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Results for “Estuaries”

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At least 415 records · Page 23Linked to original sources
USGS2002

Bioavailability of organic matter in a highly disturbed Estuary: The role of detrital and algal resources

The importance of algal and detrital food supplies to the planktonic food web of a highly disturbed, estuarine ecosystem was evaluated in response to declining zooplankton and fish populations. We assessed organic matter bioavailability among a diversity of habitats and hydrologic inputs over 2 years in San Francisco Estuary's Sacramento-San Joaquin River Delta. Results show that bioavailable dissolved organic carbon from external riverine sources supports a large component of ecosystem metabolism. However, bioavailable particulate organic carbon derived primarily from internal phytoplankton production is the dominant food supply to the planktonic food web. The relative importance of phytoplankton as a food source is surprising because phytoplankton production is a small component of the ecosystem's organic-matter mass balance. Our results indicate that management plans aimed at modifying the supply of organic matter to riverine, estuarine, and coastal food webs need to incorporate the potentially wide nutritional range represented by different organic matter sources.

Proceedings of the National Academy of Sciences of↗
USGS1963

The hydraulic geometry of a shallow estuary

An analogy with entropy production in steady-state systems leads to a statement that the geometry of natural waterways is governed by two opposing influences: a ) equal work per unit of area of bed, and b) minimum work done in the system as a whole. The resulting calculations applied to shallow , estuaries are verified by field measurements.

International Association of Scientific Hydrology ↗
USGS2009

Osprey: Worldwide sentinel species for assessing and monitoring environmental contamination in rivers, lakes, reservoirs, and estuaries

In the United States, many fish and wildlife species have been used nationwide to monitor environmental contaminant exposure and effects, including carcasses of the bald eagle ( Haliaeetus leucocephalus ), the only top avian predator regularly used in the past. Unfortunately, bald eagles are sensitive to investigator intrusion at the nest. Thus, the osprey ( Pandion haliaetus ) is evaluated as a potential sentinel species for aquatic ecosystems. Several characteristics support the choice of the osprey as a sentinel species, including: (1) fish-eating diet atop the aquatic food web, (2) long-lived with strong nest fidelity, (3) adapts to human landscapes (potentially the most contaminated), (4) tolerates short-term nest disturbance, (5) nests spatially distributed at regular intervals, (6) highly visible nests easily located for study, (7) ability to accumulate most, if not all, lipophilic contaminants, (8) known sensitivity to many contaminants, and (9) nearly a worldwide distribution. These osprey traits have been instrumental in successfully using the species to understand population distribution, abundance, and changes over time; the effects of various contaminants on reproductive success; how contaminants in prey (fish on biomass basis) contribute to egg concentrations (i.e., biomagnification factors); and spatial residue patterns. Data summarized include nesting population surveys, detailed nesting studies, and chemical analyses of osprey egg, organ, blood, and feather samples for contaminants that bioaccumulate and/or biomagnify in aquatic food webs; and biochemical evaluations of blood and various organs. Studies in the United States, Canada, Mexico, Europe, and elsewhere have shown the osprey to be a useful sentinel species for monitoring selected environmental contaminants, including some emerging contaminants in lakes, reservoirs, rivers, and estuaries.

Journal of Toxicology and Environmental Health, Pa↗
USGS2012

Spatial and temporal diet patterns of subadult and small adult striped bass in Massachusetts estuaries: Data, a synthesis, and trends across scales

Subadult and small adult (375–475 mm total length) striped bass Morone saxatilis are abundant and represent an important component of the recovered U.S. Atlantic coast stocks. However, little is known about these large aggregations of striped bass during their annual foraging migrations to New England. A quantitative understanding of trends in the diets of subadult and small adult migrants is critical to research and management. Because of the complexity of the Massachusetts coast, we were able to compare diets at multiple spatial, temporal, and taxonomic scales and evaluate which of these provided the greatest insights into the foraging patterns of this size of fish. Specifically, during spring through autumn, we quantified the diets of 797 migratory striped bass collected from 13 Massachusetts estuaries distributed among three geographic regions in two biogeographic provinces. Our data provided three useful results. First, subadult and young adult striped bass ate a season-specific mixture of fish and invertebrates. For example, more juvenile Atlantic herring Clupea harengus were eaten in spring than in summer or autumn, more juvenile Atlantic menhaden Brevoortia tyrannus were eaten in autumn than in spring or summer, amphipods were eaten primarily in the southern biogeographic province, and shrimp Crangon sp. were eaten in all locations and seasons. Second, examining diets by season was essential because of the temporal variability in striped bass prey. Grouping prey by fish and invertebrates revealed the potential for predictable differences in growth across geographic locations and seasons, based on the output from simple bioenergetics simulations. Third, of the three spatial scales examined, region provided the most quantitative and interpretable ecological trends. Our results demonstrate the utility of comparing multiple scales to evaluate the best way to depict diet trends in a migrating predator that seasonally uses different geographic locations.

Massachusetts↗
USGS2025

Fish composition in a complex freshwater estuary: Environmental DNA metabarcoding versus capture surveys

Objective The potential for environmental DNA (eDNA) to disperse widely from source organisms enables high detection efficiency but raises questions about eDNA's ability to differentiate fine-scale spatial patterns relative to conventional fish capture data. Methods We evaluate these questions in the St. Louis River estuary—a hydrologically and spatially complex coastal system within Lake Superior that supports a diverse assemblage of resident and migratory fish species—via comparison of eDNA metabarcoding (12S and 16S loci) to multigear capture survey data from 2 years and two seasons. Results The eDNA and capture surveys collectively yielded 68 fish species: 2 species detected only by capture, 27 detected only by eDNA, and 39 shared across both survey types but having generally higher occurrence frequencies with eDNA than capture. Six species detected only by eDNA were unexpected, having no prior records in the Lake Superior basin. Data from paired eDNA and capture stations showed little relationship between the two survey types, with capture yielding species at stations that eDNA did not, eDNA detecting species in different habitats and distant locations from any captures, and assemblage patterns homogenized in eDNA surveys relative to capture surveys. Conclusions Our study finds that eDNA is a sensitive tool for assessing species presence at the system scale but that capture surveys may better yield the fine-scale spatial distribution information of interest to fisheries and habitat managers, especially in spatially and hydrologically complex systems.

Transactions of the American Fisheries Society↗
USGS2008

Wintering site fidelity and movement patterns of Western Sandpipers Calidris mauri in the San Francisco Bay estuary

Western Sandpipers Calidris mauri are the most numerous shorebird species in the San Francisco Bay estuary during winter. A sample of 106 Western Sandpipers was captured in mist nets and radio-marked with 1-g transmitters to examine their wintering site fidelity and movements. Differences in distances moved, home range extent and core area size were examined by age, sex, season, site, time of day and tide. All birds remained in the south San Francisco Bay region during winter and exhibited strong site fidelity, with a mean home range of 22.0 km 2 or only 8% of the study area. First-year birds had larger home ranges (26.6 ± 3.6 km 2 ) than adults (17.2 ± 2.5 km 2 ) in winter, but home range sizes of males and females were not significantly different in any period. Home range sizes were similar between seasons, but core areas were smaller in spring (6.3 ± 1.2 km 2 ) than in early (9.6 ± 4.0 km 2 ) or late (11.6 ± 1.6 km 2 ) winter. Movements and home range size were similar for radio-marked birds located during day and night. The high degree of regional and local site fidelity demonstrated that the mixture of natural mud fiats and artificial salt ponds in southern San Francisco Bay provided sufficient resources for large wintering populations of Western Sandpipers.

Ibis↗
USGS2005

Simulation of Submarine Ground Water Discharge to a Marine Estuary: Biscayne Bay, Florida

Variable density ground water flow models are rarely used to estimate submarine ground water discharge because of limitations in computer speed, data availability, and availability of a simulation tool that can minimize numerical dispersion. This paper presents an application of the SEAWAT code, which is a combined version of MODFLOW and MT3D, to estimate rates of submarine ground water discharge to a coastal marine estuary. Discharge rates were estimated for Biscayne Bay, Florida, for the period from January 1989 to September 1998 using a three-dimensional, variable density ground water flow and transport model. Hydrologic stresses in the 10-layer model include recharge, evapotranspiration, ground water withdrawals from municipal wellfields, interactions with surface water (canals in urban areas and wetlands in the Everglades), boundary fluxes, and submarine ground water discharge to Biscayne Bay. The model was calibrated by matching ground water levels in monitoring wells, baseflow to canals, and the position of the 1995 salt water intrusion line. Results suggest that fresh submarine ground water discharge to Biscayne Bay may have exceeded surface water discharge during the 1989, 1990, and 1991 dry seasons, but the average discharge for the entire simulation period was only ???10% of the surface water discharge to the bay. Results from the model also suggest that tidal canals intercept fresh ground water that might otherwise have discharged directly to Biscayne Bay. This application demonstrates that regional scale variable density models are potentially useful tools for estimating rates of submarine ground water discharge.

Ground Water↗
USGS2016

Changes in habitat availability for outmigrating juvenile salmon (Oncorhychus spp.) following estuary restoration

The restoration of the Nisqually River Delta (Washington, U.S.A.) represents one of the largest efforts toward reestablishing the ecosystem function and resilience of modified habitat in the Puget Sound, particularly for anadromous salmonid species. The opportunity for outmigrating salmon to access and benefit from the expansion of available tidal habitat can be quantified by several physical attributes, which are related to the ecological and physiological responses of juvenile salmon. We monitored a variety of physical parameters to measure changes in opportunity potential from historic, pre-restoration, and post-restoration habitat conditions at several sites across the delta. These parameters included channel morphology, water quality, tidal elevation, and landscape connectivity. We conducted fish catch surveys across the delta to determine if salmon was utilizing restored estuary habitat. Overall major channel area increased 42% and major channel length increased 131% from pre- to post-restoration conditions. Furthermore, the results of our tidal inundation model indicated that major channels were accessible up to 75% of the time, as opposed to 30% pre-restoration. Outmigrating salmon utilized this newly accessible habitat as quickly as 1 year post-restoration. The presence of salmon in restored tidal channels confirmed rapid post-restoration increases in opportunity potential on the delta despite habitat quality differences between restored and reference sites.

Washington↗
USGS1998

Does the Sverdrup critical depth model explain bloom dynamics in estuaries?

In this paper we use numerical models of coupled biological-hydrodynamic processes to search for general principles of bloom regulation in estuarine waters. We address three questions: what are the dynamics of stratification in coastal systems as influenced by variable freshwater input and tidal stirring? How does phytoplankton growth respond to these dynamics? Can the classical Sverdrup Critical Depth Model (SCDM) be used to predict the timing of bloom events in shallow coastal domains such as estuaries? We present results of simulation experiments which assume that vertical transport and net phytoplankton growth rates are horizontally homogeneous. In the present approach the temporally and spatially varying turbulent diffusivities for various stratification scenarios are calculated using a hydrodynamic code that includes the Mellor-Yamada 2.5 turbulence closure model. These diffusivities are then used in a time- and depth-dependent advection-diffusion equation, incorporating sources and sinks, for the phytoplankton biomass. Our modeling results show that, whereas persistent stratification greatly increases the probability of a bloom, semidiurnal periodic stratification does not increase the likelihood of a phytoplankton bloom over that of a constantly unstratified water column. Thus, for phytoplankton blooms, the physical regime of periodic stratification is closer to complete mixing than to persistent stratification. Furthermore, the details of persistent stratification are important: surface layer depth, thickness of the pycnocline, vertical density difference, and tidal current speed all weigh heavily in producing conditions which promote the onset of phytoplankton blooms. Our model results for shallow tidal systems do not conform to the classical concepts of stratification and blooms in deep pelagic systems. First, earlier studies (Riley, 1942, for example) suggest a monotonic increase in surface layer production as the surface layer shallows. Our model results suggest, however, a nonmonotonic relationship between phytoplankton population growth and surface layer depth, which results from a balance between several 'competing' processes, including the interaction of sinking with turbulent mixing and average net growth occurring within the surface layer. Second, we show that the traditional SCDM must be refined for application to energetic shallow systems or for systems in which surface layer mixing is not strong enough to counteract the sinking loss of phytoplankton. This need for refinement arises because of the leakage of phytoplankton from the surface layer by turbulent diffusion and sinking, processes not considered in the classical SCDM. Our model shows that, even for low sinking rates and small turbulent diffusivities, a significant % of the phytoplankton biomass produced in the surface layer can be lost by these processes.

Journal of Marine Research↗
USGS1981

An empirical methodology for estimating entrainment losses at power plants sited on estuaries

A model based on empirically derived age‐, time‐, and space‐variant entrainment susceptibility data may be used for estimating conditional entrainment mortality of aquatic organisms, particularly fish and shellfish, caused by operation of one or more power plants on an estuary. Model application requires knowledge of the morphometry of the water body, the power‐plant flow rates, the probability of entrainment survival, and the duration, distribution, and abundance of entrainable age‐groups. A novel feature of the model is that organism distribution and movement within the model are defined by information derived from field samples rather than by hydrodynamic principles and equations.

Transactions of the American Fisheries Society↗
USGS2016

Habitat selection by Forster's Terns (Sterna forsteri) at multiple spatial scales in an urbanized estuary: The importance of salt ponds

The highly urbanized San Francisco Bay Estuary, California, USA, is currently undergoing large-scale habitat restoration, and several thousand hectares of former salt evaporation ponds are being converted to tidal marsh. To identify potential effects of this habitat restoration on breeding waterbirds, habitat selection of radiotagged Forster's Terns ( Sterna forsteri ) was examined at multiple spatial scales during the pre-breeding and breeding seasons of 2005 and 2006. At each spatial scale, habitat selection ratios were calculated by season, year, and sex. Forster's Terns selected salt pond habitats at most spatial scales and demonstrated the importance of salt ponds for foraging and roosting. Salinity influenced the types of salt pond habitats that were selected. Specifically, Forster's Terns strongly selected lower salinity salt ponds (0.5–30 g/L) and generally avoided higher salinity salt ponds (≥31 g/L). Forster's Terns typically used tidal marsh and managed marsh habitats in proportion to their availability, avoided upland and tidal flat habitats, and strongly avoided open bay habitats. Salt ponds provide important habitat for breeding waterbirds, and restoration efforts to convert former salt ponds to tidal marsh may reduce the availability of preferred breeding and foraging areas.

California↗
USGS2014

Below the disappearing marshes of an urban estuary: historic nitrogen trends and soil structure

Marshes in the urban Jamaica Bay Estuary, New York, USA are disappearing at an average rate of 13 ha/yr, and multiple stressors (e.g., wastewater inputs, dredging activities, groundwater removal, and global warming) may be contributing to marsh losses. Among these stressors, wastewater nutrients are suspected to be an important contributing cause of marsh deterioration. We used census data, radiometric dating, stable nitrogen isotopes, and soil surveys to examine the temporal relationships between human population growth and soil nitrogen; and we evaluated soil structure with computer-aided tomography, surface elevation and sediment accretion trends, carbon dioxide emissions, and soil shear strength to examine differences among disappearing (Black Bank and Big Egg) and stable marshes (JoCo). Radiometric dating and nitrogen isotope analyses suggested a rapid increase in human wastewater nutrients beginning in the late 1840s, and a tapering off beginning in the 1930s when wastewater treatment plants (WWTPs) were first installed. Current WWTPs nutrient loads to Jamaica Bay are approximately 13 995 kg N/d and 2767 kg P/d. At Black Bank, the biomass and abundance of roots and rhizomes and percentage of organic matter on soil were significantly lower, rhizomes larger in diameter, carbon dioxide emission rates and peat particle density significantly greater, and soil strength significantly lower compared to the stable JoCo Marsh, suggesting Black Bank has elevated decomposition rates, more decomposed peat, and highly waterlogged peat. Despite these differences, the rates of accretion and surface elevation change were similar for both marshes, and the rates of elevation change approximated the long term relative rate of sea level rise estimated from tide gauge data at nearby Sandy Hook, New Jersey. We hypothesize that Black Bank marsh kept pace with sea level rise by the accretion of material on the marsh surface, and the maintenance of soil volume through production of larger diameter rhizomes and swelling (dilation) of waterlogged peat. JoCo Marsh kept pace with sea-level rise through surface accretion and soil organic matter accumulation. Understanding the effects of multiple stressors, including nutrient enrichment, on soil structure, organic matter accumulation, and elevation change will better inform management decisions aimed at maintaining and restoring coastal marshes.

New York↗
USGS1969

Epifauna and thermal additions in the upper Patuxent River estuary

In the upper Patuxent Estuary environmental changes in temperature, salinity, and turbidity over a 5-year period are linked to changes in epifaunal production and species distribution. During 1967 a series of monthly panels showed dry weight production averaged 2.8 times greater in a steam electric station heated effluent than in the intake. A downriver shift in epifanual production in 1967 and changes in species abundance was noted and attributed to natural changes in salinity and turbidity and man-induced changes in temperature.

Maryland↗
USGS1971

Distribution of the fiddler crab (Uca minax) in relation to marsh plants within a Virginia estuary

The distribution and abundance of the red-jointed fiddler crab, Uca minax, was related to the distribution of marsh plants within a Virginia estuary. The crab was found in association with 15 species of marsh phanerogams, occurring with five plant species more than 20 percent of the time. These plants were Spartina alterniflora, Scirpus robustus, Distichlis spicata, Spartina patens, and Spartina cynosuroides. Densities ranged from 0-76 burrows per square meter, mean densities being 7.88 within the brackish-water marsh and 14.35 within the salt-water marsh. The crab was not obtained by sampling the freshwater marsh.

Chesapeake Science↗
USGS1970

Temperature and water-quality conditions of the Patuxent River estuary, Maryland, January 1966 through December 1967

The effect of power plant cooling water in raising natural water temperatures at a location near the power plant on the Patuxent River estuary is clearly evident from thermograph records. Surface temperature at a station 333 m (1,000 ft) downstream from the discharge canal was raised an average of about 4 C, and at times by as much as 8 C. Temperature rises were greatest during the winter. Infrared imagery showed that elevated surface temperatures could be detected about 5.5 km (3 nautical miles) upstream at flood tide. Temperature profiles obtained from airborne radiation equipment revealed a complicated surface temperature pattern and also showed the effects of density differences and wind action on the steam-electric station (S.E.S.) effluent plume. Mean annual salinity for a 5-year period (1963–1967) was highest in 1966, about 12.3 ‰, and lowest in 1967, about 9.9‰. Dissolved oxygen values for 1966–1967 ranged from 3.2 to 15.6 mg/l, and saturation ranged from 55 to 152%. Turbidity levels were inversely related to salinity, with the highest annual, mean of 28 JCU (Jackson Candle Units) occurring in 1967, the lowest salinity year. The extreme tide range was 2.1 m (6.7 ft); mean water levels at the Patuxent Bridge were highest in summer and lowest in winter. Water stages are more affected by wind speed and direction than by flow in the river.

Maryl↗
USGS1974

Changes in oxygen and primary production of the Patuxent estuary, Maryland, 1963 through 1969

From 1963 through 1969, the U.S. Geological Survey operated a water-quality monitor system in the upper-middle Patuxent estuary, near Benedict, Maryland. Over the period of record, a pronounced change occurred in the diel (24 hr.) oxygen measurement, particularly during the months of July, August, and September. Annual variations of dissolved oxygen ranged from 3.6 to 15.0 mg liter −1 in 1964 and from 2.3 to 16.5 mg liter −1 in 1969 with percentage saturation varying from 60 to 130 percent in 1964 and from 30 to 184 percent in 1969. The magnitude of diel summer oxygen variation changed from about 3 to 7 mg liter −1 day −1 over the same period. From hourly values of temperature, oxygen, and conductivity, gross primary production (GP) and respiration (R) were estimated. Data representing greatest daily change for spring, summer, and autumn of each year and “average” values for each month of years 1964 and 1969 were analyzed for GP and R. From the seasonal data, GP ranged from about 3 to 25 g O 2 m −2 day −1 , and R ranged from about 4 to 32 g O 2 m −2 day −1 . From the “average” days, GP ranged from 2 to 10 g O 2 m −2 day −1 in 1964 and from 1 to 16 in 1969. In 1964, daily average GP was 5.2 g O 2 m −2 day −1 as compared to 6.1 in 1969, and respiration was 6.1 g O 2 m −2 day −1 in 1964 versus 10.2 g O 2 m −2 day −1 in 1969, increases of 20 and 16 percent, respectively. Ratios of GP/R averaged 0.84 in 1964 versus 0.60 in 1969, reflecting a larger respiration in 1969 and suggesting a trend towards community instability. Productivity estimates by other investigators showed a two-to threefold increase in production over the same period of time. The increases in production were attributed to upstream domestic waste loading. If the present trend increases, metabolic imbalance and anaerobic conditions may develop.

Maryland↗
USGS2006

Water-quality data, Columbia River estuary, 2004-05

This report describes the water-quality data collected by the USGS from 2004 through 05 as part of the Ecosystem Monitoring Project and attempts to quantify the spatial distribution and temporal variation of water-quality conditions, including contaminant concentrations, in water and suspended sediment in the Columbia River Estuary, and evaluate these water-quality conditions against aquatic-life standards and guidelines. The analytes to be measured in this study were selected because they are either known to be present in Columbia River salmonids at levels of concern; known to be present in salmonids, but not known if present at levels of concern; present in water at concentrations known to affect endocrine function in adult salmonids; or not previously measured in water, but if present, are of potential concern to salmonid populations.

Data Series↗
USGS2018

Coastal estuaries and lagoons: The delicate balance at the edge of the sea

Coastal communities are increasingly concerned about the dynamic balance between freshwater and saltwater because of its implications for societal, economic, and ecological resources. While the mixing of freshwater and saltwater sources defines coastal estuaries and lagoons, sudden changes in this balance can have a large effect on critical ecosystems and infrastructure. Any change to the delivery of water from either source has the potential to affect the health of both humans and natural biota and also to damage coastal infrastructure. This fact sheet discusses the potential of major shifts in the dynamic freshwater-saltwater balance to alter the environment and coastal stability.

Fact Sheet↗