Impacts of Tropical Cyclone Isabel on Shallow Water Quality of the York River Estuary

Water quality impacts from Tropical Cyclone Isabel on the York River estuary were assessed based on long-term, near-continuous, shallowwater monitoring stations along the York River proper (poly- and mesohaline regimes) and its two tidal tributaries—the Mattaponi and Pamunkey rivers (oligohaline and tidal freshwater regimes). Regional rainfall from 18 to 19 September 2003 ranged from 5.8 to 11.7 cm. Peak mean daily stream flow occurred on 21 September 2003 and represented a 20- and 30-fold increase over prestorm conditions on the Mattaponi and Pamunkey rivers, respectively. Isabel produced a storm surge of 1.7 m near the mouth of the estuary and 2.0 m in the upper tidal freshwater regions. The tidal surge resulted in a short-term (12- to 36-hour) pulse of high salinity water (approximately 10 ppt greater than pre-storm conditions) within the oligohaline portion of the estuary. In comparison, salinity levels within the upper tidal fresh water and down-river poly-and mesohaline regions remained relatively unchanged. Following the storm surge, salinity levels within lower portions of the estuary declined 1.5 to 4.5 ppt for an extended period in response to freshwater runoff. Elevated turbidity—in some cases extreme—was in direct response to the storm surge and waves associated with Tropical Cyclone Isabel. With the exception of a single station, maximum storm-associated turbidity levels varied between 192 and \u3e1000 NTUs (nephelometric turbidity units). Turbidity levels returned to prestorm conditions within a 24- to 30-hour period at most stations. Perhaps the most significant environmental impact associated with the passage of Isabel was the persistent low dissolved oxygen (DO) levels (3–4 mg⋅L-1) that occurred at the tidal freshwater stations. Low DO at these stations coincided with increased freshwater inflow to the Mattaponi and Pamunkey rivers, suggesting augmented loadings of readily degradable organic material from the watershed. Mean daily DO levels took approximately two weeks to return to prestorm levels at these sites. Dissolved oxygen levels at the poly- and mesohaline stations within the York River proper remained at or above 5 mg⋅L-1 prior to, during, and after the storm’s passage.https://scholarworks.wm.edu/vimsbooks/1005/thumbnail.jp

A Site profile of the Chesapeake Bay National Estuarine Research Reserve in Virginia

The purpose of this Site Profile is to review the existing state of knowledge for important geological, physical, chemical and biological components of the York River ecosystem within which the four individual reserve sites of Chesapeake Bay National Estuarine Research Reserve in Virginia (CBNERRVA) are located. It is developed from a combination of literature and field research studies that provide an overall picture of the Reserve in terms of its ecosystem, management, and research needs. It is not designed to be a complete review of all the ecosystem components, but rather it is designed to provide, through a series of reviews, an overview of the York system to students, researchers, resource managers and the general public, and to provide a system context for the individual reserve sites located within the York River estuary. It starts first with an Introduction to the Reserve including its mission and objectives. Next the geological, physical and water quality setting of the individual reserve sites and the overall York River ecosystem are described. Scientific overviews of three important primary producer components and habitats within the region (phytoplankton, wetlands and submerged aquatic vegetation) are presented next. Secondary and higher trophic components (zooplankton, benthos, and fishes) are then reviewed, and finally the principal reptiles, amphibians, birds and mammals that are associated with the local estuarine waters are described. This Site Profile concludes with a description of the Reserve’s ongoing research and monitoring programs, the Reserve goals and strategies, and an overview of research and monitoring needs for the future

Sea level driven marsh expansion in a coupled model of marsh erosion and migration

Coastal wetlands are among the most valuable ecosystems on Earth, where ecosystem services such as flood protection depend nonlinearly on wetland size and are threatened by sea level rise and coastal development. Here we propose a simple model of marsh migration into adjacent uplands and couple it with existing models of seaward edge erosion and vertical soil accretion to explore how ecosystem connectivity influences marsh size and response to sea level rise. We find that marsh loss is nearly inevitable where topographic and anthropogenic barriers limit migration. Where unconstrained by barriers, however, rates of marsh migration are much more sensitive to accelerated sea level rise than rates of edge erosion. This behavior suggests a counterintuitive, natural tendency for marsh expansion with sea level rise and emphasizes the disparity between coastal response to climate change with and without human intervention

A Multi-scale Approach for Simulating Tidal Marsh Evolution

This study presents a new approach to modeling marsh evolution. The Tidal Marsh Model (TMM) has been developed as a module within the SCHISM (Semi-implicit Cross-scale Hydroscience Integrated System Model) framework. Some unique features of the TMM are dynamic rates, cross-scale simulations, and incorporation of anthropogenic stressors, which allow it to overcome many limitations that current marsh models possess. To evaluate model performance, the TMM was applied in Carter Creek and Taskinas Creek within the York River system (Virginia, USA). We assessed model outputs against field observations focusing on two main aspects: marsh boundary evolution and distribution of marsh sediments. Marsh change is captured with an accuracy of 81% in Carter Creek and an accuracy of 78% in Taskinas Creek. Different statistical descriptors were used to evaluate the model’s ability to reproduce the distribution of observed marsh sediment fractions. Results in both study areas show a satisfactory agreement between sediment model outputs and field observations. This innovative modeling approach will help close some critical knowledge gaps in the current understanding of the system dynamics and allow better implementation of management actions to preserve these ecosystems and their services. https://rdcu.be/b5j0C Read only

Accuracy and Precision of Tidal Wetland Soil Carbon Mapping in the Conterminous United States

Tidal wetlands produce long-term soil organic carbon (C) stocks. Thus for carbon accounting purposes, we need accurate and precise information on the magnitude and spatial distribution of those stocks. We assembled and analyzed an unprecedented soil core dataset, and tested three strategies for mapping carbon stocks: applying the average value from the synthesis to mapped tidal wetlands, applying models fit using empirical data and applied using soil, vegetation and salinity maps, and relying on independently generated soil carbon maps. Soil carbon stocks were far lower on average and varied less spatially and with depth than stocks calculated from available soils maps. Further, variation in carbon density was not well-predicted based on climate, salinity, vegetation, or soil classes. Instead, the assembled dataset showed that carbon density across the conterminous united states (CONUS) was normally distributed, with a predictable range of observations. We identified the simplest strategy, applying mean carbon density (27.0 kg C m−3), as the best performing strategy, and conservatively estimated that the top meter of CONUS tidal wetland soil contains 0.72 petagrams C. This strategy could provide standardization in CONUS tidal carbon accounting until such a time as modeling and mapping advancements can quantitatively improve accuracy and precision

High-frequency CO2-system variability over the winter-to-spring transition in a large coastal plain estuary

Understanding the vulnerability of estuarine ecosystems to anthropogenic impacts requires a quantitative assessment of the dynamic drivers of change to the carbonate (CO2) system. Here we present new high‐frequency pH data from a moored sensor. These data are combined with discrete observations to create continuous time series of total dissolved inorganic carbon (TCO2), CO2 partial pressure (pCO2), and carbonate saturation state. We present two deployments over the winter‐to‐spring transition in the lower York River (where it meets the Chesapeake Bay mainstem) in 2016/2017 and 2017/2018. TCO2 budgets with daily resolution are constructed, and contributions from circulation, air‐sea CO2 exchange, and biology are quantified. We find that TCO2 is most strongly influenced by circulation and biological processes; pCO2 and pH also respond strongly to changes in temperature. The system transitions from autotrophic to heterotrophic conditions multiple times during both deployments; the conventional view of a spring bloom and subsequent summer production followed by autumn and winter respiration may not apply to this region. Despite the dominance of respiration in winter and early spring, surface waters were undersaturated with respect to atmospheric CO2 for the majority of both deployments with mean fluxes ranging from −9 to −5 mmol C·m−2·day−1. Deployments a year apart indicate that the seasonal transition in the CO2 system differs significantly from one year to the next and highlights the necessity of sustained monitoring in dynamic nearshore environments