Apalachicola Bay Research Articles

Combining Organic Matter Source and Relative Trophic Position Determinations to Explore Trophic Structure

Stable isotope ratios of carbon and sulfur were used to assess organic matter utilization of numerically abundant consumers present in Apalachicola Bay, FL, USA. These results were used to infer nitrogen isotopic enrichment of organic matter sources in an effort to establish baseline δ15N enrichment for trophic evaluations. We compared results from concentration-independent and concentration-dependent mixing models and found that the two methods resulted in widely different conclusions about the importance of organic matter sources that varied ninefold in sulfur concentrations. Nitrogen isotopic enrichment was used to determine relative trophic positions of consumer organisms. Source elemental concentrations of nitrogen were also considered in the calculation of relative trophic levels in a concentration-dependent approach. Concentration-independent and concentration-dependent methods of calculating trophic results were compared. While relative trophic levels of individual species varied continuously from approximately 1.7 to 3.5, comparisons of trophic level among consumers indicated four possible trophic groupings. Filter feeders (mussels and oysters) made up the lowest trophic tier while teleost fishes made up the highest trophic tier. Invertebrates sampled were assigned intermediate nondiscrete trophic levels. Because δ15N values of important organic matter sources in the system were similar, the concentration-independent and concentration-dependent methods did not result in significantly different conclusions about trophic level for any of the consumers examined. However, a comparison of the two methods applied to a hypothetical case found that differences in base δ15N values ranging approximately 4‰ resulted in significantly different trophic-level assignments when comparing the concentration-dependent and concentration-independent methods of trophic-level calculations. Our results confirm that consideration of the elemental concentrations of the base organisms is an important factor in determining source contributions and may affect trophic-level calculations in systems with a sufficient range of base nitrogen enrichment. However, this result depended on the relative isotopic signatures of the chosen sources and their elemental concentrations and should be considered individually for each system.

Modeling sediment resuspension and transport induced by storm wind in Apalachicola Bay, USA

Sediment is an important environmental factor for aquatic ecosystem and oyster productivities of Apalachicola Bay located in Florida, USA. Based on the data analysis in this study, surface wind speed is highly correlated to the turbidity of water column, which results from sediment resuspension and transport in the Apalachicola Bay. In this paper, an application of a 3D sediment transport model to predict the wind-induced sediment transport in Apalachicola Bay is described. The sediment model is coupled with a 3D hydrodynamic module in the Environmental Fluid Dynamics Code (EFDC) model that provides information on estuarine circulation and salinity transport under normal temperature conditions. The hydrodynamic model was calibrated with field observations of water levels and salinity. The sediment transport model solves the transport equation with sources and sinks terms to describe sediment deposition and resuspension. The coupled hydrodynamic and sediment transport models were used to investigate wind-induced total suspended sediments (TSS) resuspension and transport in the bay. For the period June 1–July 30, 2005 two storm events with strong winds gave model results of TSS concentrations that compared well with the field observations. Model simulations reasonably reproduce the sudden increase of sediment concentrations during the storm events. Maximum sediment concentrations in the bay during the two storm events were 10 times or more than those in the pre-storm conditions. Spatial sediment transport from model simulations indicate active sediment resuspension and transport near areas of highly productive oyster beds. The model predictions of TSS and salinity can be used as inputs to an oyster dynamic model (Wang, H., Huang, W., Harwell, M., Edmiston, L., Johnson, E., Hsieh, P., Milla, K., Christensen, J., Stewart, J., Liu, X., 2008. Modeling eastern oyster population dynamics in response to changing environment in Apalachicola Bay, Florida. Journal of Ecological Modeling 211, 77–89) to support the ecological study of oyster growth and mortality in the aquatic ecosystem of Apalachicola Bay.

Isotopic variation ( δ15N, δ13C, and δ34S) with body size in post-larval estuarine consumers

Stable isotope analyses were conducted on fish and crabs in Apalachicola Bay, Florida (USA) to determine whether δ 15N values are correlated with length within these species. Our objective was to define the smallest trophic unit of the system as a prelude to further isotopic evaluations of consumer trophic level in Apalachicola Bay. In some cases, the smallest trophic unit is the individual species; however, previous gut content analysis on organisms in this system indicated that subdivision by size class within species might be required. However, over the size ranges observed, there was no systematic change in the δ 15N values of individual consumers. Analysis of the δ 13C and δ 34S values of these species reveal no obvious shifts in the utilization of organic matter sources with length that could be obscuring a trend in the δ 15N signal. We find no isotopic evidence for a systematic trophic level increase within the species examined over the size ranges observed in this estuary. These results indicate that species rather than size class is the best predictor of trophic habit among these Apalachicola Bay consumers.

Impact of sideways and bottom-up control factors on bacterial community succession over a tidal cycle

In aquatic systems, bacterial community succession is a function of top-down and bottom-up factors, but little information exists on "sideways" controls, such as bacterial predation by Bdellovibrio-like organisms (BLOs), which likely impacts nutrient cycling within the microbial loop and eventual export to higher trophic groups. Here we report transient response of estuarine microbiota and BLO spp. to tidal-associated dissolved organic matter supply in a river-dominated estuary, Apalachicola Bay, Florida. Both dissolved organic carbon and dissolved organic nitrogen concentrations oscillated over the course of the tidal cycle with relatively higher concentrations observed at low tide. Concurrent with the shift in dissolved organic matter (DOM) supply at low tide, a synchronous increase in numbers of bacteria and predatorial BLOs were observed. PCR-restriction fragment length polymorphism of small subunit rDNA, cloning, and sequence analyses revealed distinct shifts such that, at low tide, significantly higher phylotype abundances were observed from gamma-Proteobacteria, delta-Proteobacteria, Bacteroidetes, and high G+C gram-positive bacteria. Conversely, diversity of alpha-Proteobacteria, beta-Proteobacteria, and Chlamydiales-Verrucomicrobia group increased at high tides. To identify metabolically active BLO guilds, tidal microcosms were spiked with six (13)C-labeled bacteria as potential prey and studied using an adaptation of stable isotope probing. At low tide, representative of higher DOM and increased prey but lower salinity, BLO community also shifted such that mesohaline clusters I and VI were more active; with an increased salinity at high tide, halotolerant clusters III, V, and X were predominant. Eventually, (13)C label was identified from higher micropredators, indicating that trophic interactions within the estuarine microbial food web are potentially far more complex than previously thought.

Changes in Phytoplankton and Bacterioplankton Biomass and Rate Processes in Apalachicola Bay, Florida, in Response to Reduction in River Discharge

Bacterioplankton abundance and chlorophyll concentration and the factors that control them (temperature, nutrient concentrations, and rates of growth, grazing, and export) were studied in Apalachicola Bay, FL, during two summers with contrasting river discharge. A reduction in river discharge from the summer of 2003 (S03) to the summer of 2004 (S04) led to a reduction in estuarine concentrations of dissolved inorganic nitrogen and rates of export, phytoplankton and bacterioplankton growth, and microzooplankton grazing on phytoplankton and bacterioplankton. Bacterioplankton abundance and chlorophyll concentration during S03 were not significantly different from those during S04. Neither the growth rates and abundances of ciliates nor the egg production rates and abundances of Acartia tonsa were significantly affected by the reduction in rate processes of bacterioplankton or phytoplankton. The proposed diversion of freshwater from the Apalachicola River during summer months may lead to substantial changes in the rate processes of bacterioplankton and phytoplankton, but little change in the standing stocks of bacterioplankton, phytoplankton, ciliates, A. tonsa, or ciliate growth rates and A. tonsa egg production rates.

Blood Flukes (Digenea: Aporocotylidae) of Stingrays (Myliobatiformes: Dasyatidae): Orchispirium heterovitellatum From Himantura imbricata in the Bay of Bengal and a New Genus and Species of Aporocotylidae From Dasyatis sabina in the Northern Gulf of Mexico

We redescribe Orchispirium heterovitellatum based on the holotype and 3 original voucher specimens collected from the mesenteric blood vessels of scaly whiprays Himantura imbricata (Bloch and Schneider, 1801) (as Dasyatis imbricatus) captured in the western Bay of Bengal off Waltair, India. We emend the diagnosis of Orchispirium to include anterior sucker present, testis looping, cirrus sac enveloping large internal seminal vesicle, oviducal seminal receptacle present, and metraterm short and thin-walled. We describe Myliobaticola richardheardi n. gen., n. sp. based on live observations, light microscopy, and scanning electron microscopy of adult specimens collected from between the cardiac trabeculae of Atlantic stingrays Dasyatis sabina (Lesueur, 1824) captured in Mississippi Sound (type locality), Mississippi, and Apalachicola Bay, Florida. The new species has a minute, aspinous body lacking lateral tubercles; an aspinous and eversible anterior sucker lacking a peduncle; a posterior esophageal swelling; an inverse U-shaped intestine; smooth ceca terminating in the anterior body half; a looping testis lacking lobes; a cirrus sac enveloping a large internal seminal vesicle; a medial and primarily post-testicular ovary; an oviducal seminal receptacle; a postgonadal uterus flanking the internal seminal vesicle; a short and thin-walled metraterm; and a common genital pore. It lacks a pharynx and Laurer's canal. No other named aporocotylids infect a member of cohort Batoidea or have the combination of an aspinous body, an aspinous anterior sucker, a posterior esophageal swelling, an inverse U-shaped intestine, a looping testis, a cirrus sac enveloping a large internal seminal vesicle, and a common genital pore; these observations indicate that O. heterovitellatum and M. richardheardi are closely related. The discovery of a second species representing a second genus of Aporocotylidae in diamond stingrays (Dasyatidae) suggests that Batoidea is an undersampled host group for aporocotylid infections.

Tropical Storm and Hurricane Impacts on a Gulf Coast Estuary: Apalachicola Bay, Florida

Abstract Since 1985, various long-term monitoring programs have been in place in the Apalachicola Bay area that can be utilized to determine the effects of tropical storms and hurricanes on the natural resources of the area. The size, speed of movement, severity, angle and direction of landfall, as well as storm surge height and the amount and location of precipitation all play a role in determining impacts. Short-term impacts seen in the bay from these tropical events include water quality alterations, such as salinity and turbidity changes, water level changes, and loss of sea turtle nests. Long-term impacts include changes to the structure of the beach, dunes, and bayside areas on a barrier island, loss of or changes in submerged aquatic vegetation distribution, and the physical alteration of oyster reefs as well as oyster populations. In particular, Hurricane Dennis in 2005 caused the complete loss of fresh and brackish submerged aquatic vegetation in the upper areas of the bay. Larger storms in 1995 ...

Chronology of Sediment Nutrient Geochemistry in Apalachicola Bay, Florida (U.S.A)

Land use changes have been shown to alter the balance of nutrient and mineral sources and sinks to coastal systems. These shifts are often preserved in sediment records. In Apalachicola Bay, productivity is dependent on nutrient loading from the Apalachicola-Chattahoochee-Flint (ACF) river basin; alterations to ACF watershed flow by management activities coupled with increased marine water inundation associated with rising sea level threaten this productivity. The objective of this research was to evaluate past changes in nutrient loading to Apalachicola Bay as recorded in sediment history and determine if these changes could be associated with both anthropogenic and natural alterations in the system. Sediment cores from three sites in the bay were collected and analyzed for organic carbon (C), total nitrogen (N), and total phosphorus (P) concentrations and δ13C and δ15N stable isotopic abundances. The three sites are located at the river mouth (S1), mid-bay (S2), and in the northeastern region of the bay (S3). Carbon and nitrogen concentrations, ratios, and stable isotopes coupled with grain-size shifts for the bay suggest a decrease in river organic matter supply and a change in sediment clay content supply and/or distribution for the bay. Overall, the applied indicators suggest an increase in marine influence on the organic matter in the estuary. These shifts appear to be associated with Apalachicola River management practices coupled with sea-level rise in the Gulf of Mexico.

Biostimulation of Estuarine Microbiota on Substrate Coated Agar Slides: A Novel Approach to Study Diversity of Autochthonous Bdellovibrio- and Like Organisms

Characterization of Bdellovibrio- and like organisms (BALOs) from environmental samples involves growing them in the presence of Gram-negative prey bacteria and isolation of BALO plaques. This labor-intensive enrichment and isolation procedure may impede the detection and phylogenetic characterization of uncultivable BALOs. In this article, we describe a simple slide biofilm assay to improve detection and characterization of BALO microbiota. Agar spiked with biostimulants such as yeast extract (YE), casamino acids (CA), or concentrated cells of Vibrio parahaemolyticus P5 (most widely used prey bacteria for isolation of halophilic BALOs) was plated onto buffed glass slides and exposed to water samples collected from Apalachicola Bay, Florida. After incubating for a week, diversity of the biofilm bacterial community was studied by culture-dependent and culture-independent molecular methods. The results revealed that most probable numbers (MPNs) of BALOs and total culturable bacteria recovered from YE agar slide were significantly higher than the numbers on CA- or P5-spiked agar slides. Polymerase chain reaction-restriction fragment length polymorphism followed by 16S rDNA sequencing of clones from different biostimulants resulted in identification of a plethora of Gram-negative bacteria predominantly from the alpha, gamma, delta-proteobacteria, and the Cytophaga-Flavobacterium-Bacteroides group. Corresponding to the higher biomass on the YE agar slide, the BALO clone library from YE was most diverse, consisting of Bacteriovorax spp. and a novel clade representing Peredibacter spp. Microbiota from all three biostimulated biofilms were exclusively Gram-negative, and each bacterial guild represented potential prey for BALOs. We propose the use of this simple yet novel slide biofilm assay to study oligotrophic aquatic bacterial diversity which could also potentially be utilized to isolate marine bacteria with novel traits.

Modeling oyster growth rate by coupling oyster population and hydrodynamic models for Apalachicola Bay, Florida, USA

The eastern oyster ( Crassostrea virginica) plays an important role both ecologically and economically in Apalachicola Bay, Florida. Oyster population features such as population size, age structure, spawning, growth, and reproduction are closely related to bay salinity, which is often affected by freshwater flows from the Apalachicola River. Existing modeling approaches have used statistical models to examine the effects of changing freshwater inflow/salinity regime on oyster growth rates in Apalachicola Bay. However, little has been done using population process-based models. In this study, we adapted an oyster population model that simulates a diversity of population processes (including ingestion, assimilation, respiration, reproduction, spawning, recruitment, and mortality) and coupled it with a hydrodynamic model to examine the effects of changes in freshwater flow/salinity on oyster growth rates. We simulated oyster populations at two sites, Cat Point, a less-freshwater-influenced oyster reef, and Dry Bar, a more-freshwater-influenced oyster reef. The model simulations agree reasonably well with field measurements ( r 2 = 0.84). Statistical analyses suggested that oyster growth rates are significantly related to salinity. Lowest oyster growth rates tend to occur in mid-spring due to lowest salinity caused by highest Apalachicola River freshwater inflows whereas the growth peaks tend to occur in mid-summer because of the warm temperature and high food supply. Meanwhile, changes in freshwater inflows affect oyster growth rates through influencing salinities as well as other environmental factors such as food availability; and the magnitudes of the change in oyster growth rates depend on the difference between salinity and salinity range for optimal growth. The salinity range for optimal growth (≥2.0 mg AFDW oyster −1 day −1) is between 20 and 25 ppt at Cat Point and 17–26 ppt at Dry Bar. Only at the optimal salinity level can oysters achieve the maximum growth rates. Our simulations indicate that coupling oyster population process-based models with hydrodynamic models has significant advantage over statistical models in examining the multivariable system and understanding nonlinear relationships between oyster dynamics and environmental factors.

Phytoplankton biomass in a subtropical estuary: Distribution, size composition, and carbon:Chlorophyll ratios

The seasonal pattern of phytoplankton biomass (chlorophyll and particulate organic carbon) and the salinity-related pattern of phytoplankton biomass and size composition were determined in Apalachicola Bay, Florida, throughout 2004. Phytoplankton biomass was highest during summer and lowest during winter. During summer, phytoplankton biomass was highest in waters with salinity between about 5 and 23. In waters between 5 and 23, phytoplankton biomass was primarily (> 50%) composed of < 5 μm cells. The results from this study support the idea that a microbial food web characterizes mass and energy flow through the planktonic food web in Apalachicola Bay and other estuaries. During winter, the carbonxhlorophylla ratio averaged 56 ± 60 (standard deviation). During summer, the ratio ranged from 23 to 345, with highest values occurring in waters with salinity between about 8 and 22. The carbonxhlorophylla ratio was positively related to the percent of chlorophyll < 5 μm in size during summer.

Microzooplankton: major herbivores in an estuarine planktonic food web

Microzooplankton, on average, ingested 10 times more phytoplankton productivity than Acartia tonsa, which dominates the mesozooplankton community in Apalachicola Bay, Florida, USA. Microzooplankton ingested 75% of phytoplankton productivity during winter and summer, respectively. Ciliates, particularly ciliates 50%) component of the microzooplankton diet during the summer high produc- tivity period. Because microzooplankton are prey for organisms occupying higher trophic levels, such as copepods, fish larvae, and oysters, we propose that energy and mass flows mainly from phyto- plankton through microzooplankton to higher trophic levels in Apalachicola Bay. A reduction in dis- charge from the Apalachicola River during our study period led to reductions in rates of grazing, ingestion, and productivity of microzooplankton at a particular salinity. Reduced river discharge also increased the areal extent of higher salinity water where ingestion and productivity of microzoo- plankton were relatively low. Because microzooplankton are key constituents of the estuarine food web in Apalachicola Bay, upstream water diversion that increases the areal extent of higher salinity water in the bay, can be expected to lower microzooplankton productivity and therefore reduce higher trophic level productivity in the bay.

Evaluation of the flushing rates of Apalachicola Bay, Florida via natural geochemical tracers

We used naturally occurring radium isotopes as tracers of water exchange in Apalachicola Bay, a shallow coastal-plain estuary in northwestern Florida. The bay receives fresh water and radium from the Apalachicola River, and mixes with Gulf of Mexico waters through four inlets. We deployed moored buoys with attached Mn-fibers at several stations throughout the estuary during two summer and two winter periods. After deployment for at least one tidal cycle we measured the ratio of the two short-lived radium isotopes 223Ra (half-life = 11 d) and 224Ra (3.6 d) to estimate “radium ages” of the water in the bay. During our four seasonal deployments the river discharge ranged from 338 to 1016 m 3 s − 1. According to our calculations the water turnover time in the bay during these samplings ranged from 6 to 12 days. Age contours in the bay showed that winds and tides as well as river discharge influence the water movement and the residence time of freshwater in the bay. We also calculated the mean age of river water in the bay which was between 5 to 9 days during the studied periods. We suggest that this approach can be used to quantify transport processes of dissolved substances in the bay. For example, soluble nutrient or pollutant transport rates from a point source could be examined. We conclude that the radium age technique is well suited for flushing rate calculations in river dominated shallow estuaries.

Ecology of Acartia tonsa in Apalachicola Bay, Florida, and implications of river water diversion

Acartia tonsa herbivory, carnivory, egg production rate, egg production efficiency, and abundance were studied within various salinity regimes in Apalachicola Bay throughout a 2 yr period. The percent of phytoplankton productivity ingested by A. tonsa ranged from 0 to 24% (median 0.4%). The diet of A. tonsa was mixed. On average, 53% of the diet was composed of phyto- plankton. Per capita total ingestion rate averaged 1.1 ± 1.3 (± SD) μg C adult -1 d -1 during winter, peaked to about 6 μg C adult -1 d -1 during summer, and averaged 2.2 ± 1.8 μg C adult -1 d -1 during summer. A. tonsa ingested the equivalent of 38 ± 48% and 120 ± 93% of its body carbon during win- ter and summer, respectively. During summer, per capita total ingestion rate increased below 20 psu. Average egg production rate (EPR) was lower during winter (13 ± 15 eggs female -1 d -1 ) than during summer (28 ± 24 eggs female -1 d -1 ). During summer, EPR peaked between about 4 and 10 psu. During winter and summer, egg production efficiency (EPE) peaked between about 8 and 14 psu. Salinity tolerance and biochemical composition of phytoplankton ingested may have influenced EPE. Phytoplankton allocated more carbon to protein and lipid synthesis in lower salinity water. The areal extent of lower (<20 psu) salinity water decreases in Apalachicola Bay during periods when river dis- charge is low. Therefore, upstream water diversion during summer can be expected to reduce the areal extent of lower (<20 psu) salinity waters where ingestion rate, EPE, and EPR of A. tonsa are greatest and where A. tonsa is an important prey for Anchoa mitchilli.

Recruitment and Essential Habitat of Juvenile Sand Seatrout (Cynoscion arenarius) in Four Estuaries Along the West Coast of Florida

The sand seatrout (Cynoscion arenarius) is an ecologically and economically important species common to estuarine and nearshore waters of the Gulf of Mexico. Currently, comprehensive information on the essential habitat of juvenile sand seatrout is limited. We analyzed data from a long-term fisheries-independent monitoring program to assess the spatial and temporal distributions of juvenile sand seatrout relative to various habitat parameters in four estuaries (Apalachicola Bay, the Suwannee River estuary, Tampa Bay, and Charlotte Harbor) along the gulf coast of Florida. A total of 25,668 sand seatrout (≤100 mm SL) were collected during monthly stratified-random sampling from Jan. 1996 through Dec. 1997 and Jan. 2001 through Dec. 2003. Specimens were collected with 21.3-m bag seines and 6.1-m otter trawls; the majority of specimens were captured in trawls from water ≥ 1.8 m deep. Juvenile sand seatrout primarily recruited into the estuaries from May through Oct., although recruitment began 1 mo earlier in Tampa Bay. Juveniles were most abundant over unvegetated mud bottoms, in mesohaline salinities, and near salt marsh vegetation. Highest abundances also occurred in small rivers, tidal creeks, and areas adjacent to the mouths of large rivers. Juveniles between 30 mm SL and 70 mm SL primarily occupied mesohaline salinities before shifting toward higher salinities as they approached 100 mm SL.

Voices of Apalachicola

One of Florida's most endangered river systems is the Apalachicola River and Bay basin, and it is not just the natural areas that are threatened but also the history and culture of its people. In Voices of the Apalachicola, veteran storyteller Faith Eidse, together with the staff of the Northwest Florida Water Management District, has compiled a remarkable collection of oral histories from more than 30 individuals who have lived out their entire lives in this region, including the last steamboat pilot on the Apalachicola-Chattahoochee-Flint river system, sharecroppers who escaped servitude, turpentine workers in Tate's Hell, sawyers of old-as-Christ cypress, bee-keepers working the last large tupelo stand, and a Creek chief descended from a 200-year unbroken line of chiefs. As developers increase pressure and populations grow within the basin, this timely collection captures a fascinating and unique moment in history, recalling a resource that once brimmed with life - bigger oysters, larger sturgeon, healthier Torreya trees. The Apalachicola River system is one of the main resources of water not only for Florida, but also Alabama and Georgia. It flows unimpeded for 106 miles from Lake Seminole - where the Chattahoochee and Flint Rivers merge - through the Florida Panhandle into Apalachicola Bay and finally into the Gulf of Mexico. From emerging technologies to environmental health, Eidse captures the battle to preserve and persevere, providing historic and current photos that show how the basin has changed. Habitat maps indicate where our sensitive species live and land preservation maps illustrate how the state of Florida is trying to protect them.

Response of Bdellovibrio and Like Organisms (BALOs) to the Migration of Naturally Occurring Bacteria to Chemoattractants

A dual culture-based and non-culture-based approach was applied to characterize predator bacterial groups in surface water samples collected from Apalachicola Bay, Florida. Chemotaxis drop assays were performed on concentrated samples in an effort to isolate predator bacteria by their chemotactic ability. Yeast extract (YE) and casamino acids (CA) proved to be strong chemoattractants and resulted in three visibly distinct bands; however, dextrose, succinate, pyruvate, and concentrated cells of Vibrio parahaemolyticus P5 as prey did not elicit any response. The three distinct bands from YE and CA were separately collected to identify the chemotactic microbial assemblages. Plaque-forming unit assays from different chemotaxis bands with P5 as prey indicated 5- (CA) to 10-fold (YE) higher numbers of predator bacteria in the outermost chemotactic bands. Polymerase chain reaction-restriction fragment length polymorphism and 16S rDNA sequencing of clones from different chemotaxis bands resulted in identification of Pseudoalteromonas spp., Marinomonas spp., and Vibrio spp., with their numbers inversely proportional to the numbers of predators-i.e., Bdellovibrio spp. and Bacteriovorax spp-in the chemotaxis bands. This study indicates that predatorial bacteria potentially respond to high densities of microbial biomass in aquatic ecosystems and that chemotaxis drop assay may be an alternate culture-independent method to characterize predatorial bacterial guilds from the environment.

Selachohemecus benzi n. sp. (Digenea: Sanguinicolidae) from the blacktip shark Carcharhinus limbatus (Carcharhinidae) in the northern Gulf of Mexico

Selachohemecus benzi Bullard & Overstreet n. sp. infects the heart and kidney of the blacktip shark Carcharhinus limbatus in the northern Gulf of Mexico off Florida and Mississippi, USA. Specimens of S. olsoni Short, 1954, the only congener and only other named blood fluke reported from a chondrichthyan in the Gulf of Mexico, were collected from the heart of the Atlantic sharpnose shark Rhizoprionodon terraenovae from two new localities, Apalachicola Bay, Florida, and Mississippi Sound, Mississippi, USA. The new species differs from S. olsoni by having a larger body (1.4-3.8 mm long), robust tegumental body spines numbering 51-63 along each lateral body margin, a testis extending from the posterior caeca to the ovary, and a medial ovary with lobes. We amend the diagnosis of Selachohemecus Short, 1954 to accommodate it and provide a diagnostic key for all named chondrichthyan blood flukes.

Visual Rating and Strength Testing of 40-Year-Old Precast Prestressed Concrete Bridge Piling

The rating of bridge piles is primarily visual and requires judgment to quantify damage levels and, ultimately, to estimate the pile's remaining structural capacity. A series of tests was run to evaluate the existing capacity of piles that have been in service in a harsh saltwater environment for more than 40 years. In 2004, the Bryant Patton Bridge over Apalachicola Bay in the Florida Panhandle was replaced with a new bridge. The original bridge, which was demolished as part of the construction project, was constructed in 1963. During demolition, 12 pre-stressed concrete piles with varying levels of corrosion damage were recovered. Two of the selected piles were equipped with cathodic protection at the time of their installation in 1994 as part of a repair project that involved most of the pilings supporting the bridge. Visual inspections were conducted by Florida Department of Transportation divers on the selected piles before they were removed. After recovery of the piles, they were cleaned and flexurally tested to failure in a four-point bending test. The results of the flexural tests are presented along with a visual rating of the piles from the divers’ inspection. Flexural capacities of the existing piles were compared with the calculated moment capacities and the undamaged flexural capacities (determined from testing). A few piles that showed little outward sign of damage had a severe reduction in the actual flexural capacity, indicating that assessments by visual inspection do not necessarily correlate well with the actual flexural capacity of piles.

Visual Rating and Strength Testing of 40-Year-Old Precast Prestressed Concrete Bridge Piling

The rating of bridge piles is primarily visual and requires judgment to quantify damage levels and, ultimately, to estimate the pile's remaining structural capacity. A series of tests was run to evaluate the existing capacity of piles that have been in service in a harsh saltwater environment for more than 40 years. In 2004, the Bryant Patton Bridge over Apalachicola Bay in the Florida Panhandle was replaced with a new bridge. The original bridge, which was demolished as part of the construction project, was constructed in 1963. During demolition, 12 prestressed concrete piles with varying levels of corrosion damage were recovered. Two of the selected piles were equipped with cathodic protection at the time of their installation in 1994 as part of a repair project that involved most of the pilings supporting the bridge. Visual inspections were conducted by Florida Department of Transportation divers on the selected piles before they were removed. After recovery of the piles, they were cleaned and flexural...