Estuaries and Coasts最新文献

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.

Tidal marsh plant communities in the Pacific Northwest are characterized by tall, perennial graminoids (TPGs), which provide forage for herbivores such as Canada geese. Excessive grazing by Canada geese leads to loss of marsh habitat, and removal of grazing pressure is required for the vegetation to recover. Grazing exclosures (fences) are used to allow time and space for vegetation to recover following intensive herbivory; however, their effects on native plant community recovery has not been tested. Generalized linear models were used to compare TPG abundance in aboveground vegetation and surface seed banks in 1-year-old and 10-year-old exclosures at Nanaimo River Estuary (NRE) and Little Qualicum River Estuary (LQRE), respectively, to areas of the marshes that had no known history of grazing (undisturbed) and areas still actively grazed (grubbed). Compared to undisturbed sites, grubbed sites had 187.3% less mean TPG vegetation cover and 190.7% lower proportion of TPG seeds. The 1-year-old exclosures at NRE had 105.0% less mean TPG vegetation cover and 193.2% lower proportion of TPG seeds. The 10-year-old exclosures at LQRE had 7.0% greater mean TPG cover and 55.7% greater proportion of TPG seed than all undisturbed sites; however, these exclosures had 110.0% greater mean relative abundance of non-native TPGs than undisturbed sites. These results indicate vegetation may not recover towards comparable historic conditions through grazing exclusion alone, and that active restoration methods may be required following intensive grazing, especially in estuaries where the vegetation community and surface seed bank has a high abundance of non-native, invasive species.

Rates of ecosystem metabolic properties, such as plankton community respiration, can be used as an assessment of the eutrophication state of a waterbody and are the primary biogeochemical rates causing oxygen depletion in coastal waters. However, given the additional labor involved in measuring biogeochemical rate processes, few monitoring programs regularly measure these properties, and thus, few long-term monitoring records of plankton respiration exist. An 8-year, biweekly plankton community respiration rate time series was analyzed as part of a monitoring program situated in the lower Patuxent River estuary, a tributary of Chesapeake Bay. We found that particulate nutrients (nitrogen and phosphorus) were the most highly correlated covariates with respiration rate. Additionally, statistical and kinetic models including variables both water temperature and particulate nitrogen were able to explain 74% of the variability in respiration. Over the long-term record, both particulate nutrients and respiration rate were elevated when measured at higher tides. Separate measurements of respiration rate during 10 consecutive days and during high and low tide on three separate days also support the enhancement of respiration with high tide. The enhancement was likely due to the import of particulate nutrients from the highly productive mid-bay region. This analysis of the longest consistently measured community respiration rate dataset in Chesapeake Bay has implications for how to interpret long-term records of measurements made at fixed locations in estuaries.

Recent large-scale spatial products have been developed to assess wetland position in the tidal frame, but nationwide comparisons and validations are missing for these products. Wetland position within the tidal frame is a commonly used characteristic to compare wetlands across biogeomorphic gradients and factors heavily into wetland vulnerability models. We utilize a dataset of 365 surface elevation table stations across the conterminous USA containing ground-surveyed tidal datum and elevation data to validate two gridded, conterminous USA–wide relative tidal elevation products. We identified substantial differences between our ground-surveyed dataset and the gridded products, with the Gulf coast exhibiting the greatest error (p < 0.0001, n = 140). Error in relative tidal elevation products varied by coast, tidal range, and latitude. These differences in errors indicate that gridded relative tidal elevation products may be more accurate in coastal wetlands with larger tidal ranges (> 30 cm) and are less accurate in freshwater wetlands near the coast. This paper makes advances in understanding why relative tidal elevation differences occur among national datasets and identifies areas of future work that could support more robust vulnerability models.

The common marsh snail Melampus bidentatus is an omnivore-detritivore that is typically restricted to the upper marsh zone in salt marshes of southern New England and further south. However, in Maritime Canadian salt marshes (specifically in the Northumberland Strait), M. bidentatus occurs throughout the high and low marsh zones (mean summer densities ~ 50 individuals m⁻²). This study determined the within-marsh distribution of M. bidentatus near its northern range limit and investigated the mechanisms responsible for this distribution. Intensive spatial and temporal sampling in 2015–2016 confirmed that all stages (adults, juveniles, and egg masses) occurred throughout the salt marsh. Investigations of snail survival (using tethering assays) and movement (using mark-recapture trials) indicated that mortality was very low and independent of marsh zone, and movement was moderate, random, and circuitous, generally maintaining snails in local areas. Thus, lack of differential survival and movement between marsh zones support an unrestricted distribution. This wide spatial distribution of M. bidentatus within salt marshes in north temperate latitudes is likely due to the species’ high physiological tolerances, absence of competition from other gastropod omnivores-detritivores, and low predation pressure in the low marsh zone. Given these findings, further research on the snails’ role in, for example, trophic dynamics would provide further insights as to latitudinal differences in the ecology of resident salt marsh fauna.

Up to 85% of shellfish reefs have been lost worldwide, resulting in declining ecosystem services, and increasing restoration demand. However, more information regarding the conditions which maximise oyster settlement and growth is required to optimise restoration. We deployed oyster settlement tiles at 21 intertidal sites throughout Moreton Bay, Australia; a region where > 96% of rock oyster reefs are lost and demand for restoration is high. We quantified effects of variables describing the spatial (from GIS), local habitat (using quadrats and water quality measures), and oyster predator (using underwater videography) characteristics of sites on oyster density and size on tiles. Oyster density was highest at sites with intermediate predator abundance and temperature, highest nearby invertebrate cover, and low and high values of turbidity and nearby rock and algae cover. Conversely, oyster size was highest at sites with intermediate predator density, higher fish species richness and turbidity, and lowest temperatures. Together, this showed that optimal restoration requires sites with 22 to 23 °C average water temperatures, between 10 and 15 oyster predators, and either low (< 2 NTU) or high (> 6 NTU) turbidity levels. Notably, we observed multiple peaks for several variables, suggesting the potential presence of multiple cryptic oyster species on settlement tiles. We found that oysters shared preferred environmental conditions with polychaetes, coralline algae, and tunicates, and were more prevalent and abundant at sites with lower turf algae, barnacle, and mussel cover. Identifying environmental variables influencing oyster population distribution, settlement, and growth can guide the selection and approach of oyster restoration sites.

The Atlantic sturgeon Acipenser oxyrinchus oxyrinchus is an anadromous species with a wide range along the Atlantic coast of North America. Because of overharvest and a variety of other anthropogenic stressors, the numbers of estuaries that currently host successful natural reproduction and the abundances of extant populations are depressed compared to historic numbers, resulting in its listing under the US Endangered Species Act as five Distinct Population Segments (DPS). Atlantic sturgeon are vulnerable to stressors not only within their natal estuaries but also at distant locales because of the highly migratory behavior of their subadult and adult life stages. In this study, we used our previously derived microsatellite DNA catalogue of 13 reference spawning populations and Individual-Based Assignment testing to determine the origin of 202 adult Atlantic sturgeon that were collected from the lower Altamaha River during spring, several months prior to their fall upriver spawning. We found that approximately one third (37%) of these adults assigned to populations other than the Altamaha, almost all (96%) to other populations within the South Atlantic DPS, a finding consistent with our earlier acoustic telemetry results. These results have management implications, including the likelihood of recolonization of depleted populations in the South Atlantic DPS and the compilation of reference population genetic profiles used in population delineation and mixed-stock analyses.