NW Florida Research Articles

Influence of nearby environment on recreational bycatch of sea turtles at fishing piers in the eastern Gulf of Mexico

Incidental bycatch of sea turtles from recreational fisheries is generally undocumented globally. At Gulf of Mexico fishing piers in the USA, bycatch is a source of injury and potential mortality of sea turtles. Recreational sea turtle bycatch has grown substantially over the last 6 yr, especially at the Navarre Beach Fishing Pier (NW Florida); the reasons for the increase and the impacts this has on the recovery of northern Gulf of Mexico sea turtle populations are largely unknown. In particular, the reasons why fishing piers are attracting sea turtles are not well understood or if the environmental context of other nearby habitats contributes to the bycatch. Using GIS, we analyzed potential environmental predictors of total sea turtle bycatch, across green sea turtles Chelonia mydas, loggerhead sea turtles Caretta caretta, and Kemp’s ridley sea turtles Lepidochelys kempii. We collated bycatch and environmental data from 20 Florida Gulf of Mexico fishing piers. We statistically assessed relationships using generalized additive models and selected the best fit model using the information-theoretic approach. We found that tonnage of nearby artificial reefs (based on defined home range and core use areas) and distance to nearest seagrass bed exhibit positive relationships with green sea turtle bycatch. For combined loggerhead and Kemp’s ridley bycatch, area of preserved water, distance to nearest seagrass bed, tonnage of nearby artificial reefs, and latitude of fishing piers were all predictors in the confidence set, but the shape of the relationships is variable and nonlinear. Further examination of sea turtle bycatch, occupancy of piers, and environmental factors pertaining to sea turtles will likely improve mitigation measures for recreational bycatch.

Role of outer marginal collapse on salt deposition in the eastern Gulf of Mexico, Campos and Santos basins

Abstract Outer marginal collapse (OMC), a recently proposed process by which top-rift and base-salt unconformities formed near sea level may subside rapidly to 2.5–3 km at continental margins as mantle exhumation or seafloor spreading begins, needs further examination. We examine salt deposition at three margins and find that the differing positions and volumes of salt can be related to different durations of salt deposition as OMC and subsequent mantle exhumation proceed. Along NW Florida, salt is thin but deep and is interpreted as having formed at the start of OMC, before drowning further to abyssal depths. In the Campos Basin, salt is thick and extends across tens of kilometres of interpreted exhumed mantle, interpreted as having formed during the entire period of OMC before spreading onto mantle during exhumation. In the Santos Basin, salt is thick and extends across c. 100 km of interpreted exhumed mantle and/or oceanic crust, arguably requiring ‘lateral tectonic accommodation’, whereby salt deposition persists near global sea level across the conjugated salt basin during mantle exhumation beneath mobile salt. The supposition that OMC can account for salt deposition in three different basins without invoking problematic 1.5–2 km-deep subaerial depressions provides further support for the process.

Spatio-temporal analysis of decadal-scale patterns in barrier island response to storms: Perdido Key, NW Florida

The ability to accurately quantify shoreline variability is essential in order to establish aggressive mitigation strategies, based on recent global climate change projections. This investigation employed a suite of coastal data (topographic maps, aerial photography, satellite imagery and lidar) to establish decadal trends of shoreline movement along Perdido Key, a sandy barrier island off Florida’s northwest coast. The technique used to detect morphologic change with time was a recently developed tool, Analyzing Moving Boundaries Using R. This innovative methodology improves our understanding of the evolution of coastal systems by modeling shoreline variance using a method that is sensitive to shoreline shape. Results show that the barrier shoreline is a highly dynamic feature with distinct zones of erosion and accretion that are pervasive over time. In general, the island is displaying a mechanism of rotational instability with the eastern half retreating, and the western portion advancing. The inflection point, around which this rotational shifting is taking place, lies at the center of a Pleistocene headland located along the island’s midpoint. The results of this study suggest that coastal evolution along the island may be meta-stable, with trends in shoreline variance corresponding mainly to discrete storm events in time.

Distribution of Surficial and Buried Oil Contaminants across Sandy Beaches along NW Florida and Alabama Coasts Following the Deepwater Horizon Oil Spill in 2010

ABSTRACT Wang, P. and Roberts, T.M., 2013. Distribution of surficial and buried oil contaminants across sandy beaches along NW Florida and Alabama coasts following the deepwater horizon oil spill in 2010. The failed Deepwater Horizon (DWH) well released approximately 7.0 × 105 m3 of oil into the northern Gulf of Mexico during an 84-day period from 20 April 2010 to 15 July 2010. This study examined the beach oiling that resulted from the DWH spill, specifically the cross-shore distribution of both surface and buried oil, based on a series of field investigations and transport mechanisms following principles of beach morphodynamics. Five types of oil contamination were distinguished, including tar balls, tar patties, tar cakes, oil sheet, and stained sand. All five types were identified both on the beach surface and buried underneath contaminated and clean sand. The cross-shore distribution of surface oil was bound landward by the maximum high-tide wave run-up, which was, in turn, controlled by the incident...

Where did the lower Paleozoic rocks of Yucatan come from? A U–Pb, Lu–Hf, and Sm–Nd isotope study

Detrital zircon grains from Lower Paleozoic sedimentary rocks in the Yucatan Peninsula have an age distribution characterized by major probability peaks at ~1.0, ~1.2, and ~1.5Ga (Martens et al., 2010). Here, we present new Lu–Hf data (MC–ICPMS) paired with U–Pb ages (ID-TIMS) for additional zircon grains from the same rocks. This analytical approach yields precise information about the time and geochemical environment of zircon growth, which in turn helps to distinguish between different crustal source regions that just happen to host zircon populations of similar age. In addition, single zircon grains from granitoids that intruded the sedimentary rocks were dated by U–Pb laser ablation MC–ICPMS and ID-TIMS, and their Hf-isotope compositions were determined by solution MC–ICPMS. The zircon data are complemented by Sm–Nd analyses of the sedimentary and igneous whole rocks.The Yucatan Peninsula, which forms part of the Maya block of Central America, includes lower Paleozoic rocks in the Maya Mountains of Belize. The pre-Mesozoic geologic history of the Maya block is related to the evolution of the mid-Proterozoic basement in Mexico (Oaxaquia), other Paleozoic peri-Gondwanan terranes, and the Pan-African–Brasiliano type basement of Florida. The initial 176Hf/177Hf values of ~1.0Ga detrital zircon grains lie on a crustal evolution trajectory similar to that defined by older, ~1.2 to ~1.5Ga grains. This trajectory is consistent with those that would be produced by crustal reservoirs that separated from the depleted mantle between 1.70 and 2.05Ga. However, some grains have significantly less radiogenic 176Hf/177Hf(t), indicating influence from even older cratonic crust. Zircon grains from granitoids that intruded the Early Paleozoic sedimentary rocks of the Yucatan Peninsula yielded Late Silurian to Early Devonian (~415–400Ma) crystallization ages. More radiogenic Hf isotope ratios indicate anatexis of a crustal reservoir that is distinct from that of the Early Paleozoic sedimentary rocks. The Sm–Nd systematics of whole rock samples further support the results from the Hf isotopes in zircon grains. The data suggest a more continental provenance for the sedimentary rocks from Yucatan as compared to typical ca. 1.3 to 1.0Ga outcrops in southern and central Mexico. The results indicate that sediments were shed either from mid-Proterozoic complexes of NW Amazonia or from similar continental sequences that were thrust over Oaxaquia during the Grenville orogeny and subsequently eroded in the early Paleozoic. Integrating the data into a new model for early Paleozoic times, the southern Maya block is inferred to have formed during the opening of the Rheic Ocean along the western margin of Amazonia adjacent to Oaxaquia. The paucity of Ediacaran (Pan African–Brasiliano) signatures implies that before the Silurian, the southern Maya block evolved geographically separated from NW Yucatan and Florida, where Pan African–Brasiliano crystalline rocks have been reported.

Ground-Penetrating Radar Study of North Padre Island: Implications for Barrier Island Internal Architecture, Model for Growth of Progradational Microtidal Barrier Islands, and Gulf of Mexico Sea-Level Cyclicity--Discussion

Garrison et al. (2010) are the latest among several authors to claim significant Gulf level fluctuations in the last several millennia (see discussions in Otvos 2001, 2004, 2005a). The onus in their particular case rests on the rather unusual assumptions by Tanner (1992), who linked granulometric kurtosis values and his subjective age estimates of the progradation rate of a St. Vincent Island, NW Florida ridgeplain sequence to late Holocene climate and sea-level changes. The recurring major sea-level and shoreline shifts proposed by Garrison et al. can not be reconciled with the straightforward subsurface documentation presented. ### Proposed Evidence for Late Holocene Sea-Level Fluctuations Tanner (1992), on whose assumptions Garrison et al. base their sea-level chronology starts with three sweeping claims: (1) Essentially all St. Vincent strandplain ridge lithosomes were wave-built. Eolian contribution (so-called “dune decoration”) of unspecified thickness was not significant. (2) Low beach-ridge sets formed during lower sea levels; taller ones during highstands. Tanner provided no specific ridge elevation figures. Lacking corroborating dates of his own, he has arbitrarily assigned ridge-set ages by postulating a subjectively conceived rate of steady strandplain progradation. (3) Based on statistical moment-measure calculations, Tanner assumed a direct relationship between ridge sets of different average elevations, fluctuating late Holocene sea levels, and values of granulometric mean kurtosis from ridge sands. As foundation for their own contention, Garrison et al. (their Fig. 16) also repeat misstatements by Tanner (1992) that late Holocene highstands and lowstands are also reflected in Mississippi subdelta complexes. Frazier (1967), Otvos and Giardino (2004), Otvos (2005a), Tornqvist et al. (2004), Rogers et al. (2009), and others provided no stratigraphic base to support this contention. A similar assertion, equally unfounded, was applied to the SW Louisiana chenier plain as well (Tanner 1992). However, significant lateral elevation differences along these shell-dominated ridges are …

Benthic metabolism across a gradient of anthropogenic impact in three shallow coastal lagoons in NW Florida

Seagrasses are being lost at alarming rates worldwide, most often due to anthropogenic effects, but few reports have examined how seagrass loss affects the metabolism of coastal ecosys- tems. Here, we address this question by comparing both areal and system-integrated daytime ben- thic metabolic rates across 3 lagoons in the North Central Gulf of Mexico that display varying levels of abundance of the shoalgrass Halodule wrightii (i.e. from 64% of the bottom covered with shoal- grass down to between 4 and 0%), partially due to contrasting anthropogenic pressures. When com- paring the 2 shoalgrass-containing lagoons, shoalgrass patches featured higher areal rates of gross primary production (GPP) and respiration (R), and, to a lesser extent, higher rates of net production (NP), than did bare sediment. These results were robust despite across-lagoon differences in percent- age cover and areal biomass of shoalgrass and benthic microalgae (i.e. the lagoon with less cover also had lower areal shoalgrass biomass in the shoalgrass patches and higher areal microalgal chlorophyll a concentrations in the sediment). We did not find any consistent differences in the metabolic rates of bare sediment across the 3 lagoons, despite the fact that areal microalgal chlorophyll a concentra- tions in bare sediment increased as shoalgrass abundance decreased across the 3 lagoons. System- integrated rates of benthic GPP and R were higher in the lagoon with the highest shoalgrass cover when compared with the lagoons with little or no shoalgrass; but, surprisingly, system-integrated rates of benthic NP did not differ significantly across lagoons. This result suggests that the large decrease in shoalgrass abundance across the lagoons examined does not greatly affect the lagoon's potential capacity for accumulation and/or export of organic carbon. It also underlines the importance of deriving system-integrated estimates to properly understand how decreasing seagrass abundance can alter the daytime metabolism of coastal systems.

Drowned shelf-edge deltas, barrier islands and related features along the outer continental shelf north of the head of De Soto Canyon, NE Gulf of Mexico

Four drowned shelf-edge delta complexes, two drowned shelf deltas, three drowned barrier islands, large areas of “hardground”, and fields of bedforms on the mid and outer continental shelf and uppermost slope north of the head of De Soto Canyon, NE Gulf of Mexico were mapped with high-resolution multibeam echosounder. Deltas formed not during the last eustatic low stand, but during one or more interstadials when eustatic sea levels were only 60 to 80 m below present sea level. The barrier islands and deltas must have been cemented prior to rapid falls of eustatic sea level that occurred during global glaciations. Cementation is necessary to have preserved the barrier islands from erosion and subsequent destruction by the rapid sea-level rise during the last deglaciation. The preservation of the relict bathymetry is so good that features that superficially resemble trough blowouts are found in association with one of the relict barrier islands. Asymmetric bedforms on the midshelf in water depths of 50 to 60 m indicate transport directions to the SW but asymmetric bedforms in water depths of the upper slope between 100 and 120 m on the S and SE flanks of the drowned shelf-edge deltas indicate a different current direction, a separate flow that is a continuation of a SW-flowing current that was previously found on the upper slope off NW Florida.

Characteristics of the burial environment related to quartz SAR-OSL dating at St. Vincent Island, NW Florida, USA

St. Vincent Island, on the northwest Gulf coast of Florida, USA, preserves a well-developed beach ridge plain that began to form ∼4000 years ago based on inferred ages of pottery artefact assemblages. Seven vibra cores up to 2.88 m in length (uncompacted sediment) were retrieved from six ridges across the island. The single-aliquot regenerative-dose (SAR) procedure was used to obtain two optically stimulated luminescence (OSL) ages per core at different depths within each core. The geographically youngest ridges gave ages of 370±50–1900±300 years, yielding an inter-ridge accumulation time of ∼150 years assuming uniform sediment accumulation. The oldest ridge sets yielded ages of 2700±400–2800±300 years. Dating results are evaluated in terms of equivalent dose ( D E) distributions and other characteristics in relation to aspects of the burial environment, including pedogenesis.

Fibre-tempered pottery of the Stallings Island Culture from the Crescent site, Beaufort County, South Carolina: a mineralogical and petrographical study

Abstract Late Archaic to Early Woodland (4500–3000 years bp ) Stallings Island Culture fibre-tempered plainware pottery is found from northern North Carolina to NW Florida and is often separated into two temper groups (Stalling and Orange series) based upon fibre type. Thirty-four sherds were studied to determine textural or mineralogical characteristics to assist in form and type separation. This study finds that only a few of the sherds were dominated by fibre. The fibre is visible as secondary porosity (voids) with some carbonized remains and exhibits specific shape and orientation at different locations within the sherd. Only two sherds had carbonized stem fragments that allowed identification of the Spanish moss ( Tillandsia usnedoides ). The remainder of the Crescent site plainware pottery has such low (to no) fibre contents as to be indistinguishable from similar age sand-tempered Thom’s Creek wares. The identity and textural features of the fine-grained aplastic minerals (quartz, feldspar, biotite and opaque minerals) in the paste are similar in both fibre- and non-fibre-tempered sherds, and this suggests that the materials used are consistent with sediment extraction from a fluvial coastal plain or estuarine setting. These observations indicate that the degree of fibre incorporation in these sherds may be related to the specific clay source (or manufacturing location) or represent examples of an evolving pottery manufacturing process within the Stallings Island Culture.

Effect of salinity on the distribution, growth, and toxicity of Karenia spp.

The first recorded bloom of Karenia spp., resulting in brevetoxin in oysters, in the low salinity waters of the Northern Gulf of Mexico (NGOMEX) occurred in November 1996. It raised questions about the salinity tolerance of Karenia spp., previously considered unlikely to occur at salinities <24 psu, and the likelihood that the bloom would reoccur in the NGOMEX. Salinity was investigated as a factor controlling Karenia spp. abundance in the field, using data from the NGOMEX 1996 bloom and Florida coastal waters from 1954 to 2004, and growth and toxin production in cultures of Karenia brevis (Davis) G. Hansen and Moestrup. During the NGOMEX bloom, Karenia spp. occurred much more frequently at low salinities than in Florida coastal waters over the last 50 years. The data suggest that the NGOMEX bloom started on the NW Florida Shelf, an area with a higher frequency of Karenia spp. at low salinities than the rest of Florida, and was transported by an unusual westward surface current caused by Tropical Storm Josephine. The minimum salinity at which growth occurred in culture ranged between 17.5 and 20 psu, but the optimal salinity ranged between low values of 20 or 25 and high values of 37.5–45 psu, depending on the clone. The effect of salinity on toxin production in one clone of K. brevis was complex, but at all salinities brevetoxin levels were highest during the stationary growth phase, suggesting that aging, high density blooms may pose the greatest public health threat. The results demonstrate that Karenia spp. can be a public health threat in low salinity areas, but the risk in the NGOMEX is relatively low. No bloom has occurred since the 1996 event, which was probably associated with a special set of conditions: a bloom along the Florida Panhandle and a tropical storm with a track that set up a westward current.

Numerical chronology of Pleistocene coastal plain and valley development; extensive aggradation during glacial low sea-levels

Based on more than 60 newly acquired luminescence ages, field information, and sediment granulometry data, a comprehensive chronostratigraphic framework is presented for Pleistocene alluvial coastal plain and valley terraces and coastal barrier trends on the northern Gulf of Mexico between Texas and NW Florida. Luminescence ages 216–188 ka from the second youngest coastal terrace coincide with the highstand during the second youngest Pleistocene Marine Isotope Stage (MIS 7a). TL ages from the oldest Prairie alluvium and OSL-ages from the Gulfport barriers; 124–116 ka, are consistent with the Sangamon interglacial substage, MIS 5e. Forest assemblages of the last two Pleistocene highstands are very similar to the present hard pine-dominated arboreal flora, established under warm-temperate, humid conditions. Ages of the youngest, Prairie–Beaumont coastal terrace overlap with the Eowisconsin (MIS 5d–5a) and Wisconsin (MIS 4 and 3) stages, associated with a sea-level range of −80 to −30 m. Coastal plain aggradation, not limited to interglacial highstands occurred during the much longer preglacial and glacial low sea-level stages. The Prairie–Beaumont coastal plain is a collage of seamlessly merged surfaces, aggraded between ca.135 and 30 ka in several alluviation stages. Periodically dry conditions, associated with enhanced slope erosion and consequent increase in sheetwash, colluvial, and fluvial sediment flux may have induced substantial aggradation at significant distances inland from the coeval shorelines during depressed preglacial and glacial sea-levels. This balance between erosion and sediment delivery may explain the diminished control of lower Eowisconsin and Wisconsin sea-levels (base-levels) on coastal entrenchment and aggradation. The combined effects of alluvial aggradation and subsequent uplift, modified by surface erosion produced the present coastal plain topography. An early post-Sangamon phase of deep entrenchment involved the Amite, Sabine, Neches, and the Pearl Valleys in Eowisconsin and early Wisconsin times. Except for the universal impact of the deep Last Glacial Maximum (LGM) entrenchment, the alluviation–incision cycles that produced two to four sets of terraces of aggradational and strath origin did not occur in all valleys synchronously and with identical effects. In certain valleys terrace aggradation coincided with the LGM record lowstand and the following late Wisconsin transgressive deglacial hemicycle. In contrast with intensive valley filling, inferred for the MIS 6 glacial interval, Holocene backfilling is far from complete in most late glacial entrenched valleys.

Holocene Gulf Levels: Recognition Issues and an Updated Sea-Level Curve

Abstract Several new concepts have challenged the traditional view of northern Gulf coast sea-level history in recent years. Claims for higher than present mid and late Holocene sea-levels implied substantial sea-level oscillations. Such high-stands, known globally in low latitudes, have never been credibly documented on the Gulf or on unglaciated Atlantic coasts. Lacking direct indications, numerous lines of indirect proof have been suggested. Proxy evidence was based on items as the reinterpreted geological record of NW Florida lakes, estuaries, and depositional conditions of Texas coast landforms. Pleistocene barrier sectors, barrier islands, relict foredune ridges, washover fans/flood-tidal deltas, and other sedimentary units and their morphology were claimed as highstand indicators. Unrealistically old or young radiocarbon and luminescence dates, the result of diagenetic changes and other contamination have resulted in questionable conclusions. A large body of sediment, stratigraphic and geomorphic d...

Submerged Paleoindian and Archaic Sites of the Big Bend, Florida

The discovery and investigation of submerged prehistoric sites in the Big Bend region of the Gulf coast of NW Florida has revealed occupation ranging from the latest Pleistocene to the middle Holocene age. A summary of the local prehistoric record and the history of sea level rise are used to present the kinds of sites that may exist offshore and how far out on the continental shelf they might be discovered. A local paleoriver channel (the PaleoAucilla) has been traced offshore and parts of it have been surveyed for archaeological sites with excellent results. The local offshore environment is described, the history and methods of research are presented, and the results of selected analyses are briefly discussed.

In situ measurements of near-surface porosity in shallow-water marine sands

An in situ resistivity profiler was developed to measure with minimal disruption, the near-surface porosity of shallow-water marine sands. Results from a siliciclastic site off NW Florida and two Bahamian carbonate sites (an ooid shoal and coral reef sand flat) suggest the following general features. First, there is a 5- to 15-mm thick zone of elevated porosity adjacent to the sediment-water interface. Porosity in this layer was from 0.05 to 0.25 (decimal porosity) greater than the subjacent values, and would be difficult to resolve using traditional measurement techniques. Second, average porosity at >10-mm depth was 0.38 /spl plusmn/ 0.01 at the siliciclastic site, 0.39 /spl plusmn/ 0.01 at the ooid shoal site, and 0.49 /spl plusmn/ 0.02 at the coral reef sand flat site; consistent with literature values. Third, individual profiles exhibited 0.05-0.15 fluctuations about the mean, with vertical length scales of 5-15 mm. These fluctuations may be the result of grain packing heterogeneities caused by hydrodynamic sorting during deposition and subsequent physical and biological mixing or could be artifacts caused by disruption of the grain framework. Fourth, ripple troughs at the siliciclastic sand site had a significantly higher near-surface porosity compared to ripple crests, due most likely to the presence of detrital material in the troughs.

HIGH BREVETOXIN CONCENTRATIONS IN GYMNODINIUM BREVE BLOOMS ALONG THE NORTHWEST FLORIDA COAST DURING 1999

Blooms of the dinoflagellate Gymnodinium breve (i.e. red tides) produce brevetoxins (PbTx) that negatively impact the Gulf of Mexico ecosystem, human health, and local economies. Characterizing and predicting bloom events and their impacts requires knowledge of G. breve abundance and PbTx concentrations in the water column. We report results from a bloom that occurred during the fall and winter of 1999 in NW Florida coastal waters. Data were collected from 16 stations on 3 sampling dates (29 Sept., 9 Nov., 1 Dec.), including basic hydrography, nutrient concentrations, G. breve abundances, and brevetoxin concentrations. G. breve cells were enumerated using flow cytometry and PbTx's were isolated from seawater using dichloromethane (DCM) partitioning. Brevetoxins were quantified by HPLC‐DAD using a C‐18 column and an acetonitrile‐water gradient elution. Literature estimates of total PbTx concentration (PbTx's 1, 2, 3) of cultured and field‐collected G. breve suggest a range in concentration from 7 to 17 pg cell−1. We measured total PbTx levels that greatly exceeded these values [Sept., 47–67 pg cell−1 (n=5); Nov., 59–126 pg cell−1 (n=3), Dec., 12–63 pg cell−1 (n=8)]. PbTx‐2 was the predominant (67–75%) PbTx isomer found in these blooms. PbTx‐1 and PbTx‐3 were found at 11–22% and ND–28% of total PbTx, respectively.

LONG DISTANCE OFFSHORE MOVEMENTS OF BOTTLENOSE DOLPHINS1

AbstractDespite recent progress defining the morphological and genetic characteristics of forms of the bottlenose dolphin inhabiting offshore waters, little is known of their behavior or ranging patterns. Reports suggest that an “offshore form” exists between the 200‐ and 2,000‐m isobaths in distinct Gulf of Mexico and western North Atlantic stocks, while one or more coastal forms inhabit the waters inshore. Two opportunities to track rehabilitated adult male bottlenose dolphins with satellite‐linked transmitters occurred in 1997. “Rudy” stranded in NW Florida and was released in the Gulf of Mexico off central west Florida. He moved around Florida and northward to off Cape Hatteras, NC, covering 2,050 km in 43 d. “Gulliver” stranded near St. Augustine and was released off Cape Canaveral, FL. He moved 4,200 km in 47 d to a location northeast of the Virgin Islands. Gulliver swam through 5,000‐m‐deep waters 300 km offshore of the northern Caribbean islands, against the North Equatorial Current. These records expand the range and habitat previously reported for the offshore stock of bottlenose dolphins inhabiting the waters off the southeastern United States, underscore the difficulties of defining pelagic stocks, illustrate the success of rehabilitation efforts, indicate the value of follow‐up monitoring of rehabilitated and released cetaceans, and expand our understanding of the long‐range movement capabilities of a dolphin species more commonly thought of as a resident in coastal waters.

An episodic chlorophyll plume on the West Florida Shelf

The episodic formation of an extensive pigment plume on the West Florida Shelf was detected using historical Coastal Zone Color Scanner (CZCS) data collected between 1979 and 1986. The phenomenon is confirmed by in situ observations made in March 1992. The plume occurs mainly during spring, when high pigment concentrations persist 1–6 weeks in a pattern which extends >250 km southward along the shelf. In general, the shelf and continental slope had low pigment concentrations during summer and high pigment concentrations during spring. The information currently available is insufficient to determine the cause of the plume with certainty. Plume formation may be associated with one or a combination of the following processes: (1) discharge from small, local rivers along the NW Florida coast; (2) seasonal changes in steric height differences between the shelf and deep Gulf of Mexico waters; (3) circulation of water associated with the Loop Current and upwelling in the DeSoto Canyon; and (4) discharge from the Mississippi and Mobile Rivers.

Vertical and Lateral Distribution of Stable Flies in Northwestern Florida1

Sticky traps were operated in 1972 and 1973 to study the vertical distribution of the stable fly, Stomoxys calcitrans L.) in NW Florida. In 1972, the traps were placed on a fire lookout tower at each of 2 inland sites near Vicksburg and West Bay. In 1973, only the Vicksburg fire tower was utilized, addition to a U. S. Navy coastal observation tower on the beach. The largest number of flies, 91%, was collected at 1 and 4 ft (0.3 m and 1.2 m), only 9% was collected between ft and 28 ft (2.1 m and 8.5 m) and no flies were collected at elevations of 50 ft and 75 ft (15.2 m and 22.9 m). These studies show that between 0 and 75 ft (0 and 22.9 m) elevation, stable flies are concentrated near ground level in NW Florida. Also, sticky traps positioned in the middle of a power line right-of-way collected the largest number of flies, 73.8% in 1972 and 66.2% in 1973, while traps placed in adjacent wooded areas in a line perpendicular to the right-of-way collected fewer flies.

Sticky traps for sampling population of Stomoxys calcitrans.

Sticky panel traps were more than 7 times as effective in collecting stable flies along beaches in NW Florida than previously used box traps. Translucent white was the most effective of 3 tested colors. Stable flies were collected in greater numbers on the leeward side of the traps, and usually the highest concentration collected on any individual trap was along its border.