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B. F. McPherson

Publications and source records attributed to B. F. McPherson.

At least 19 recordsLinked to original sources
USGS2007

Relationships between wind velocity and underwater irradiance in a shallow lake (Lake Okeechobee, Florida, USA)

ABSTRACT: Relationships between wind velocity and the vertical light attenuation coefficient (K 0 ) were determined at two locations in a large, shallow lake (Lake Okeechobee, Florida, USA). K 0 was significantly correlated with antecedent wind conditions, which explained as much as 90 percent of the daily variation in K 0 . Sub-surface irradiance began to change within 60 to 90 minutes of the time when wind velocity exceeded or dropped below a threshold value. Maximum one hour changes in K 0 were > 50 percent, however, 20 to 30 percent changes were more common. The magnitude of change in K 0 varied spatially based on differences in sediment type. K 0 never exceeded 2.8 at a location where bottom sediments were dominated by a mixture of coarse sand and shells. In comparison, K 0 exceeded 9 during episodic wind events where the bottom sediment was comprised of fine grain mud. Underwater irradiance data can be used to determine threshold wind velocity and account for the influence sediment type has on K 0 . Once a threshold velocity has been established, the frequency, rate, and duration of expected change in underwater irradiance can be evaluated. This is critical information for scientists who are studying algal productivity or other light-related phenomena.

Journal of the American Water Resources Associatio↗
USGS2006

Biogeochemical transport in the Loxahatchee River estuary, Florida: The role of submarine groundwater discharge

The distributions of dissolved organic carbon (DOC), Ba, U, and a suite of naturally occurring radionuclides in the U/Th decay series (222Rn, 223,224,226,228Ra) were studied during high- and low-discharge conditions in the Loxahatchee River estuary, Florida to examine the role of submarine groundwater discharge in estuarine transport. The fresh water endmember of this still relatively pristine estuary may reflect not only river-borne constituents, but also those advected during active groundwater/surface water (hyporheic) exchange. During both discharge conditions, Ba concentrations indicated slight non-conservative mixing. Such Ba excesses could be attributed either to submarine groundwater discharge or particle desorption processes. Estuarine dissolved organic carbon concentrations were highest at salinities closest to zero. Uranium distributions were lowest in the fresh water sites and mixed mostly conservatively with an increase in salinity. Suspended particulate matter (SPM) concentrations were generally lowest (< 5??mg L- 1) close to zero salinity and increased several-fold (??? 18??mg L- 1; low discharge) toward the seaward endmember, which may be attributed to dynamic resuspension of bottom sediments within Jupiter Inlet. Surface water-column 222Rn activities were most elevated (> 28??dpm L- 1) at the freshwater endmember of the estuary and appear to identify regions of the river most influenced by the discharge of fresh groundwater. Activities of four naturally occurring isotopes of Ra (223,224,226,228Ra) in this estuary and select adjacent shallow groundwater wells yield mean estuarine water-mass transit times of less than 1 day; these values are in close agreement to those calculated by tidal prism and tidal frequency. Submarine groundwater discharge rates to the Loxahatchee River estuary were calculated using a tidal prism approach, an excess 226Ra mass balance, and an electromagnetic seepage meter. Average SGD rates ranged from 1.0 to 3.8 ?? 105??m3 d- 1 (20-74??L m- 2 d- 1), depending on river-discharge stage. Such calculated SGD estimates, which must include both a recirculated as well as fresh water component, are in close agreement with results obtained from a first-order watershed mass balance. Average submarine groundwater discharge rates yield NH4+ and PO4- 3 flux estimates to the Loxahatchee River estuary that range from 62.7 to 1063.1 and 69.2 to 378.5????mol m- 2 d- 1, respectively, depending on river stage. SGD-derived nutrient flux rates are compared to yearly computed riverine total N and total P load estimates. ?? 2006 Elsevier B.V. All rights reserved.

Marine Chemistry↗
USGS1995

Modeling photosynthetically active radiation in water of Tampa Bay, Florida, with emphasis on the geometry of incident irradiance

A model is developed that uses a simplified geometric description of incident direct solar beam and diffuse skylight. The model incorporates effects of solar elevation angle and cloudiness on the amount of in-air photosynthetically active radiation (PAR) that passes through the air-water interface and on K0 in waters of relatively low turbidity. The value of K0 was estimated to vary as much as 41% on a clear summer day due to changes in solar elevation angle. The model was used to make estimates of the depth to which sea-grasses might receive adequate light for survival for a range of values of K0. -from Authors

Estuarine, Coastal and Shelf Science↗
USGS1991

Estimating estuarine flushing and residence times in Charlotte Harbor, Florida, via salt balance and a box model

The new concept is that, over many tidal cycles, the tidally averaged "flow' (Qg) of water from the Gulf of Mexico, with a salinity of 35???, can be treated as a constant at any point in the estuary. This flow is used in a simple mixing equation to predict salinity in the estuary at different river inflows, and the predicted salinities are used to compute residence times for water in the estuary. The techniques developed to achieve optimal precision in the relation between river inflow and salinity include a newly derived equation to fit Qg by a least-squares method and a procedure to determine the optimal averaging period for river inflow. Results from Charlotte Harbor indicate that, under average (70 m3s-1) river inflow, 95% of the original water present in the harbor flushes into the gulf in 130 d. -from Authors

Limnology and Oceanography↗
USGS1990

Radium and radon in Charlotte Harbor Estuary, Florida

Radium-226 and 222 Rn activities are greater in the estuarine waters of northern Charlotte Harbor and the lower tidal Peace and Myakka Rivers, Florida, than in either the freshwater reaches of the rivers or waters of the lower estuary and the Gulf of Mexico. The activity of 226 Ra in the tidal rivers increases with decreasing river inflow, with a maximum value of 548 dpm 1001 −1 measured in the tidal Myakka River. The source of the high activity of 226 Ra and 222 Rn is predominantly ground water inflow. Because of the large ground water input, the contribution of 226 Ra from suspended and bottom sediments is a smaller fraction of the total 226 Ra input than in many other estuaries. Although ground water 226 Ra activity in the area varies widely, we estimate that artesian ground water inflow to the tidal rivers is similar in magnitude to the flow of the rivers above the tidal reach during the dry season.

Florida↗
USGS1989

Hydraulic and salinity characteristics of the tidal reach of the Peace River, southwestern Florida

The tidal reach of the Peace River in southwestern Florida extends about 26 miles upstream from Charlotte Harbor and is characterized by flow-direction reversals, low velocities, and salinity gradients that vary with freshwater inflow, tides, and wind. Flow reversals generally occur on each tide throughout most of the tidal reach, their upstream limit determined primarily by freshwater inflow and tide. Flow reversals occur at river mile 18.9 whenever freshwater inflows are less than about 1,000 cu ft/sec. Velocities were less than 0.3 ft/sec more than half the time at river mile 18.9. The volume of the flood and ebb tidal flows in the midreach of the tidal river (mile 11.5) on July 12-13, 1984, was about five times the volume of flood and ebb tidal flow near the upstream end of the tidal reach July 10-11, 1984 (mile 18.9). Salinity varied along the 26-mile river reach, across channel and with depth, depending upon complex patterns of flow, freshwater runoff, wind, tide, and salinity in Charlotte Harbor. Daily variations in salinity increased downstream and variations were larger near the surface than near the bottom. Regression analysis indicated that the location of the 0.5 ppt salinity will move upstream more than 2 river miles if low flows are reduced by 50%. Freshwater flushing of the lower 20-mile tidal reach, approximated from freshwater replacement time, varied from about 2 days during heavy freshwater runoff to 40 days during extreme low flows. (USGS)

Water-Resources Investigations Report↗
USGS1987

The vertical attenuation of light in Charlotte Harbor, a shallow, subtropical estuary, south-western Florida

The relative contribution of different components to the attenuation of photosynthetically active radiation was determined in the Charlotte Harbor estuarine system based on laboratory and in situ measurements. Agreement between laboratory and in situ measurements of the attenuation coefficient ( k t ) was good ( r 2 = 0·92). For all in situ measurements ( n = 100 ), suspended, non-chlorophyll matter accounted for an average of 72% of k t , dissolved matter accounted for 21%, suspended chlorophyll for 4%, and water for the remaining 3%. For individual determinations, suspended non-chlorophyll matter, dissolved matter, suspended chlorophyll, and water, each accounted for as much as 99%, 79%, 21%, and 18% of k t . Attenuation by suspended matter was greatest near the mouth of the northern tidal rivers and was variable over the rest of the estuarine system. Attenuation by dissolved matter was greatest in the brackish tidal rivers and decreased with increasing salinity. Attenuation due to dissolved matter was positively correlated with water color. The source of the color was basin runoff. Wavelength transmittance changed along the salinity gradient. Maximum transmittance shifted from 500 to 600 nm in gulf waters to 650 to 700 nm in colored, brackish waters. Dissolved matter was primarily responsible for the large attenuation at short wavelengths (400–500 nm).

Florida↗
USGS1984

Fouling community of the Loxahatchee River estuary, Florida, 1980-81

Monthly growth of the fouling community at eight test panel sites in the Loxahatchee River Estuary was related to salinity and temperature. Growth was lowest in January 1981 (averaging 23 g per m 2 , dry weight), and increased during spring and early summer with increasing water temperature. Maximum growth occurred during early or midsummer at upstream locations, before river or canal discharge substantially reduced salinity, and in late summer at downstream locations. Growth was greatest at salinities slightly less than that of seawater and decreased at salinities less than about 10‰. Growth was suppressed throughout the estuary in August 1981, probably because of the sudden decrease in temperature and salinity, and perhaps the increase in physical scouring, caused by runoff from Tropical Storm Dennis. Large loads of nutrients transported to the estuary from storm runoff, however, may have subsequently stimulated growth, which increased in September 1981 to the maximum for the year (averaging 683 g per m 2 , dry weight).

Florida↗
USGS1984

Freshwater runoff and salinity distribution in the Loxahatchee River estuary, southeastern Florida, 1980-82

Freshwater mixed with seawater over a distance of 5 to 10 river miles in the Loxahatchee River estuary during a recent study. Large freshwater inflows vertically stratified the estuary and shifted the mixing zone seaward. In the northwest fork of the estuary, the saltwater-freshwater interface moved daily about 0.5 to 1.5 river miles as a result of tides, and annually about 3 to 5 miles as a result of seasonal changes in freshwater inflow. In the southwest fork, saltwater movement upstream was blocked by a gate and dam structure in Canal-18, 4.7 miles upstream from the Atlantic Ocean. Although Canal-18 discharged about one-third of the total freshwater tributary inflow to the estuary, the effects of canal discharge on salinity were limited to relatively brief periods. Much of the time, no freshwater was discharged. (USGS)

Florida↗
USGS1984

Nutrient input from the Loxahatchee River Environmental Control District sewage-treatment plant to the Loxahatchee River Estuary, southeastern Florida

Two test discharges of treated-sewage effluent were made to the Loxahatchee River in February and September 1981 from the ENCON sewage-treatment plant to document nutrient loading and downstream transport of the effluent to the estuary under maximum daily discharge allowable by law (4 million gallons per day). Concentrations of total nitrogen in the effluent exceeded background concentrations by as much as 7 times during the February test, while concentrations of total phosphorus exceeded background concentrations by as much as 112 times during the September test. The effluent was transported downstream to the estuary in less than 24 hours. Discharge of treated sewage effluent to the river-estuary system in the 1981 water year accounted for less than 0.5 percent of the total nitrogen and 8 percent of the total phosphorus discharged from the major tributaries to the estuary. If maximum discharges of effluent (4 million gallons per day) were sustained throughout the year, annual nitrogen loading from the effluent would account for 5 to 18 percent of the total nitrogen input by the major tributaries to the estuary. With maximum discharges of effluent, annual phosphorus loading would exceed the amount of phosphorus input by the major tributaries to the estuary by 54 to 167 percent. (USGS)

Florida↗
USGS1983

Chemical and hydrologic assessment of the Caloosahatchee River basin, Lake Okeechobee to Franklin Lock, Florida

Annual discharge (1970-79 water years) from Lake Okeechobee to the Caloosahatchee River averaged 51 percent of the total river discharge at Franklin Lock and ranged from 10 to 71 percent of total discharge. Excluding rainfall on the river surface and upstream seepage, surface and subsurface runoff from the basin accounted for the remaining total river discharge at Franklin Lock. Nitrogen and phosphorus were in sufficient supply most of the time to support algal growth in the river. During algal blooms, however, nitrite plus nitrate nitrogen was depleted and probably became limiting. Nitrite plus nitrate was the predominant form of inorganic nitrogen in the river and in most tributaries. Average concentrations in the river were 0.18 to 0.21 milligram per liter. Average concentrations in most tributaries were less than those in the river. Average concentrations of total phosphorus in many tributaries fell within the same range as that in the river (0.08 to 0.15 milligram per liter), but some tributaries in the eastern part of the basin had greater average concentrations.

Florida↗