The spatiotemporal variability in strontium (Sr), barium (Ba), magnesium (Mg), and manganese (Mn) elemental signatures of water and fish otoliths was assessed from July to October 2008 across river ...habitats of Albemarle Sound, North Carolina. We examined whether relationships in these signatures exist and the potential of otoliths to serve as innate chemical tags. Hatchery-reared age-0 striped bass Morone saxatilis were placed in cages at four different locations to test development of habitat-specific otolith signatures. Dissolved elemental water and otolith signatures exhibited spatial variability but did not vary temporally. Chemical water signatures classified habitats with 76–81% accuracy, and otolith signatures of caged fish displayed 59–63% total classification accuracy depending on the classification method used. The elements Sr, Ba, and Mn were the main habitat discriminators, as their concentrations in otoliths were significantly correlated with concentrations in the water. Otolith Mg was not related to water chemistry and did not vary among habitats. Natural physiochemical gradients, geochemical processes, and possibly anthropogenic inputs influenced the trace elemental signatures of Albemarle Sound habitats. The unique chemical signals of the sound's river habitats validate the use of otolith signatures for determining striped bass habitat utilization in this system. Use of otolith elemental signatures as natural tags provides a quantitative method to determine the proportion of juvenile striped bass recruiting to the adult spawning stock from specific habitats, thus aiding resource managers in identifying habitats that should receive priority in restoration and conservation decisions.
Tide-gauge measurements in the western North Atlantic Ocean show coherent, multi-decadal relative sea-level (RSL) trends across multiple spatial scales. Proxy reconstructions developed from ...salt-marsh sediment can extend this instrumental record. However, the degree of coherence in proxy reconstructions is underexamined through within-region replication. To explore within-region replication, we developed a new RSL reconstruction from Fox Hill Marsh, Rhode Island to complement similar records at nearby sites. We established the elevation of former sea level from assemblages of foraminifera and bulk-sediment δ13C values using a Bayesian transfer function. We employed radiocarbon dating and recognition of pollution horizons to construct a core chronology. Since ∼1200 BCE, RSL rose by ∼3.7 m at Fox Hill Marsh. After correction for glacial isostatic adjustment, application of a statistical model intended to quantify (multi-) century-scale trends showed that the fastest rate of rise in at least the past 3000 years was 1.71 ± 0.84 mm/yr (95% credible interval) in 2020 CE. This result replicates regional tide-gauge measurements and other proxy reconstructions. Using an alternative statistical model constructed to identify sub-centennial sea-level changes, we examined if there was a hotspot of 18th century rise in the northeastern United States and found no spatially-coherent trend (i.e., occurring at all or most sites). This lack of replication indicates that accelerated rise during the 18th century is likely local (site-specific) in scale, or an artifact of individual reconstructions. Continued efforts to replicate RSL reconstructions will increase confidence in the accuracy of records and their subsequent interpretation.
•Proxy reconstructions are used to investigate late Holocene relative sea-level changes in southern New England.•A new relative sea-level record from Fox Hill Marsh, Rhode Island, documents ∼3.7 m of rise since ∼1200 BCE.•The fastest century-scale rate of sea-level rise in at least the past 3000 years was 1.71 ± 0.84 mm/yr in 2020 CE•We find no spatially-coherent trend supportive of an 18th century hotspot of sea-level rise in the northeastern United States.•Accelerated 18th century sea-level rise at some sites is likely local in scale, or an artifact of individual reconstructions.
This paper describes a device (“piezomanometer”) that combines three components (an oil‐water manometer, a pushable screened PVC probe, and a system for groundwater sample collection) into a single ...inexpensive ($130), easily built, reliable tool for rapid collection of shallow groundwater from a streambed or lake bed and accurate measurement of even very small head differences between this groundwater and overlying surface water. The piezomanometer has been tested with excellent results both in the lab and in a stream shallow enough for wading; in principle, it could be adapted for use in deeper water where work is done from a dock, boat, or other platform. The problem of gas bubbles collecting in the groundwater line (a common drawback of field manometers) was nearly eliminated by use of a three‐way valve at a local elevation maximum in the groundwater line (gas bubbles in the groundwater line can be purged through this valve). Field application is illustrated here with data from a 2‐day study using four piezomanometers in a North Carolina stream.
Increasing the setback to 50 m and raising drainfields 1 m above groundlevel could reduce nutrient inputs.
Groundwater from a shallow freshwater lens on St. George Island, a barrier island located in ...the Panhandle of Florida, eventually discharges into Apalachicola Bay or the Gulf of Mexico. Nutrient concentrations in groundwaters were monitored downfield from three onsite sewage treatment and disposal systems (OSTDS) on the island. Estimates of natural groundwater nutrient concentrations were obtained from an adjacent uninhabited island. Silicate, which was significantly higher in the imported drinking water relative to the surficial aquifer on St. George Island (12.2±1.9 mg Si l
−1 and 2.9±0.2 mg Si l
−1, respectively), was used as a natural conservative tracer. Our observations showed that nitrogen concentrations were attenuated to a greater extent than that of phosphorus relative to the conservative tracer. At the current setback distance (23 m), both nitrogen and phosphate concentrations are still elevated above natural levels by as much as 2 and 7 times, respectively. Increasing the setback distance to 50 m and raising the drainfields 1 m above the ground surface could reduce nutrient levels to natural concentrations (1.1±0.1 mg N l
−1, 0.20±0.02 mg P l
−1).
To identify priority information needs for sea-level rise planning, we conducted workshops in Florida, North Carolina, and Massachusetts in the summer of 2012. Attendees represented professionals ...from five stakeholder groups: federal and state governments, local governments, universities, businesses, and nongovernmental organizations. Over 100 people attended and 96 participated in breakout groups. Text analysis was used to organize and extract most frequently occurring content from 16 total breakout groups. The most frequent key words/phrases were identified among priority topics within five themes: analytic tools, communications, land use, ecosystem management, and economics. Diverse technical and communication tools were identified to help effectively plan for change. In many communities, planning has not formally begun. Attendees sought advanced prediction tools yet simple messaging for decision-makers facing politically challenging planning questions. High frequency key words/phrases involved fine spatial scales and temporal scales of less than 50 years. Many needs involved communications and the phrase "simple messaging" appeared with the highest frequency. There was some evidence of geographic variation among regions. North Carolina breakout groups had a higher frequency of key words/phrases involving land use. The results reflect challenges and tractable opportunities for planning beyond current, geophysically brief, time scales (e.g., election cycles and mortgage periods).
Increased sound production by fishes, which is used for communication during mating, in territorial defense, and possibly in echolocation, has been associated with decreased light and increased ...temperature and salinity (Luczkovich et al. 2008; Mok and Gilmore 1983). There has not been an attempt to associate changes in sound production with other environmental factors such as turbidity. Sediment deposition and resuspension commonly occur in estuaries due to changes in current velocity and direction, water runoff, and wave height. These factors can lead to shearing on the bed surface and thus an overall increase in water column turbidity (Whitehouse et al. 2000). It has been hypothesized that increased water column turbidity will lead to increased sound production in fishes because visual cues will be impaired. The goal of this research is to associate the incidence of sound production by Micropogonias undulatus (Atlantic croaker) to variations in estuarine temperature, salinity, dissolved oxygen, and particularly turbidity.
Underlying questions that are central to field studies of the groundwater–surface water interaction are the extent of error in means and spatial distributions of streambed attributes such as ...groundwater seepage rate or solute flux, and the relation of this error to the number and location of point measurements. To investigate these questions, spatially intensive point measurements of five streambed attributes were made in two 63-m long stream reaches in the North Carolina Coastal Plain: hydraulic conductivity (K), hydraulic head gradient between groundwater and stream water (J), nitrate concentration in streambed groundwater (C), and groundwater seepage (v=KJ) and nitrate flux (f=vC) through the streambed. In all, 10 datasets (2 reaches, 5 attributes), each with 54 closely-spaced point values, were created (540-point values in all). For each dataset, subsets of 8- to 40-point values were selected from the 54 available to evaluate the effects of sampling density (the number of point values per reach, or per m2 of streambed) and sampling design (the relative number of point values from the right side, left side, and center of the channel) on the mean and the spatial field of the streambed attribute. Specifically, we evaluated the following as a function of sampling density and sampling design: (1) the likelihood of error in the reach-average value of each streambed attribute, (2) the average magnitude of error and distribution of error in the reach-average value of each attribute, (3) the magnitude of error in the prediction of point values of each attribute, and (4) the geometry of interpolated surfaces of two attributes (K and f). In all cases, “error” in a value or interpolated surface based on a subset of points was taken as a deviation from the corresponding result based on the full dataset of 54 points.
The probability (p) that error did not occur increased with sampling density for each sampling design and attribute in both reaches, though the effect of “diminishing returns” was evident for sampling densities greater than ∼24 points per reach (roughly 0.05–0.06 points per m2 of streambed). Relative to sampling density, sampling design had little effect on values of p. Average error in streambed attributes was generally small (⩽10%) and less than the 95% confidence limits about the reach-average values of the attributes. The ability to estimate unknown point values by interpolation among other point values was poor using both 12- and 36-point subsets, though results suggest the 24 additional known point values (in going from 12 to 36) were helpful in one case in which there was some degree of autocorrelation between the additional known values and the values to be predicted in the interpolation. Visual inspection of 130 contour maps showed that those based on 36-point values were far more realistic in appearance than those based on 12-point values (where the standard for “realistic” appearance was the contour maps based on the full datasets of 54-point values).
Mangroves are encroaching into salt marshes throughout the world as a result of environmental change. Previous studies suggest mangroves trap sediment more efficiently than adjacent salt marshes, ...providing mangroves greater capacity to adapt to sea level rise; this may occur by displacing salt marshes. However, sediment transport in adjacent marsh-mangrove systems and its role in mangrove encroachment upon salt marsh remain poorly understood. Here we directly test the hypothesis that mangroves reduce the ability of adjacent marsh to adjust to sea level rise by measuring sediment transport across salt marsh platforms, with and without 6 m of fringing mangroves at the tidal creek edge. We find that salt marshes and mangroves have equivalent sediment trapping efficiencies along the wetland edge. Suspended sediment concentrations, mass accumulation rates, and long-term accretion rates are not lower in salt marshes landward of mangroves than salt marshes without fringing mangroves. Therefore, our work suggests that a relatively narrow zone of mangroves does not impact salt marsh accretion, and activities that limit mangrove encroachment into salt marsh, such as removal of seedlings, will not improve the capacity of salt marsh to trap sediments.
•The geomorphic impact of mangrove encroachment on an Australian salt marsh.•Investigation of sediment dynamics via high-resolution turbidity monitoring.•Presence of mangroves does not reduce marsh sediment supply or accretion rates.•Removal of mangroves likely a poor management strategy to protect salt marsh.
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