaningful comparisons between water use sectors’ impacts. The objective of this short communication is to briefly discuss data sources, outline two relatively simple methods for calculating consumptive use with available data, identify challenges and opportunities for additional research, and provide preliminary estimates of consumptive water use volumes per water use sectors in South Carolina. Expanded discussion of consumptive water use of thermoelectric energy generation is included due to the significant total water withdrawals and unique challenges with calculating consumptive use of this sector. These results inform water resource planning and identify additional research opportunities.
PubDate: Fri, 23 Jun 2023 07:39:44 PDT
- Chlorophyll a Predictions in a Piedmont Lake in Upstate South Carolina
Using Machine-Learning Approaches
Authors: Ibrahim O. Busari et al.
Abstract: Freshwater systems are often breeding grounds for harmful algal blooms (HABs), although they are more dominant in ponds and lakes due to the prevailing conditions in those bodies of water. Therefore, the monitoring, modeling, and management of HABs requires knowledge of the complex interrelationship between factors that influence HABs and their detrimental effect on the ecosystem. High concentrations of chlorophyll a are often used to measure algal blooms in bodies of water. Generally, water samples are collected from the field and the concentration of chlorophyll a is measured in a laboratory and compared to water quality standards in order to indicate the potential presence or absence of an algal bloom. While numerical water quality models can help answer some of the critical environmental conditions that affect HABs and their effective management, numerous model inputs, the uncertainty in model predictions, and the complexity of HABs ecosystems encourage the application of newly rising data-driven models. The current study utilized high-frequency water quality data and investigated machine-learning algorithms (random forest (RF) and artificial neural network (ANN)) to predict chlorophyll a concentrations in Boyd Millpond, a lake in Upstate South Carolina. The model performances were compared using root mean square error (RMSE), coefficient of determination (R2), and correlation coefficient. The water quality parameters used as inputs were pH, specific conductivity, dissolved oxygen, saturated dissolved oxygen, temperature, oxidation-reduction potential (ORP), and turbidity, while chlorophyll a was selected as the target variable. The results from this study showed that RF performed better than ANN. The error metrics observed using all parameters as input were RMSE, R2, and correlation with values 0.00013, 0.86, and 0.93, respectively, when testing the RF model and 0.00025, 0.74, and 0.86, respectively, during the testing stage of the ANN model. The Least Absolute Shrinkage and Selection Operator (LASSO) was used for variable selection and identified pH and specific conductivity as essential parameters. The broader outcome of this research upon further field validation will enable the timely detection of HABs with chlorophyll a as a signal to instigate further tests and early warning for recreational activities and livestock protection and initiate countermeasures to safeguard the lives of aquatic organisms.
PubDate: Fri, 23 Jun 2023 07:39:11 PDT
- Full Issue - Volume 9, Issue 1
Abstract: none
PubDate: Thu, 22 Jun 2023 13:46:22 PDT
- Lessons Learned from Incorporating Climate Considerations in the Three
Rivers Watershed-Based Plan
Authors: Gregory Carbone et al.
Abstract: The South Carolina Department of Health and Environmental Control has recently incentivized planners to incorporate climate change projections into watershed-based plans. Methods for doing so vary by geography, specific basin-level conditions, and available resources. This short communication documents an early example developed by a collaborative team including a council of governments, private contractor, and university researchers. We outline steps taken to construct climate change scenarios, incorporate them into a basin-level model, and develop a holistic approach to climate adaptation and resilience for the Three Rivers Watershed-Based Plan in the Columbia, South Carolina, metropolitan area. We present lessons learned about integrating appropriate climate change scenarios with hydrological tools and incorporating a community development strategy that addresses freshwater pollution and integrates cobenefits and equitable adaptation frameworks into the watershed-based planning process.
PubDate: Tue, 16 May 2023 13:58:06 PDT
- Mapping and Characterization of Center Pivot and Lateral Move Irrigation
Systems in South Carolina Using Quantum Geographic Information System
Authors: Udayakumar Sekaran et al.
Abstract: In recent decades, the adoption of overhead irrigation systems, especially center pivots, to irrigate row crops has been steadily increasing in South Carolina. The adoption of irrigation in the state has been enhanced by the predominance of coarse-textured soils with low water-holding capacities, which increases the likelihood of obtaining a significant and profitable crop yield response to irrigation. As the number of overhead irrigation systems in the state increases, it is vital to understand their number, location, and characteristics for better planning and managing available water resources. The objective of this project was to map and characterize the overhead irrigation systems (center pivots and lateral moves) available in each county in South Carolina. The Quantum Geographic Information System (QGIS) was used to manually locate and measure each overhead irrigation system in the state using a 2022 Google satellite image. Basic measurements included the length, number of spans, and wetted radius. In addition, the rotation angle of center pivots and the field length of lateral move systems were measured. This study found that with a few exceptions, the overwhelming majority of the overhead irrigation systems in the state were located in the central part of the Coastal Plain region, between the Fall Line and the coast, where groundwater resources are more abundant. Also, this study found a total of 2,980 center pivots and 15 lateral move irrigation systems in South Carolina. A total of 64,694 hectares were irrigated by center pivots, while lateral moves irrigated only 80 hecatares. Out of the 46 counties in the state, those with the highest number of center pivots were Orangeburg (633 pivots), Calhoun (361), Lee (296), Clarendon (249), Sumter (248), Lexington (197), Bamberg (130), Darlington (121), Hampton (117), and Barnwell (114). All the lateral move systems were located in the counties of Barnwell (11) and Darlington (4). Water stakeholders and agencies in South Carolina could use this information for long-term water resources planning at various levels. This research is also useful nationally to inform the understanding of irrigation practices in the southeastern United States.
PubDate: Tue, 16 May 2023 13:57:40 PDT
- Relative Sea Level Rise in the Winyah Bay-Waccamaw River Tidal System Over
the Last Thirteen Years
Authors: Thomas M. Williams et al.
Abstract: Prediction of sea level rise (SLR) in response to climate change has been the focus of worldwide research, most focusing on the impact by human development. The research has been limited to estuaries and tidal rivers near harbors dealing with the hydrodynamics of reversing tidal flows. This article focuses on the Waccamaw River National Wildlife Refuge in coastal South Carolina where freshwater unidirectional flow is common. We examined the record of water levels in the Waccamaw and Pee Dee Rivers over the period 2007–2019 and the length of record of the United States Geographical Survey (USGS) gauge at Pawleys Island on the Waccamaw River. The Atlantic Ocean, off the southeastern coast of the US, has experienced accelerated SLR since 2000. National Oceanic and Atmosphere Administration (NOAA) tide gauges from Fort Pulaski on Cockspur Island in Georgia to Beaufort, North Carolina, show significant increase in long-term SLR since then with an average since 2007 of approximately 10 mm y-1. Since the study period was less than the 18.6-year cycle of lunar precession, tidal ranges were expanding for much of the study period resulting in the rate of rise of Mean Higher High Water (MHHW; the average of the highest tide levels during each day) being greater than the rate of increase of Mean Lower Low Water (MLLW; the average of the lowest tide levels during each day) in all ocean stations. We examined water levels at NOAA and USGS gauges from Oyster Creek, in North Inlet to Conway on the Waccamaw River and Near Bucksport on the Pee Dee River. We found mean water levels increased more rapidly with distance from the ocean with an apparent SLR> 40 mm y-1 at Conway on the Waccamaw and Bucksport on the Pee Dee. In contrast to the ocean NOAA gauges, the estuary/river gauges showed more rapid increase of daily minimum water level (an approximation of MLLW) than daily maximum water level (an approximation of MHHW) with an extreme of apparent rise of minimum water levels of 58 mm y-1 at Bucksport on the Pee Dee. Nearly 50% of the increase in apparent SLR was due to an increase in the annual average freshwater flow of the Pee Dee and Waccamaw Rivers. Over the past 13 years the Waccamaw National Wildlife Refuge has experienced an apparent SLR that was more than double that observed at the edge of the ocean. The rise has been greater in the height of daily low water than in the height of daily high water. The increase was driven by both tidal hydrodynamics and an increase in the rate of flow in the Pee Dee and Waccamaw Rivers. These findings have important implications for land managers, policymakers, and homeowners in the region as people in the middle to upper estuaries need to plan for rates of relative SLR rise much greater than the frequently discussed rates in the ocean.
PubDate: Tue, 16 May 2023 13:57:13 PDT
- Evaluating the Ability of Constructed Intertidal Eastern Oyster
(Crassostrea virginica) Reefs to Address Shoreline Erosion in South
Carolina
Authors: Peter R. Kingsley-Smith et al.
Abstract: The application of nature-based solutions to address shoreline erosion and the loss of salt marsh in coastal South Carolina has centered around the creation of intertidal oyster (Crassostrea virginica) reefs that act as natural breakwaters. The installation of such living shoreline materials often results in a rapid accumulation of fine sediments, followed by wild oyster recruitment to suitable materials, and then more gradually the growth of salt marshes (primarily Spartina alterniflora). Leveraging more than two decades of oyster reef restoration and living shorelines research at the South Carolina Department of Natural Resources, this study quantitatively assessed performance rates for both percent oyster cover and marsh protection in relation to reef age. Determining such rates will serve to inform the expectations of prospective adopters of living shorelines as to the timeframes of some of the biological processes, as measures of performance success, that will occur following material installation. Performance success was investigated in terms of recruitment of oysters to installed materials and the creation of new marsh habitat or protection of existing marsh from erosion. Reef age was an important determinant of reef “success”, with significant relationships between reef age and both performance success metrics. Percent oyster cover reached 40% by two years post-installation and 50% by four years post-installation, indicative of high rates of oyster recruitment. The relative marsh protection rate of living shorelines compared to unprotected reference plots was 0.4 m yr-1 Reef performance differed based on bank substrate firmness, bank width, shoreline morphology, and location relative to the Intracoastal Waterway (ICW). Firmer bank substrate was associated with greater percent oyster cover. Broader bank width was associated with greater marsh protection. Higher percent oyster cover measurements were observed on straight, natural shorelines and reefs located along the ICW. Reefs located on the ICW were also associated with greater marsh protection than reefs at non-ICW sites. Further, this study demonstrates that bagged oyster shell reefs are capable of providing shoreline protection services for more than a decade and can endure multiple intense storm events. The results of this study were also used to facilitate the implementation of new living shoreline regulations in coastal South Carolina in the hope of broadening adoption of this approach to addressing shoreline erosion and salt marsh habitat loss.
PubDate: Tue, 16 May 2023 13:56:45 PDT
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