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At least 1,495 records · Page 83Linked to original sources
USGS1997

An optimized network for phosphorus load monitoring for Lake Okeechobee, Florida

Phosphorus load data were evaluated for Lake Okeechobee, Florida, for water years 1982 through 1991. Standard errors for load estimates were computed from available phosphorus concentration and daily discharge data. Components of error were associated with uncertainty in concentration and discharge data and were calculated for existing conditions and for 6 alternative load-monitoring scenarios for each of 48 distinct inflows. Benefit-cost ratios were computed for each alternative monitoring scenario at each site by dividing estimated reductions in load uncertainty by the 5-year average costs of each scenario in 1992 dollars. Absolute and marginal benefit-cost ratios were compared in an iterative optimization scheme to determine the most cost-effective combination of discharge and concentration monitoring scenarios for the lake. If the current (1992) discharge-monitoring network around the lake is maintained, the water-quality sampling at each inflow site twice each year is continued, and the nature of loading remains the same, the standard error of computed mean-annual load is estimated at about 98 metric tons per year compared to an absolute loading rate (inflows and outflows) of 530 metric tons per year. This produces a relative uncertainty of nearly 20 percent. The standard error in load can be reduced to about 20 metric tons per year (4 percent) by adopting an optimized set of monitoring alternatives at a cost of an additional $200,000 per year. The final optimized network prescribes changes to improve both concentration and discharge monitoring. These changes include the addition of intensive sampling with automatic samplers at 11 sites, the initiation of event-based sampling by observers at another 5 sites, the continuation of periodic sampling 12 times per year at 1 site, the installation of acoustic velocity meters to improve discharge gaging at 9 sites, and the improvement of a discharge rating at 1 site.

Florida↗
USGS1997

Geohydrology and simulations of ground-water flow at Verona well field, Battle Creek, Michigan, 1988

Public water supply for the city of Battle Creek, Mich. is withdrawn from the Marshall Sandstone through wells at the Verona well field. Analysis of borehole acoustic televiewer, gamma, and single-point-resistance logs from wells in Bailey Park, near the well field, indicates 12 fracture zones in the Marshall Sandstone. Further interpretation of flow-meter and temperature logs from the same wells indicates that the fracture zones are locally interconnected but appear to remain isolated over a lateral distance of 3,000 feet. Organic chemicals were detected in water samples collected from water-supply wells in the Verona well field in 1981. In 1985, six water-supply wells were converted to purge wells to intercept organic chemicals and divert them from the remaining water-supply wells. Removal of these wells from service resulted in a water-supply shortage. A proposal in which an alternative purge system could be installed so that wells that are out of service may be reactivated was examined. A ground-water-flow model developed for this study indicates that, under the current purge configuration, most water from contaminant-source areas either is captured by purge wells or flows to the Battle Creek River. Some water, however, is captured by three water-supply wells. Model simulations indicate that with the addition of eight purge wells, the well field would be protected from contamination, most water from the contaminant-source areas would be captured by the purge system, and only a small portion would flow to the Battle Creek River. In an effort to augment the city's water supply, the potential for expansion of the Verona well field to the northeast also was investigated. Because of the addition of three municipal wells northeast of the well field, some water from the site of a gasoline spill may be captured by two water-supply wells. Ground water in the area northeast of Verona well field contains significantly lower concentrations of iron, manganese, and calcium carbonate than does water in the existing well field area. However, the Marshall Sandstone in this area has significantly lower transmissivities than those within Verona well field.

Michigan↗
USGS1998

Determining discharge-coefficient ratings for selected coastal control structures in Broward and Palm Beach counties, Florida

Discharges through 10 selected coastal control structures in Broward and Palm Beach Counties, Florida, are presently computed using the theoretical discharge-coefficient ratings developed from scale modeling, theoretical discharge coefficients, and some field calibrations whose accuracies for specific sites are unknown. To achieve more accurate discharge-coefficient ratings for the coastal control structures, field discharge measurements were taken with an Acoustic Doppler Current Profiler at the coastal control structures under a variety of flow conditions. These measurements were used to determine computed discharge-coefficient ratings for the coastal control structures under different flow regimes: submerged orifice flow, submerged weir flow, free orifice flow, and free weir flow. Theoretical and computed discharge-coefficient ratings for submerged orifice and weir flows were determined at seven coastal control structures, and discharge ratings for free orifice and weir flows were determined at three coastal control structures. The difference between the theoretical and computed discharge-coefficient ratings varied from structure to structure. The theoretical and computed discharge coefficient ratings for submerged orifice flow were within 10 percent at four of seven coastal control structures; however, differences greater than 20 percent were found at two of the seven structures. The theoretical and computed discharge-coefficient ratings for submerged weir flow were within 10 percent at three of seven coastal control structures; however, differences greater than 20 percent were found at four of the seven coastal control structures. The difference between theoretical and computed discharge-coefficient ratings for free orifice and free weir flows ranged from 5 to 32 percent. Some differences between the theoretical and computed discharge-coefficient ratings could be better defined with more data collected over a greater distribution of measuring conditions.

Florida↗
USGS1998

Results of borehole geophysical logging and hydraulic tests conducted in Area D supply wells, former U.S. Naval Air Warfare Center, Warminster, Pennsylvania

Borehole geophysical logging, aquifer tests, and aquifer-isolation (packer) tests were conducted in four supply wells at the former U.S. Naval Air Warfare Center (NAWC) in Warminster, PA, to identify the depth and yield of water-bearing zones, occurrence of borehole flow, and effect of pumping on nearby wells. The study was conducted as part of an ongoing evaluation of ground-water contamination at the NAWC. Caliper, natural-gamma, single-point resistance, fluid resistivity, and fluid temperature logs and borehole television surveys were run in the supply wells, which range in depth from 242 to 560 ft (feet). Acoustic borehole televiewer and borehole deviation logs were run in two of the wells. The direction and rate of borehole-fluid movement under non-pumping conditions were measured with a high-resolution heatpulse flowmeter. The logs were used to locate water-bearing fractures, determine probable zones of vertical borehole-fluid movement, and determine the depth to set packers. An aquifer test was conducted in each well to determine open-hole specific capacity and the effect of pumping the open borehole on water levels in nearby wells. Specific capacities ranged from 0.21 to 1.7 (gal/min)/ft (gallons per minute per foot) of drawdown. Aquifer-isolation tests were conducted in each well to determine depth-discrete specific capacities and to determine the effect of pumping an individual fracture or fracture zone on water levels in nearby wells. Specific capacities of individual fractures and fracture zones ranged from 0 to 2.3 (gal/min)/ft. Most fractures identified as water-producing or water-receiving zones by borehole geophysical methods produced water when isolated and pumped. All hydrologically active fractures below 250 ft below land surface were identified as water-receiving zones and produced little water when isolated and pumped. In the two wells greater then 540 ft deep, downward borehole flow to the deep water-receiving fractures is caused by a large difference in head (as much as greater then 49 ft) between water-bearing fractured in the upper and lower part of the borehole. Vertical distribution of specific capacity between land surface and 250 ft below land surface is not related to depth.

Water-Resources Investigations Report↗
USGS2001

Salt-front movement in the Hudson River estuary, New York — Simulations by one-dimensional flow and solute-transport models

The Hudson River is being considered for use as a supplemental source of water supply for New York City during droughts. One proposal entails withdrawal of Hudson River water from locations near Newburgh, Chelsea, or Kingston, but the extent to which this could cause the salt front to advance upstream to points where it could adversely affect community water supplies is unknown. The U.S. Geological Survey (USGS) one-dimensional Branch-Network Dynamic Flow model (BRANCH) was used in conjunction with the USGS one-dimensional Branched Lagrangian Solute-Transport Model (BLTM) to simulate the effect of five water-withdrawal scenarios on the salt-front location. The modeled reach contains 132 miles of the lower Hudson River between the Federal Dam at Troy and Hastings-on-Hudson (near New York City). The BRANCH model was calibrated and verified to 19 tidal-cycle discharge measurements made at 11 locations by conventional and acoustic Doppler current-profiler methods. Maximum measured instantaneous tidal flow ranged from 20,000 ft 3 /s (cubic feet per second) at Albany to 368,000 ft 3 /s at Tellers Point; daily-mean flow at Green Island near Troy ranged from 3,030 ft 3 /s to 45,000 ft 3 /s during the flow measurements. Successive ebb- and flood-flow volumes were measured and compared with computed volumes; daily-mean bias was -1.6 percent (range from -21.0 to +23.7 percent; 13.5 percent mean absolute error). Daily-mean deviation between simulated and measured stage at eight locations (from Bowline Point to Albany) over the 19 tidal-cycle measurements averaged +0.06 ft (range from -0.31 to +0.40 ft; 0.21 ft root mean square error, RMSE). These results indicate that the model can accurately simulate flow in the Hudson River under a wide range of flow, tide, and meteorological conditions. The BLTM was used to simulate chloride transport in the 61-mi reach from Turkey Point to Bowline Point under two seasonal conditions in 1990.one representing spring conditions of high inflow and low salinity (April-June), the other representing typical summer conditions of low inflow and high salinity (July-August). Measured chloride concentrations at Bowline Point were used to drive the BLTM simulations, and data collected at West Point were used for calibration. Mean bias in simulated chloride concentration for the April-June 1990 (high flow) data (observed range from 12 to 201 mg/L [milligrams per liter]; 30 mg/L RMSE) was .16 mg/L, and mean bias for the July-August 1990 (low flow) data (observed range from 31 to 2,000 mg/L; 535 mg/ L RMSE) was +126 mg/L. The salt front (saltwater/ freshwater interface) on the Hudson River was defined as the furthest upstream location where the chloride concentration exceeded 100 mg/L. Data from August 1991 were used to evaluate solute transport between West Point and Poughkeepsie because a chloride concentration of 100 mg/L was not observed at Clinton Point in 1990. The BLTM then was used to simulate chloride concentrations at Chelsea Pump Station and Clinton Point. Regression equations, based on daily mean values of specific conductance measured at West Point, were used to estimate daily mean chloride concentrations at Chelsea Pump Station and Clinton Point for model analysis. Mean biases in BLTM-simulated daily mean chloride concentrations for August 1991 were .38 mg/L at Chelsea Pump Station (range from 189 to 551 mg/L; 103 mg/L RMSE) and .9 mg/L at Clinton Point (range from 53 to 264 mg/L; 62 mg/L RMSE). Hypothetical withdrawals at (1) Newburgh, (2) Chelsea, (3) Chelsea and Newburgh, (4) Chelsea and Kingston, and (5) Kingston and Newburgh, were simulated to compute the effects of withdrawals on salt-front movement. Withdrawals of 300 Mgal/d from any combination of Chelsea or Newburgh could result in upstream movement of the salt front of as much as 1.0 mi, given an initial salt-front location between West Point and Rogers Point. Scenarios that included withdrawals at Kingston caused the greatest upstream salt-front movement. Simulation of a 90-day April-June high-flow period during which discharges at Green Island averaged 25,200 ft 3 /s indicated that withdrawals of 1,939 Mgal/d (million gallons per day) at Chelsea Pump Station would not measureably increase chloride concentrations at Chelsea Pump Station under normal tidal and meteorological conditions, but withdrawals at twice that rate (3,878 Mgal/d) could increase the chloride concentration at Chelsea Pump Station to 250 mg/L.

New York↗
USGS1999

Hydrodynamic measurements in Suisun Bay, California, 1992-93

Sea level, velocity, temperature, and salinity (conductivity and temperature) data collected in Suisun Bay, California, from December 11, 1992, through May 31, 1993, by the U.S. Geological Survey are documented in this report. Sea-level data were collected at four locations and temperature and salinity data were collected at seven locations. Velocity data were collected at three locations using acoustic Doppler current profilers and at four other locations using point velocity meters. Sea-level and velocity data are presented in three forms (1) harmonic analysis results, (2) time-series plots (sea level, current speed, and current direction versus time), and (3) time-series plots of the low-pass filtered data. Temperature and salinity data are presented as plots of raw and low-pass filtered time series. The velocity and salinity data collected during this study document a period when the residual current patterns and salt field were significantly altered by large Delta outflow (three peaks in excess of 2,000 cubic meters per second). Residual current profiles were consistently seaward with magnitudes that fluctuated primarily in concert with Delta outflow and secondarily with the spring-neap tide cycle. The freshwater inputs advected salinity seaward of Suisun Bay for most of this study. Except for a 10-day period at the beginning of the study, dynamically significant salinities (>2) were seaward of Suisun Bay, which resulted in little or no gravitational circulation transport.

Water-Resources Investigations Report↗
USGS1971

Techniques and equipment required for precise stream gaging in tide-affected fresh-water reaches of the Sacramento River, California

Current-meter measurements of high accuracy will be required for calibration of an acoustic flow-metering system proposed for installation in the Sacramento River at Chipps Island in California. This report presents an analysis of the problem of making continuous accurate current-meter measurements in this channel where the flow regime is changing constantly in response to tidal action. Gaging-system requirements are delineated, and a brief description is given of the several applicable techniques that have been developed by others. None of these techniques provides the accuracies required for the flowmeter calibration. A new system is described--one which has been assembled and tested in prototype and which will provide the matrix of data needed for accurate continuous current-meter measurements. Analysis of a large quantity of data on the velocity distribution in the channel of the Sacramento River at Chipps Island shows that adequate definition of the velocity can be made during the dominant flow periods--that is, at times other than slack-water periods--by use of current meters suspended at elevations 0.2 and 0.8 of the depth below the water surface. However, additional velocity surveys will be necessary to determine whether or not small systematic corrections need be applied during periods of rapidly changing flow. In the proposed system all gaged parameters, including velocities, depths, position in the stream, and related times, are monitored continuously as a boat moves across the river on the selected cross section. Data are recorded photographically and transferred later onto punchcards for computer processing. Computer programs have been written to permit computation of instantaneous discharges at any selected time interval throughout the period of the current meter measurement program. It is anticipated that current-meter traverses will be made at intervals of about one-half hour over periods of several days. Capability of performance for protracted periods was, consequently, one of the important elements in system design. Analysis of error sources in the proposed system indicates that errors in individual computed discharges can be kept smaller than 1.5 percent if the expected precision in all measured parameters is maintained.

Water Supply Paper↗
USGS2011

Nocturnal activity patterns of northern myotis (Myotis septentrionalis) during the maternity season in West Virginia (USA)

Nocturnal activity patterns of northern myotis (Myotis septentrionalis) at diurnal roost trees remain largely uninvestigated. For example, the influence of reproductive status, weather, and roost tree and surrounding habitat characteristics on timing of emergence, intra-night activity, and entrance at their roost trees is poorly known. We examined nocturnal activity patterns of northern myotis maternity colonies during pregnancy and lactation at diurnal roost trees situated in areas that were and were not subjected to recent prescribed fires at the Fernow Experimental Forest, West Virginia from 2007 to 2009. According to exit counts and acoustic data, northern myotis colony sizes were similar between reproductive periods and roost tree settings. However, intra-night activity patterns differed slightly between reproductive periods and roost trees in burned and non-burned areas. Weather variables poorly explained variation in activity patterns during pregnancy, but precipitation and temperature were negatively associated with activity patterns during lactation. ?? Museum and Institute of Zoology PAS.

Acta Chiropterologica↗
USGS2015

Dim ultraviolet light as a means of deterring activity by the Hawaiian hoary bat Lasiurus cinereus semotus

Widespread bat fatalities at industrial wind turbines are a conservation issue with the potential to inhibit efficient use of an abundant source of energy. Bat fatalities can be reduced by altering turbine operations, but such curtailment decreases turbine efficiency. If additional ways of reducing bat fatalities at wind turbines were available such tradeoffs might not be needed. Based on the facts that bats perceive distant objects primarily through vision and can see in very dim lighting conditions, and the possibility that bats might interact with turbines after approaching them as they would trees, we propose a novel method of reducing bat activity at wind turbines: illumination of the structure with dim light. As a first step toward assessing this approach, we illuminated trees with dim flickering ultraviolet (UV) light in areas frequented by Hawaiian hoary bats Lasiurus cinereus semotus , an endangered subspecies affected by wind turbines. We used a repeated-measures design to quantify bat activity near trees with acoustic detectors and thermal video cameras in the presence and absence of UV illumination, while concurrently monitoring insect numbers. Results indicate that dim UV reduces bat activity despite an increase in insect numbers. Experimental treatment did not completely inhibit bat activity near trees, nor did all measures of bat activity show statistically significant differences due to high variance in bat activity among sites. However, the observed decreases in bat activity with dim UV illumination justify further testing of this method as a means to reduce bat fatalities at wind turbines.

Hawaii↗
USGS2017

Potential for spatial displacement of Cook Inlet beluga whales by anthropogenic noise in critical habitat

The population of beluga whales in Cook Inlet, Alaska, USA, declined by nearly half in the mid-1990s, primarily from an unsustainable harvest, and was listed as endangered in 2008. In 2014, abundance was ~340 whales, and the population trend during 1999-2014 was -1.3% yr -1 . Cook Inlet beluga whales are particularly vulnerable to anthropogenic impacts, and noise that has the potential to reduce communication and echolocation range considerably has been documented in critical habitat; thus, noise was ranked as a high potential threat in the Cook Inlet beluga Recovery Plan. The current recovery strategy includes research on effects of threats potentially limiting recovery, and thus we examined the potential impact of anthropogenic noise in critical habitat, specifically, spatial displacement. Using a subset of data on anthropogenic noise and beluga detections from a 5 yr acoustic study, we evaluated the influence of noise events on beluga occupancy probability. We used occupancy models, which account for factors that affect detection probability when estimating occupancy, the first application of these models to examine the potential impacts of anthropogenic noise on marine mammal behavior. Results were inconclusive, primarily because beluga detections were relatively infrequent. Even though noise metrics (sound pressure level and noise duration) appeared in high-ranking models as covariates for occupancy probability, the data were insufficient to indicate better predictive ability beyond those models that only included environmental covariates. Future studies that implement protocols designed specifically for beluga occupancy will be most effective for accurately estimating the effect of noise on beluga displacement.

Alaska↗
USGS2024

Widespread occupancy of the endangered northern myotis on northeastern Atlantic Coastal Plain islands

Northern myotis Myotis septentrionalis are one of the bat species most affected by white-nose syndrome (WNS), and disease-induced declines may cause compounding effects when combined with other threats such as habitat loss and fragmentation. Recent evidence suggests that peripheral populations are persisting in post-WNS years; however, the environmental factors that influence the occurrence of this species along the Atlantic Coastal Plain are virtually unknown. We conducted a large-scale acoustic survey on 3 islands: Long Island, New York, and Martha’s Vineyard and Nantucket, Massachusetts, USA, and used a multi-scale occupancy modeling approach to determine the landscape and abiotic factors affecting the distribution of northern myotis. Our estimates of occupancy and detection probability suggest widespread presence across the islands. At the local (200 m) scale, we identified strong negative effects of development on Long Island and Nantucket and a strong positive effect of forest habitat on Martha’s Vineyard. None of the variables we measured sufficiently explained the landscape (1 km 2 ) occupancy of this species, which was very high (ψ = 0.81–0.97), representing an outlier for this species in the post-WNS landscape. The lack of association at the landscape scale suggests that general differences in land cover are not a driving factor of higher occupancy of peripheral northern myotis populations, while local site- specific conditions may be supporting critical foraging or roosting habitat. Because islands are particularly vulnerable to human-driven habitat alteration due to the constraint of limited space, and development pressure is expected to increase, this study provides a baseline to enable managers to assess the effects of future environmental disturbances and monitor population trends to support long-term survival of northern myotis.

Massachusetts, New York↗
USGS2025

New insights reveal a temporally distinct two-stock genetic structure for Suwannee River Gulf sturgeon

Understanding population genetic structure and patterns of gene flow is important for effective decision making and the preservation of genetic diversity, especially when managing protected species. Historically, Gulf sturgeon have been managed by river system, with early evidence supporting spatially distinct genetic structure across 7 natal populations. However, an increasing number of studies recognize that some rivers possess 2 genetically distinct sturgeon stocks residing within the same drainage. This, combined with evidence of both spring and fall spawning events within these drainages, suggests the distinction between these stocks may be temporally mediated, as similarly exhibited by the closely related Atlantic sturgeon. We analyzed the movements of 136 Gulf sturgeon within the Suwannee River, Florida, USA, between 2008 and 2022 using acoustic telemetry. We assessed migratory patterns and presence within known spawning habitat to categorize individuals as exhibiting either spring, fall, or unknown spawning behaviors each year. These individuals were also genotyped for 14 microsatellite loci to assign them to a genetic group. Our results reinforce previous work suggesting the presence of 2 genetically distinct stocks in the Suwannee River and indicate this genetic structure is driven by fidelity to temporally distinct spawning events, with one stock spawning in the spring and the other in fall. The delineation of these 2 sympatric stocks, historically managed as one, has management implications for the recovery of this species.

Florida, Georgia↗
USGS2026

Resource selection for an endangered flying squirrel, Glaucomys sabrinus coloratus, in a montane sky-island system

Geographically isolated endemic species and their habitats in montane systems face stressors of rapid climate change as well as legacy and contemporary land use change. In the case of endangered species in fragmented terrestrial montane habitats, effectively sky-islands, insight into habitat use and resource selection is vital for effective conservation measures. We created a resource selection function using a long-term dataset of multiple monitoring techniques (live-trapping, radio-telemetry, camera traps, acoustic detectors, and nest boxes) across a wide geographical range for an endangered subspecies, the Carolina northern flying squirrel Glaucomys sabrinus coloratus , in a vulnerable high-elevation sky-island boreal forest ecosystem in the southeastern USA. Using fine-scale habitat and topographic coverage on 8 sky-islands, we employed various models to capture nuanced habitat relationships that can better inform the conservation of remaining subpopulations as well as other endemic species that share their habitat. Our analyses confirmed that red spruce Picea rubens -Fraser fir Abies fraseri was the most significant habitat component for determining Carolina northern flying squirrel presence, but that relationships varied somewhat among sky-islands owing to differences in extent, elevation range, and forest community configurations. Further, we found that solely using nest boxes, as previously reported, to create a resource selection function biased the results, but that nest boxes remain an effective tool for overcoming habitat fragmentation and decreasing exposure to antagonistic species.

North Carolina, Tennessee, Virginia↗
USGS2012

Home range, habitat use, and migrations of hawksbill turtles tracked from Dry Tortugas National Park, Florida, USA

To determine habitat-use patterns of sub-adult hawksbills Eretmochelys imbricata , we conducted satellite- and acoustic-tracking of 3 turtles captured in August 2008 within Dry Tortugas National Park (DRTO), south Florida, USA, in the Gulf of Mexico; turtles ranged in size from 51.9 to 69.8 cm straight carapace length. After 263, 699, and 655 d of residence in the park, turtles migrated out of the DRTO. Within the park, core-use areas (i.e. 50% kernel density estimates) were 9.2 to 21.5 km 2 ; all 3 turtle core-use areas overlapped in an area 6.1 km 2 within a zone of the park with multiple human uses (e.g. fishing, anchoring). Two turtles migrated to Cuba and ceased transmitting after 320 and 687 tracking days; the third turtle migrated toward Key West, Florida, and ceased transmitting after 884 tracking days. The present study highlights previously unknown regional connections for hawksbills, possible turtle-harvest incidents, and fine-scale habitat use of sub-adult hawksbills within a United States National Park.

Florida↗
USGS2019

Confluences function as ecological hotspots: Geomorphic and regional drivers can help identify patterns of fish distribution within a seascape

Quantifying heterogeneity in animal distributions through space and time is a precursor to addressing many important research and management issues. Obtaining these distributional data is especially difficult for mobile organisms that use broader geographic extents. Here, we asked if the merger between 2 research directions—(1) quantifying spatial linkages between fish and geomorphic features (e.g. confluences) and (2) analyzing larger-scale, multi-metric organismal patterns—can provide a broader geographic context for ecological issues that depend on understanding dynamic fish distribution. To address these objectives, we collected data from 59 tagged striped bass Morone saxatilis that were detected by a 26 acoustic receiver array deployed within Plum Island Estuary, MA, USA. We examined these telemetry data using generalized linear mixed models and chi-squared, cluster, and network analyses. Geomorphic site types informed the estuary-wide distribution of striped bass in that tagged fish spent the most time at confluence junctions; however, they did not spend the same amount of time at all junctions. Relative to integrating multiple metrics, number of tagged fish, residence time, and number of movements were not the same across all receivers. When all 3 metrics were considered together, 4 distinct clusters of distributional patterns emerged. Network analyses connected geomorphology and multi-metric seascape patterns. Confluence junctions in the Rowley and Middle regions were the most connected (high centrality) and most used sites (high residence time). Although confluence junctions function as ecological hotspots, researchers and managers will benefit from interpreting geomorphology within a larger geographic context.

Massachusetts↗
USGS2005

Tidal and seasonal effects on transport of pink shrimp postlarvae

Transport simulations were conducted to investigate a large seasonal peak in postlarvae of the pink shrimp Farfantepenaeus duorarum that occurs every summer on the northwestern border of Florida Bay. Daily vertical migration, a known behavior in pink shrimp postlarvae, was assumed in all scenarios investigated. A Lagrangian trajectory model was developed using a current field derived from a 3 yr ADCP (Acoustic Doppler Current Profiler) time series. To fit the estimated planktonic development time of pink shrimp, the model simulated larvae traveling at night over a 30 d period. We investigated 2 types of effects: (1) the effect of mismatch periodicity between tidal constituents and daily migration, and (2) the effect of seasonal changes in night length. The maximum eastward displacement with the semidiurnal lunar tidal constituent (M2) was 4 km, with periods of enhanced transport in both summer and winter. In contrast, eastward displacement with the semidiurnal solar tidal constituent (S2) and the lunisolar diurnal K1 was 65 km and the period of maximum distance occurred in summer every year. Because the periods of S2 and K1 are so close to the 24 h vertical migration period, and the eastward current (flood) of these constituents matches the diel cycle over extended intervals, they can induce strong horizontal transport during summer. Thus, diel vertical migration can interact with the S2 and the K1 tidal constituents and with the annual cycle of night length to produce a distinct annual cycle that may enhance transport of pink shrimp and other coastal species during summer in shallow areas of the Gulf of Mexico. ?? Inter-Research 2005.

Marine Ecology Progress Series↗
USGS2018

Bat activity following restoration prescribed burning in the central Appalachian Upland and riparian habitats

After decades of fire suppression in eastern North America, land managers now are prioritizing prescribed fire as a management tool to restore or maintain fire-adapted vegetation communities. However, in long—fire-suppressed landscapes, such as the central and southern Appalachians, it is unknown how bats will respond to prescribed fire in both riparian and upland forest habitats. To address these concerns, we conducted zero-crossing acoustic surveys of bat activity in burned, unburned, riparian, and non-riparian areas in the central Appalachians, Virginia, USA. Burn and riparian variables had model support (ΔAICc < 4) to explain activity of all bat species. Nonetheless, parameter estimates for these conditions were small and confidence intervals overlapped zero for all species, indicating effect sizes were marginal. Our results suggest that bats respond to fire differently between upland and riparian forest habitats, but overall, large landscape-level prescribed fire has a slightly positive to neutral impact on all bats species identified at our study site post—fire application.

Virginia↗
USGS2019

Hydroacoustic, meteorologic and seismic observations of the 2016 Nansen Ice Shelf calving event and iceberg formation

On 7 April 2016, the Nansen Ice Shelf (NIS) front calved into two icebergs, the first large-scale calving event in >30 years. Three hydrophone moorings were deployed seaward of the NIS in December 2015 and over the following months recorded hundreds of short duration, broadband (10-400 Hz) cryogenic signals, likely caused by fracturing of the ice-shelf. The majority of these icequakes occur between January and early March 2016, several weeks prior to the calving observed by satellite on 7 April. Barometric pressure and wind speed records show the day the icebergs drifted from the NIS coincided with the largest low-pressure storm system recorded in the previous 7 months. A nearby seismic station also shows an increase in low-frequency energy, harmonic tremor, and microseisms on 7 April. Our interpretation is the northern segment of the NIS leading edge broke free during mid-January to February, producing high acoustic energy, but the icebergs remained stationary until the combination of a strong low-pressure system, with high winds freed the icebergs. As the unpinning of Antarctic ice shelves is not a well-documented process, our observations show that storm systems may play an under-appreciated role in Antarctic ice shelf break-up.

Frontiers in Earth Science↗