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This paper explores how Chesapeake-based watermen and seafood processors may experience occupational harm from microbial hazards like Vibrio spp. Fishing industry research primarily focuses on musculoskeletal injury, even though microbial hazards present risks to Total Worker Health® that clinicians should consider. This paper provides qualitative insights to address that gap. Commercial fishing is a dangerous profession with known hazards for musculoskeletal injuries, yet minimal examination of microbiological or attendant psychosocial hazards from water- and food-borne pathogens like Vibrio vulnificus and V. parahaemolyticus exists. Improving knowledge of Vibrio -related hazards addresses Total Worker Health® concerns for commercial fisheries workers. Methods: Following a grounded theory approach, we conducted semistructured interviews with watermen and related workers who fish and harvest shellfish in the Chesapeake Bay, USA, to investigate risk perceptions and understanding, and compliance with regulations intended to reduce worker and consumer illnesses and injuries from pathogen exposures. Results: Worker and consumer illnesses and injuries, and threat of fishery closures—with regulatory and organizational factors—influence this workforce. Conclusions: Our findings support interventions that promote monitoring, surveillance, and awareness of Vibrio- related risk among watermen, regulatory officials, medical professionals, and the public. [ABSTRACT FROM AUTHOR]

Encouraging agricultural landowners to adopt conservation practices is crucial to enhancing ecosystem services in privately-owned farm landscapes. To improve engagement with landowners and increase adoption rates, much research has been dedicated to investigating how different psychological, social, economic, and political factors correlate with adoption. However, these studies largely measure adoption as a discrete, binary event. Doing so obscures sequences of landowner decisions and engagement techniques that conservation practitioners use to encourage landowners' progression through the adoption process. We report on two studies that contribute to the emerging literature on the agricultural conservation practice adoption process and the varying effectiveness of engagement techniques throughout. First, interviews with conservation practitioners in the Chesapeake Bay watershed, USA, yielded a preliminary model of the different stages in the adoption process and what techniques practitioners find effective at each stage. Second, an online experiment examined the effectiveness of a visualization intervention across two sequential outcomes in the adoption process, seeking further information and contacting a practitioner. Our results suggested that practitioners use a wide variety of engagement techniques, most of which are unique to a single stage in the adoption process, and that the effectiveness of the visualization technique varies substantially between different stages. Together these studies outline a suite of techniques that other practitioners may find effective at different stages of the adoption process, and suggest that research can better inform practice by accounting for variation in the effectiveness of different techniques across stages of adoption. [ABSTRACT FROM AUTHOR]

Variations in estuarine carbonate chemistry can have critical impacts on marine calcifying organisms, yet the drivers of this variability are difficult to quantify from observations alone, due to the strong spatiotemporal variability of these systems. Terrestrial runoff and wetland processes vary year to year based on local precipitation, and estuarine processes are often strongly modulated by tides. In this study, a 3D-coupled hydrodynamic-biogeochemical model is used to quantify the controls on the carbonate system of a coastal plain estuary, specifically the York River estuary. Experiments were conducted both with and without tidal wetlands. Results show that on average, wetlands account for 20–30% of total alkalinity (TA) and dissolved inorganic carbon (DIC) fluxes into the estuary, and double-estuarine CO2 outgassing. Strong quasi-monthly variability is driven by the tides and causes fluctuations between net heterotrophy and net autotrophy. On longer time scales, model results show that in wetter years, lower light availability decreases primary production relative to biological respiration (i.e., greater net heterotrophy) resulting in substantial increases in CO2 outgassing. Additionally, in wetter years, advective exports of DIC and TA to the Chesapeake Bay increase by a factor of three to four, resulting in lower concentrations of DIC and TA within the estuary. Quantifying the impacts of these complex drivers is not only essential for a better understanding of coastal carbon and alkalinity cycling, but also leads to an improved assessment of the health and functioning of coastal ecosystems both in the present day and under future climate change. [ABSTRACT FROM AUTHOR]

Estuarine environments are recognized as critical nursery habitats that are necessary to sustain overall fish production. Striped bass Morone saxatilis support recreational and commercial fisheries along the Atlantic coast of the United States, and annual surveys to assess juvenile (age-0) abundance in Chesapeake Bay, the major producing area for the population, have long been used in management. Factors that contribute to high juvenile abundance are not fully understood. We used catch data from fishery-independent surveys coupled with hindcasts from a pair of numerical models to quantify the extent of summer habitats used by age-0 striped bass throughout Chesapeake Bay for 1996–2017. Specific conditions that defined habitat suitability for age-0 striped bass varied throughout the summer and among years, reflecting changes in water quality and habitat use. Shallow, nearshore areas throughout the Bay consistently supported suitable conditions for age-0 striped bass, but the estimated extent of suitable habitat varied annually at both regional and local, tributary-specific, scales. Although the areal extent of suitable habitat Bay-wide in early summer declined since 1996, fish production was not limited. Nonetheless, a pattern of increasing relative abundance of age-0 striped bass with greater extent of suitable habitats in Chesapeake Bay was observed, suggesting that the availability of suitable habitats at the scale of individual tributaries and Bay-wide may play an important role in production of this estuarine-dependent species. [ABSTRACT FROM AUTHOR]

Oxygen depletion in coastal waters is increasing globally due primarily to eutrophication and warming. Hypoxia responses to nutrient loading and climate change have been extensively studied in large systems like the Chesapeake Bay and the Baltic Sea, while fewer studies have investigated smaller, shallower hypoxic zones. Thus, an improved understanding of the interactions of eutrophication and warming on hypoxia expansion (or reduction) in the wide variety of different estuarine environments is needed. We examined interannual controls on oxygen depletion in the Patuxent River estuary, a eutrophic sub-estuary of Chesapeake Bay where seasonal hypoxia develops annually. We conducted a spatial and temporal analysis of dissolved oxygen (DO) trends, timing, and several metrics of depletion over a long-term record (1985–2021). We found an internally generated hypoxic zone that initiates in the middle estuary, spreading upstream and downstream as the summer progresses, and that hypoxic volume days (HVD) have been increasing (0.11 per year, p = 0.03) over the record despite reduced watershed nitrogen loads and stable phosphorus loads. River flow and temperature have been increasing and are major drivers of increased HVD, with river flow explaining 40% of the interannual variation in HVD (temperature has increased 0.03 and 0.06 °C per year in summer and fall, respectively). Apparent oxygen utilization (AOU) is increasing in bottom waters in the fall, consistent with increasing trends of both water temperature and stratification strength. HVD was negatively related (r2 = 0.34, slope = −0.59*HVD) to the biomass of benthic invertebrates in the middle region of the estuary, suggesting that benthic forage for higher trophic levels will be limited by sustained hypoxia. These results indicate that current and future climate variability plays an important role in regulating oxygen depletion in the Patuxent River estuary, which reinforces the need to factor climate change into strategies for the restoration and management of estuaries. [ABSTRACT FROM AUTHOR]

Floodplain restoration is an approved stormwater management method, but rarely chosen by developers due to the perceived high cost and lengthy approvals required from regulatory agencies. Yet, when chosen, restoring a floodplain yields significant environmental benefits for the community due to improved flood resiliency and wetland habitat and superior reduction of negative externalities. In 2012, a corporation in Lancaster County, Pennsylvania, explored the option to restore a historic floodplain on its 40‐hectare property to fulfill the stormwater management requirements for a planned development project. There was a social dynamic at play in this instance that allowed the developer, municipality, and citizens to achieve a win across three dimensions often in conflict: maximizing private economic returns, achieving environmental compliance, and benefiting the community ecologically. Using a social–ecological system (SES) framework, this paper analyzes the course of the development project through the government approvals process and the actual restoration of the floodplain. Two influential actors are identified who do not often appear in the literature on SESs: sports advocacy groups and religious groups. We posit that the developer's industry was uniquely receptive to conservation appeals and that the proximity of an urban metropolis made collective action a relevant strategy for the region. Critical factors in the decision process were the cost–benefit analysis contracted by the developer, local (county) government leadership, and a history of local citizen activism. We conclude that a misalignment of anthropogenic and ecological boundaries can prevent such positive outcomes and that collective action is a viable strategy to overcome that challenge. [ABSTRACT FROM AUTHOR]

The article "Commentary: Demographic response of osprey within the lower Chesapeake Bay to fluctuations in menhaden stock" published in Frontiers in Marine Science discusses the decline in osprey reproductive rates and fish provisioning, particularly menhaden, in the Mobjack Bay subestuary of the lower Chesapeake Bay. The study suggests a link between osprey reproductive rates and coastwide indices of juvenile menhaden abundance, prompting calls for the restoration of menhaden stocks to 1980s levels. However, the article raises concerns about the statistical analysis used and the lack of a clear relationship between osprey demographics and menhaden abundance, emphasizing the need for further research and appropriate methodologies to assess their ecological linkage. [Extracted from the article]

The Chesapeake Bay watershed encompasses six states and the District of Columbia. Consequently, the people within it display great diversity in terms of values, allegiances, and experiences. That diversity may help to explain an apparent inability to coordinate actions aimed at redressing the dismal water quality throughout the watershed. In this paper, we bridge theory to an applied scenario to examine the importance of developing a collective identity within the watershed to bring about changes in individual behavior and policies. We present the current conditions of the Chesapeake Bay watershed, propose a stage model for the development of a collective watershed identity, outline theoretically grounded determinants of each stage, and discuss the challenges in developing a collective identity. We further suggest several guiding questions for future research. [ABSTRACT FROM AUTHOR]

Particles, including aggregates, fecal pellets, and inorganic matter, modulate the transport of carbon and nutrients through estuarine environments. Particles’ size, mass, and density influence their trajectories and ability to transport carbon and other elements. In the Chesapeake Bay, particles fuel the emergence of a seasonal oxygen-deficient zone, with their origin and trajectories being shaped by their characteristics. However, the variability of particle characteristics has not previously been characterized across the length of the Chesapeake Bay, particularly in and around the oxygen-deficient zone. In this study, we measured of the size, abundance, and mass of suspended particles along the Chesapeake Bay during a major deoxygenation event. We demonstrate that particles in the anoxic region have a sandwich structure, with higher particle abundance and mass in the oxic overlying waters and in the deep nepheloid layer, than in the pelagic anoxic zone. These particles in the anoxic zone appear to have similar size properties as particles elsewhere. Stratified water above the oxygen minimum zone may keep particles from the productive top layer from mixing into this region, and our results suggest that this lack of mixing isolates the anoxic zone and limits the amount of reductant entering this environment. Particles in the less saline northern end of the Bay were less massive relative to size than particles farther south, suggesting differences in origin and physical makeup of these particles. [ABSTRACT FROM AUTHOR]

Salt marshes act as natural barriers that reduce wave energy during storm events and help protect coastal communities located in low-lying areas. This ecosystem can be an important asset for climate adaptation due to its particular capability of vertically accrete to adjust to long-term changes in water levels. Therefore, understanding marsh protection benefits thresholds in the face of sea-level rise (SLR) is important for planning future climate adaptation. In this context, the main goal of this manuscript is to examine how the storm protection benefits provided by salt marshes might evolve under SLR projections with different probability levels and emission pathways. In this study, a modeling framework that employs marsh migration predictions from the Sea Level Affecting Marshes Model (SLAMM) as parameterization into a hydrodynamic and wave model (ADCIRC + SWAN) was utilized to explicitly represent wave attenuation by vegetation under storm surge conditions. SLAMM predictions indicate that the SLR scenario, a combination of probability level and emission pathways, plays a substantial role in determining future marsh migration or marsh area loss. For example, results based on the 50% probability, stabilized emissions scenario show an increase of 45% in the marsh area on Maryland's Lower Eastern Shore by 2100, whereas Dorchester County alone could experience a 75% reduction in total salt marsh areas by 2100 under the 1% probability, growing emissions scenario. ADCIRC + SWAN results using SLAMM land cover and elevation outputs indicate that distinct temporal thresholds emerge where marsh extent sharply decreases and wave heights increase, especially after 2050, and exacerbates further after 2080. These findings can be utilized for guiding environmental policies and to aid informed decisions and actions in response to SLR-driven environmental changes. [ABSTRACT FROM AUTHOR]

In the middle of the Chesapeake Bay sits small and shrinking Tangier Island, Virginia. Home to 1,200 residents a century ago, the island now has fewer than 400 residents, a population decreasing as the land subsides into the bay. Scientists predict the island will be uninhabitable by the 2040s, while residents themselves profess to be climate change deniers and science skeptics. I examine the politics and social order of engineering interventions and their afterlives on Tangier, endlessly studied and sometimes implemented by the federal government, the Commonwealth of Virginia, and the U.S. Army Corps of Engineers. A northern channel bisecting the island, first dredged in 1966, and a seawall on the western side of the island, constructed in 1990, were both obsolete before they were created, showing the ways in which infrastructure, especially dredging of waterways, and its afterlives are channeled as processes controlled by state experts, justified by and justifying endless cascades of interventions, naturalizing the landscape, and ultimately placing Tangiermen as willing victims and imminent refugees in an uncertain crisis. [ABSTRACT FROM AUTHOR]

Study region: Chesapeake Bay Watershed Study focus: Climate plays a critical role in regulating N loading from terrestrial ecosystems to coastal waters and further affecting the health and functioning of coastal ecosystems. However, the sensitivities of riverine exports of different N species to climate change have rarely been investigated. This study examines the response of riverine exports of ammonia (NH4+), nitrate (NO3–), dissolved organic nitrogen (DON), and particulate organic nitrogen (PON) to future changes in precipitation and temperature. A suite of climate forcings was used to drive a process-based terrestrial–aquatic model, DLEM (Dynamic Land Ecosystem Model), to project changes in N loading to the Chesapeake Bay in the mid-21st century, relative to the 1990s. New hydrological insights for the region: Our simulations show that, despite a relatively small average change in freshwater discharge driven by future climate change, annual average NH4+, NO3–, DON, PON, and total nitrogen exports are likely to change by –12 %, +13 %, +2 %, –9 %, and +9 %, respectively. Driven by rising temperature, NH4+ decreases as a result of enhanced volatilization and nitrification, but NO3– export may increase due to high mineralization and nitrification. The change in DON export is mainly regulated by discharge, and the PON change is highly uncertain due to its high sensitivity to extreme precipitation events. This study highlights the importance of considering different responses of N species to climate change when designing nutrient reduction strategies to mitigate estuarine hypoxia.

The early Paleozoic Era (∼540–420 Ma) was an interval of profound biogeochemical changes including increasing oxygen (O 2) and the onset of bioturbation (sediment mixing by animals). It is hypothesized that incipient bioturbation caused a monotonic decrease in sedimentary burial of pyrite (FeS 2), which would have slowed atmospheric O 2 accumulation. However, pyrite accumulation can exhibit complex responses to dynamic, low-O 2 environmental conditions. To assess pyrite burial in a potential modern analogue to early Paleozoic environments, we collected sediment cores from the Chesapeake Bay, an estuary with multiple gradients in sulfate concentration, hypoxia intensity, organic carbon flux and lability, and bioturbation. Results indicate that pyrite accumulation is maximized not under strong sulfate depletion in highly reducing sediments, but rather in sediments that occupy the mid-range of sulfate–chloride ratios. This probably occurs through efficient replenishment of pore water sulfate and/or through the generation of sulfur redox intermediates, which promote pyrite formation via the polysulfide reaction pathway. In light of these results and in contrast to earlier models, we hypothesize that mild early Paleozoic bioturbation temporarily increased pyrite burial efficiency by stimulating higher sulfate reduction rates and increasing sedimentary sulfide retention. Compiled sulfur and carbon data from a geochemical database indicate that median sulfur-carbon ratios of fine-grained marine siliciclastic rocks increased from the Ediacaran through the Ordovician, then decreased and became much less variable from the Silurian onward. Thus, the Cambrian and Ordovician Periods may constitute a distinct interval of the Proterozoic-Phanerozoic transition in which bioturbation temporarily accelerated O 2 buildup. This transition probably ended in the Silurian, when p O 2 rose to sufficient levels to homogenize sedimentary carbon–sulfur cycling. [ABSTRACT FROM AUTHOR]

Complete eradication of invasive plants is often infeasible but in some cases it is possible to reduce the invader to low levels with reduced ongoing management costs, referred to as functional eradication. Non-native Phragmites australis has challenged land managers across North America but functional eradication may yet be possible in some scenarios. Here we present data from Chesapeake Bay brackish tidal wetlands where two approaches to Phragmites management (long-term, continuous management and short-term, non-continuous management) were used. We demonstrate that the application of herbicides will lead to the establishment of native species, but long-term, continuous management is required to facilitate functional eradication of Phragmites by keeping it at low levels of occurrence and restoring native plant communities. Ultimately, historical data from sites that were sampled as part of this study indicate that if management is successful and results in functional eradication of Phragmites, then the recovering vegetation will include native species that were present before the sites were invaded by Phragmites. [ABSTRACT FROM AUTHOR]

In 2020, the Chesapeake Bay Program moved to offset impacts from climate change for the 30‐year period from 1995 through 2025 by having its seven watershed jurisdictions (Delaware, Maryland, New York, Pennsylvania, Virginia, West Virginia, and the District of Columbia) apply additional nutrient pollutant reduction practices. The climate change assessment was performed with integrated models of the Chesapeake watershed, airshed, and estuary. Scenarios run for the years 2025, 2035, 2045, and 2055 estimated effects from the different future climatic conditions. This article presents the results of that assessment and is intended to provide a guide to assist other modeling practitioners in assessing climate change impacts in coastal watersheds. Major influences of climate change that were quantified include increases in precipitation volume, potential evapotranspiration, watershed nutrient loads, tidal water temperature, and sea level. Minor influences quantified in the climate change analysis include changes in nutrient speciation and increases in wet deposition of nitrogen, CO2, rainfall intensity, tidal wetland loss, up‐estuary salt intrusion, and phytoplankton biomass. To offset climate change impacts from 1995 to 2025 on water quality, the scenarios indicate an additional 2.3 million and 0.3 million kg of nitrogen and phosphorus per annum, respectively, will need to be reduced beyond what is called for in the Chesapeake Total Maximum Daily Load. [ABSTRACT FROM AUTHOR]

Many agricultural watersheds rely on the voluntary use of management practices (MPs) to reduce nonpoint source nutrient and sediment loads; however, the water‐quality effects of MPs are uncertain. We interpreted water‐quality responses from as early as 1985 through 2020 in three agricultural Chesapeake Bay watersheds that were prioritized for MP implementation, namely, the Smith Creek (Virginia), Upper Chester River (Maryland), and Conewago Creek (Pennsylvania) watersheds. We synthesized patterns in MPs, climate, land use, and nutrient inputs to better understand factors affecting nutrient and sediment loads. Relations between MPs and expected water‐quality improvements were not consistently identifiable. The number of MPs increased in all watersheds since the early 2010s, but most monitored nutrient and sediment loads did not decrease. Nutrient and sediment loads increased or remained stable in Smith Creek and the Upper Chester River. Sediment loads and some nutrient loads decreased in Conewago Creek. In Smith Creek, a 36‐year time‐series model suggests that changes in manure affected flow‐normalized total nitrogen loads. We hypothesize that increases in nutrient applications may overshadow some expected MP effects. MPs might have stemmed further water‐quality degradation, but improvements in nutrient loads may rely on reducing manure and fertilizer applications. Our results highlight the importance of assessing MP performance with long‐term monitoring‐based studies. [ABSTRACT FROM AUTHOR]

Broad‐scale mapping of stream channel and floodplain geomorphic metrics is critical to improve the understanding of geomorphic change, biogeochemical processes, riverine habitat quality, and opportunities for management intervention. The Floodplain and Channel Evaluation Tool (FACET) was developed to provide an open‐source tool for automated processing of digital elevation models (DEMs) to generate regional‐scale estimates of bank height, channel width, floodplain width, and a suite of other fluvial geomorphic dimensions that can be summarized at the stream reach‐ or catchment‐scale. FACET was tested on 3‐m DEMs covering the Delaware River watershed and 85% of the Chesapeake Bay watershed in the United States (U.S.) and on 1‐m DEMs for a subset of the study area. Accuracy was assessed from data collected at 67 field sites in the study area. FACET successfully measured geomorphometry for over 270,000 stream reaches (88% of streams attempted) in the study area. Factors that reduced the ability of FACET to accurately estimate geomorphic metrics included errors in DEM hydro‐conditioning, gradually sloping banks, incised stream channels, and the use of fixed input parameters to define buffer lengths. Even with these limitations, FACET was able to map regional patterns in stream and floodplain geomorphometry providing a robust dataset that can enhance modeling and management efforts throughout the mid‐Atlantic region, U.S. [ABSTRACT FROM AUTHOR]

Recent studies found that on long time scales there are often unexplained opposite trends in sea level variability between the upper and lower Chesapeake Bay (CB). Therefore, daily sea level and temperature records were analyzed in two locations, Norfolk in the southern CB and Baltimore in the northern CB; surface currents from Coastal Ocean Dynamics Application Radar (CODAR) near the mouth of CB were also analyzed to examine connections between the CB and the Atlantic Ocean. The observations in the bay were compared with daily Atlantic Meridional Overturning Circulation (AMOC) observations during 2005–2021. Empirical Mode Decomposition (EMD) analysis was used to show that variations of sea level and temperature in the upper and lower CB are positively correlated with each other for short time scales of months to few years, but anticorrelated on low frequency modes representing decadal variability and long-term nonlinear trends. The long-term CB modes seem to be linked with AMOC variability through variations in the Gulf Stream and the wind-driven Ekman transports over the North Atlantic Ocean. AMOC variability correlates more strongly with variability in the southern CB near the mouth of the bay, where surface currents indicate potential links with AMOC variability. For example, when AMOC and the Gulf Stream were especially weak during 2009–2010, sea level in the southern bay was abnormally high, temperatures were colder than normal and outflow through the mouth of CB was especially high. Sea level in the upper bay responded to this change only 1–2 years later, which partly explains phase differences within the bay. A persistent trend of 0.22 cm/s per year of increased outflow from the CB, may be a sign of a climate-related trend associated with combination of weakening AMOC and increased precipitation and river discharge into the CB. [ABSTRACT FROM AUTHOR]

The onset of hypoxia is a consequence of the competition between oxygen replenishment, production, and consumption. Dissolved oxygen (DO) levels inside an estuary depend on the balance between physical processes that transport oxygen-rich water into the estuary, including upstream freshwater advection, gravitational circulation, and vertical mixing, and biochemical processes that produce and consume oxygen, such as photosynthesis, respiration, and organic decomposition. We propose a general relationship between the physical and biochemical processes with a Lagrangian perspective to interpolate mean DO concentrations at local and system levels to assess the onset of hypoxia in an estuary. Simple parameters using timescales are proposed for cross-system comparison of hypoxia and anoxia conditions. Our study demonstrates that the hypoxia of an estuary system is determined by the timescales of vertical exchange, freshwater and saltwater transport, and DO consumption. When the vertical exchange timescale is shorter than the residence time in a system, vertical exchange dominates DO replenishment, while shorter residence time enhances advection, which quickly inputs DO-rich water to regulate hypoxia. The interplay between DO consumption and dynamic DO replenishment is the primary determinant of hypoxia in an estuary. [ABSTRACT FROM AUTHOR]

Tidal freshwaters in upper estuarine reaches provide important ecosystem services but are threatened by relative sea-level rise and pollution from increased development. Tidal freshwaters are highly productive and support estuarine and riparian food webs alike. Aquatic insects are common prey subsidies crossing into riparian habitats; however, the magnitude, timing, and composition of insect emergence in tidal systems has received little attention. Our objective was to better understand the magnitude and variability of aquatic insect emergence in tidal freshwaters. To do so, we quantified insect emergence from tidal creeks and estuarine shorelines of the James River Estuary, Virginia, USA, and characterized spatial and temporal patterns in the amount of emergent biomass. We continuously monitored insect emergence from 7 April to 8 November 2019 with floating emergence traps to estimate daily emergence, then used generalized additive mixed models to analyze spatial and temporal variation in daily emergence rates. We estimated aquatic insect biomass to emerge at a mean rate (±1 SE) of 15.6 ± 2.0 g dry mass m−2 y−1, which is among the highest of previously published estimates from nontidal systems (mean ±1 SE = 12.9 ± 6.2 g dry mass m−2 y−1). Spatial variability in emergence was highly taxon specific. Diptera and Trichoptera had more biomass emerging from the subtidal than intertidal zone, Odonata biomass emerged more from tidal creeks than along the estuarine shoreline, and the amount of Trichoptera biomass increased—whereas Ephemeroptera decreased—with distance from the estuarine shoreline. The magnitude and composition of emergent taxa varied throughout the sampling period, with sequential peaks in biomass that altered the prey available to riparian consumers. Our results suggest that tidal freshwaters export substantial quantities of aquatic insects, which are valuable prey items for riparian consumers in these systems. [ABSTRACT FROM AUTHOR]

A high‐resolution wave model is crucial for accurate modeling of sediment and organic material transports, but its computational costs hinder direct coupling to an ecosystem model. We developed a machine learning model using long short‐term memory to simulate large‐scale, high‐resolution waves. Trained with numerical wave model (NWM) outputs and wind data from nine locations, our model successfully replicates NWM results for daily mean significant wave height and period in Chesapeake Bay with identical spatial resolution. Compared to the NWM, the data‐driven model has root‐mean‐square errors below 6 cm for daily mean significant wave height and 1 s for the wave period in the bay. It demonstrates excellent model skills and can accurately forecast daily mean significant wave height and period at NOAA wave stations comparable to NWMs. Using minimal wind data and having a short runtime, our data‐driven model shows promise as an alternative for wave forecasting and coupling with sediment and ecological models. Plain Language Summary: Accurately modeling sediment and organic transport necessitates the use of a high‐resolution numerical wave model (NWM). However, the computational expenses of running an NWM within an ecosystem model pose significant challenges. We conducted a study using a machine learning approach based on long short‐term memory to replicate the results of an NWM. The data‐driven wave model (DWM) was trained with the NWM outputs and wind data from nine locations. The trained DWM can replicate the NWM results of daily mean significant wave height and period in Chesapeake Bay with identical spatial resolution and the same predictive skill with a root‐mean‐square error of less than 6 cm and 1 s, respectively for the model domain. The model successfully forecasted daily mean significant wave height and period at NOAA wave stations, showing great forward prediction capability. Notably, the DWM only relied on a minimal amount of wind data from selected locations and had a short runtime. These findings indicate that machine learning is promising as an alternative approach to NWM for wave forecasting. Moreover, it can serve as an alternative wave model and be coupled to ecological models for simulating sediment transport, light attenuation, and resuspension of organic materials. Key Points: A machine learning‐based wave model reproduces the numerical wave model (NWM) results at the same spatial resolution with good accuracyThe data‐driven model, trained on daily significant wave height and period using NWM outputs, has comparable wave prediction skillThe fast‐running data wave model, driven by wind data from nine locations, can forecast waves and couple with sediment and ecological models [ABSTRACT FROM AUTHOR]

The Chesapeake Bay is one of the most widely studied bodies of water in the United States and around the world. Routine monitoring of water quality indicators (e.g., salinity) relies on fixed sampling stations throughout the Bay. Utilizing this rich monitoring data, various methods produce surface predictions of water quality indicators to further characterize the health of the Bay as well as to support wildlife and human health research studies. Bayesian approaches for geostatistical modelling are becoming increasingly popular and can be preferred over frequentist approaches because full and exact inference can be computed, along with more accurate characterization of uncertainty. Traditional geostatistical prediction methods assume a Euclidean distance between two points when characterizing spatial dependence as a function of distance. However, Euclidean approaches may not be appropriate in estuarine environments when water-land boundaries are crossed during the modelling process. In this study, we compare stationary and barrier INLA geostatistical models with a classic kriging geostatistical model to predict salinity in the Chesapeake Bay during 4 months in 2019. Cross-validation is conducted for each approach to evaluate model performance based on prediction accuracy and precision. The results provide evidence that the two Bayesian-based models outperformed ordinary kriging, especially when examining prediction accuracy (most notably in the tributaries). We also suggest that the non-Euclidean model accounts for the appropriate water-based distances between sampling locations and is likely better at characterizing the uncertainty. However, more complex bodies of water may better showcase the capabilities and efficacy of the physical barrier INLA model. [ABSTRACT FROM AUTHOR]

Subsurface impacts associated with Marine Heatwaves (MHWs) in estuaries are not well understood, largely due to data scarcity. Using over three decades (1986–2021) of observations from several monitoring programs, this study investigates subsurface temperature and dissolved oxygen (DO) anomalies associated with surface MHWs in the Chesapeake Bay (CB). Seasonal variability in temperature anomalies followed a simple 1‐D response to surface heating with downward heat transport and diffusion controlled by seasonally variable stratification and mixing. Two distinct temperature regimes were found: a thermally stratified spring‐summer regime, when positive temperature anomalies were confined to the surface mixed layer (SML); and a homogeneous fall‐winter regime. Additionally, surface (subsurface) temperatures were elevated for months (days to weeks) before and after MHWs, indicating individual events were shorter than the timescales of elevated temperatures. A simple 1‐D SML heat budget identified air‐estuary heat flux changes as the leading driver of MHW onsets and declines, with latent heat flux being the dominant term. DO anomaly patterns were more complex, with considerable along‐channel gradients. Notable DO decreases (1–4 mg L−1) primarily occurred in the winter/spring below the SML, and the hypoxic zone expanded from spring through fall. Only a small fraction of these DO anomalies could be attributed to MHW temperature‐induced solubility changes, demonstrating that other physical and/or biogeochemical processes dominate changes in DO during these events. In CB, concurrent low DO and persistent high temperatures could compound the impacts of MHWs on this valuable ecosystem, with MHW event impacts likely to be exacerbated by climate change. Plain Language Summary: Marine heatwaves (MHWs), prolonged events with elevated water temperatures comparable to atmospheric heatwaves, have not been well studied in the subsurface (depths >1 m) due to data scarcity. Using three decades (1986–2021) of observations from several monitoring programs, we were able to investigate subsurface warming and changes in dissolved oxygen (DO) during surface MHW in the Chesapeake Bay main stem. We found that two seasonal regimes of subsurface warming occurred: a fall/winter "Homogeneous Regime," when extreme warming occurred throughout the water column; and a spring/summer "Stratified Regime," when extreme warming occurred only in the surface (top 15 m) and not the bottom. These regimes were caused by surface heating from the atmosphere and regulated by the seasonal changes in freshwater present in the Bay, which can inhibit heat penetration. During MHW, DO concentrations decreased, especially at the bottom of the deep channel during the winter/spring. These DO decreases were also associated with a hypoxic‐zone expansion; the region of harmfully low DO. Additionally, we found that surface and subsurface warming occurred days to months before and after marine heatwave events. These findings indicate that persistent warming and concurrent low DO could exacerbate the impacts of MHW on Bay ecosystem. Key Points: Subsurface temperature anomalies during Marine Heatwaves (MHWs) are controlled by seasonal stratification resulting in two seasonal regimesMHWs are associated with a hypoxic zone expansion and large negative bottom dissolved oxygen anomalies during the winter/springThe leading driver of estuarine MHWs is air‐sea heat flux, with latent heat flux changes being the dominant constituent [ABSTRACT FROM AUTHOR]

Forage fish support the largest fisheries in the world and play a vital role in marine food webs by transferring energy from plankton to consumers within higher trophic levels. Growing commercial demand for these species and concern for the impact of over harvest on predator populations has driven a paradigm shift in management objectives from maximizing economic return to the establishment of ecosystem-based limits on harvest rates. How well current harvest policy supports noncommercial species like piscivorous birds remains poorly understood. We investigated the relationship between osprey breeding performance within the lower Chesapeake Bay and a menhaden stock index during a period (1974-2021) when the menhaden index fluctuated over 35-fold. Reproductive rate (young/pair/year), brood provisioning (fish/10-h) and the proportion of menhaden in the diet all declined during the study period. Indicators of food stress including brood reduction and nest failure increased during the study period. The population transitioned from reproductive surplus (demographic source) to reproductive deficit (demographic sink). A significant relationship between reproductive rate and the menhaden index suggests that osprey population viability requires that the menhaden stock be restored to 1980s levels. Current ecological reference points based on the food requirements of predatory fish are unlikely to protect the osprey population. We suggest the establishment of menhaden or reproductive thresholds designed to allow osprey to meet demographic targets (1.15 young/pair/year). [ABSTRACT FROM AUTHOR]

On 19 October 1781, at the surrender of Yorktown, the Comte de Rochambeau replied to the British general Charles O'Hara, who wanted to give his sword to Rochambeau rather than George Washington, that the French army was only auxiliary on this continent. This reply corresponded exactly to the mission defined at Versailles the previous year. But it is surprising: how can a great military power take orders from a smaller one? The answer lies in the evolution of the practical arrangements for Franco-American military cooperation between 1778 and 1781. France sent large naval and land forces across the Atlantic. But for success to be possible, the French and Americans had to be able to act together, and French sailors and soldiers had to be able to master combined operations. [ABSTRACT FROM AUTHOR]

Coastal managers are facing imminent decisions regarding the fate of coastal wetlands, given ongoing threats to their persistence. There is a need for objective methods to identify which wetland parcels are candidates for restoration, monitoring, protection, or acquisition due to limited resources and restoration techniques. Here, we describe a new spatially comprehensive data set for Chesapeake Bay salt marshes, which includes the unvegetated-vegetated marsh ratio, elevation metrics, and sediment-based lifespan. Spatial aggregation across regions of the Bay shows a trend of increasing deterioration with proximity to the seaward boundary, coherent with conceptual models of coastal landscape response to sea-level rise. On a smaller scale, the signature of deterioration is highly variable within subsections of the Bay: fringing, peninsular, and tidal river marsh complexes each exhibit different spatial patterns with regards to proximity to the seaward edge. We then demonstrate objective methods to use these data for mapping potential management options on to the landscape, and then provide methods to estimate lifespan and potential changes in lifespan in response to restoration actions as well as future sea level rise. We account for actions that aim to increase sediment inventories, revegetate barren areas, restore hydrology, and facilitate salt marsh migration into upland areas. The distillation of robust geospatial data into simple decision-making metrics, as well as the use of those metrics to map decisions on the landscape, represents an important step towards science-based coastal management. [ABSTRACT FROM AUTHOR]

In estuarine and coastal systems, anthropogenic activities and directional changes in global air temperatures have led to increased water temperatures, as well as increased frequency and severity of episodic hypoxia. These alterations have had population-level effects on aquatic organisms, including changes in species-specific distributions. Because physiology is the transfer function connecting environmental conditions to individual behaviors and eventually to population-level effects, we used individual-based models (IBMs) that incorporate changes in metabolic scope as motivation for movement. Our objective was to investigate the effects of temperature and hypoxia on the distribution of Atlantic croaker and spot in Chesapeake Bay. We compared the predicted monthly fish distributions from the IBMs with apparent fish distributions recorded by the VIMS Juvenile Fish Trawl Survey during 1988–2014. IBMs failed to reproduce accurately the apparent spatial distributions of Atlantic croaker and spot. More specifically, compared with the trawl survey, IBMs predicted larger proportions of these two species would be captured in the lower regions of Chesapeake Bay and smaller proportions in the York and Rappahannock rivers. We postulate that, because similar thermal and oxygen conditions were occupied by fish in the IBMs and in the wild, temperature may not be the most important factor motivating the movement of Atlantic croaker and spot in Chesapeake Bay, and other spatial factors (e.g., prey availability) act in concert with temperature and hypoxia to determine the spatial distributions of Atlantic croaker and spot in Chesapeake Bay. Alternatively, surveys used to estimate species occurrences could be biased if gear vulnerability is affected by temperature or oxygen conditions (or both). Additional research is needed to clarify which condition is true or if a combination of these factors (and others) led to discrepancies between predicted and apparent fish distributions based on trawl survey data. [ABSTRACT FROM AUTHOR]

ABSTRACTPhytoplankton are important drivers of aquatic ecosystem function and environmental health. Their community compositions and distributions are directly impacted by environmental processes and human activities, including in the largest estuary in North America, the Chesapeake Bay. It is crucial to uncover how planktonic eukaryotes play fundamental roles as primary producers and trophic links and sustain estuarine ecosystems. In this study, we investigated the detailed community structure and spatiotemporal variations of planktonic eukaryotes in the Chesapeake Bay across space and time for three consecutive years. A clear seasonal and spatial shift of total, abundant, and rare planktonic eukaryotes was evident, and the pattern recurred interannually. Multiple harmful algal species have been identified in the Bay with varied distribution patterns, such as Karlodinium, Heterosigma akashiwo, Protoperidinium sp., etc. Compared to abundant taxa, rare subcommunities were more sensitive to environmental disturbance in terms of richness, diversity, and distribution. The combined effects of temporal variation (13.3%), nutrient availability (10.0%), and spatial gradients (8.8%) structured the distribution of eukaryotic microbial communities in the Bay. Similar spatiotemporal patterns between planktonic prokaryotes and eukaryotes suggest common mechanisms of adjustment, replacement, and species interaction for planktonic microbiomes under strong estuarine gradients. To our best knowledge, this work represents the first systematic study on planktonic eukaryotes in the Bay. A comprehensive view of the distribution of planktonic microbiomes and their interactions with environmental processes is critical in understanding the underlying microbial mechanisms involved in maintaining the stability, function, and environmental health of estuarine ecosystems.IMPORTANCEDeep sequencing analysis of planktonic eukaryotes in the Chesapeake Bay reveals high community diversity with many newly recognized phytoplankton taxa. The Chesapeake Bay planktonic eukaryotes show distinct seasonal and spatial variability, with recurring annual patterns of total, abundant, and rare groups. Rare taxa mainly contribute to eukaryotic diversity compared to abundant groups, and they are more sensitive to spatiotemporal variations and environmental filtering. Temporal variations, nutrient availability, and spatial gradients significantly affect the distribution of eukaryotic microbial communities. Similar spatiotemporal patterns in prokaryotes and eukaryotes suggest common mechanisms of adjustment, substitution, and species interactions in planktonic microbiomes under strong estuarine gradients. Interannually recurring patterns demonstrate that diverse eukaryotic taxa have well adapted to the estuarine environment with a long residence time. Further investigations of how human activities impact estuarine planktonic eukaryotes are critical in understanding their essential ecosystem roles and in maintaining environmental safety and public health.

Abstract A high‐resolution wave model is crucial for accurate modeling of sediment and organic material transports, but its computational costs hinder direct coupling to an ecosystem model. We developed a machine learning model using long short‐term memory to simulate large‐scale, high‐resolution waves. Trained with numerical wave model (NWM) outputs and wind data from nine locations, our model successfully replicates NWM results for daily mean significant wave height and period in Chesapeake Bay with identical spatial resolution. Compared to the NWM, the data‐driven model has root‐mean‐square errors below 6 cm for daily mean significant wave height and 1 s for the wave period in the bay. It demonstrates excellent model skills and can accurately forecast daily mean significant wave height and period at NOAA wave stations comparable to NWMs. Using minimal wind data and having a short runtime, our data‐driven model shows promise as an alternative for wave forecasting and coupling with sediment and ecological models.

Forage fish support the largest fisheries in the world and play a vital role in marine food webs by transferring energy from plankton to consumers within higher trophic levels. Growing commercial demand for these species and concern for the impact of over harvest on predator populations has driven a paradigm shift in management objectives from maximizing economic return to the establishment of ecosystem-based limits on harvest rates. How well current harvest policy supports noncommercial species like piscivorous birds remains poorly understood. We investigated the relationship between osprey breeding performance within the lower Chesapeake Bay and a menhaden stock index during a period (1974-2021) when the menhaden index fluctuated over 35-fold. Reproductive rate (young/pair/year), brood provisioning (fish/10-h) and the proportion of menhaden in the diet all declined during the study period. Indicators of food stress including brood reduction and nest failure increased during the study period. The population transitioned from reproductive surplus (demographic source) to reproductive deficit (demographic sink). A significant relationship between reproductive rate and the menhaden index suggests that osprey population viability requires that the menhaden stock be restored to 1980s levels. Current ecological reference points based on the food requirements of predatory fish are unlikely to protect the osprey population. We suggest the establishment of menhaden or reproductive thresholds designed to allow osprey to meet demographic targets (1.15 young/pair/year).

The 2010 Chesapeake Bay Total Maximum Daily Load was established for the water quality and ecological restoration of the Chesapeake Bay. In 2017, the latest science, data, and modeling tools were used to develop revised Watershed Implementation Plans (WIPs). In this article, we examine the vulnerability of the Chesapeake Bay watershed to the combined pressures of climate change and growth in population, agricultural intensity, and economic activity for the 60‐year period 1995–2055. The results will be used to revise WIPs, as needed, to account for expected increases in loads. Assessing changes relative to 1995 for the years 2025, 2035, 2045, and 2055, mean annual precipitation increases of 3.11%, 4.21%, 5.34%, and 6.91%, respectively, air temperature increases of 1.12, 1.45, 1.84, and 2.12°C, respectively, and potential evapotranspiration increases of 3.36%, 4.43%, 5.54%, and 6.35%, respectively, are projected. Population in the watershed is expected to grow by 3.5 million between 2025 and 2055. Watershed model results show incremental increases in streamflow (2.3%–6.2%), nitrogen (2.6%–10.8%), phosphorus (4.5%–26.7%), and sediment (3.8%–18.8%) loads to the tidal Bay due to climate change. Growth in population, agricultural intensity, development, and economic activity resulted in relatively smaller increases in loads compared to climate change. [ABSTRACT FROM AUTHOR]

The Chesapeake Bay Land Change Model (CBLCM) is an open‐source pseudo‐cellular automata land change model tailored for loose coupling with watershed models. The CBLCM simulates infill development, residential and commercial development, natural land and agricultural land conversion, and growth served by sewer or septic wastewater treatment. The CBLCM is unique among land change models by simulating multiple types of development and explicitly accounting for infill development and the spatial patterns of development densities. The CBLCM was used to simulate five future land use scenarios, holding population constant, for all counties within and adjacent to the Chesapeake Bay watershed from 2013 to 2055. Results are presented here for the state of Maryland over the period 2013–2025 to illustrate model functionality and validation. The growth management (GM) scenario achieved the least development and potential impacts to natural and agricultural lands while accommodating the same amount of population growth as the other four scenarios. Scenarios focusing exclusively on natural or agricultural land protection shifted development to unprotected areas resulting in unforeseen water quality consequences. Simultaneously achieving more compact development while protecting the most valued natural and agricultural lands requires a combination of GM and land conservation policies and actions. [ABSTRACT FROM AUTHOR]

Sea level rise (SLR) is the most significant climate change-related threat to coastal wetlands, driving major transformations in coastal regions through marsh migration. Landscape transformations due to marsh migration are manifested in terms of horizontal and vertical changes in land cover and elevation, respectively. These processes will have an impact on saltmarsh wave attenuation that is yet to be explored. This study stands as a comprehensive analysis of spatially distributed wave attenuation by vegetation in the context of a changing climate. Our results show that: i) changes in saltmarsh cover have little to no effect on the attenuation of floods, while ii) changes in elevation can significantly reduce flood extents and water depths; iii) overland wave heights are directly influenced by marsh migration, although iv) being indirectly attenuated by the water depth limiting effects of water depth attenuation driven by changes in elevation; v) the influence of saltmarsh accretion on wave attenuation is largely evident near the marsh edge, where the increasing elevations can drive major wave energy losses via wave breaking. Lastly, vi) considering the synergy between SLR, marsh migration, and changes in elevation results in significantly more wave attenuation than considering the eustatic effects of SLR and/or horizontal marsh migration alone, and therefore should be adopted in future studies. [ABSTRACT FROM AUTHOR]

Living shorelines (LSs) increasingly are implemented as a defense against coastal erosion and rising seas; however, their ecological function for wading birds has not been evaluated. Here, we compared heron and shorebird use of LSs (created fringe salt marshes with a wave break fronting the planted marshes) to natural‐fringe marshes (NFMs) in the Chesapeake Bay. We assessed the use between May and August in 2018 and 2019 at 13 tidal marsh pairs, each consisting of one LS and NFM site, with sites within pairs having similar surrounding land use and wave exposure. In each year, we assessed diurnal use with video cameras recording at least four 30‐min segments/day for a total of 677 h of video, and nocturnal/diurnal use with acoustic recording equipment recording 10‐min sound files every 2 h/day for a total of 160 h of recording. We quantified diurnal use by measuring the total time a species spent at a site, and nocturnal/diurnal use by estimating the probability of detection (i.e., presence/absence). We detected four heron and five shorebird species when data were aggregated across pairs and sampling methods. Using Bayesian mixed models, time of use did not differ between LS and NFM sites for great blue herons (Ardea herodias) and yellow‐crowned night‐herons (Nyctanassa violacea). In contrast, time of use was higher for green herons (Butorides virescens) and spotted sandpipers (Actitis macularis) at LS sites but tended to be higher for great egrets (Ardea alba) at NFM sites. The probability of detection did not differ between LS and NFM sites for great blue herons and great egrets (combined as "Ardea spp." due to difficulty in differentiating calls under noisy conditions), yellow‐crowned night‐herons, and spotted sandpipers. Green herons and killdeer (Charadrius vociferous), however, tended to be detected more frequently at LS sites. Collectively, our research indicates that LSs are functionally equivalent to NFMs for herons and shorebirds. We hypothesize that the low‐profile rock sills of LS provide platforms for resting and preening and offer prey even when vegetated marshes are unavailable to short‐legged species during flooding tides. In addition to their established reduction of coastal erosion, LSs provide habitat for herons and shorebird species. [ABSTRACT FROM AUTHOR]

The imagery collected by medium-resolution earth-observing satellites is a powerful and cost-effective tool for the quantitative assessment of shoreline dynamics for water bodies of different spatial scales. In this study, we utilize imagery collected in 1984–2021 on the Middle Peninsula, Virginia, bordering the Chesapeake Bay, USA, by medium-resolution (10–30 m) satellites Landsat-5/7/8 and Sentinel-2A/B. The data was managed in the Earth Analytics Interoperability Lab (EAIL) Data Cube built and configured by the Commonwealth Scientific and Industrial Research Organization (CSIRO, Australia and Chile). The assessments of shoreline change demonstrate adequate agreement with assessments based on aerial photography collected during 1937–2009 by the Virginia Institute of Marine Science, with reasonable disagreement attributed to the differences in the analyzed periods and in the accuracy of land/water edge detection. Most of the studied coastline was subject to land loss (erosion), in some locations exceeding 3 m year−1, usually along low-lying sandy beaches. The shoreline segments with man-made structures such as marinas, bulkheads, revetments, and offshore breakwaters demonstrated a significantly lower range of changes as compared to natural reaches. Regular analysis of medium-resolution satellite imagery appears to be an effective method for routine assessment of shoreline changes along the land/water edge. [ABSTRACT FROM AUTHOR]

Vanadium (V) is a redox-sensitive trace metal. Interconversion between different vanadium species (e.g., VIII, VIV, VV) occurs rapidly in association with changes in redox conditions in natural environments. Different vanadium species exhibit variable geochemical behavior that impacts if and how they are sequestered into sediments, which makes vanadium a useful proxy for ancient ocean redox conditions. However, we still lack constraints on how different dissolved vanadium sink pathways impact distributions of vanadium in water column, pore waters, and sediments, especially in natural sulfidic settings. In the present study, we combined field and experimental data to constrain the major scavenging processes that influence the partitioning of vanadium between aqueous and solid phases to provide an improved picture of vanadium geochemical cycling under anoxic-sulfidic conditions. We find that in the sulfidic bottom waters and sediment pore waters of the Chesapeake Bay, vanadium concentrations are correlated with manganese (Mn) concentrations in both aqueous and solid phases. Our experimental results support our interpretation that elevated concentrations of vanadium in anoxic-sulfidic waters result from the release of vanadium due to desorption from and/or dissolution of Mn oxides in anoxic/sulfidic waters. While sorption of vanadium results in strongly adsorbed complexes on both Mn oxides and pyrite surfaces, vanadium preferentially sorbs to Mn oxides rather than to pyrite. Thus, the impact of Mn oxides on vanadium geochemistry is greater than that imposed by scavenging via sorption on pyrite, although both processes should be considered. Mn oxides also have a greater impact on vanadium geochemistry than reductive formation of solid V(OH) 3 by H 2 S. Sorption of vanadium is sensitive to pH conditions (especially in anoxic waters), moderately sensitive to ionic strength, and weakly sensitive to phosphate concentrations. In addition, our results show that as waters become more sulfidic, dissolved V/Mn molar ratios increase, whereas solid phase V/Mn molar ratios decrease, indicating that the V/Mn molar ratio can be used to trace redox changes. Finally, we investigate the V/Mn record of black shales that span the Proterozoic and Phanerozoic to show a framework of utilizing this proxy with applicability to identify changes in redox conditions associated with both oxygenation and anoxic events in ancient oceans. [ABSTRACT FROM AUTHOR]

Objective: Three hypotheses about poor recruitment and collapse of Striped Bass Morone saxatilis in Chesapeake Bay during the 1970s and 1980s (excessive larval mortality related to water quality, recruitment overfishing, or a combination) emerged from intense investigations during the mid‐1980s into the early 1990s. Stock collapse during the 1970s and 1980s and recovery in 1995 were largely attributed to fishing mortality and this premise largely drives management. Stock and larval habitat assessments were not available before the early 1980s and habitat assessments were discontinued after recovery. I used egg and juvenile index time‐series that extended back to 1955 to test these three hypotheses about changes in productivity. Methods: Long‐term (1955–2019) indices of recruitment (juvenile index [JI]), spawning dispersion in time and space (Ep, proportion of plankton net samples with eggs), and an index of relative larval survival (RLS = JI/Ep) for spawning areas in Maryland's portion of Chesapeake Bay were used to investigate whether larval survival patterns were stable (supported the overfishing hypothesis) or changed (supported the larval mortality hypothesis). Result: Baywide Ep estimates were within similar higher ranges during 1957–1981 and 1989–2019, and were low enough to affect recruitment during 1982–1988. While there was a strong relationship of baywide Ep to spawning stock biomass (SSB) estimated by the stock assessment during recovery (1982–1995), estimates of Ep went from depleted to a high level earlier than SSB estimates. Estimates of postrecovery Ep and SSB were both high, but did not have a relationship. A decline in SSB that began in 2012 was not evident with Ep. A shift to low JIs in the early 1970s was followed by a decline in baywide Ep after 1979. Estimates of RLS were higher in 1960s, declined in the early to mid‐1970s, were mostly low into the early 1990s, and became higher afterward. Recovery of Ep after 1988 was accompanied by recovery of larval survival a few years later. Strong correlations of juvenile indices of Striped Bass, White Perch Morone americana, and Yellow Perch Perca flavescens further supported the larval survival hypothesis; these anadromous fish share larval nurseries in space and time, but have different life histories and fisheries that make simultaneous overfishing unlikely. Conclusion: Deterioration of larval survival initiated the collapse of Chesapeake Bay Striped Bass and improvement contributed to recovery. The hypothesis that collapse and recovery was solely driven by fishing was not supported, but excessive fishing pressure lowered Ep and SSB and contributed to poor recruitment during 1982–1988. Long‐term climate patterns and warming, deterioration and improvement in acidic deposition, concurrent increases in freshwater salinization and alkalinization, and shifts in agriculture and watershed management indicated shifts in larval habitat suitability were plausible. Impact statementI used Striped Bass juvenile and egg indices to examine how spawning stock and larval survival (habitat) influenced year‐class success in Chesapeake Bay during 1955–2019. Larval survival played a major role throughout the time series and low spawning stock contributed during 1982–1988. [ABSTRACT FROM AUTHOR]

Abstract Living shorelines (LSs) increasingly are implemented as a defense against coastal erosion and rising seas; however, their ecological function for wading birds has not been evaluated. Here, we compared heron and shorebird use of LSs (created fringe salt marshes with a wave break fronting the planted marshes) to natural‐fringe marshes (NFMs) in the Chesapeake Bay. We assessed the use between May and August in 2018 and 2019 at 13 tidal marsh pairs, each consisting of one LS and NFM site, with sites within pairs having similar surrounding land use and wave exposure. In each year, we assessed diurnal use with video cameras recording at least four 30‐min segments/day for a total of 677 h of video, and nocturnal/diurnal use with acoustic recording equipment recording 10‐min sound files every 2 h/day for a total of 160 h of recording. We quantified diurnal use by measuring the total time a species spent at a site, and nocturnal/diurnal use by estimating the probability of detection (i.e., presence/absence). We detected four heron and five shorebird species when data were aggregated across pairs and sampling methods. Using Bayesian mixed models, time of use did not differ between LS and NFM sites for great blue herons (Ardea herodias) and yellow‐crowned night‐herons (Nyctanassa violacea). In contrast, time of use was higher for green herons (Butorides virescens) and spotted sandpipers (Actitis macularis) at LS sites but tended to be higher for great egrets (Ardea alba) at NFM sites. The probability of detection did not differ between LS and NFM sites for great blue herons and great egrets (combined as “Ardea spp.” due to difficulty in differentiating calls under noisy conditions), yellow‐crowned night‐herons, and spotted sandpipers. Green herons and killdeer (Charadrius vociferous), however, tended to be detected more frequently at LS sites. Collectively, our research indicates that LSs are functionally equivalent to NFMs for herons and shorebirds. We hypothesize that the low‐profile rock sills of LS provide platforms for resting and preening and offer prey even when vegetated marshes are unavailable to short‐legged species during flooding tides. In addition to their established reduction of coastal erosion, LSs provide habitat for herons and shorebird species.

American Oystercatcher (Haematopus palliatus) began relocating to noncoastal and atypical habitats decades ago potentially due to changing environmental factors. Historic literature does not address a route or progression timeline of species ingress to Chesapeake Bay. This study uses 286 Chesapeake Bay occurrence records to approximate the route, timeline of scout exploration, and nesting pioneer ingress, plus updating the species status and range last published in 1979. The records indicate relocating coastal oystercatchers entered through mouth of the Bay shortly after middle of the 20th century with the first scout being found in 1964 at Hampton from where exploration north reached Baltimore 23 years later. Records note the first nesting pioneers in 1976 on a remote island in Pocomoke Sound followed in 1977 by a pair on an uninhabited island in Tar Bay. Pocomoke Sound, Tangier Sound, and Tar Bay archipelagos form a nearly 70 km (43 mi) long contiguous chain of mostly uninhabited islands where pioneer ingress appeared to focus in the latter half of the 1970s and early 1980s before radiating in southwest directions during the 1980-1990s to areas scouted in the 1960s. Ingress pioneer activity remained in the lower half of Chesapeake Bay for several years before appearing north at Poplar Island in 2004. [ABSTRACT FROM AUTHOR]

For over three decades, Chesapeake Bay (USA) has been the focal point of a coordinated restoration strategy implemented through a partnership of governmental and nongovernmental entities, which has been a classical model for coastal restoration worldwide. This synthesis aims to provide resource managers and estuarine scientists with a clearer perspective of the magnitude of changes in water quality within the Bay watershed, including nitrogen (N), phosphorus (P), and sediment for the River Input Monitoring (RIM) watershed and the unmonitored below‐RIM watershed. The flow‐normalized N load from the RIM watershed has declined in the period of 1985–2017, but P and sediment loads have lacked progress. Reductions of riverine N are largely driven by reductions of point sources and atmospheric deposition. Future reductions will require significant progress in managing agricultural nonpoint sources. The below‐RIM watershed, which comprises a disproportionately high fraction of inputs to the Bay, has shown long‐term declines in major sources, including point sources (N and P), atmospheric deposition (N), manure (N and P) and fertilizer (P), based on a combination of monitoring and modeling assessments. To date, the Bay cleanup efforts have achieved some progress toward reducing nutrients from the watershed, which have resulted in improving water quality in the estuary. However, further reductions are critical to achieve the Chesapeake Bay Total Maximum Daily Load goals, and emerging challenges due to Conowingo Reservoir, legacy nutrients, climate change, and population growth should be considered. Continued monitoring, modeling, and assessment are critically important for informing the restoration of this complex ecosystem. This article is categorized under:Science of Water > Water QualityWater and Life > Stresses and Pressures on EcosystemsWater and Life > Conservation, Management, and Awareness [ABSTRACT FROM AUTHOR]

We used a numerical model to investigate the effects of sea‐level rise (SLR) on the biogeochemical processes in the York River Estuary with extensive tidal marshes. The fully‐coupled hydrodynamic‐water quality‐marsh model accounts for the spatial and temporal variations of physical‐biogeochemical interactions between the tidal marshes and surrounding waters. This study focuses on an SLR scenario where the vertical accretion of tidal marshes keeps pace with the rising sea levels. Results show that SLR amplifies the tidal range and prolongs flooding duration, which results in enhanced porewater exchanges of materials between the tidal marshes and the surrounding waters. The increased availability of shallow‐water habitats and enhanced light utilization in the shallow areas under SLR promote phytoplankton production (PP) in the shallow‐water regions of the York River. Consequently, the organic carbon in the open water is fueled by the contributions from shallow waters and the enhanced export of organic carbon from the marshes. The change in the dissolved oxygen (DO) budget in the York River Estuary is attributed to changes in water column respiration, net metabolism of the benthic layer, reaeration, PP, and increased stratification under SLR. The net DO flux out of the York River increases at the York River mouth. Diel DO variation, especially in the marshes in the upper estuary, promotes phosphorus release from the sediment. The changes in dissolved nitrogen under SLR are relatively minimal. Plain Language Summary: As one of the consequences of climate change, sea‐level rise (SLR) has a wide‐ranging impact on the estuarine environment. SLR has a significant impact on tidal marshes, which are located at the interface between estuarine water and inner land. Despite the possibility of marsh retreat, many tidal marshes will keep up with the SLR through vertical accretion if sufficient sediment sources are available. SLR will result in deeper water and elevated tidal marshes in the estuary. The biogeochemical processes under this condition were predicted using a numerical modeling approach in this study. The tidal range is estimated to increase, encouraging more material exchange between marshes and estuarine water. More organic carbon is produced in this system, resulting in increased oxygen consumption. In this condition, there is a greater likelihood of low‐DO events occurring during the diel cycle, which will further affect nutrient dynamics. Key Points: A coupled tidal marsh and eutrophication model is applied to study the impacts of sea‐level rise (SLR) on estuarine biogeochemical processesThe tidal marshes that keep up with SLR are predicted to have more porewater‐surface water exchange and dissolved material exportsThe York River Estuary is predicted to have lower bottom dissolved oxygen and more hypoxia events under SLR [ABSTRACT FROM AUTHOR]

Climate and land‐use/land‐cover change ("global change") are restructuring biodiversity, globally. Broadly, environmental conditions are expected to become warmer, potentially drier (particularly in arid regions), and more anthropogenically developed in the future, with spatiotemporally complex effects on ecological communities. We used functional traits to inform Chesapeake Bay Watershed fish responses to future climate and land‐use scenarios (2030, 2060, and 2090). We modeled the future habitat suitability of focal species representative of key trait axes (substrate, flow, temperature, reproduction, and trophic) and used functional and phylogenetic metrics to assess variable assemblage responses across physiographic regions and habitat sizes (headwaters through large rivers). Our focal species analysis projected future habitat suitability gains for carnivorous species with preferences for warm water, pool habitats, and fine or vegetated substrates. At the assemblage level, models projected decreasing habitat suitability for cold‐water, rheophilic, and lithophilic individuals but increasing suitability for carnivores in the future across all regions. Projected responses of functional and phylogenetic diversity and redundancy differed among regions. Lowland regions were projected to become less functionally and phylogenetically diverse and more redundant while upland regions (and smaller habitat sizes) were projected to become more diverse and less redundant. Next, we assessed how these model‐projected assemblage changes 2005–2030 related to observed time‐series trends (1999–2016). Halfway through the initial projecting period (2005–2030), we found observed trends broadly followed modeled patterns of increasing proportions of carnivorous and lithophilic individuals in lowland regions but showed opposing patterns for functional and phylogenetic metrics. Leveraging observed and predicted analyses simultaneously helps elucidate the instances and causes of discrepancies between model predictions and ongoing observed changes. Collectively, results highlight the complexity of global change impacts across broad landscapes that likely relate to differences in assemblages' intrinsic sensitivities and external exposure to stressors. [ABSTRACT FROM AUTHOR]

Manure from poultry operations is typically applied to nearby cropland and may affect nutrient loading and the spread of antibiotic resistance (ABR). We analyzed the concentrations of nitrogen and phosphorus and the occurrence of ABR in Escherichia coli (E. coli) and extra-intestinal pathogenic E. coli isolates from streams draining 15 small (

Manure from poultry operations is typically applied to nearby cropland and may affect nutrient loading and the spread of antibiotic resistance (ABR). We analyzed the concentrations of nitrogen and phosphorus and the occurrence of ABR in Escherichia coli (E. coli) and extra-intestinal pathogenic E. coli isolates from streams draining 15 small (

Anthropogenic activity impacts stream ecosystems, resulting in a loss of diversity and ecosystem function; however, little is known about the response of aquatic microbial communities to changes in land use. Here, microbial communities were characterized in 82 headwater streams across a gradient of urban and agricultural land uses using 16S rRNA gene amplicon sequencing and compared to a rich data set of physicochemical variables and traditional benthic invertebrate indicators. Microbial diversity and community structures differed among watersheds with high agricultural, urban, and forested land uses, and community structure differed in streams classified as being in good, fair, poor, and very poor condition using benthic invertebrate indicators. Microbial community similarity decayed with geodesic distance across the study region but not with environmental distance. Stream community respiration rates ranged from 21.7 to 1,570 mg O2 m-2 day-1 and 31.9 to 3,670 mg O2 m-2 day-1 for water column and sediments, respectively, and correlated with nutrients associated with anthropogenic influence and microbial community structure. Nitrous oxide (N2O) concentrations ranged from 0.22 to 4.41 μg N2O liter-1; N2O concentration was negatively correlated with forested land use and was positively correlated with dissolved inorganic nitrogen concentrations. Our findings suggest that stream microbial communities are impacted by watershed land use and can potentially be used to assess ecosystem health.IMPORTANCE Stream ecosystems are frequently impacted by changes in watershed land use, resulting in altered hydrology, increased pollutant and nutrient loads, and habitat degradation. Macroinvertebrates and fish are strongly affected by changes in stream conditions and are commonly used in biotic indices to assess ecosystem health. Similarly, microbes respond to environmental stressors, and changes in community composition alter key ecosystem processes. The response of microbes to habitat degradation and their role in global biogeochemical cycles provide an opportunity to use microbes as a monitoring tool. Here, we identify stream microbes that respond to watershed urbanization and agricultural development and demonstrate that microbial diversity and community structure can be used to assess stream conditions and ecosystem functioning.

Incidence of vibriosis is rising globally, with evidence that changing climatic conditions are influencing environmental factors that enhance growth of pathogenic Vibrio spp. in aquatic ecosystems. To determine the impact of environmental factors on occurrence of pathogenic Vibrio spp., samples were collected in the Chesapeake Bay, Maryland, during 2009 to 2012 and 2019 to 2022. Genetic markers for Vibrio vulnificus (vvhA) and Vibrio parahaemolyticus (tlh, tdh, and trh) were enumerated by direct plating and DNA colony hybridization. Results confirmed seasonality and environmental parameters as predictors. Water temperature showed a linear correlation with vvhA and tlh, and two critical thresholds were observed, an initial increase in detectable numbers (.15°C) and a second increase when maximum counts were recorded (.25°C). Temperature and pathogenic V. parahaemolyticus (tdh and trh) were not strongly correlated; however, the evidence showed that these organisms persist in oyster and sediment at colder temperatures. Salinity (10 to 15 ppt), total chlorophyll a (5 to 25 mg/L), dissolved oxygen (5 to 10 mg/L), and pH (8) were associated with increased abundance of vvhA and tlh. Importantly, a long-term increase in Vibrio spp. numbers was observed in water samples between the two collection periods, specifically at Tangier Sound (lower bay), with the evidence suggesting an extended seasonality for these bacteria in the area. Notably, tlh showed a mean positive increase that was ca. 3-fold overall, with the most significant increase observed during the fall. In conclusion, vibriosis continues to be a risk in the Chesapeake Bay region. A predictive intelligence system to assist decision makers, with respect to climate and human health, is warranted. IMPORTANCE The genus Vibrio includes pathogenic species that are naturally occurring in marine and estuarine environments globally. Routine monitoring for Vibrio species and environmental parameters influencing their incidence is critical to provide a warning system for the public when the risk of infection is high. In this study, occurrence of Vibrio parahaemolyticus and Vibrio vulnificus, both potential human pathogens, in Chesapeake Bay water, oysters, and sediment samples collected over a 13-year period was analyzed. The results provide a confirmation of environmental predictors for these bacteria, notably temperature, salinity, and total chlorophyll a, and their seasonality of occurrence. New findings refine environmental parameter thresholds of culturable Vibrio species and document a long-term increase in Vibrio populations in the Chesapeake Bay. This study provides a valuable foundation for development of predicative risk intelligence models for Vibrio incidence during climate change. [ABSTRACT FROM AUTHOR]

It is widely assumed that phytoplankton abundance and productivity decline during temperate winters because of low irradiance and temperatures. However, winter phytoplankton blooms commonly occur in temperate estuaries, but they are often undocumented because of reduced water quality monitoring in winter. The small body of in situ work that has been done on winter blooms suggests they can be of enormous consequence to ecosystems. However, because monitoring is often reduced or stopped altogether during winter, it is unclear how widespread these blooms are or how long they can last. We analyzed an over 30-year record of monthly phytoplankton monitoring samples along with ad hoc sampling throughout Chesapeake Bay to assess the distributions of two common winter bloom species, Heterocapsa rotundata and Heterocapsa steinii, and the environmental conditions associated with these blooms. The long-term monitoring data revealed that H. rotundata blooms occur within a narrow salinity range (7–12) and potentially have different triggers depending upon the nutrient status of waters affected. The ad hoc sampling confirmed the occurrence of H. steinii blooms in the lower Chesapeake Bay, despite the lack of evidence for them from monthly monitoring data. Together, our findings demonstrate that winter blooms routinely occur in numerous locations throughout Chesapeake Bay and can last up to a month. Our findings suggest that while winter blooms are a staple of the Bay's annual phytoplankton community, there are major data gaps reporting their occurrence highlighting the need for more frequent monitoring to understand factors promoting these blooms and their consequences on ecosystem productivity. [ABSTRACT FROM AUTHOR]

In this study, we examined the succession of soil microbial communities across a chronosequence of newly constructed salt marshes constructed primarily of fine-grained dredge material, using 16S rRNA amplicon sequences. Alpha diversity in the subsurface horizons was initially low and increased to reference levels within 3 years of marsh construction, while alpha diversity in the newly accumulating organic matter-rich surface soils was initially high and remained unchanged. Microbial community succession was fastest in the surface horizon (~ 24 years to reference equivalency) and became progressively slower with depth in the subsurface horizons (~ 30–67 years). Random forest linear regression analysis was used to identify important taxa driving the trajectories toward reference conditions. In the parent material, putative sulfate-reducers (Desulfobacterota), methanogens (Crenarchaeota, especially Methanosaeta), and fermenters (Chloroflexi and Clostridia) increased over time, suggesting an enrichment of these metabolisms over time, similar to natural marshes. Concurrently in the surface soils, the relative abundances of putative methane-, methyl-, and sulfide oxidizers, especially among Gammaproteobacteria, increased over time, suggesting the co-development of sulfide and methane removal metabolisms in marsh soils. Finally, we observed that the surface soil communities at one of the marshes did not follow the trajectory of the others, exhibiting a greater relative abundance of anaerobic taxa. Uniquely in this dataset, this marsh was developing signs of excessive inundation stress in terms of vegetation coverage and soil geochemistry. Therefore, we suggest that soil microbial community structure may be effective bioindicators of salt marsh inundation and are worthy of further targeted investigation. [ABSTRACT FROM AUTHOR]

The effects of nutrient loading on estuaries are well studied, given the multitude of negative water quality and ecosystem effects that have been attributed to excess nitrogen and phosphorus. A current gap in this knowledge involves the sensitivity of seasonal cycles of estuarine biogeochemical processes to direct (warming) and indirect influences (nutrient load timing) of climate change. We used a coupled hydrologic–biogeochemical model to investigate changes in the phenology of hypoxia and related biogeochemical processes in Chesapeake Bay under three different hydrologic regimes. Shifts to earlier nutrient load timing during idealized simulations reduced the overall annual hypoxic volume, resulting from discernable, but relatively small reductions in phytoplankton biomass and both sediment and water‐column respiration. Simulated increases in water temperature caused an increase in spring/early summer hypoxic volume associated with elevated respiration rates, but an associated exhaustion of organic matter in the early summer caused a decrease in late summer/fall hypoxic volume due to lowered respiration. Warming effects on hypoxia were larger than nutrient timing effects in scenarios where warming was restricted to spring and when it was applied to all months of the year. These idealized simulations begin the process of understanding the potential impacts of future climatic changes in the seasonal timing of key biogeochemical processes associated with eutrophication. [ABSTRACT FROM AUTHOR]