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R. B. Halley

Publications and source records attributed to R. B. Halley.

At least 19 recordsLinked to original sources
USGS2008

Low reservoir ages for the surface ocean from mid-Holocene Florida corals

The 14C reservoir age of the surface ocean was determined for two Holocene periods (4908-4955 and 3008-3066 calendar (cal) B.P.) using U/Th-dated corals from Biscayne National Park, Florida, United States. We found that the average reservoir ages for these two time periods (294 ?? 33 and 291 ?? 27 years, respectively) were lower than the average value between A.D. 1600 and 1900 (390 ?? 60 years) from corals. It appears that the surface ocean was closer to isotopic equilibrium with CO2 in the atmosphere during these two time periods than it was during recent times. Seasonal ??18O measurements from the younger coral are similar to modern values, suggesting that mixing with open ocean waters was indeed occurring during this coral's lifetime. Likely explanations for the lower reservoir age include increased stratification of the surface ocean or increased ??14C values of subsurface waters that mix into the surface. Our results imply that a more correct reservoir age correction for radiocarbon measurements of marine samples in this location from the time periods ???3040 and ???4930 cal years B.P. is ???292 ?? 30 years, less than the canonical value of 404 ?? 20 years. Copyright 2008 by the American Geophysical Union.

Paleoceanography↗
USGS2007

Diurnal variation of oxygen and carbonate system parameters in Tampa Bay and Florida Bay

Oxygen and carbonate system parameters were measured, in situ, over diurnal cycles in Tampa Bay and Florida Bay, Florida. All system parameters showed distinct diurnal trends in Tampa Bay with an average range of diurnal variation of 39.1 μmol kg − 1 for total alkalinity, 165.1 μmol kg − 1 for total CO 2 , 0.22 for pH, 0.093 mmol L − 1 for dissolved oxygen, and 218.1 μatm for pCO 2 . Average range of diurnal variation for system parameters in Tampa Bay was 73% to 93% of the seasonal range of variability for dissolved oxygen and pH. All system parameters measured in Florida Bay showed distinct variation over diurnal time-scales. However, clear diurnal trends were less evident. The average range of diurnal variability in Florida Bay was 62.8 μmol kg − 1 for total alkalinity, 130.4 μmol kg − 1 for total CO 2 , 0.13 for pH, 0.053 mmol L − 1 for dissolved oxygen, and 139.8 μatm for pCO 2 . The average range of diurnal variation was 14% to 102% of the seasonal ranges for these parameters. Diurnal variability in system parameters was most influenced by primary productivity and respiration of benthic communities in Tampa Bay, and by precipitation and dissolution of calcium carbonate in Florida Bay. Our data indicate that use of seasonal data sets without careful consideration of diurnal variability may impart significant error in calculations of annual carbon and oxygen budgets. These observations reinforce the need for higher temporal resolution measurements of oxygen and carbon system parameters in coastal ecosystems.

Florida↗
USGS2006

CO32- concentration and pCO2 thresholds for calcification and dissolution on the Molokai reef flat, Hawaii

The severity of the impact of elevated atmospheric pCO2 to coral reef ecosystems depends, in part, on how sea-water pCO2 affects the balance between calcification and dissolution of carbonate sediments. Presently, there are insufficient published data that relate concentrations of pCO 2 and CO32- to in situ rates of reef calcification in natural settings to accurately predict the impact of elevated atmospheric pCO2 on calcification and dissolution processes. Rates of net calcification and dissolution, CO32- concentrations, and pCO2 were measured, in situ, on patch reefs, bare sand, and coral rubble on the Molokai reef flat in Hawaii. Rates of calcification ranged from 0.03 to 2.30 mmol CaCO3 m-2 h-1 and dissolution ranged from -0.05 to -3.3 mmol CaCO3 m-2 h-1. Calcification and dissolution varied diurnally with net calcification primarily occurring during the day and net dissolution occurring at night. These data were used to calculate threshold values for pCO2 and CO32- at which rates of calcification and dissolution are equivalent. Results indicate that calcification and dissolution are linearly correlated with both CO32- and pCO2. Threshold pCO2 and CO32- values for individual substrate types showed considerable variation. The average pCO2 threshold value for all substrate types was 654??195 ??atm and ranged from 467 to 1003 ??atm. The average CO32- threshold value was 152??24 ??mol kg-1, ranging from 113 to 184 ??mol kg-1. Ambient seawater measurements of pCO2 and CO32- indicate that CO32- and pCO2 threshold values for all substrate types were both exceeded, simultaneously, 13% of the time at present day atmospheric pCO2 concentrations. It is predicted that atmospheric pCO2 will exceed the average pCO2 threshold value for calcification and dissolution on the Molokai reef flat by the year 2100.

Biogeosciences↗
USGS2006

Pulley reef: a deep photosynthetic coral reef on the West Florida Shelf, USA

Pulley Reef (24°50′N, 83°40′W) lies on a submerged late Pleistocene shoreline feature that formed during a sea-level stillstand from 13.8 to 14.5 ka (Jarrett et al. 2005). The reef is currently 60–75 m deep, exhibits 10–60% coral cover, and extends over approximately 160 km2 of the sea floor. Zooxanthellate corals are primarily Agaricia lamarcki, A. fragilis, Leptoseris cucullata, and less common Madracis formosa, M. pharensis, M. decactis, Montastraea cavernosa, Porites divaricata, Scolymia cubensis and Oculina tenella. Coralline algae are comparable in abundance to stony corals. Other macroalgae include Halimeda tuna, Dictyota divaricata, Lobophora variegata, Ventricatri ventricosa, Verdigelas pelas, and Kallymenia sp. Anadyomene menziesii is abundant. The reef provides a habitat for organisms typically observed at much shallower depths, and is the deepest known photosynthetic coral reef on the North America continental shelf (Fig. 1).

Florida↗
USGS2006

Reproducibility of geochemical and climatic signals in the Atlantic coral Montastraea faveolata

Monthly resolved, 41-year-long stable isotopic and elemental ratio time series were generated from two separate heads of Montastraea faveolata from Looe Key, Florida, to assess the fidelity of using geochemical variations in Montastraea, the dominant reef-building coral of the Atlantic, to reconstruct sea surface environmental conditions at this site. The stable isotope time series of the two corals replicate well; mean values of ??18O and ??13C are indistinguishable between cores (compare 0.70??? versus 0.68??? for ??13C and -3.90??? versus - 3.94??? for ??18O). Mean values from the Sr/Ca time series differ by 0.037 mmol/mol, which is outside of analytical error and indicates that nonenvironmental factors are influencing the coral Sr/ Ca records at Looe Key. We have generated significant ?? 18O-sea surface temperature (SST) (R = -0.84) and Sr/ Ca-SST (R = -0.86) calibration equations at Looe Key; however, these equations are different from previously published equations for Montastraea. Variations in growth parameters or kinetic effects are not sufficient to explain either the observed differences in the mean offset between Sr/Ca time series or the disagreement between previous calibrations and our calculated ??18O-SST and Sr/Ca-SST relationships. Calibration differences are most likely due to variations in seawater chemistry in the continentally influenced waters at Looe Key. Additional geochemical replication studies of Montastraea are needed and should include multiple coral heads from open ocean localities complemented whenever possible by seawater chemistry determinations. Copyright 2006 by the American Geophysical Union.

Paleoceanography↗
USGS2006

Northern Florida reef tract benthic metabolism scaled by remote sensing

Holistic rates of excess organic carbon production (E) and calcification for a 0.5 km 2 segment of the backreef platform of the northern Florida reef tract (NFRT) were estimated by combining biotope mapping using remote sensing with community metabolic rates determined with a benthic incubation system. The use of ASTER multispectral satellite imaging for the spatial scaling of benthic metabolic processes resulted in errors in E and net calcification (G) of 48 and 431% respectively, relative to estimates obtained using AISA hyperspectral airborne scanning. At 19 and 125%, the E and G errors relative to the AISA-based estimates were less pronounced for an analysis that used IKONOS multispectral satellite imagery to spatially extrapolate the chamber process measurements. Our scaling analysis indicates that the holistic calcification rate of the backreef platform of the northern Florida reef tract is negligible at 0.07 g CaCO 3 m -2 d -1 . All of the mapped biotopes in this reef zone are net heterotrophic, resulting in an estimated holistic excess production rate of -0.56 g C m -2 d -1 , and an overall gross primary production to respiration ratio of 0.85. Based on our finding of ubiquitous heterotrophy, we infer that the backreef platform of the NFRT is a sink for external inputs of suspended particulate organic matter. Further, our results suggest that the inward advection of inorganic nutrients is not a dominant forcing mechanism for benthic biogeochemical function in the NFRT. We suggest that the degradation of the northern Florida reef tract may parallel the community phase shifts documented within other reef systems polluted by organic detritus.

Florida↗
USGS2005

Strange bedfellows - A deep-water hermatypic coral reef superimposed on a drowned barrier island; Southern Pulley Ridge, SW Florida platform margin

The southeastern component of a subtle ridge feature extending over 200 km along the western ramped margin of the south Florida platform, known as Pulley Ridge, is composed largely of a non-reefal, coastal marine deposit. Modern biostromal reef growth caps southern Pulley Ridge (SPR), making it the deepest hermatypic reef known in American waters. Subsurface ridge strata are layered, lithified, and display a barrier island geomorphology. The deep-water reef community is dominated by platy scleractinian corals, leafy green algae, and coralline algae. Up to 60% live coral cover is observed in 60-75 m of water, although only 1-2% of surface light is available to the reef community. Vertical reef accumulation is thin and did not accompany initial ridge submergence during the most recent sea-level rise. The delayed onset of reef growth likely resulted from several factors influencing Gulf waters during early stages of the last deglaciation (???14 kyr B.P.) including; cold, low-salinity waters derived from discrete meltwater pulses, high-frequency sea-level fluctuations, and the absence of modern oceanic circulation patterns. Currently, reef growth is supported by the Loop Current, the prevailing western boundary current that impinges upon the southwest Florida platform, providing warm, clear, low-nutrient waters to SPR. The rare discovery of a preserved non-reefal lowstand shoreline capped by rich hermatypic deep-reef growth on a tectonically stable continental shelf is significant for both accurate identification of late Quaternary sea-level position and in better constraining controls on the depth limits of hermatypic reefs and their capacity for adaptation to extremely low light levels. ?? 2004 Elsevier B.V. All rights reserved.

Florida↗
USGS2005

GIS compilation of data collected from the Pulley Ridge Deep Coral Reef region

Pulley Ridge is a chain of drowned barrier islands that extends almost 200 km in 60-90 m water depths (Fig. 1). This drowned ridge is located on the Florida Platform in the southeastern Gulf of Mexico about 250 km west of Cape Sable, Florida (Jarrett and others, 2005). These islands formed during the early Holocene marine transgression approximately 12,000 - 14,000 years before present, and were then submerged by sea level rise and preserved near the outer edge of the Florida Platform. The southern portion of Pulley Ridge is the focus of this study. This area hosts zooxanthellate scleractinian corals, green, red and brown macro algae, and a mix of deep and typically shallow-water tropical fishes. This largely photosynthetic community is unique in that it thrives with less than 5% of the light typically associated with shallow-water reefs with similar fauna. Several factors help to account for the existence of this unique deep-water community. First, the underlying drowned barrier islands provide both elevated topography and lithified substrate for the establishment of the hardbottom community. Second, the region is commonly bathed by the Loop Current, which brings relatively clear and warm water to this area. Third, the ridge's position on the continental shelf places it within the thermocline which provides nutrients to the reef during upwelling (Halley and others, 2003). The USGS has made two proposals to resource managers for the designation of marine protected areas based on the geophysical and photographic data in this report. The proposals describe areas that may require some regulatory protection of marine life utilizing the sea floor (Fig. 1). The first proposal is that the area of greatest hermatypic coral cover (Fig. 1) is considered for future management actions and designated a Habitat Area of Particular Concern (HAPC) by the Gulf of Mexico Fishery Management Council. HAPCs are identified on the basis of habitat level considerations: The importance of the ecological function provided by the habitat. The extent to which the habitat is sensitive to human-induced environmental degradation. Whether and to what extent development activities are or will be stressing the habitat. The rarity of the habitat type. The second proposed area is for Coral Essential Fish Habitat (CEFH, Fig. 1). CEFHs are defined as "those waters and substrate necessary to corals for spawning, breeding, feeding, or growth to maturity." The following definitions are provided for clarification: waters is defined as "aquatic areas and their associated physical, chemical, and biological properties that are used by corals" substrate means "sediment, hard bottom, structures underlying the waters, and associated biological communities" necessary means "the habitat required to support a sustainable population and the managed species' contribution to a healthy ecosystem" spawning,breeding, feeding, or growth to maturity covers the full life cycle of a species. The CEFH shown in Figure 1 is the greatest coral cover in the region as determined by the bottom photo and video transects acquired during this study. This report presents the geophysical and photographic data that were collected to describe the surficial and shallow subsurface geologic framework of the area where these deep-water corals are known to occur. The data types include multibeam bathymetry, sidescan-sonar imagery, images of high-resolution seismic-reflection profiles, and bottom photographs. In addition, the tracklines for the seismic data, locations of bottom photographs and camera drifts, and tracklines along which submersible and remotely operated vehicle (ROV) observations were made are contained in the GIS files accompanying this report. Unfortunately, video footage from the camera drifts, submersible, and ROV cruises is not available on this DVD due to the quantity of data. The bottom photograph data set has been previously published (Cross and others, 2004), however it is included in this publication in an effort to integrate the varying data sets in one location. This integration is accomplished through the GIS data included on this DVD.

Florida↗
USGS1999

The influence of seagrass on shell layers and Florida Bay mudbanks

Aerial photography indicates that sometime since the early 1970's, an emergent ridge of shell debris developed on a mudbank north of Calusa Key in Florida Bay. Coarse shell deposits on and within the Bay's shallow mudbanks are believed to be the product of transport during major storm events and subsequent winnowing. However, shell material from the ridge contains nuclear bomb 14C, supporting formation within the past 30 years and the last major hurricanes to influence Florida Bay were Donna and Betsy (1960 and 1965). Results from this study suggest that the Calusa ridge and other coarse shell deposits in Florida Bay can result from, 1) periodic seagrass mortality and wave-induced transport during frequent winter cold fronts and/or 2) mollusc blooms and subsequent burial. A survey of bottom types indicates that dense to intermediate beds of seagrass, mainly Thalassia testudinum (turtle grass), occur within the shallow basins of western Florida Bay and along the margins of Bay mudbanks. Wave measurements and modeling indicate that Thalassia along mudbank margins can reduce incoming wave-energy by over 80%. Seagrass beds also host particularly dense populations of molluscs from periodic 'blooms' and are believed to be the major source of coarse sediments in the Bay. Thus, if bank-edge seagrass dies, sediments, including shell debris, become exposed and subject to greatly increased wave energy. Modeling indicates that winds typical of winter cold fronts in South Florida can produce near-bottom velocities and shear stress at a grass-free bank edge which are sufficient to transport coarse carbonate grains. Shell layers found at depth in mudbank cores can also be explained by previous episodes of sediment accretion over mollusc-rich seagrass beds or grass bed mortality at the edge of a mudbank and shell transport during cold front passage. The latter implies that mortality of marginal seagrass beds has occurred throughout the history of Florida Bay and that the historical influence of hurricanes on sedimentation in the Bay may have been overestimated.

Journal of Coastal Research↗
USGS1995

Preliminary analysis of down-core biotic assemblages Bob Allen Keys, Everglades National Park, Florida Bay

Introduction A series of short piston cores (< 2m) were taken from eleven stations in Florida Bay in May, 1994 by researchers from the U.S. Geological Survey (St. Petersburg, FL., Woods Hole, MA., and Denver CO.) in cooperation with South Florida Water Management District, and the Everglades National Park, and the National Oceanic and Atmospheric Administration (NOAA). Core 6A from Bob Allen Keys (25° 1.391” N, 80°39.41” W) penetrated 172 cm of Holocene sediments in 0.6 m of water on a grass covered mud bank, approximately 1.75 miles (2.82 km) east of the water monitoring station on the southern end of the Bob Allen Keys. Core 6A was sampled for particle size, insoluble residue, water content, loss on ignition, Pb 210 , Rasup>222, and paleontologic analyses. Here we present the results of the preliminary paleontologic analyses of the biotic components from core #6A. The Everglades/Florida Bay ecosystem has formed over the last 5000 years at the southern tip of peninsular Florida. Here it has been influenced by Atlantic, Caribbean and Gulf of Mexico waters, and by tropical and subtropical climatic regimes. This location ensures that over time the ecosystem has undergone climatic changes on both a seasonal and long term basis, and that it has been subjected to many major storms. Additionally, in the last century, the hydrologic regime of the region has been altered profoundly through construction of a canal system to control flooding in southern Florida. This system regulates the timing and amount of freshwater flow into Florida Bay. Recently, algal blooms, seagrass, and sponge die-offs, and declining numbers of shellfish, have been reported in Florida Bay; although it has been assumed that these changes have resulted from human alteration of freshwater flow into the bay, this assumption has not been rigorously tested. The research described here is part of a project designed to examine the history of the Everglades/Florida Bay ecosystem over the last 150 years and to test assumptions of cause and effect. The purpose of the project is two-fold; first, to determine the characteristics of the ecosystem prior to significant human-induced alteration, including the natural range of variation in the ecosystem. This information will establish a baseline for restoration of the system. Second, the project aims to establish the extent, range, and timing of changes to the ecosystem over the last 150 years, and to determine whether these changes correlate with human alteration of the environment, or meteorological patterns, such as precipitation and major storms, or a combination of factors.

Florida↗