Northern Bahamas Research Articles

Reproductive biology of wahoo, Acanthocybium solandri, from the Atlantic coast of Florida and the Bahamas

Despite its economic importance to many coastal nations, assessments of wahoo, Acanthocybium solandri, are hampered by a lack of basic life history information. In this study, wahoo were collected from Florida’s Atlantic coast and the northern Bahamas during 1997–2006 to examine reproductive seasonality, maturation, spawning frequency and fecundity. These samples demonstrated only a single, summer-spawning season, which did not support earlier postulations of spring spawning by wahoo near the Bahamas. The size and age at 50% female maturity were 925 mm fork length and 0.64 years, respectively. Spawning frequency was, on average, every 5 days during June–August, but 13% of mature females were inactive during this period. Batch fecundity was positively correlated with fish size, and varied between 0.44 and 1.67 million eggs. Parasites, previously unreported to occur in wahoo gonads and identified only as philometrid nematodes, were evident in 11% of these females. Most parasitised fish had vitellogenic oocytes, several even with oocytes with migrating nuclei or post-ovulatory follicles, so these parasitised fish were capable of spawning. Although wahoo have been noted to have relatively small gonads, and parasites are often found in female gonads, annual fecundity estimates are of the order of 10–100 million eggs. The significant contribution of older, larger females to egg production should be considered in managing this fishery.

Interactions Between Tidal Flows and Ooid Shoals, Northern Bahamas

Abstract Oolitic strata are common through the geologic record. Ooids generally form in high-energy environments, but it remains unclear how ooids remain in such systems and form geomorphic features such as bars and shoals. Integrating remote sensing, hydrodynamic, bathymetric, granulometric, and field observations of modern tidal systems in the Bahamas provides insight into this fundamental question. Oolitic tidal sands in the northern Abacos display a geomorphic pattern in which bedrock islands restrict and focus tidal flow down a main channel. Within the channel, a shallow shoal separates an ebb-dominated subchannel from a flood-dominated subchannel. Tidal velocities in these subchannels can exceed 1 m/s, enough to transport the oolitic sediments. Hydrodynamics and bathymetry in these subchannels produce a net circular hydrodynamic pattern around the shoal (the spin cycle), allowing the sands to remain in motion without being transported out of the ooid factory. This general pattern is apparent in several other ooid shoal complexes. This concept provides integrated insights into the physical influences impacting the formation, suspension, transport, and deposition of ooids and the resulting geomorphic forms. These results represent first steps toward developing more comprehensive and predictive analogs of spatial heterogeneity in ancient tidally dominated oolitic shoals.

Seabird Nesting and Conservation in the Northern Bahamas

Seabirds and other colonial waterbirds nesting in the northern Bahamas are nearly undocumented. This study is the first complete inventory of seabirds and other colonial waterbirds nesting in the northern Bahamas (including the islands of the Abacos, Grand Bahamas, Biminis, and Berries). The survey found 20,267 nests of 19 species of seabirds and other colonial waterbirds at 113 colony sites. The over 40,000 seabirds and other colonial waterbirds found nesting in the northern Bahamas doubles population estimates previously published for The Bahamas as a whole, which included few of these sites. Sooty Tern (Sterna fuscata) was the most abundant species, having a nesting population of over 10,000 pairs. Next most abundant were the Bridled Tern (Sterna anaethetus), Laughing Gull (Larus atricilla), and Brown Noddy (Sterna stolidus). This paper documents the first nesting record in the Commonwealth of The Bahamas of the White Ibis (Eudocimus albus), the first recent nesting in northern Bahamas of the Magnificent Frigatebird (Fregatta magnificens), and the first recent nesting in Grand Bahama of the Brown Pelican (Pelecanus occidentalis). Based on the results, 27 sites may be recognized as of special importance to seabird conservation in the northern Bahamas. Opportunities for conservation, including community-based colony site stewardship and protection of the most important sites within twelve protected areas are discussed.

Species assemblages of leptocephali in the southwestern Sargasso Sea

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 344:197-212 (2007) - DOI: https://doi.org/10.3354/meps06923 Species assemblages of leptocephali in the southwestern Sargasso Sea Michael J. Miller1,*, James D. McCleave2 1Ocean Research Institute, University of Tokyo, Minamidai, Nakano, Tokyo 164-8639, Japan 2School of Marine Sciences, University of Maine, Orono, Maine 04469, USA *Email: miller@ori.u-tokyo.ac.jp ABSTRACT: Catches of leptocephali of shelf and slope marine eels of the Chlopsidae, Congridae, Moringuidae, Muraenidae, and Ophichthidae collected during a survey in the southwestern Sargasso Sea in late September and early October 1984 were analyzed to learn about their reproductive ecology and larval transport. Sampling along a transect from the Florida Current (FC) out across the southwestern Sargasso Sea and in the Northwest Providence Channel (NWPC) of the Northern Bahamas enabled the evaluation of the larval distributions, abundances and size ranges, regional assemblage structure, and the apparent spawning areas of these marine eels. Distinctly different assemblages observed in the FC and NWPC included the congrid genera Heteroconger, Paraconger, Uroconger, and many ophichthid species, which were rare or absent offshore. Other taxa of congrids, chlopsids, muraenids and moringuids were present in all areas, but the smallest specimens of most taxa were only caught at the NWPC or FC stations. Multivariate analyses reflected higher richness and abundance in the FC and NWPC and also similar species compositions in offshore areas. The patterns of distribution of these leptocephali differed from those of anguillid, nettastomatid, and mesopelagic eel leptocephali collected in the same survey. These findings support the hypothesis that most taxa of marine eels spawn close to their adult habitats, and indicate that despite high biodiversity of marine eels in the Northern Bahamas, only some species of leptocephali appear to get transported far offshore by ocean currents. KEY WORDS: Leptocephali · Larval distribution · Marine eels · Spawning area · Sargasso Sea · Northern Bahamas · Florida Current Full text in pdf format PreviousNextCite this article as: Miller MJ, McCleave JD (2007) Species assemblages of leptocephali in the southwestern Sargasso Sea. Mar Ecol Prog Ser 344:197-212. https://doi.org/10.3354/meps06923 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 344. Online publication date: August 23, 2007 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2007 Inter-Research.

Geochemistry of meteoric diagenesis in carbonate islands of the northern Bahamas: 1. Evidence from field studies

AbstractProcesses driving carbonate diagenesis in islands of the northern Bahamas are investigated using major ion, dissolved oxygen and dissolved organic carbon analyses of water samples from surface and ground waters, and measurements of soil gas P. Meteoric waters equilibrate with aragonite, but reactions are water controlled rather than mineral‐controlled and drive dissolution rather than concurrent precipitation of calcite. Surface runoff waters equilibrate with atmospheric P and rapidly recharge the vadose zone, limiting subaerial bedrock dissolution to only 6·6–15 mg l−1 Ca. P of soil gas measured in the summer wet season ((7·4 ± 3·7) × 10−3 atm) is elevated compared with that of the atmosphere, despite the thin skeletal organic nature of the soil and the discontinuous soil cover. Soil waters retained in surface pockets are equilibrated with respect to aragonite and have dissolved 51 ± 19 mg l−1 Ca. This is substantially less than the 93 ± 18 mg l−1 Ca in samples from pumping boreholes that sample meteoric waters from the freshwater lens. The high P of the freshwater lens ((16 ± 8·3) × 10−3 atm for pumping boreholes) suggests that significant additional CO2 may be derived by oxidation of soil‐ and surface‐derived organic carbon within the lens. The suboxic nature of the majority of the freshwater lens and the observed depletion in sulphate support this suggestion, and indicate that both aerobic and anaerobic oxidation may take place. Shallow lens samples from observation boreholes are calcite supersaturated and have a lower P than deeper lens waters, indicating that CO2 degasses from the water table, driving precipitation of calcite cements. We suggest that the geochemical evolution of waters in the vadose zone and upper part of the freshwater lens may be determined by the presence of a body of ground air with P controlled by production in the freshwater lens and soil and by degassing to the atmosphere. Copyright © 2007 John Wiley & Sons, Ltd.

Geochemistry of meteoric diagenesis in carbonate islands of the northern Bahamas: 2. Geochemical modelling and budgeting of diagenesis

AbstractGeochemical characterization and numerical modelling of surface water and ground water, combined with hydrological observations, provide quantitative estimates of meteoric diagenesis in Pleistocene carbonates of the northern Bahamas.Meteoric waters equilibrate with aragonite, but water‐ rather than mineral‐controlled reactions dominate. Dissolutional lowering of the undifferentiated bedrock surface is an order of magnitude slower than that within soil‐filled topographic hollows, generating small‐scale relief at a rate of 65–140 mm ka−1 and a distinctive pocketed topography. Oxidation of organic matter within the subsoil and vadose zones generates an average P of 4·0 × 10−3 atm, which drives dissolution during vadose percolation and/or at the water table. However, these dissolution processes together account for <60% of the average rock‐derived calcium in groundwaters pumped from the freshwater lens. The additional calcium may derive from oxidation of organic carbon within the lens, accounting for the high P of the lens waters. Mixing between meteoric waters of differing chemistry is diagenetically insignificant, but evapotranspiration from the shallow water table is an important drive for subsurface cementation.Porosity generation in the shallow vadose zone averages 1·6–3·2% ka−1. Phreatic meteoric diagenesis is focused near the water table, where dissolution generates porosity at 1·4–2·8% ka−1. Maximum dissolution rates, however, are similar to those of evaporation‐driven precipitation, which occludes porosity of 4·0 ± 0·6% ka−1. This drives porosity inversion, from primary interparticle to secondary mouldic, vug and channel porosity. In the deeper freshwater lens, oxidation of residual organic carbon and reoxidation of reduced sulphur species from deeper anaerobic oxidation of organic carbon may generate porosity up to 0·06% ka−1.Meteoric diagenesis relies critically on hydrological routing and vadose thickness (controlled by sea level), as well as the geochemical processes active. A thin vadose zone permits direct evaporation from the water table and drives precipitation of meteoric phreatic cements even where mineral stabilization is complete. Copyright © 2007 John Wiley & Sons, Ltd.

POPULATION GENETIC STRUCTURE OF COASTAL BOTTLENOSE DOLPHINS (TURSIOPS TRUNCATUS) IN THE NORTHERN BAHAMAS

AbstractPopulation substructure has important implications for a species' ecology and evolution. As such, knowledge of this structuring is critical for the conservation and management of natural populations. Among marine mammals, many examples exist of species that enjoy a broad geographical distribution, yet are characterized by fine‐scale population subdivisions. Coastal bottlenose dolphins have been studied extensively in a few regions globally, and these studies have highlighted a great diversity in both social strategies and demographic isolation. Here we use molecular genetic markers to examine the degree of population subdivision among three study sites separated by less than 250 km on Little Bahama Bank in the northern Bahamas. Mitochondrial DNA (mtDNA) sequence variation and microsatellite genotypes were used to assess partitioning of genetic variance among 56 individually recognized coastal ecotype bottlenose dolphins. Although resolved levels of genetic differentiation suggest gene flow among the three study sites, both nuclear and mitochondrial data indicate a significant degree of subdivision within the Little Bahama Bank population, and sex‐based analyses suggest that patterns of dispersal may not be strictly biased toward males. These results corroborate the site fidelity documented through long‐term photo‐identification studies in the NE Bahamas, and highlight the need to consider independent subpopulation units for the conservation and management of coastal bottlenose dolphins in the Bahamas.

Health Assessment of Allen Cays Rock Iguana, Cyclura cychlura inornata

ABSTRACT The Allen Cays rock iguana, Cyclura cychlura inornata, though endangered, has stable and natural populations in the Allen Cays, in the Exuma Islands of the northern Bahamas. Thirty-seven animals (20 male and 17 female) were sampled during a long-term mark and recapture study in May 2004. Complete blood counts were performed on 18 animals and plasma biochemical analyses were performed on all 37 animals. Results of hematologic and plasma biochemical analyses for all animals showed that male Cyclura cychlura inornata had significantly lower levels of aspartate aminotransferase than female Cyclura cychlura inornata. Fecal parasite screens were completed on six animals and fecal cultures were performed on 17 animals. Oxyurid sp. were found in four of six fecal samples, and multiple bacteria, including Salmonella spp., were isolated from cloacal cultures.

Habitat utilization by Blainville’s beaked whales off Great Abaco, northern Bahamas, in relation to seabed topography

We investigated habitat utilization in Blainville’s beaked whale, Mesoplodon densirostris, in the northern Bahamas and, as such, this is the first analysis of fine-scale habitat utilization of any member of the genus Mesoplodon. We divided the area into 500×500 m grid squares and each square was assigned a classification for presence or absence of Blainville’s beaked whales, along with details of water depth, seabed gradient and seabed aspect. All squares where Blainville’s beaked whales occurred had gradients from 68 to 296 m/km and depths from 136 to 1,319 m and most faced northeast compared with 0–526 m/km, 10–3,000 m and all aspects for the whole study area. Generalized additive models and classification trees indicated that, in order of importance, aspect, gradient and depth were related to occurrence of Blainville’s beaked whales within the study area. We hypothesize that the relationships between habitat utilization and these topographic variables relates to the effects of interactions between a deepwater current and the seabed topography on preferred prey. Locally, prey animals may be concentrated in areas with a northeast aspect, intermediate gradients and depths between 200 and 1,000 m where the Deep Western Boundary Current is forced towards the surface by the local topography. These are the areas where Blainville’s beaked whales preferentially occurred.

Diversity, relative density and structure of the cetacean community in summer months east of Great Abaco, Bahamas

Little is known about cetacean communities in the tropical and sub-tropical Atlantic. This paper describes the cetacean community found east of Great Abaco in the northern Bahamas (26·5°N) during summer months between 1998 and 2001. Nine species of cetaceans were recorded, which could be divided into two distinct groupings: firstly, ‘permanent’ species, which had relative sightings rates between 0·026–0·084 sightings per hour and which were recorded on many occasions in all years and most months; secondly, ‘sporadic’ species, which had relative sightings rates an order of magnitude lower (0·004–0·008 sightings per hour) and which were recorded on very few occasions. The ‘permanent’ species were the Stenella frontalis (Atlantic spotted dolphin), Kogia simus (the dwarf sperm whale), Mesoplodon densirostris (Blainville's beaked whale) and Ziphius cavirostris (Cuvier's beaked whale). These four species differed significantly in the depth of grid squares utilized (χ=20·25, df=9, P<0·01) suggesting that these species occupied four separate niches. Stenella frontalis dominated the surface feeding niche, while the remaining three deep-diving species segregated into different depth ranges. Kogia simus was the dominant species in water depths of less than 200 m, M. densirostris in water depths of 200 to 1000 m and Z. cavirostris in water depths of greater than 1000 m. The overall relative density (2·533 individuals per hour of effort) and diversity of species in the study area was relatively low and may relate to low levels of local productivity. It is hypothesized that the four ‘permanent’ species may competitively exclude ecologically similar species, resulting in a reduced number of species and that ‘sporadic’ species may only enter the study area during times of higher than usual productivity when the ‘permanent’ species are no longer able to dominate their individual niches.

Variable ecological effects of hurricanes: the importance of seasonal timing for survival of lizards on Bahamian islands.

Two recent hurricanes passed directly over the northern Bahamas 2 years apart, allowing a comparison of their effects on lizard populations inhabiting exactly the same islands. The hurricanes differed in two ways: one struck during the reproductive season and was relatively severe; the other struck after most reproduction had taken place and was milder. The late-season hurricane produced a significant relation between population reduction and lowness of the island that lasted at least through two seasons; the earlier hurricane produced no such relationship. The late-season hurricane wiped out populations of lizards on two islands (two of the three lowest) that the earlier hurricane failed to exterminate even though it was stronger. We relate these effects to the fact that the study lizards regenerated from the earlier hurricane only via the egg stage, whereas eggs were unavailable when the later storm struck and regeneration was via hatched lizards. We discriminate and illustrate four kinds of hurricanes, cross-classified by two contrasts: earlier vs. later and stronger vs. weaker. A later, stronger hurricane completely exterminated lizard populations at a second Bahamian site, whereas an earlier, weaker hurricane had no detectable effect at a third Bahamian site. We suggest that, in addition to severity, the timing of a hurricane as it coincides with reproductive scheduling or other phenological aspects may determine the magnitude of its effect on a variety of organisms.

Patterns of intraspecific diversification in the Piriqueta caroliniana complex in southeastern North America and the Bahamas.

We use chloroplast DNA (cpDNA) variation and nested clade phylogeographic analyses to infer the historical processes that have contributed to the high level of morphological and ecological diversification present in a group of herbaceous perennials (the Piriqueta caroliniana complex) in North America and the Bahamas. The presence of morphologically distinct and intercompatible varieties (morphotypes) that can be distinguished based on suites of taxonomic characters (e.g., leaf shape, pubescence type, stature) and contrasting habitat affinities (from marshes to dry pinelands and sand scrub) makes this group particularly appropriate for studies of intraspecific diversification. To examine the distribution of haplotypes among populations, we sampled 467 individuals from 55 locations in Florida, Georgia, and the northern Bahamas (Grand Bahama and Abaco) and screened each individual for cpDNA variation using restriction fragment length polymorphism (RFLP) and heteroduplex analyses. We develop a one-step haplotype phylogeny for this group and use the geographic distributions of haplotypes and clades to test specific phylogeographic hypotheses using the methods developed by Templeton and his colleagues (Templeton 1998). In general, the distribution of haplotypes was strongly influenced by limited dispersal distances, with the more recently derived haplotypes having much lower levels of dispersion and lower frequencies in populations than the ancestral haplotypes. The patterns of clade and haplotype dispersion and displacement and the distribution of morphotypes imply at least three cases of long-distance dispersal and one case of historical fragmentation. The historical patterns inferred for populations of Piriqueta are consistent with known biogeographical events, historical vegetation change, and the concordant patterns of multiple Pleistocene refugia that have been observed for a number of other taxa in southeastern North America.

PATTERNS OF INTRASPECIFIC DIVERSIFICATION IN THE PIRIQUETA CAROLINIANA COMPLEX IN SOUTHEASTERN NORTH AMERICA AND THE BAHAMAS

We use chloroplast DNA (cpDNA) variation and nested clade phylogeographic analyses to infer the historical processes that have contributed to the high level of morphological and ecological diversification present in a group of herbaceous perennials (the Piriqueta caroliniana complex) in North America and the Bahamas. The presence of morphologically distinct and intercompatible varieties (morphotypes) that can be distinguished based on suites of taxonomic characters (e.g., leaf shape, pubescence type, stature) and contrasting habitat affinities (from marshes to dry pinelands and sand scrub) makes this group particularly appropriate for studies of intraspecific diversification. To examine the distribution of haplotypes among populations, we sampled 467 individuals from 55 locations in Florida, Georgia, and the northern Bahamas (Grand Bahama and Abaco) and screened each individual for cpDNA variation using restriction fragment length polymorphism (RFLP) and heteroduplex analyses. We develop a one-step haplotype phylogeny for this group and use the geographic distributions of haplotypes and clades to test specific phylogeographic hypotheses using the methods developed by Templeton and his colleagues (Templeton 1998). In general, the distribution of haplotypes was strongly influenced by limited dispersal distances, with the more recently derived haplotypes having much lower levels of dispersion and lower frequencies in populations than the ancestral haplotypes. The patterns of clade and haplotype dispersion and displacement and the distribution of morphotypes imply at least three cases of long-distance dispersal and one case of historical fragmentation. The historical patterns inferred for populations of Piriqueta are consistent with known biogeographical events, historical vegetation change, and the concordant patterns of multiple Pleistocene refugia that have been observed for a number of other taxa in southeastern North America.Corresponding Editor: M. Dudash

Nerocila benrosei n. sp. (Isopoda: Cymothoidae), an External Parasite of Hogfishes from the Northern Bahamas

Nerocila benrosei n. sp. is described from the hogfish, Lachnolaimus maximus (Walbaum), and the Spanish hogfish, Bodianus rufus (Linnaeus), (Perciformes: Labridae) from the northern Bahamas. Nerocila benrosei differs from all species of Nerocila by having the body of females 1.4-1.9 times as wide as long, instead of 2.0-3.0 times, and pleopods 1 and 2 lacking accessory lamellae. It differs from the only species of Nerocila with which it overlaps geographically, N. lanceolata (Say, 1818), by having the lateral margins of pleonites 1-5 strongly produced ventrally, coxae 5-7 manifestly shorter than the posterolateral projection of the respective pereonite, and a vaulted dorsal surface. The species of Nerocila in the northwestern Atlantic have almost mutually exclusive geographic ranges: New England to Panama, including Bermuda and the northern coast of Cuba (Nerocila lanceolata); Brazil to Trinidad and Tobago (Nerocila fluviatilis Schiödte and Meinert, 1881); and the northern Bahamas and Bermuda (Nerocila benrosei). No species of Nerocila have been reported from the insular Caribbean. Nerocila benrosei appears to be highly host and site specific.

A Quantitative Analysis of Winter Distribution and Habitats of Kirtland's Warblers in the Bahamas

We compiled and analyzed 101 accessible reports of 194 individual Kinland's Warblers (Dendroica kirtlandii) from the Bahama Archipelago, 1841-1997. Most individuals were reported from northern islands (88%), and most sight reports (84%) and specimen/banding records (76%) were on island groups that support or formerly supported open woodlands of Caribbean pine (Pinus caribaea). Where habitat descriptions were provided, 60% mentioned specifically pines or pine understory. After analyses for potential biases from misidentification in sight reports and unequal effort across islands, we found no evidence to support previous claims that Kirtland's Warblers prefer scrub or avoid pine habitats. Rather, based upon 1995-1997 winter surveys using acoustic broadcasts, Kirtland's Warblers were detected in pine woodlands of Abaco and Grand Bahama more frequently than expected compared to encounter rates generated by a null model of random habitat use. Two periods of apparent decline of the Kirtland's Warbler this century, and a modest population increase on the breeding grounds since 1990, occurred contemporaneously with degradation and recovery, respectively, of the fire-dependent pine ecosystem in the northern Bahamas. We recommend a rigorous re-evaluation of conservation priorities now premised largely upon breeding-season limitation.

Deep Flow along the Western Boundary South of the Blake Bahama Outer Ridge

Abstract In June–July 1990, hydrographic, chlorofluorocarbon (CFC), and velocity observations were taken along the western boundary of the North Atlantic south of the Blake Bahama Outer Ridge from 30° to 24°N between the northern Bahamas and 71°W. The deep flow in the region, associated with the deep western boundary current, forms a pattern of strong, narrow currents and cyclonic gyres close to the continental slope with broad, slower southward flow offshore. The CFCs reveal that the most recently “ventilated” water (i.e., having the highest CFC concentrations due to more recent contact with the atmosphere in the northern North Atlantic) is found along the western boundary in two distinct cores between potential temperatures 4°–6°C and 1.9°–2.4°C. Geostrophic transport streamlines were constructed for the deep flow, referenced using direct velocity observations at 26.5°N and assuming mass conservation between closed areas bounded by the hydrographic sections. The tracers and transports are used together ...

Climatic Control of Hydraulic Conductivity of Bahamian Limestones

AbstractData from 244 single‐well pumping tests of the karstified Lucayan Limestone on 14 different islands distributed through the Bahamian Archipelago, demonstrate a strong log‐linear relationship between annual rainfall and the effective mean island effective hydraulic conductivity, which averages over two orders of magnitude higher in the wetter northern Bahamas (mean anual rainfall 1550 mm) than in the more arid southern islands (mean annual rainfall 810 mm). This relationship is independent of the saturated depth of the boreholes tested, although the hydraulic conductivity of the lower part of the formation is significantly greater (about 0.6–0.7 order of magnitude) than the upper unit, reflecting progressive secondary porosity generation with time.The direct effect of increasing ground‐water flux on rates of dissolutional porosity generation in the wetter northern islands is supplemented by the greater geochemical potential for carbonate dissolution resulting from higher primary vegetative production. This both increases soil pCO2 via root respiration (a process augmented by higher soil moisture permitting more microbial activity), and the availability of organic matter for in situ oxidation within the aquifer. Effective hydraulic conductivity may also be directly related to island size. Islands in the north of the Archipelago are larger than those in the south, thus the fresh‐water lens and fresh‐/ salt‐water mixing zone are greater in size and expose more bedrock to dissolution.

New allocyclic dimensions in a prograding carbonate bank; evidence for eustatic, tectonic, and paleoceanographic control (late Neogene, Bahamas)

ABSTRACT The deep-sea record, examined recently for the first time in a shallow-depocenter setting, has unveiled remarkable evidence for new sedimentary components and allocyclic complexity in a large, well-studied carbonate bank, the western Great Bahama Bank. The evidence is a composite foraminiferal signature--Paleocene to early Miocene (allogenic or reworked) and late Miocene to late Pliocene (host) planktic taxa, and redeposited middle Miocene shallow benthic faunas. Ages of the oldest and youngest planktic groups range from ~ 66 to ~ 2 Ma. The reworked and redeposited taxa are a proxy for significant sediment components that otherwise have no lithofacies or seiic resolution. The composite signature, reinforced by a distinctive distribution of the reworked and redeposited faunas, documents a much more complex late Neogene depositional system than previously known. The system is more than progradational. The source sequences that supplied the constituent bank-margin grains formed at different water depths and over hundreds of kilometers and tens of millions of years apart. New evidence from the literature and from data obtained during Ocean Drilling Program (ODP) Leg 166 in the Santaren Channel (Bahamas) support early interpretations based on the composite fossil record and provide valuable new dimensions to regional allocyclicity. The middle Miocene taxa were confined to the lower part of the section by the latest Miocene-earliest Pliocene(?) lowstand of sea level. An orderly occurrence of the allogenic taxa is unique to the global reworked geologic record and appears to have been controlled by a combination of Paleogene-early Neogene tectonics at the source, eustatic changes, and late Neogene current activity at the source and across the bank. The allogenic taxa expand the spatial and temporal range of information in the northern Bahamas by nearly an order of magnitude. In essence, some of the major processes active in the region during ~ 64 m.y. of the Cenozoic can be viewed from within a narrow (~ 6 m.y.) late Neogene window. In this case, the fossil record also serves to demonstrate the potential and significance in evaluating reworked and redeposited assemblages.

Temporal and spatial distribution of whitings on Great Bahama Bank and a new lime mud budget

Analysis of 69 shuttle and satellite images of the northern Bahamas taken from 1965 to 1993 allowed us to calculate the regional and temporal distribution and longevity of 888 whitings on the Great Bahama Bank. At any time, whitings cover between 35 and 200 km 2 in the area centered at lat 25°N and 78°50 ′W. The highest occurrences of whitings are in April and October, suggesting a seasonal component. Using a measured average of 10.6 mg/L suspended sediment in typical whitings, we calculated that 1.35 〈 10 6 metric tons of lime mud are suspended every year. If the suspended carbonate is precipitated in the water column, these phenomena account for 280% of all of the Holocene accumulated bank top mud and more than 40% of the total bank top mud and periplatform mud that have accumulated on the west side of Great Bahama Bank.

Topographic Influences on Recirculation in the Deep Western Boundary Current: Results from RAFOS Float Trajectories between the Blake–Bahama Outer Ridge and the San Salvador “Gate”

Abstract Over a period of several years, RAFOS floats were launched into three levels of the deep western boundary current (DWBC) east of the northern Bahamas in order to identify and study any local recirculations that might be present in addition to the thermohaline-driven component of the current. These float trajectories reveal the presence of recirculations that are clearly caused by features of the lateral and bottom topography. In particular, the San Salvador Spur exerts a major influence on the paths of these floats. Although the floats exhibit a complicated set of motions, some order is imposed by relating periods when floats move directly along the boundary versus periods when they leave the launch site “anomalously” (i.e., to the cast or northeast) due to motions of the DWBC core. Comparison to current meter records along 26°30(N near the launch site shows that floats in the latter group were deployed when the DWBC core was located offshore. The “eruption” of floats into the interior recirculat...