Estuaries and Coasts最新文献

Zooplankton play a key role in the cycling of carbon in aquatic ecosystems, yet their production of carbon-rich fecal pellets, which sink to depth and can fuel benthic community metabolism, is rarely quantified in estuaries. We measured fecal pellet carbon (FPC) production by the whole near-surface mesozooplankton community in the York River sub-estuary of Chesapeake Bay. Zooplankton biomass and taxonomic composition were measured with monthly paired day/night net tows. Live animal experiments were used to quantify FPC production rates of the whole community and dominant individual taxa. Zooplankton biomass increased in surface waters at night (2- to 29-fold) due to diel vertical migration, especially by Acartia spp. copepods. Biomass and diversity were seasonally low in the winter and high in the summer and often dominated by Acartia copepods. Whole community FPC production rates were higher (3- to 65-fold) at night than during the day, with the 0.5-1 mm size class contributing 2-26% to FPC production in the day versus 40-70% at night. An increase in the relative contribution of larger size fractions to total FPC production occurred at night due to diel vertical migration of larger animals into surface waters. Community FPC production was highest in fall due to increased diversity and abundance of larger animals producing larger fecal pellets, and lowest in summer likely due to top-down control of abundant crustacean taxa by gelatinous predators. This study indicates that zooplankton FPC production in estuaries can surpass that in oceanic systems and suggests that fecal pellet export is important in benthic-pelagic coupling in estuaries.

Supplementary information: The online version contains supplementary material available at 10.1007/s12237-024-01442-8.

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.

Seagrass beds are composed of foundation species, providing essential nursery grounds, feeding areas, and refuge for various marine life. Several species of fish and invertebrates utilize seagrasses as essential habitat. The Dwarf Seahorse (Hippocampus zosterae) is an understudied species in Texas, and little is known about its density, distribution, and habitat associations in this area of their range. Physicochemical water parameters, nekton community data, habitat data, and Dwarf Seahorse catch data were collected at 80 sites in Texas. The highest catch per unit effort (CPUE) of the target species was in Aransas Bay (0.038/m²). There was a positive relationship between the presence and percent cover of turtle grass (Thalassia testudinum) and the presence and CPUE of Dwarf Seahorses. Dwarf Seahorses were detected more often and at a higher CPUE in locations with a higher seagrass community diversity and richness. The nekton community at sites where Dwarf Seahorses were detected was also more abundant, diverse, and species rich. This is the first comprehensive study of the distribution of the Dwarf Seahorse along the Texas coast. Dwarf Seahorses were generally found in higher abundances in association with mature, stable, and diverse seagrass beds. Recommended conservation strategy to protect Dwarf Seahorses should prioritize the protection of established and mature seagrass beds. Continued directed monitoring of this species is recommended to better understand their distribution and population status.

Major storms can cause significant changes to coastal and wetland environments. A series of storm events in 2020 resulted in closure of the historically open estuary at Cabbage Tree Basin, Port Hacking, New South Wales (NSW), Australia. Prolonged tidal impoundment (3 months) led to substantial changes in hydrological and sedimentological processes, resulting in widespread mangrove dieback. This study aimed to quantify the degree of impact and recovery for mangroves, identify factors contributing to dieback, and consider the implications for carbon sequestration. This was achieved using remotely piloted aircraft structure-from-motion approaches, aerial photography, and field-based assessments of vegetation health and above-ground biomass (AGB). Mangroves were classified as ‘dead’, ‘partially dead’, and ‘live’. In October 2019, there was 10.8 ha of live mangroves, with this reduced to 6.6 ha by August 2022. Digital surface models (DSMs) were intersected with classified mangroves to assess the vertical distribution of each zone. All mangroves classified as ‘dead’ were distributed at elevations < 0.4 m with respect to the Australian Height Datum (AHD), suggesting these regions were persistently inundated, which was confirmed by water level loggers (inundated during logger deployment). Field data confirmed substrate elevation related to dieback with the proportion of ‘live’ mangroves greatest at elevations > 0.6 m AHD. Substrate elevation and distance to the estuary mouth were significantly correlated with species, with Avicennia marina located at lower tidal positions and closer to the entrance compared to Aegiceras corniculatum. The dieback event equated to a loss of 81.5 ± 48 Mg of above-ground biomass, 38.1 ± 22.5 Mg C, or 140 ± 82 Mg CO₂ equivalence (CO₂e). This study provides an important baseline for monitoring dieback events. Continued monitoring is crucial to assess recovery and to tailor management strategies.

Small crustaceans, such as the mysid Neomysis americana (S.I. Smith 1873), are a central component of coastal food webs and, while generally tolerant of a wide-range of environmental conditions, can be negatively affected by poor water quality. In this study, daily growth rates (GR_D) and clutch size metrics of N. americana collected during the early and late summer of 2018–2019 were evaluated for the Choptank and Patuxent rivers, major tributaries of Chesapeake Bay known to exhibit different oxygenation regimes. Genetic variation in the mitochondrial CO1 locus was assessed to evaluate the potential intraspecific genetic structure within Chesapeake Bay. CO1 haplotype network analysis, phylogenetic analysis, and analysis of molecular variance revealed no genetic differences between Choptank and Patuxent river populations, with all Chesapeake Bay individuals belonging to a single genetic lineage (lineage C), of the N. americana cryptic species complex. Total and size-specific clutch size were approximately 18% and 53% higher, respectively, in the normoxic Choptank River during the early summer. Embryos within the marsupium, corrected for clutch size and female length, were consistently larger in the Choptank River during later larval development stages. Size-specific clutch size showed correlations with bottom water dissolved oxygen concentration (positive) and water temperature (negative). GR_D did not differ between rivers or seasonally but juveniles grew twice as fast as adults. Given that all individuals genotyped from both rivers belonged to lineage C of the N. americana cryptic species complex, it is hypothesized that bottom water hypoxia (rather than genetic differentiation) is responsible for reduced clutch size in the Patuxent River. Our findings build on other recent work by providing evidence of a direct, negative relationship between hypoxia and local population dynamics of N. americana, a key ecological component of Chesapeake Bay’s food web.

Most living shoreline site selection and design decision support tools are based upon existing environmental conditions. We developed a web-based, geospatial tool called Future Shorelines that integrates high-resolution landscape elevation data and a matrix of locally derived NOAA Interagency Sea Level Rise Scenarios to characterize future conditions of submergence and shoreline translation induced by sea level rise. Once the practitioner selects a location of interest, sea level rise scenario (e.g., high), and target year (e.g., 2050), the tool will generate plan view and cross-sectional informational graphics specific to their choices. This information can then be paired with other menu options, like parcel ownership, to facilitate the planning and construction of nature-based shoreline stabilization solutions that (1) are located where opportunities for horizontal migration are optimized, (2) remain accessible for monitoring and maintenance, and (3) perform as intended over the design life of the installation. The tool’s menu options and the user interface were informed by project partner input solicited during numerous workshops convened over the duration of the 2-year project. This coproduction created a product that was familiar to the end user and therefore increased the likelihood that it would be utilized by them during the planning and design of living shoreline projects. Although developed for use in the Indian River Lagoon, located along the east-central Florida coast, it can be seamlessly replicated for application in other coastal regions of the USA where the requisite data are available.

The carbon cycle process of coastal ecosystems is extremely complex subjected to the coupling effects of hydrodynamics from land and sea. To investigate the distribution and biogeochemistry of organic carbon in estuaries area, particulate organic carbon (POC) and dissolved organic carbon (DOC) in water and total organic carbon (TOC) in surface sediments were measured over four tidal cycles at Sanjiagang (121.8°E, 31.2°N) in the Yangtze River estuary (YRE) from November 2022 to February 2023. Our results showed that the concentration of POC and DOC in water was positively correlated during the autumn and winter. Additionally, the significant positive correlation between tidal elevation and TOC concentrations indicated that organic carbon accumulation to estuarine areas was greatly influenced by tides. According to the principal component analysis (PCA) and stepwise multiple regression, the tidal dynamics and physicochemical properties of water, including salinity, dissolved oxygen (DO), temperature, turbidity, and pH, showed significant correlations to organic carbon. DOC and TOC concentrations were significantly higher in autumn than in winter. Due to the tidal asymmetry in the YRE, the POC and DOC concentrations during ebb tides were higher than those during flood tides. Furthermore, the influence of hydrometeorological conditions such as monthly precipitation and average temperature on the accumulation of organic carbon cannot be ignored in coastal areas. In addition, the grey correlation analysis revealed that strong relevance between the development of the processing manufacturing industry and the TOC in sediments at Site SJG. The socio-economic development and anthropogenic activities along the YRE interfered with the biogeochemical cycle of organic carbon through the massive discharge of wastewater and CO₂.

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.

Salinity is a major environmental factor that influences the population dynamics of fish and shellfish along coasts and estuaries, yet empirical methods for hindcasting salinity at specific sampling stations are not widely available. The specific aim of this research was to predict the salinity experienced by juvenile and adult oysters (Crassostrea virginica) collected at sampling stations in Delaware Bay. To do so, empirical relationships were created to predict salinity at five oyster bed stations using observing systems data. These relationships were then applied to construct indices of salinity exposure over an oyster’s lifetime. Three independent salinity data sources were used in conjunction with observing systems data to construct and validate the predictive relationships. The root mean square error (RMSE) of the models ranged from 0.5 to 1.6 psu when model predictions were compared with the three independent data sets. Results demonstrated that data from an observing system near the head of Delaware Bay could be used to predict salinity within ± 2 psu at oyster bed stations as far down-estuary as 39 km. When these models were applied to estimate low salinity exposure of 2-year-old oysters via the metric of consecutive days below 5 psu, the indices suggested that there could be as much as a 42-day difference in low salinity exposure for oysters at stations just 31 km apart. The approach of using observing systems data to hindcast salinity could be applied to advance understanding of salt distribution and the effect of low salinity exposure on organisms in other estuaries, especially bottom-associated species.

Worldwide, coastal wetlands are threatened by disrupted hydrology, urbanization, and sea-level rise. In southwest Florida, coastal wetlands include tidal creeks and coastal ponds, which are the primary habitats used by juvenile Tarpon, Megalops atlanticus, an important sport fish. Coastal ponds can occur near uplands and are ephemerally connected to the open estuary, creating conditions of variable dissolved oxygen and salinity. Juveniles can tolerate wide-ranging abiotic conditions, but little is known about how they egress from their remote nursery habitats, which often requires them to cross > 1 km of mangrove forest to reach the open estuary. The objective of this study was to (1) compare Tarpon body condition among ponds close to the open estuary versus those ponds farther away on the Cape Haze peninsula of Charlotte Harbor, Florida, and (2) using acoustic telemetry determine what factors contribute to Tarpon emigration from the ponds to open estuarine waters. We tested the hypothesis that distinct groups of Tarpon occur in isolated ponds, leading to variation in fish length and body condition, and that opportunities for emigration from these ponds hinge on high water events. No pond stood out as having Tarpon of low body condition. Factors contributing to increased probabilities of Tarpon emigration were low barometric pressure, high-water level, and Tarpon body length. Tarpon emigrated from ponds near tidal creeks during summer king tides, while tropical cyclone conditions were needed to allow for movement from ponds farther in the landscape. The juvenile Tarpon were later detected at the mouths of large rivers 30 km up-estuary. The characterizations of water levels and event criteria needed for successful Tarpon nurseries should aid in habitat conservation and the creation of Tarpon nursery habitat in restoration designs.