Padre Island National Seashore Research Articles

INVITED ARTICLE FROM THE 2021 TEXAS ACADEMY OF SCIENCE TEXAS DISTINGUISHED SCIENTIST

Donna Shaver is the Chief of the Division of Sea Turtle Science and Recovery at Padre Island National Seashore and the Texas Coordinator of the U.S. Sea Turtle Stranding and Salvage Network. She received the Lifetime Achievement Award from the International Sea Turtle Society in 2018, the 2013 U.S. Fish and Wildlife Service Endangered Species Recovery Champion Award for Agency Partner in 2014, the Corpus Christi Caller Times 2011 Newsmaker of the Year in 2012, and she was the ABC World News Tonight’s Person of the Week on July 29, 2005. She has studied Texas sea turtles since 1980 and is well known for her leadership role in the recovery of the critically endangered Kemp’s ridley sea turtle. Her studies describing sea turtle migratory and foraging habitat use, as well as nesting and stranding trends, have led to increased protections for sea turtles in Texas and beyond. With over 400 scientific publications and presentations, Shaver is distinguished as one of the top sea turtle biologists in the USA and was named the 2021 Texas Distinguished Scientist at the annual meeting of the Texas Academy of Science. Shaver oversees a variety of sea turtle research and conservation projects conducted in Texas, collaborates with other researchers in the USA and Mexico, and provides training and leadership to hundreds of biologists and volunteers working with sea turtles in Texas.

Embryo deformities and nesting trends in Kemp’s ridley sea turtles Lepidochelys kempii before and after the Deepwater Horizon oil spill

Kemp’s ridley sea turtles Lepidochelys kempii were disproportionately affected by the Deepwater Horizon (DWH) oil spill, which began on 20 April 2010. Embryo deformities were documented in inviable L. kempii eggs before (2008-2010) and after (2011-2013) the DWH spill in 2 Texas (USA) nesting areas (Upper Texas Coast and Padre Island National Seashore). Additional nesting trends, including clutch size and hatching success, were also investigated. Total and late-stage embryo deformity prevalence were 1.5 times greater after 2010 than before, but low in all nesting seasons (mean ± SD: 0.7 ± 8.5% total; 0.6 ± 8.0% late-stage) and did not differ between locations. Craniofacial and carapace deformities were the most frequently observed deformity types. Documented nests in both areas declined in 2010 relative to previous years, ending an exponential increase observed beginning in 1995. Clutch size remained consistent before and after the spill. Hatching success averaged 87.0 ± 33.3% in all years, but no effects from DWH were determined. Collectively, these data represent useful benchmarks against which to judge impacts of future crude oil spills and other catastrophic events.

Green Turtle (Chelonia mydas) Nesting Underscores the Importance of Protected Areas in the Northwestern Gulf of Mexico

Knowledge of the spatial and temporal distribution of green sea turtle (Chelonia mydas) nesting is crucial for management of this species. Limited data exist on the nesting patterns of green turtles along the northwestern Gulf of Mexico (GOM) coast. From 1987 to 2019, 211 green turtle nesting activities were documented on the Texas coast, including 111 confirmed nests and 100 non-nesting emergences. Of the 111 nests, 99 were located on North Padre Island (97 at Padre Island National Seashore (PAIS), 2 north of PAIS) and 12 on South Padre Island (6 within the Laguna Atascosa or Lower Rio Grande Valley National Wildlife Refuges (NWR), 6 outside of a NWR). Of the 100 non-nesting emergences, 75 were on North Padre Island (70 at PAIS, 5 north of PAIS), 21 on South Padre Island (9 within a NWR, 12 outside of a NWR), 1 on Boca Chica Beach, 2 on San Jose Island, and 1 on Mustang Island. Nearly all of the nests (92.8%) and most of the non-nesting emergences (79.0%) were on property protected by the U.S. Department of the Interior as PAIS or a NWR, and confirmed nest density was largest at PAIS, highlighting the importance of these federally protected lands as nesting habitat for this threatened species. Of the 111 located nests, 8 were predated. Mean hatching success of the 103 non-predated nests was 77.4%, and 9,475 hatchlings were released from the predated and non-predated nests. The largest annual number of green turtle nests documented was 29 in 2017. Nesting appeared to increase since 2010, but at a much lower rate than at other GOM nesting beaches. To aid with recovery, efforts should be undertaken to monitor long-term nesting trends, protect nesting turtles and nests, and investigate potential causes for the slower recovery in Texas. Additionally, the genetic structure of the population that nests in Texas should be determined to reveal if the population warrants recognition as a unique management unit, or if it is part of a broader unit that is a shared nesting resource with Mexico which is already being considered as a unique management unit.

Hydrogen peroxide, an ecofriendly remediation method for controlling Microcystis aeruginosa toxic blooms

In February 2017, a Microcystis aeruginosa bloom (maximum 55 μg L−1 chl a and microcystin concentration of 40 μg L−1) occurred in a freshwater pond in Padre Island National Seashore (PINS), TX, USA, causing mortality of migratory redhead ducks and local animals. To treat the pond without further damage to the ecosystem, we proposed the use of H2O2. A nomograph of H2O2 required for oxidizing different initial cyanobacterial biomass levels to achieve desired final microcystin and chl a concentration was developed. With a chl a concentration > 50 μg L−1, the nomograph predicted > 97% removal efficiency when 50 mg L−1 peroxide was used. Then, an outdoor mesocosm experiment with four treatment levels (0, 10, 50 mg L−1 H2O2 and 10 mg L−1 H2O2 with ultrasonication) was tested. In the mesocosm experiment, discrete samples were assessed for cell morphology, pigment, and microcystin toxin content (n = 3) at six different time intervals during the 48-h treatment period. Cell morphology was affected after 4-h exposure at 50 mg L−1 H2O2 treatment. Overall, > 75% of microcystin and > 80% of chl a were destroyed after 48-h exposure to 50 mg L−1 H2O2. The pond was treated with 10 mg L−1 H2O2 which reduced chl a by 60% and microcystin by 35% after 2 days. Control of the cyanobacterial bloom using H2O2 was effective in lab and mesocosm experiments, but the cyanobacterial bloom recovered at PINS 2 weeks after the treatment. The recovery resulted from an insufficient H2O2 addition, identifying a need to re-evaluate current protocols. Overall, no residual H2O2 were detected in any scales of treatment.

Multiple Paternity in a Reintroduced Rookery of Kemp's Ridley Sea Turtles on South Padre Island, Texas

Multiple mating is common in Sea Turtles, and previous studies have suggested that levels of multiple paternity are higher in larger rookeries compared with smaller rookeries. As a result, smaller rookeries may be more vulnerable to the loss of genetic variation than would larger rookeries. The critically endangered Kemp's Ridley Sea Turtle (Lepidochelys kempii) has a single high-density rookery (∼5,000 females) in Rancho Nuevo, Mexico, where high levels of multiple paternity were reported (81% of nests). A secondary nesting colony was re-established on Padre Island National Seashore, Texas, USA, in the early 1980s and, by 2010, 140 nests were found along the entire Texas coast. The relatively small size of the Texas rookery led us to predict low levels of multiple paternity compared with Rancho Nuevo, and we tested our hypothesis by genotyping 158 hatchling tissue samples from 25 nests on South Padre Island (SPI) at 14 microsatellite loci. Full sibship reconstruction indicated that multiple paternity occurred in 47.6% of nests, a value that is significantly lower than the 81% of nests in Rancho Nuevo. Genetic diversity on SPI was high (HO = 0.80) and similar to Rancho Nuevo, although there was a genetic signal of a population bottleneck at SPI. Multiple paternity, small geographic range, and extensive movements by individuals probably act to maintain high genetic variation in this species, despite severe population declines.

Directional dependency and coastal framework geology: implications for barrier island resilience

Abstract. Barrier island transgression is influenced by the alongshore variation in beach and dune morphology, which determines the amount of sediment moved landward through wash-over. While several studies have demonstrated how variations in dune morphology affect island response to storms, the reasons for that variation and the implications for island management remain unclear. This paper builds on previous research by demonstrating that paleo-channels in the irregular framework geology can have a directional influence on alongshore beach and dune morphology. The influence of relict paleo-channels on beach and dune morphology on Padre Island National Seashore, Texas, was quantified by isolating the long-range dependence (LRD) parameter in autoregressive fractionally integrated moving average (ARFIMA) models, originally developed for stock market economic forecasting. ARFIMA models were fit across ∼250 unique spatial scales and a moving window approach was used to examine how LRD varied with computational scale and location along the island. The resulting LRD matrices were plotted by latitude to place the results in the context of previously identified variations in the framework geology. Results indicate that the LRD is not constant alongshore for all surface morphometrics. Many flares in the LRD plots correlate to relict infilled paleo-channels, indicating that the framework geology has a significant influence on the morphology of Padre Island National Seashore (PAIS). Barrier island surface morphology LRD is strongest at large paleo-channels and decreases to the north. The spatial patterns in LRD surface morphometrics and framework geology variations demonstrate that the influence of paleo-channels can be asymmetric (i.e., affecting beach–dune morphology preferentially in one direction alongshore) where the alongshore sediment transport gradient was unidirectional during island development. The asymmetric influence of framework geology on coastal morphology has long-term implications for coastal management activities because it dictates the long-term behavior of a barrier island. Coastal management projects should first seek to assess the framework geology and understand how it influences coastal processes in order to more effectively balance long-term natural variability with short-term societal pressure.

Statistical modeling of the long-range-dependent structure of barrier island framework geology and surface geomorphology

Abstract. Shorelines exhibit long-range dependence (LRD) and have been shown in some environments to be described in the wave number domain by a power-law characteristic of scale independence. Recent evidence suggests that the geomorphology of barrier islands can, however, exhibit scale dependence as a result of systematic variations in the underlying framework geology. The LRD of framework geology, which influences island geomorphology and its response to storms and sea level rise, has not been previously examined. Electromagnetic induction (EMI) surveys conducted along Padre Island National Seashore (PAIS), Texas, United States, reveal that the EMI apparent conductivity (σa) signal and, by inference, the framework geology exhibits LRD at scales of up to 101 to 102 km. Our study demonstrates the utility of describing EMI σa and lidar spatial series by a fractional autoregressive integrated moving average (ARIMA) process that specifically models LRD. This method offers a robust and compact way of quantifying the geological variations along a barrier island shoreline using three statistical parameters (p, d, q). We discuss how ARIMA models that use a single parameter d provide a quantitative measure for determining free and forced barrier island evolutionary behavior across different scales. Statistical analyses at regional, intermediate, and local scales suggest that the geologic framework within an area of paleo-channels exhibits a first-order control on dune height. The exchange of sediment amongst nearshore, beach, and dune in areas outside this region are scale independent, implying that barrier islands like PAIS exhibit a combination of free and forced behaviors that affect the response of the island to sea level rise.

Influence of a spatially complex framework geology on barrier island geomorphology

Barrier island response and recovery to storms, and island transgression with relative sea level rise, can be influenced by the framework geology. The influence of framework geology on barrier island geomorphology has previously been examined in areas where the framework is rhythmic alongshore or consists of an isolated paleo-channel or headland. The purpose of this paper is to examine the influence of framework geology on beach and dune geomorphology at Padre Island National Seashore (PAIS), Texas, USA, where the framework geology is variable alongshore. Alongshore beach and dune morphometrics and offshore bathymetric profiles were extracted from a combined topography and bathymetry digital elevation model (DEM) using an automated approach along the ~100 km study area, and an electromagnetic induction (EMI) survey was used to map the subsurface framework geology. Wavelet decomposition, Global Wavelet (GW), and bicoherence analyses were used to test for spatial relationships between and within the extracted alongshore metrics. GW trendlines demonstrate that beach and dune morphometrics are structurally controlled. Hotspots in wavelet coherence plots between framework geology and alongshore island morphometrics indicate that the paleo-channels dissecting the island influence beach and dune morphology, with large dunes found in the area directly landward of the paleochannels. Bicoherence analysis of alongshore beach and dune morphometrics indicates that low-frequency oscillations due to framework geology interact with higher-frequency oscillations, with greater small-scale variability in the dune line directly landward of the paleo-channels. These results suggest that the paleo-channels of PAIS non-linearly influence beach and dune morphology, which in turn alters the response of the island to storms and sea level rise. It is argued that an understanding of the framework geology is key to predicting island response to sea level rise and framework geology needs to be included in barrier island models. This paper demonstrates that an irregular framework geology influences small-scale coastal processes, and creates interactions across scales that influence beach and dune morphology and affects barrier island response to storms and sea level rise.

GREEN TREE FROG ( HYLA CINEREA) AND GROUND SQUIRREL ( XEROSPERMOPHILUS SPILOSOMA) MORTALITY ATTRIBUTED TO INLAND BREVETOXIN TRANSPORT AT PADRE ISLAND NATIONAL SEASHORE, TEXAS, USA, 2015.

: On 16 September 2015, a red tide ( Karenia brevis) bloom impacted coastal areas of Padre Island National Seashore Park, Texas, US. Two days later and about 0.9 km inland, 30-40 adult green tree frogs ( Hyla cinerea) were found dead after displaying tremors, weakness, labored breathing, and other signs of neurologic impairment. A rainstorm accompanied by high winds, rough surf, and high tides, which could have aerosolized brevetoxin, occurred on the morning of the mortality event. Frog carcasses were in good body condition but contained significant brevetoxin in tissues. Tissue brevetoxin was also found in two dead or dying spotted ground squirrels ( Xerospermophilus spilosoma) and a coyote ( Canis latrans) found in the area. Rainwater collected from the location of the mortality event contained brevetoxin. Green tree frog and ground squirrel mortality has not been previously attributed to brevetoxin exposure and such mortality suggested that inland toxin transport, possibly through aerosols, rainfall, or insects, may have important implications for coastal species.

Phases of blowout initiation and stabilization on Padre Island revealed through ground-penetrating radar and remotely sensed imagery

Blowouts cover a large section of North Padre Island, Texas, and have previously been associated with overgrazing and vehicles driving between the low water line and the toe of the foredune. In the current study, the evolution and migration of 18 blowouts within Padre Island National Seashore are tracked using aerial photographs and satellite images since 1969. Representative active and stabilized trough blowouts are also examined using ground-penetrating radar surveys and remotely sensed imagery to identify the phases of blowout initiation and stabilization between 1969 and 2010. At least five distinct phases can be identified in the radar surfaces and facies of the active blowout, including both the stabilization and reactivation of the blowout throat, whereas only four phases can be identified in the surfaces and facies of a blowout that completely stabilized in 2010. Results suggest that blowout evolution on Padre Island is episodic and is initiated by the opening and closing of the blowout throat during periods with elevated storm surge. The lack of reflectors at depth is evidence that the development of blowouts on Padre Island is a relatively new phenomenon initiated by overgrazing and maintained by compaction of the beach and backshore by vehicles.

Inter-nesting movements and habitat-use of adult female Kemp's ridley turtles in the Gulf of Mexico.

Species vulnerability is increased when individuals congregate in restricted areas for breeding; yet, breeding habitats are not well defined for many marine species. Identification and quantification of these breeding habitats are essential to effective conservation. Satellite telemetry and switching state-space modeling (SSM) were used to define inter-nesting habitat of endangered Kemp’s ridley turtles (Lepidochelys kempii) in the Gulf of Mexico. Turtles were outfitted with satellite transmitters after nesting at Padre Island National Seashore, Texas, USA, from 1998 through 2013 (n = 60); Rancho Nuevo, Tamaulipas, Mexico, during 2010 and 2011 (n = 11); and Tecolutla, Veracruz, Mexico, during 2012 and 2013 (n = 11). These sites span the range of nearly all nesting by this species. Inter-nesting habitat lies in a narrow band of nearshore western Gulf of Mexico waters in the USA and Mexico, with mean water depth of 14 to 19 m within a mean distance to shore of 6 to 11 km as estimated by 50% kernel density estimate, α-Hull, and minimum convex polygon methodologies. Turtles tracked during the inter-nesting period moved, on average, 17.5 km/day and a mean total distance of 398 km. Mean home ranges occupied were 725 to 2948 km2. Our results indicate that these nearshore western Gulf waters represent critical inter-nesting habitat for this species, where threats such as shrimp trawling and oil and gas platforms also occur. Up to half of all adult female Kemp’s ridleys occupy this habitat for weeks to months during each nesting season. Because inter-nesting habitat for this species is concentrated in nearshore waters of the western Gulf of Mexico in both Mexico and the USA, international collaboration is needed to protect this essential habitat and the turtles occurring within it.

Differentiating tidal and groundwater dynamics from barrier island framework geology: Testing the utility of portable multifrequency electromagnetic induction profilers

Electromagnetic induction (EMI) techniques are becoming increasingly popular for near-surface coastal geophysical applications. However, few studies have explored the capabilities and limitations of portable multifrequency EMI profilers for mapping large-scale ([Formula: see text]) barrier island hydrogeology. The purpose of this study is to investigate the influence of groundwater dynamics on apparent conductivity [Formula: see text] to separate the effects of hydrology and geology from the [Formula: see text] signal. Shore-normal and alongshore surveys were performed within a highly conductive barrier island/wind-tidal flat system at Padre Island National Seashore, Texas, USA. Assessments of instrument calibration and signal drift suggest that [Formula: see text] measurements are stable, but vary with height and location across the beach. Repeatability tests confirm [Formula: see text] values using different boom orientations collected during the same day are reproducible. Measurements over a 12 h tidal cycle suggest that there is a tide-dependent step response in [Formula: see text], complicating data processing and interpretation. Shore-normal surveys across the barrier/wind-tidal flats show that [Formula: see text] is roughly negatively correlated with topography and these relationships can be used for characterizing different coastal habitats. For all surveys, [Formula: see text] increases with decreasing frequency. Alongshore surveys performed during different seasons and beach states reveal a high degree of variability in [Formula: see text]. Here, it is argued that surveys collected during dry conditions characterize the underlying framework geology, whereas these features are somewhat masked during wet conditions. Differences in EMI signals should be viewed in a relative sense rather than as absolute magnitudes. Small-scale heterogeneities are related to changing hydrology, whereas low-frequency signals at the broadest scales reveal variations in framework geology. Multiple surveys should be done at different times of the year and tidal states before geologic interpretations can confidently be made from EMI surveys in coastal environments. This strategy enables the geophysicist to separate the effects of hydrology and geology from the [Formula: see text] signal.

Migratory corridors of adult female Kemp's ridley turtles in the Gulf of Mexico

For many marine species, locations of migratory pathways are not well defined. We used satellite telemetry and switching state-space modeling (SSM) to define the migratory corridor used by Kemp's ridley turtles (Lepidochelys kempii) in the Gulf of Mexico. The turtles were tagged after nesting at Padre Island National Seashore, Texas, USA from 1997 to 2014 (PAIS; n=80); Rancho Nuevo, Tamaulipas, Mexico from 2010 to 2011 (RN; n=14); Tecolutla, Veracruz, Mexico from 2012 to 2013 (VC; n=13); and Gulf Shores, Alabama, USA during 2012 (GS; n=1). The migratory corridor lies in nearshore Gulf of Mexico waters in the USA and Mexico with mean water depth of 26m and a mean distance of 20km from the nearest mainland coast. Migration from the nesting beach is a short phenomenon that occurs from late-May through August, with a peak in June. There was spatial similarity of post-nesting migratory pathways for different turtles over a 16year period. Thus, our results indicate that these nearshore Gulf waters represent a critical migratory habitat for this species. However, there is a gap in our understanding of the migratory pathways used by this and other species to return from foraging grounds to nesting beaches. Therefore, our results highlight the need for tracking reproductive individuals from foraging grounds to nesting beaches. Continued tracking of adult females from PAIS, RN, and VC nesting beaches will allow further study of environmental and bathymetric components of migratory habitat and threats occurring within our defined corridor. Furthermore, the existence of this migratory corridor in nearshore waters of both the USA and Mexico demonstrates that international cooperation is necessary to protect essential migratory habitat for this imperiled species.

Poststorm Evolution of Beach-Dune Morphology: Padre Island National Seashore, Texas

ABSTRACT Weymer, B.A.; Houser, C., and Giardino, J.R., 2015. Poststorm evolution of beach-dune morphology: Padre Island National Seashore, Texas. The response and recovery of barrier islands to extreme storms and ultimately to relative sea-level rise depends on the height and extent of the foredunes relative to storm surge. The impact of storms is complicated by the tendency of dune morphology to vary alongshore at a range of spatial scales, and it is reasonable to assume that this variable response will be preserved within subsurface stratigraphy. We used ground-penetrating radar (GPR) and vibracores to investigate subsurface structures for foredunes of different heights within a 2.5-km section of beach at Padre Island National Seashore, Texas. Identical, laterally continuous radar reflectors were observed at each site at a depth of ~1.2 m and interpreted as a storm surface. Results from the smallest dune suggest that the dune experienced little net erosion during the storm but also exhibited the least r...

Burrowing preferences of Atlantic ghost crab, Ocypode quadrata, in relation to sand compaction in Padre Island National Seashore, Texas

It is well understood that human activities can have a negative effect on the flora and fauna of sensitive coastal environments. Small invertebrates, in particular, are susceptible to damage from anthropogenic causes. This paper examines the burrowing preferences of the ghost crab Ocypode quadrata, a small, semi-terrestrial crustacean commonly found in sandy beach/tidal zone environments along the United States’ Atlantic and Gulf coasts. In particular, the effects of beach sand compaction caused by both pedestrian trampling and vehicular traffic at Padre Island National Seashore in Texas (USA) is examined with respect to ghost crab burrowing locations. A mixed method analysis of field-collected data explored the effects of sand compaction on ghost crab burrows located in both high and low traffic beach zones. Both size and number of burrows were larger at those study sites where human disturbance has been greatest. The findings suggest that, though human action does have a measurable effect on both the number and size of burrows, ghost crabs have demonstrated resilience to the effects of human traffic.

Initiation and evolution of blowouts within Padre Island National Seashore, Texas

Blowouts once covered the entire northern section of North Padre Island as a result of overgrazing, but are now restricted to a 5.5 km length of beach where driving is permitted between the low water line and the toe of the foredune. A comparison between this driving section and a directly adjacent non-driving section of the beach reveals a significant difference in the ratio of storm run-up (Rhigh) to the elevation of the dune toe (Dlow), suggesting that the foredunes within the driving section are more susceptible to scarping and blowout development. Where driving is permitted, blowouts are located in areas where Rhigh/Dlow ratio is locally large, suggesting that the location of blowouts depends on the alongshore variation in storm surge. Results of a cluster analysis reveal two distinct blowout types, in which the relatively small blowouts of Cluster 1 are characterized by a small throat and limited expansion beyond the foredune. The large and more active blowouts of Cluster 2 tend to be found closer to the access road, where driving on the beach is more concentrated and the larger Rhigh/Dlow suggests a greater potential for scarping during relatively small storms. The development of these blowouts feeds back on the height of the foredune, making it susceptible to scarping and washover during tropical storms and hurricanes. It is argued that historical overgrazing and recent beach driving have significantly altered this landscape and represents a long-term threat to island resilience and have the potential to hasten island transgression with sea level rise.

Kemp’s ridley Lepidochelys kempii nesting abundance in Texas, USA: a novel approach using genetics to improve population census

Accurate estimates of the annual numbers of nesting females are critical for assessing sea turtle populations. Nesting by Kemp's ridley Lepidochelys kempii turtles has significantly increased at Padre Island National Seashore and nearby beaches in Texas, USA. Four nests were observed in Texas during 1995 and a record of 209 in 2012. However, it is unclear how many clutches are laid by the same females. We used a genetic approach to infer the number of individ- ual nesters from genotypes determined from dead embryos and hatchlings sampled from clutches. Mitochondrial DNA sequencing was combined with nuclear DNA analysis at 10 micro satellite loci to match genotypes for nesters and offspring of unknown parentage in over 50% of the unas- signed nests. Our results indicate that traditional methods, based on observed tagged turtles, have underestimated the number of Kemp's ridleys nesting in Texas. We demonstrate how genetic approaches can be incorporated into population assessments when direct census of adult animals is not feasible. This approach also provides a basis to apply capturemarkrecapture techniques to assess the impact of events, such as the recent oil spill, on the population via sampling of nests to identify and track individual nesters over time.

COYOTE (CANIS LATRANS) AND DOMESTIC DOG (CANIS FAMILIARIS) MORTALITY AND MORBIDITY DUE TO A KARENIA BREVIS RED TIDE IN THE GULF OF MEXICO

In October 2009, during a Karenia brevis red tide along the Texas coast, millions of dead fish washed ashore along the 113-km length of Padre Island National Seashore (PAIS). Between November 2009 and January 2010, at least 12 coyotes (Canis latrans) and three domestic dogs (Canis familiaris) died or were euthanized at PAIS or local veterinary clinics because of illness suspected to be related to the red tide. Another red tide event occurred during autumn 2011 and, although fewer dead fish were observed relative to the 2009 event, coyotes again were affected. Staff at PAIS submitted carcasses of four coyotes and one domestic dog from November 2009 to February 2010 and six coyotes from October to November 2011 for necropsy and ancillary testing. High levels of brevetoxins (PbTxs) were measured by enzyme-linked immunosorbent assay in seven of the coyotes and the dog, with concentrations up to 634 ng PbTx-3 eq/g in stomach contents, 545 ng PbTx-3 eq/g in liver, 195 ng PbTx-3 eq/g in kidney, and 106 ng PbTx-3 eq/mL in urine samples. Based on red tide presence, clinical signs, and postmortem findings, brevetoxicosis caused by presumptive ingestion of toxic dead fish was the likely cause of canid deaths at PAIS. These findings represent the first confirmed report of terrestrial mammalian wildlife mortalities related to a K. brevis bloom. The implications for red tide impacts on terrestrial wildlife populations are a potentially significant but relatively undocumented phenomenon.

Accuracy assessment of a mobile terrestrial lidar survey at Padre Island National Seashore

The higher point density and mobility of terrestrial laser scanning (light detection and ranging (lidar)) is desired when extremely detailed elevation data are needed for mapping vertically orientated complex features such as levees, dunes, and cliffs, or when highly accurate data are needed for monitoring geomorphic changes. Mobile terrestrial lidar scanners have the capability for rapid data collection on a larger spatial scale compared with tripod-based terrestrial lidar, but few studies have examined the accuracy of this relatively new mapping technology. For this reason, we conducted a field test at Padre Island National Seashore of a mobile lidar scanner mounted on a sport utility vehicle and integrated with a position and orientation system. The purpose of the study was to assess the vertical and horizontal accuracy of data collected by the mobile terrestrial lidar system, which is georeferenced to the Universal Transverse Mercator coordinate system and the North American Vertical Datum of 1988. To accomplish the study objectives, independent elevation data were collected by conducting a high-accuracy global positioning system survey to establish the coordinates and elevations of 12 targets spaced throughout the 12 km transect. These independent ground control data were compared to the lidar scanner-derived elevations to quantify the accuracy of the mobile lidar system. The performance of the mobile lidar system was also tested at various vehicle speeds and scan density settings (e.g. field of view and linear point spacing) to estimate the optimal parameters for desired point density. After adjustment of the lever arm parameters, the final point cloud accuracy was 0.060 m (east), 0.095 m (north), and 0.053 m (height). The very high density of the resulting point cloud was sufficient to map fine-scale topographic features, such as the complex shape of the sand dunes.

Foraging area fidelity for Kemp's ridleys in the Gulf of Mexico

For many marine species, locations of key foraging areas are not well defined. We used satellite telemetry and switching state-space modeling (SSM) to identify distinct foraging areas used by Kemp's ridley turtles (Lepidochelys kempii) tagged after nesting during 1998–2011 at Padre Island National Seashore, Texas, USA (PAIS; N = 22), and Rancho Nuevo, Tamaulipas, Mexico (RN; N = 9). Overall, turtles traveled a mean distance of 793.1 km (±347.8 SD) to foraging sites, where 24 of 31 turtles showed foraging area fidelity (FAF) over time (N = 22 in USA, N = 2 in Mexico). Multiple turtles foraged along their migratory route, prior to arrival at their “final” foraging sites. We identified new foraging “hotspots” where adult female Kemp's ridley turtles spent 44% of their time during tracking (i.e., 2641/6009 tracking days in foraging mode). Nearshore Gulf of Mexico waters served as foraging habitat for all turtles tracked in this study; final foraging sites were located in water <68 m deep and a mean distance of 33.2 km (±25.3 SD) from the nearest mainland coast. Distance to release site, distance to mainland shore, annual mean sea surface temperature, bathymetry, and net primary production were significant predictors of sites where turtles spent large numbers of days in foraging mode. Spatial similarity of particular foraging sites selected by different turtles over the 13-year tracking period indicates that these areas represent critical foraging habitat, particularly in waters off Louisiana. Furthermore, the wide distribution of foraging sites indicates that a foraging corridor exists for Kemp's ridleys in the Gulf. Our results highlight the need for further study of environmental and bathymetric components of foraging sites and prey resources contained therein, as well as international cooperation to protect essential at-sea foraging habitats for this imperiled species.