Aransas Bay Research Articles

Dwarf Seahorse (Hippocampus zosterae) Density, Distribution, and Habitat Use in Texas

Seagrass beds are composed of foundation species, providing essential nursery grounds, feeding areas, and refuge for various marine life. Several species of fish and invertebrates utilize seagrasses as essential habitat. The Dwarf Seahorse (Hippocampus zosterae) is an understudied species in Texas, and little is known about its density, distribution, and habitat associations in this area of their range. Physicochemical water parameters, nekton community data, habitat data, and Dwarf Seahorse catch data were collected at 80 sites in Texas. The highest catch per unit effort (CPUE) of the target species was in Aransas Bay (0.038/m2). There was a positive relationship between the presence and percent cover of turtle grass (Thalassia testudinum) and the presence and CPUE of Dwarf Seahorses. Dwarf Seahorses were detected more often and at a higher CPUE in locations with a higher seagrass community diversity and richness. The nekton community at sites where Dwarf Seahorses were detected was also more abundant, diverse, and species rich. This is the first comprehensive study of the distribution of the Dwarf Seahorse along the Texas coast. Dwarf Seahorses were generally found in higher abundances in association with mature, stable, and diverse seagrass beds. Recommended conservation strategy to protect Dwarf Seahorses should prioritize the protection of established and mature seagrass beds. Continued directed monitoring of this species is recommended to better understand their distribution and population status.

Barrier to the Bays: The Islands of the Texas Coastal Bend and Their Pass by Mary Jo O'Rear

Reviewed by: Barrier to the Bays: The Islands of the Texas Coastal Bend and Their Pass by Mary Jo O'Rear Christopher Morris Barrier to the Bays: The Islands of the Texas Coastal Bend and Their Pass. By Mary Jo O'Rear. (College Station: Texas A&M University Press: 2022. Pp. 280. Illustrations, notes, bibliography, index.) This slender volume breezes through four centuries of history along the Texas Coastal Bend, from early Spanish encounters with Karankawa peoples to President Franklin Roosevelt's catching a prize tarpon. The focus of the book is on the Port Aransas area, Mustang and St. Joseph Isles, water- and wind-sculpted mounds of sand and shells that have marked the Texas Gulf Coast for the last 3,000 years, and the natural passes, shifting bars, and shallow bays around them. The region sustains a diversity of plant and animal life despite significant human-induced alterations, most significantly, the construction of Aransas Channel. Adaptation and contention rather than chronology structure this history. The title, Barrier to the Bays, has a double meaning. The islands bar tumultuous gulf seas from entering the placid waters of what the Spanish called the Laguna Madre and the organisms that thrive therein. The islands also bar ship access to the mainland, much to the frustration of battleship captains and merchant mariners. When General Zachary Taylor planned to use the Texas Coast as a staging area for war with Mexico, he discovered that getting soldiers from New Orleans to St. Joseph Island was easy. Getting from St. Joseph to Corpus Christi Bay was another matter. As O'Rear explains, "Herein lay one of the greatest drawbacks of the waterways of the coast: they silted" (37). Ocean-going schooners could not safely navigate the bay, Taylor's cartographers could not reliably chart its depths, and sailors found the passes "onerous" (39). What was a drawback for generals was a godsend for oysters, shrimp, and sea turtles. But this is no simple history of humans versus the sea. The islands barred destructive winds and waves from coastal settlements. They also prevented waste produced by sheltered towns and ranches from flowing out to sea, allowing it to collect in the bays where "estuaries began to resemble rancid smorgasbords" for sea life (79). The more sewage in the waters, the bigger and more numerous were the turtles and the more the [End Page 607] canning industry thrived. The 1880s saw more than 400,000 pounds of sea turtles processed by Aransas Bay canneries. Barrier islands that sheltered ecologies and the industrious people who lived off them also restricted access to global markets. All those cans of turtle meat had to go somewhere, and by the turn of the century dredging and infrastructural development were in full swing. By 1909, two massive rock jetties reached from the pass between Mustang and St. Joseph Islands nearly a mile and a half into the gulf. The current forced between them scoured the channel bottom to a depth of twenty feet, providing safe passage for ships between the Texas mainland and the Gulf of Mexico. By linking the Laguna Madre to the Gulf, the pass expanded opportunities for commercial fishers and for the service and tourist industries of Port Aransas, which profited from crowds of sport fishers. Fishing guide Barney Farley was a local celebrity by the time he helped President Roosevelt land his big fish a mile or two beyond the jetties. Aransas Pass brought cold gulf water into warm estuaries, altered patterns of wind and water erosion, and sent sediment but also larvae and plankton—fish food—in new directions. By the mid-twentieth century in this altered habitat, Portuguese man-of-wars, starfish, pelicans, and numerous other creatures thrived. Sunken shipwrecks became reefs for gamefish. However, all but gone were the sea turtles, and the shrimp fishery began to decline, both victims of habitat change, industrial development, and over-fishing. A practical understanding of gain and loss inspires present-day conservation efforts among many Coastal Bend residents. Readers should not permit O'Rear's cheery prose and unfortunate penchant for using sentence fragments as topic sentences and chapter openings to diminish the importance of an argument well...

Barrier to the Bays: The Islands of the Texas Coastal Bend and Their Pass by Mary Jo O’Rear

Reviewed by: Barrier to the Bays: The Islands of the Texas Coastal Bend and Their Pass by Mary Jo O’Rear Thomas Blake Earle Barrier to the Bays: The Islands of the Texas Coastal Bend and Their Pass. By Mary Jo O’Rear. Gulf Coast Books. (College Station: Texas A&M University Press, 2022. Pp. xii, 248. $34.95, ISBN 978-1-62349-940-2.) Completing her trilogy on the Texas coastal bend, Mary Jo O’Rear’s Barrier to the Bays: The Islands of the Texas Coastal Bend and Their Pass brings much-needed attention to the coastal South. O’Rear’s latest contribution argues for the importance of the littoral in integrating the region into national and international economies. The primary focus of the book is the centuries-long effort by coastal residents to make the islands, lagoons, and estuaries of the region more amenable to maritime traffic. While nineteenth-century boosters may have claimed that Corpus Christi was destined to be a great port because of its natural advantages—a sheltered bay and shoreside cliffs—it took tremendous effort to make it so. Students and scholars of other Gulf Coast ports could find it useful to follow O’Rear’s lead by explaining how ports are not natural features but manmade infrastructure. O’Rear focuses her study on the chain of barrier islands—Padre, Mustang, Harbor, St. Joseph, and Matagorda—and estuarine bays—Baffin, Corpus Christi, Aransas, Copano, San Antonio, and Matagorda—that form Texas’s coastal bend. What Barrier to the Bays may lack in geographic scope is made up for in temporal expanse. Peering into the prehistoric past, O’Rear describes the natural process that created the barrier islands as silt accreted to form a chain of unstable islands subject to shifting tides and winds. Over the course of two chapters O’Rear jumps to the mid-nineteenth century, giving scant coverage of the millennia of Native American, Spanish, and Mexican engagement (or lack thereof) with the region. The U.S.-Mexico War marks a turning point in O’Rear’s narrative. The conflict brought sustained American attention to the coastal bend. Over the next century, enterprises like cattle ranching on Padre Island, turtle fishing in Aransas Bay, and oil shipment through Harbor Island transformed the coastal bend from a frontier region to a significant commercial node. Two related [End Page 169] themes emerge in describing this transformation: the importance of built infrastructure and the ecological vulnerability of the region. While the bays and islands of the coastal bend offered advantageous settings for ports to ship the produce of the region to faraway markets, this environment had to be remade to ensure safe and efficient navigation. Dredging channels, erecting jetties, and building breakwaters were necessary, not to mention costly, undertakings to turn natural features into commercial assets. “It was the Coastal Bend,” O’Rear tells readers, “that epitomized waterway alteration in the late 1800s” (p. 85). The creation of this infrastructure took its toll on the environment. When the Army Corps of Engineers detonated thousands of pounds of dynamite to remove Old Government Jetty, which had created a sandbar that impeded traffic through Aransas Pass, “wildlife died by the thousands, fish bladders punctured, shellfish fragmented, larvae decimated, and octopuses pulverized. . . . [T]he longtime habitat had been shock-waved into smithereens” (p. 102). This kind of carnage was a predictable result as the coast was made (and remade) to accommodate maritime traffic. Barrier to the Bays will strike some readers as out-of-date. Infelicitous turns of phrase and ahistorical assertions mar the book’s earlier chapters. O’Rear describes the genocide of coastal Native Americans as a “demise” that was “inevitable” (p. 21). Elsewhere, she euphemistically claims that Confederate partisans were driven to “defend [the] Southern lifestyle” without mentioning slavery (p. 41). Furthermore, Barrier to the Bays lacks the argumentative verve and historiographical intervention readers may expect from an academic monograph. But students of the region, and the coastal South more generally, will still find much to admire in O’Rear’s careful work in mining local archives to tell a story rooted in a specific place. Thomas Blake Earle Texas A&M University at...

Differential hypoxia tolerance of eastern oysters from the northern Gulf of Mexico at elevated temperature

Increasing prevalence of hypoxia in shallow waters of U.S. Gulf of Mexico (GoM) estuaries can pose a serious threat to eastern oysters (Crassostrea virginica). Their tolerance to hypoxia, however, is not well characterized, especially at elevated temperatures (>30 °C) typical of GoM estuaries in summer. Moreover, it is unknown whether differences in hypoxia tolerance exist between GoM oyster populations growing in estuaries differing in local environmental conditions. Wild oyster broodstocks were collected from four estuarine sites in Texas (Packery Channel, PC and Aransas Bay, AB) and Louisiana (Calcasieu Lake, CL and Vermilion Bay, VB) and their adult progenies (F1) were tested (Study 1) under continuous hypoxia (<2.0 mg O2 L−1) at 32 °C. Significant differences in hypoxia tolerance were found between F1 populations with calculated median lethal time (LT50) ranging from 3.9 to 12.5 days. PC and CL oysters were the most and least tolerant populations, respectively. The study was repeated twice more (Studies 2 and 3) using PC and CL oysters, and their responses at the organismic, cellular, and biochemical levels were investigated. Valve movement was monitored, and oysters were sampled to measure hemocyte density, plasma protein, calcium and glutathione concentrations, and digestive gland alanine and succinate concentrations after either 3–5 days (Study 2) or 1–3 days (Study 3) of hypoxia exposure. From the onset of hypoxia until their death, oysters stayed opened 13–32% of the time compared to 53–64% under normoxia, but no differences between populations were detected under hypoxia. PC oyster but not CL oyster plasma glutathione concentrations increased significantly in both studies. Under longer (3–5 days) hypoxia exposure, plasma calcium and glutathione concentrations of PC oysters were significantly higher than CL oysters. These results suggest PC oysters were better able to protect tissues against acidosis and oxidative damage during hypoxia and high temperature stress than CL oysters. Overall, our results indicate that oyster populations originating from the GoM vary in their response to hypoxia and high temperature stress and possess differential tolerance.

Radioactive and stable isotopes reveal variations in nearshore submarine groundwater discharge composition and magnitude across low inflow northwestern Gulf of Mexico estuaries

To determine how submarine groundwater discharge (SGD) magnitudes and composition (fresh or saline/recirculated) vary in nearshore low inflow estuaries across ⁓125 km of a semiarid coastline, this study assessed three south Texas estuaries, using radon [222Rn], radium [226Ra and 224Ra], and water isotopes [δ18O and δD]. Mass balance models of time-series 222Rn, found to be representative of total SGD in this study, revealed much higher SGD inputs to the Nueces Estuary (average [x̅] Nueces, Corpus Christi and Oso Bays: 120, 83, and 44 cm·d−1, respectively), attributed to anthropogenically-disturbed substrates and potentially surfacing growth-faults. The lowest 222Rn-derived SGD occurred in the Upper Laguna Madre Estuary (x̅: Upper Laguna Madre and Baffin Bay: 21 and 18 cm·d−1, respectively), explained by the drier climate, lower anthropogenic disturbance, and neighboring groundwater cone of depression. Aransas Bay in the Mission Aransas Estuary received greater average annual precipitation but exhibited low total SGD rates (x̅: 23 cm·d−1). Seasonally, average 222Rn-derived SGD rates increased following Hurricane Harvey (43 cm·d−1 in spring to 64 cm·d−1 in summer). In the Nueces Estuary, the overall 222Rn-derived SGDs were substantially higher than SGDs from 224Ra and 226Ra. The closer agreement between 224Ra and 222Rn-derived SGD and larger 224Ra rates in the Upper Laguna Madre Estuary, Aransas Bay and Oso Bay indicate that saline/recirculated SGD contributions were significant. Values of δ18O and δD confirm these types of inputs, with effects of evaporation/salinization more pronounced where recirculation was predominant and the opposite where terrestrial/222Rn-derived SGD inputs dominate. 226Ra-derived SGDs were lower than the 224Ra due to different behavior of the two isotopes while released into water following transport through saline and fine-grained estuarine sediments or due to wind-driven disturbances.

Morphological Assessment of the Eastern Oyster Crassostrea virginica throughout the Gulf of Mexico

AbstractThe eastern oyster Crassostrea virginica is a commercially and ecologically important organism found throughout the western North Atlantic and Gulf of Mexico. Morphological differences in shell shape of eastern oysters are known to arise from environmental, genetic, and husbandry‐related factors. Here, live eastern oysters were collected from 17 sites along the U.S. Gulf of Mexico coast from Texas to Florida to examine morphological differences among geographic samples. Six morphological metrics were recorded for each individual, and four different composite ratios commonly used to describe oyster shape (fan, cup, volume ratio, and weight ratio) were calculated. Principal component analysis was used to demonstrate geographic differences in ordinated shape ratios, correlating roughly with eastern (Florida), northern (Alabama, Louisiana, north Texas), and western (south Texas) samples. In Texas, differences in shape were correlated with previously described genetic population boundaries, indicating that populations north versus south of Aransas Bay had different overall shell shapes. On a broader scale, shell shape variation correlated roughly with previously described genetic population boundaries throughout the Gulf of Mexico as well as tide depth (intertidal versus subtidal reefs). Among the various factors that might act as drivers of shell shape, individual variation is important, but population structure and tide height are also significant predictor variables of shape in this species.

Divergence in salinity tolerance of northern Gulf of Mexico eastern oysters under field and laboratory exposure.

The eastern oyster, Crassostrea virginica, is a foundation species within US Gulf of Mexico (GoM) estuaries that has experienced substantial population declines. As changes from management and climate are expected to continue to impact estuarine salinity, understanding how local oyster populations might respond and identifying populations with adaptations to more extreme changes in salinity could inform resource management, including restoration and aquaculture programs. Wild oysters were collected from four estuarine sites from Texas [Packery Channel (PC): 35.5, annual mean salinity, Aransas Bay (AB): 23.0] and Louisiana [Calcasieu Lake (CL): 16.2, Vermilion Bay (VB): 7.4] and spawned. The progeny were compared in field and laboratory studies under different salinity regimes. For the field study, F1 oysters were deployed at low (6.4) and intermediate (16.5) salinity sites in Alabama. Growth and mortality were measured monthly. Condition index and Perkinsus marinus infection intensity were measured quarterly. For the laboratory studies, mortality was recorded in F1 oysters that were exposed to salinities of 2.0, 4.0, 20.0/22.0, 38.0 and 44.0 with and without acclimation. The results of the field study and laboratory study with acclimation indicated that PC oysters are adapted to high-salinity conditions and do not tolerate very low salinities. The AB stock had the highest plasticity as it performed as well as the PC stock at high salinities and as well as Louisiana stocks at the lowest salinity. Louisiana stocks did not perform as well as the Texas stocks at high salinities. Results from the laboratory studies without salinity acclimation showed that all F1 stocks experiencing rapid mortality at low salinities when 3-month oysters collected at a salinity of 24 were used and at both low and high salinities when 7-month oysters collected at a salinity of 14.5 were used.

Seed Reserve Hot Spots for the Sub-Tropical Seagrass Halodule wrightii (Shoal Grass) in the Northern Gulf of Mexico

Halodule wrightii (shoal grass) is a dioecious seagrass with a widespread tropical and subtropical distribution. Like all seagrass species, H. wrightii has the ability to expand asexually through rhizome elongation and to reproduce sexually through seed. To better understand H. wrightii sexual recruitment dynamics in the northern Gulf of Mexico, we investigated seed bank densities at 815 sites from south Texas to the Florida Panhandle. H. wrightii seed reserves were spatially variable across the region, with seed densities ranging from 0 to 5290 seeds m−2. Spatial analysis revealed clusters of high seed densities (“hot spots”) in Upper Laguna Madre, TX, and Santa Rosa Sound, FL, and clusters of low seed densities (“cold spots”) in Lower Laguna Madre and Aransas Bay, TX. Hot spots were dominated by H. wrightii, whereas cold spots were dominated by Thalassia testudinum (turtle grass). We frequently found intact seed coat halves, suggesting germination; however, we also encountered broken seed coat pieces, characteristic of seed predation. Genotypic surveys within and adjacent to seed hot spots revealed genetically diverse adult populations 6 years post seed bank sampling. Our data show that H. wrightii seed reserves are heterogeneous across the northern Gulf of Mexico and that the factors driving variation in seed bank density, viability, and germination remain poorly understood. Information on the spatial heterogeneity of H. wrightii seed densities has relevance for seagrass management, including targeting meadows with high levels of reproductive effort for protection or designation as marine reserves.

Observing Hurricane Harvey’s Eyewall at Landfall

AbstractWhile Hurricane Harvey will best be remembered for record rainfall that led to widespread flooding in southeastern Texas and western Louisiana, the storm also produced some of the most extreme wind speeds ever to be captured by an adaptive mesonet at landfall. This paper describes the unique tools and the strategy used by the Digital Hurricane Consortium (DHC), an ad hoc group of atmospheric scientists and wind engineers, to intercept and collect high-resolution measurements of Harvey’s inner core and eyewall as it passed over Aransas Bay into mainland Texas. The DHC successfully deployed more than 25 observational assets, leading to an unprecedented view of the boundary layer and winds aloft in the eyewall of a major hurricane at landfall. Analysis of anemometric measurements and mobile radar data during heavy convection shows the kinematic structure of the hurricane at landfall and the suspected influence of circulations aloft on surface winds and extreme surface gusts. Evidence of mesoscale vortices in the interior of the eyewall is also presented. Finally, the paper reports on an atmospheric sounding in the inner eyewall that produced an exceptionally large and potentially record value of precipitable water content for observed soundings in the continental United States.

Marine Archaeology Assessment in Support of the Bluewater SPM Project, Nueces and Aransas Counties, Texas and Adjoining Federal Waters

Marine Archaeology Assessment in Support of the Bluewater SPM Project, Nueces and Aransas Counties, Texas and Adjoining Federal Waters

Reopening of a Remote Tidal Inlet Increases Recruitment of Estuarine-Dependent Nekton

Cedar Bayou, a natural tidal inlet, was recently dredged to allow for direct water exchange between the Gulf of Mexico and Mesquite Bay, TX, USA. We quantified changes in densities of juvenile nekton (fish, shrimps, and crabs) and community structure in Mesquite Bay after Cedar Bayou was reopened by collecting samples at both control and impact sites using an epibenthic sled 1 year before (October 2013–April 2014) and after (October 2014–April 2015) opening. Significantly higher densities of total nekton were observed at the impact sites after opening using a before-after control-impact design. Red Drum (Sciaenops ocellatus), Atlantic Croaker (Micropogonias undulatus), post-larval penaeid shrimps (Farfantepenaeus aztecus, F. duorarum, and Litopenaeus setiferus), and Blue Crabs (Callinectes sapidus) were significantly more abundant at impact sites after Cedar Bayou was opened. Multivariate analysis showed a significant change in impact site communities after opening and was driven by an increased presence of estuarine-dependent species. Overall, this study demonstrates that opening tidal inlets, such as Cedar Bayou, and reconnecting Mesquite Bay to the Gulf of Mexico increased the presence of numerous estuarine-dependent species, many of which were not present or occurred at very low densities prior to reopening. Thus, reestablishing the historical connectivity between a productive estuary and the open Gulf of Mexico via Cedar Bayou should reinstitute natural nekton recruitment processes important to the Aransas, Mesquite, and San Antonio Bay regions.

Seagrass fragmentation impacts recruitment dynamics of estuarine-dependent fish

Seagrass beds are a key component of the estuarine landscape supporting high productivity, abundant marine life, and serve as nursery areas for many estuarine-dependent species. With increasing anthropogenic activity, there is concern about overall habitat loss via fragmentation and what effects this may have on local biotas relying on seagrasses for persistence. To examine these effects, fragmented seagrass beds (Halodule wrightii, Ascherson 1868) in two different bay systems, Corpus Christi and Aransas Bay, Texas, were delineated, quantified, and mapped, and red drum (Sciaenops ocellatus, Linnaeus 1766) was used as a model species to test for impacts of fragmentation on this common estuarine-dependent species. Red drum density, growth, and movement were measured in response to varying levels of fragmentation (i.e., High, Medium, and Low). No difference in initial recruitment of red drum density was observed among fragmentation levels for newly settled arrivals. However, there was a significant size effect; larger fish were found in non-fragmented areas. Growth rates were also compared among fragmented habitats using both RNA:DNA ratios and otolith microstructure, and no significant effect of growth among fragmentation levels was found. Migration potential was measured at the landscape-level within and among fragmented seagrass meadows by tagging and releasing 200 juvenile red drum into three separate replicated fragmented networks. Within 24h, only one fish was recaptured within the original fragmented network. The vast majority of recaptured fish were found in the nearest continuous non-fragmented seagrass bed over 50m from their release point. These results suggest a temporal transition of small newly recruited red drum, where individuals settle ubiquitously among varying levels of fragmentation but over time migrate toward more continuous beds. This study provides evidence that there may be a fragmentation “threshold” for red drum, whereby once a habitat becomes too fragmented; individuals either suffer higher mortality or more likely move to more continuous landscapes. Overall, this study suggests that habitat fragmentation and loss of more continuous seagrass meadows may have negative impacts on estuarine-dependent species using these areas as their primary recruitment habitat.

Spatial Biodiversity Patterns of Fish within the Aransas Bay Complex, Texas

The goal of this study was to consider the effects of habitat type and environmental conditions on the biodiversity of fishes within the Aransas Bay Complex, Texas and provide a management framework and an ecosystem examination of Essential Fish Habitat (EFH). A stratified, randomized experimental design was used to collect fishes from seagrass, oyster, and non-vegetated habitats within the Aransas Bay Complex from February through May 2010 over large spatial scales at the “bay-complex” level. We developed a biodiversity habitat model using Boosted Regression Trees (BRT). Fitted functions from the “best” fit BRT habitat model indicated that fish biodiversity was greatest in seagrass areas closest to the inlet (< 80 cost-distance units) during early spring, with temperatures < 18°C and dissolved oxygen levels between 7-8 mg O2/L in shallow depths (< 0.5 m). Results from community assemblage analyses showed significant differences among habitats with highest abundance of fishes found in seagrass, followed by non-vegetated substrate, and oyster reef. The relatively high abundance of fishes at non-vegetated bottom compared to the low abundance found at the oyster reef was most likely due to the spatial location of the habitats sampled. Our results indicate that future conservation measures should focus along the eastern and southern areas of Aransas Bay to protect EFH with highest levels of biodiversity. The modeling approach developed in this study provides a framework for natural resource managers to identify habitats supporting the greatest biodiversity of juvenile fishes.

Upolu virus and Aransas Bay virus, two presumptive bunyaviruses, are novel members of the family Orthomyxoviridae.

Emerging and zoonotic pathogens pose continuing threats to human health and ongoing challenges to diagnostics. As nucleic acid tests are playing increasingly prominent roles in diagnostics, the genetic characterization of molecularly uncharacterized agents is expected to significantly enhance detection and surveillance capabilities. We report the identification of two previously unrecognized members of the family Orthomyxoviridae, which includes the influenza viruses and the tick-transmitted Thogoto and Dhori viruses. We provide morphological, serologic, and genetic evidence that Upolu virus (UPOV) from Australia and Aransas Bay virus (ABV) from North America, both previously considered potential bunyaviruses based on electron microscopy and physicochemical features, are orthomyxoviruses instead. Their genomes show up to 68% nucleotide sequence identity to Thogoto virus (segment 2; ∼74% at the amino acid level) and a more distant relationship to Dhori virus, the two prototype viruses of the recognized species of the genus Thogotovirus. Despite sequence similarity, the coding potentials of UPOV and ABV differed from that of Thogoto virus, instead being like that of Dhori virus. Our findings suggest that the tick-transmitted viruses UPOV and ABV represent geographically distinct viruses in the genus Thogotovirus of the family Orthomyxoviridae that do not fit in the two currently recognized species of this genus. Upolu virus (UPOV) and Aransas Bay virus (ABV) are shown to be orthomyxoviruses instead of bunyaviruses, as previously thought. Genetic characterization and adequate classification of agents are paramount in this molecular age to devise appropriate surveillance and diagnostics. Although more closely related to Thogoto virus by sequence, UPOV and ABV differ in their coding potentials by lacking a proposed pathogenicity factor. In this respect, they are similar to Dhori virus, which, despite the lack of a pathogenicity factor, can cause disease. These findings enable further studies into the evolution and pathogenicity of orthomyxoviruses.

An Assessment of Green Turtle (Chelonia mydas) Stocks Along the Texas Coast, with Emphasis on the Lower Laguna Madre

The in-water status of green turtles (Chelonia mydas) in the northwestern Gulf of Mexico has received comparatively little attention in the management and conservation of this species in US waters. We addressed this void via entanglement netting surveys at 3 estuarine areas (Lavaca-Matagorda Bay, the Aransas Bay complex, and the lower Laguna Madre [LLM]) to assess trends in the relative abundance, distribution, and size composition of green turtles in Texas inshore waters during 1991–2010. Overall catch per unit effort (CPUE) in the LLM (1.5 turtles/km-hr) was significantly higher than that observed in the other 2 estuaries and corresponded to general climate patterns and seagrass areal coverage along the Texas coast. Yearly CPUE of green turtles from the LLM exhibited a significant exponential increase from 1991 to 2010, despite variability in capture rate during recent years. Mean straight carapace length (SCL) of green turtles was statistically similar across the 3 study areas and indicative of dominance by juvenile individuals (LLM mean = 42.2 cm SCL). Historical green turtle size data in the LLM also reveal an overall decreasing trend in mean SCL and shift toward an increased percentage of smaller individuals (30–39.9- and 40–49.9-cm SCL size classes). Also, sighting frequency of postpelagic green turtles at the Brazos-Santiago Pass jetties within the LLM during 2009 was roughly 9 times that reported for comparable months during 1992–1993. These results are indicative of enhanced recruitment of neritic green turtles to the northwestern Gulf of Mexico, most likely due to elevated nesting productivity at beaches in Mexico, Florida, the Caribbean, and the western Atlantic. Overall, the lower Texas coast serves as an important developmental foraging habitat for an increasing population of juvenile green turtles in the northwestern Gulf of Mexico.

A Modeling and Field Approach to Identify Essential Fish Habitat for Juvenile Bay Whiff (Citharichthys spilopterus) and Southern Flounder (Paralichthys lethostigma) Within the Aransas Bay Complex, TX

The goal of this study was to use an ecosystem-based approach to consider the effect of environmental conditions on the distribution and abundance of juvenile bay whiff and southern flounder within the Aransas Bay Complex, TX, USA. Species habitat models for both species were developed using boosted regression trees. Juvenile bay whiff were associated with low temperatures ( 10, and moderate to high dissolved oxygen (6–9 mg O2/l, 10–14 mg/l). Juvenile southern flounder were associated with low temperatures ( 8 mg O2/l). Our results indicate that conservation measures should focus along the eastern side of Aransas Bay and the north corner of Copano Bay to protect essential fish habitat. These findings provide a valuable new tool for fisheries managers to aid in the sustainable management of bay whiff and southern flounder and provide crucial information needed to prioritize areas for habitat conservation.

Modeling Potential Coastal Vegetation Response to Sea Level Rise and Storm Surge on Estuarine Peninsulas

Abstract March, R.G. and Smith, E.H., 2012. Modeling potential coastal vegetation response to sea level rise and storm surge on estuarine peninsulas. Upland vegetation changes in response to sea level rise and storm surge were evaluated on two peninsulas adjacent to the Copano Bay–Aransas Bay system and within a semiarid coastal environment in south-central Texas. Potential natural land cover models were created in a geographical information system (GIS) using soil data attributes and elevation data to compare land cover shifts under various sea level rise and storm surge scenarios. Ecological sites used as mapping units were related to land cover classes by generating a classification crosswalk. Crosswalks were expanded in the GIS to define how each land cover type would change with each meter of estuarine inundation using digital elevation models. Potential natural land cover maps show that grassland and/or evergreen are concentrated in the center of both peninsulas with grassland lining the perimeter. ...

The direct role of enzyme hydrolysis on ammonium regeneration rates in estuarine sediments

Benthic ammonium (NH4) regeneration in coastal marine sediments has a fundamental role in nitrogen (N) cycling and N supply to primary producers. Nitrogen regeneration involves benthic microbial mineralization of organic-N, which, in turn, depends on protein hydrolysis. These processes were examined in Aransas Bay (Texas, USA) sediments by monitoring NH4 evolution as a function of enzyme activity in controlled sediment slurries. Casein and tannic acid were added to evaluate the direct role of aminopeptidase on NH4 production and the effects of a polyphenolic enzyme inhibitor, respectively. Casein additions increased the NH4 concentration from 19 ± 0.3 to 737 ± 150 μM in 120 h, a final concentration 4.3-fold higher than that of control samples and 2.9-fold higher than that of samples with casein and tannic added together. Lower NH4 concentration in samples with tannic acid indicated that inhibiting aminopeptidase activity reduced NH4 production rates. The concentration of the regenerated NH4 related directly to aminopeptidase activity in controls (r = 0.86, p < 0.01), casein-enriched (r = 0.89, p < 0.01), and casein plus polyphenol treatments (r = 0.71, p < 0.01) over the first 72 h. The results demonstrate the importance of aminopeptidase in regenerating NH4 in sediments and provide insights about mechanisms of enzyme hydrolysis and NH4 fluxes in estuarine sediments.

Geographic Variability in Salt Marsh Flooding Patterns may Affect Nursery Value for Fishery Species

Flooding of salt marshes controls access to the marsh surface for aquatic organisms and likely regulates the value and use of this habitat for juvenile fishery species. We examined geographic variability in marsh access by measuring tidal flooding characteristics in 15 Spartina alterniflora marshes in the southeastern US between South Texas and lower Chesapeake Bay. Flooding duration and flooding frequency were correlated with the elevation of the marsh edge in relation to mean low water and with the tidal range. Mean annual flooding duration over the years 2006–2008 was highest in Texas (91.5% in Aransas Bay) and North Carolina (89.3% in Pamlico Sound) and lowest in Timbalier Bay, LA (54%) and the lower Carolinas and Georgia (55–57%). We used published data on densities of blue crabs and penaeid shrimps as a measure of habitat selection, and there was a positive relationship between marsh selection and flooding duration.

Vertical Profiles of Major Organic Geochemical Constituents and Extracellular Enzymatic Activities in Sandy Sediments of Aransas and Copano Bays, TX

Vertical distribution patterns of organic geochemical constituents and the enzymes aminopeptidase and β-glucosidase provide insights about the nature and reactivity of sediment organic matter in the sandy sediments of two shallow “South Texas” estuaries. Sediment total organic carbon (TOC) δ13C values indicated that the organic matter (OM) was derived more from a mixture of seagrass and phytoplankton than from terrigenous OM. Down-core amounts of TOC and total nitrogen (TN) were <0.2% of dry weight, respectively. Enzyme activities were highest near surface and ranged from 25 to 1 μM/h for aminopeptidase as compared to 5 to 0.2 μM/h for glucosidase. In Aransas Bay, aminopeptidase activity correlated with sediment TN content (r s = 0.30) and β-glucosidase with TOC content (r s = 0.27). In Copano Bay, aminopeptidase correlated with TOC, TN, and carbohydrate content (r s = 0.89, 0.90, and 0.83, respectively). Variations of glucosidase activity also related positively to TOC, TN, and total carbohydrate content (r s = 0.68, 0.77, and 0.48, respectively). Overall, enzyme activities in these low OM, sandy sediments resembled those for other benthic marine environments.