Gulf Of Mexico Coast Research Articles

Research needs, environmental concerns, and logistical considerations for incorporating livestock grazing into coastal upland habitat management

Along the Gulf of Mexico (GoM) coast, natural resource managers continually struggle with managing coastal uplands due to front-end costs, prolonged maintenance, and habitat-specific ecological needs. Prescribed fire, mechanical removal, and chemical treatments are common habitat management techniques used to remove invasive species, clear understory, and achieve other management goals. However, rapid development and changing climate exacerbate the difficulty in using these techniques. A potential alternative or complementary technique is using livestock for habitat management (i.e., targeted or controlled grazing). In other regions of the world, using livestock for conservation or restoration of managed lands has shown to be a less intrusive and more financially viable alternative. To better understand the research needs, logistical, and environmental concerns related to using livestock for habitat management in the coastal uplands of the GoM, we developed and distributed a survey to three groups of land users, including natural resource managers, researchers, and livestock producers in the region. Survey results show that over 96% of respondents are interested in using livestock for habitat management, but less than 10% of respondents were aware of any information that could be used to inform grazing practices for coastal upland habitat management along the Gulf of Mexico coast. There were differences among surveyed groups, but generally small-sized cattle breeds and goats were identified as the livestock with the most potential for environmental benefit and ease of containment. General concerns and areas for further investigation were implementation (e.g., which livestock type to use and grazing intensity), logistical considerations (e.g., fencing and rotational frequency), impacts of grazing on water quality, wildlife, vegetation, and livestock nutrition. Survey respondents overwhelmingly (at least 75% of each group) indicated that livestock grazing ideally would not be a standalone management practice and should be used in conjunction with other habitat management techniques such as prescribed burns, mechanical clearing, or chemical treatments. The results of the survey could be used to develop applied research projects and guidance documents that directly address informational needs related to using livestock for habitat management of coastal uplands along the Gulf of Mexico coast.

Mexico, State of Yucatan, Gulf of Mexico Coast

Mexico, State of Yucatan, Gulf of Mexico Coast

Use of sediments and soils (paleosols) in construction fills of La Joya archaeological site, Veracruz, Mexico: micromorphological evidence

In this paper, we study the materials used for the construction of earthen structure in the La Joya archaeological site, on the Gulf of Mexico coast, built on top of a paleodune, from the Late Preclassic (400 BC) to the Classic period (AD 100-1000). The first constructions arise around 100 BC, on a paleodune top rising slightly above the surrounding alluvial terraces of the Jamapa river; then it grows into a 15-ha monumental compound. The total construction volume reaches 250,000 m3, all made of earth, surrounded by large artificial water pounds (reservoirs). To understand the kind of components found in the structures and their provenance, we compare the micromorphological features of the materials from the earthen constructions with the sediments and paleosols located in the surrounding areas. Samples were taken from the fills of three first building stages, as well as from a natural soil profile and the natural paleosol horizons found beneath the structures. Micromorphological features found in fills permit to establish the correlation between them and their parent material. The fills from the first stage of construction have fragments of a Btb horizon, mixed with an A horizon, compacted and crushed, in which abundant artifacts are identified. However, these artifacts were not intentionally incorporated to the fills, but had been accumulated on the pre-occupation A horizon as residential and agriculture trash. Particular attention was paid to a gley material occurring in the third building stage, that was believed to come from the sediments accumulated in the original borrow pits transformed into water reservoirs, enclosing the main architectural compound. These reservoir fills share properties of the natural sediments and paleosols but transformed by the waterlogging conditions. In consequence, these materials are interpreted as a case of anthropogenic pedogenesis, where the gley micromorphology indicates waterlogging conditions, but in artificially made reservoirs, as they do not have dark organic sediments that would result of the vegetation typical of a natural pond in a humid tropical environment.

Nuclear genetic diversity and structure of Anastrepha ludens wild populations evidenced by microsatellite markers

The Mexican fruit fly,Anastrepha ludens, is an important pest that causes widespread damage to a number of fruit crops in Mexico. The sterile insect technique (SIT) is commonly used for its control. However, the existence of natural barriers can give rise to a population structure in neutral loci and possibly behavioral or adaptive traits that interfere with SIT. For this reason, it is important to understand the genetic diversity and structure ofA. ludenspopulations and to better understand the evolutionary ecology and population processes in view of possible expansions and possible host shifts due to climate change. We genotyped nine nuclear DNA (nDNA) microsatellite loci among fruit fly populations collected from five biogeographic areas within Mexico, namely, the Mexican Plateau, the Northeastern Coastal Plain, the Pacific Coast, the Gulf Coast of Mexico, and the Soconusco, and a laboratory strain. The nuclear genetic diversity was moderate (fromHe = 0.34 toHe = 0.39) within the wild mexfly population. We found that populations were clustered in three genetic groups (K= 3). The diversity and the genetic structure ofA. ludensare determined by environmental and geological conditions, as well as local conditions like anthropogenic perturbation, which would produce population expansion and the existence of possible predators that would affect the population density. Gene flow showed recent migration among populations. The laboratory strain showed fewer diversity than the wild samples. Large values of current and ancestral population size suggest high resistance to climatic changes, probably due to biological attributes, such as its polyphagous, multivoltine, and high dispersal characteristics. In particular, ecosystem fragmentation and perturbation as well as the existence of new plant hosts would probably increase the abundance of flies.

History and Hydrology: Engineering Canoe Canals in the Estuaries of the Gulf of Mexico

ABSTRACT Local lore has long identified an entrenched feature crossing Fort Morgan peninsula on Alabama’s Gulf of Mexico coast (USA) as an ancient canoe canal, a folk identification now confirmed by archival, artifactual, geochronological, geoarchaeological, and hydrological evidence. A 1.39 km canal (site 1BA709) linked two estuaries, Oyster Bay and Little Lagoon, connecting Mobile Bay to the Gulf of Mexico late in the Middle Woodland period, ca. a.d. 600. Construction of such a large hydraulic engineering feature by a non-agricultural, non-hierarchical society seems unusual but not inconsistent with the sorts of monumental landscape alterations accomplished more routinely by other Woodland populations in eastern North America. Although such canals certainly expedited local travel, communication, and transport, their construction and use had broader social ramifications.

In-Stream Marine Litter Collection Device Location Determination Using Bayesian Network.

Increased generation of waste, production of plastics, and poor environmental stewardship has led to an increase in floating litter. Significant efforts have been dedicated to mitigating this globally relevant issue. Depending on the location of floating litter, removal methods would vary, but usually include manual cleanups by volunteers or workers, use of heavy machinery to rake or sweep litter off beaches or roads, or passive litter collection traps. In the open ocean or streams, a common passive technique is to use booms and a collection receptacle to trap floating litter. These passive traps are usually installed to intercept floating litter; however, identifying the appropriate locations for installing these collection devices is still not fully investigated. We utilized four common criteria and fifteen sub-criteria to determine the most appropriate setup location for an in-stream collection device (Litter Gitter—Osprey Initiative, LLC, Mobile, AL, USA). Bayesian Network technology was applied to analyze these criteria comprehensively. A case study composed of multiple sites across the U.S. Gulf of Mexico Coast was used to validate the proposed approach, and propagation and sensitivity analyses were used to evaluate performance. The results show that the fifteen summarized criteria combined with the Bayesian Network approach could aid location selection and have practical potential for in-stream litter collection devices in coastal areas.

Microtextures on quartz grains from the Gulf of Mexico and the Mexican Pacific coastal sediments: Implications for sedimentary processes and depositional environment

Microtexture analyes on quartz from coastal sediments of the Gulf of Mexico and the Mexican Pacific Coast reveal 35 and 30 types of microtextures, respectively, which were grouped into mechanical, mechanical/chemical and chemical categories based on their mode of origin. Microtextures of chemical origin are rarer in the El Carrizal than in the Manzanillo beach sediments of the Mexican Pacific Coast. Microtextures of mechanical origin like straight and curved scratches, pits, broken edges, and V-shaped marks indicate high energy, fluvial to marine depositional environments. The scarcity to absence of chemical features suggest that the energy level was higher at the Mexican Pacific coast than on the Gulf of Mexico coast. V-shaped marks are common in the Gulf of Mexico sediments, whereas they are abundant in the quartz grains from the Mexican Pacific coast. Increased frequency and density of V-shaped marks are produced by exceedingly high wave velocity during storm events or tsunamis. Abundance of V-shaped marks with fresh surfaces of quartz grains from the Mexican Pacific coast indicate an extremely high-energy impact event. Many quartz grains from the El Carrizal beach of the Mexican Pacific coast have abundant closely spaced V-shaped marks with fewer fresh surfaces. Such high frequency of V-shaped marks is mainly linked to grain-to-grain collision, typically associated with high-energy sub-aqueous conditions with a large volume of sedimentary particles in the water column that are produced during a tsunami or storm events. In contrast, many quartz grains from the Gulf of Mexico have large fresh surfaces with moderate percentages of V-shaped marks that might have been produced by high-energy waves with low sediment concentrations during storm events.

Precise Elevation Thresholds Associated with Salt Marsh–Upland Ecotones along the Mississippi Gulf Coast

Coastal marshes provide essential ecosystem services related to biodiversity, water quality, and protection from erosion. As increasing rates of relative sea-level rise affect many coastal marsh systems, a thorough understanding of marsh responses to sea-level change, particularly the migration of marsh–upland boundaries, becomes essential. The goal of this study was to determine precise elevation thresholds associated with coastal marsh, the marsh–upland ecotone, and upland plant communities along Mississippi’s Gulf of Mexico coast (diurnal, microtidal). Elevations (NAVD88) were measured using survey-grade Global Navigation Satellite System solutions integrated with high-precision leveling. Plant species were sampled at approximately 1-m intervals along each of thirty-three transects extending from intermediate marsh through the marsh–upland ecotone. Elevation thresholds associated with plant community change were determined based on relevant quartiles of the data. Probabilities of occurrence of each plant community type were computed for elevations at the centimeter scale. Results indicated transitions from marsh to ecotone and ecotone to upland at elevations of approximately 0.40 m and 0.60 m, respectively. Understanding the precise nature of these centimeter-scale dependencies of marsh vegetation on coastal elevation will facilitate spatial modeling of marsh transgression in response to sea-level rise, subsidence, changes in sediment flux, and land use change.

Impacts of anthropogenic contaminants and elevated temperature on prevalence and proliferation of Escherichia coli in the wild-caught American oyster, Crassostrea virginica in the southern Gulf of Mexico coast

ABSTRACT Escherichia coli is one of the most common indicators of environmental contamination and health risk to aquatic organisms including shellfish. E. coli can adapt to various stress conditions (e.g. heat, pollution, acidification, etc.). American oyster, Crassostrea virginica, a marine bivalve mollusc, is a seafood popular due to its delicacy and high nutritional value. Based on increasing concern about global warming, coastal pollution and microbial contamination in live or raw seafood, the present study focused on the detection and enumeration of the bacterial pathogen E. coli in the American oyster in south Texas waters, and in controlled laboratory heat-exposure conditions. Immunohistochemical, reverse transcription-polymerase chain reaction (RT-PCR) and quantitative real-time PCR (qRT-PCR) analyses showed substantial bacterial pathogen presence in the gills and digestive glands of oysters collected from polluted sites in San Martin Lake and South Padre Island on the southern Gulf coast of Texas. Laboratory heat-exposure studies showed an increasing trend of E. coli protein and mRNA expression in gills and digestive glands in elevated temperatures (28°C and 32°C) compared with control (24°C) and reduced integrated protein density of E. coli in gills at high temperature. Biochemical analyses were also performed to examine the extrapallial fluid (EPF, an integral body fluid) conditions in oysters. EPF glucose levels, pH and protein concentration varied at high temperatures and appeared to be pertinent to pathogen intensity in oysters. Collectively, these results suggest that American oyster is prone to waterborne pathogen contamination in the southern Gulf of Mexico coast, and E. coli proliferation escalates at rising sea surface temperatures.

Gulf fisheries supported resilience in the decade following unparalleled oiling

AbstractThe 2010 Deepwater Horizon (DwH) disaster challenged the integrity of the Gulf of Mexico (GOM) large‐marine ecosystem at unprecedented scales, prompting concerns of devastating injury for GOM fisheries in the post‐spill decade. Following the catastrophe, projected economic losses for regional commercial, recreational, and mariculture sectors for the decade after oiling were US$3.7–8.7 billion overall, owing to the vulnerability of economically prized, primarily nearshore taxa that support fishing communities. State and federal fisheries data during 2000–2017 indicated that GOM fishery sectors appeared to serve as remarkable anchors of resilience following the largest accidental marine oil spill in human history. Evidence of post‐disaster impacts on fisheries economies was negligible. Rather, GOM commercial sales during 2010–2017 were US$0.8–1.5 billion above forecasts derived using pre‐spill (2000–2009) trajectories, while pre‐ and post‐spill recreational fishery trends did not differ appreciably. No post‐spill shifts in target species or effort distribution across states were apparent to explain these findings. Unraveling the mechanisms for this unforeseen stability represents an important avenue for understanding the vulnerability or resilience of human–natural systems to future disturbances. Following DwH, the causes for fishery responses are likely multifaceted and complex (including exogenous economic forces that typically affect fisheries‐dependent data), but appear partially explained by the relative ecological stability of coastal fishery assemblages despite widespread oiling, which has been corroborated by multiple fishery‐independent surveys across the northern GOM. Additionally, we hypothesize that damage payments to fishermen led to acquisition or retooling of commercial fisheries infrastructure, and subsequent rises in harvest effort. Combined, these social–ecological dynamics likely aided recovery of stressed coastal GOM communities in the years after DwH, although increased fishing pressure in the post‐spill era may have consequences for future GOM ecosystem structure, function, and resilience.

Atmospheric circulation regimes for prescribed burns along the U.S. Gulf of Mexico coast

The regional-to-synoptic-scale steering atmospheric circulation is important for advecting energy, mass, and momentum across space, with the near-surface wind being the local manifestation of this circulation. The local winds can affect phenomena of economic, ecological, and/or aesthetic values, such as bird migrations and prescribed burns to restore bird habitats. The purpose of this research is to classify the days from 1979 to 2018 based on circulation patterns near the surface (i.e., 1000-hPa) and at the highest level of airflow affecting bird migration (i.e., 700-hPa), across the Gulf Coast region of the United States. The resulting patterns, derived from Ward's clustering method on rotated principal component scores, are used as input in a fire management plan to restore niches for bird species such as black and yellow rails and mottled ducks. Results suggest that for the (near-surface) 1000-hPa level, a classification system consisting of eight circulation types maximizes the between-group variability while minimizing the within-group variability, with a total of 95.8 percent of the dataset variance explained, and reasonable correspondence with existing manual, subjective and semi-automated techniques. At the 700-hPa level, a system of eight circulation types was derived, explaining 95.05 percent of the dataset variance. In general, the western U.S. Gulf of Mexico arc is more likely than the eastern to respond to synoptic control in the form of weather types, while the eastern region may have more influence from local-to-meso-scale land and sea breezes. These results will assist in optimizing the success of controlled burn conditions while enhancing efforts to minimize advection to populated areas.

Mexico, Gulf of Mexico Coast

Mexico, Gulf of Mexico Coast

Mexico, State of Veracruz, Gulf of Mexico Coast

Mexico, State of Veracruz, Gulf of Mexico Coast

Mexico, Gulf of Mexico Coast

Mexico, Gulf of Mexico Coast

Sperm Repository for a Breeding Program of the Eastern Oyster Crassostrea virginica: Sample Collection, Processing, Cryopreservation, and Data Management Plan.

Simple SummaryThe Eastern oyster Crassostrea virginica is one of the most important fishery and aquaculture species in the USA and is a keystone species for coastal reefs. A breeding program was initiated in 2019 to support the fast-growing aquaculture industry for this species in the Gulf of Mexico. Oysters from wild populations in embayment along the U.S. Gulf of Mexico coast were used as broodstock for the program to maximize genetic diversity. A sperm repository of the broodstock, including a total of 102 male oysters from the 17 collection sites, was established to support the breeding project. Sperm collection was accomplished by strip spawn, and fresh sperm production, motility, and fertility were recorded for quality analysis. Cryopreserved sperm samples were sorted, labelled, archived, and stored in liquid nitrogen for future use. Post-thaw motility and plasm membrane integrity were recorded as post-thaw quality parameters. Overall, this study demonstrated sperm sample collection, processing, cryopreservation, and a data management plan involved in the establishment of the sperm repository. The streamlined procedure can serve as a template for construction of oyster germplasm repositories for breeding programs.The Eastern oyster Crassostrea virginica (Family Ostreidae) is one of the most important fishery and aquaculture species in the U.S. and is a keystone species for coastal reefs. A breeding program was initiated in 2019 to support the fast-growing aquaculture industry culturing this species in the Gulf of Mexico. Oysters from 17 wild populations in embayment along the U.S. Gulf of Mexico coast from southwest Florida to the Matagorda Bay, Texas were used as broodstock for the program to maximize genetic diversity in the base population. A sperm repository of the broodstock was established to support the breeding project. The goal of this study was to demonstrate the sperm sample collection, processing, cryopreservation, and the data management plan involved in the establishment of a sperm germplasm repository of base populations. The supporting objectives were to: (1) develop a data management plan for the sperm repository; (2) streamline the procedure for sample collection, processing, and cryopreservation; (3) incorporate sperm quality analysis into the procedure, and (4) archive the cryopreserved samples as a repository for future use in the breeding program. This sperm repository included a total of 102 male oysters from the 17 collection sites (six oysters per site). A data management plan was developed with six categories, including sample collection, phenotype, fresh sperm, genotype, cryopreservation, and post-thaw sperm, as guide for data collection. Sperm collection was accomplished by strip spawn, and fresh sperm production, motility, and fertility were recorded for quality analysis. Cryopreserved sperm samples were sorted, labelled, archived, and stored in liquid nitrogen for future use. Post-thaw motility (1–30%) and plasm membrane integrity (15.34–70.36%) were recorded as post-thaw quality parameters. Overall, this study demonstrated a streamlined procedure of oyster sperm collection, processing, and cryopreservation for establishing a sperm repository that can serve as a template for construction of oyster germplasm repositories for breeding programs.

West Indian Manatees Use Partial Migration to Expand Their Geographic Range Into the Northern Gulf of Mexico

Partial migration provides a mechanism for species to shift their geographic ranges into new, environmentally favorable regions but has been poorly studied as a means to alleviate effects of climate change. Populations at the edge of their geographic range are ideal to investigate how migratory behaviors may enable range expansion as adjacent areas become more climatically favorable. We determined the contribution of partial migration to the range expansion of West Indian manatees (Trichechus manatus) using GPS data from tagged individuals that migrated between the northern Gulf of Mexico (nGoM) and primary habitat in peninsular Florida. Most of these manatees migrated to the nGoM annually and exhibited high site fidelity among years. Many individuals spent cumulatively more time in the nGoM than in peninsular Florida, indicating the nGoM is a regular part of their geographic range, and they returned to peninsular Florida to meet temperature-related physiological needs for survival. Autumn migrations most frequently terminated at Crystal River, Florida, and manatees that commenced migration late in the season stopped less frequently and had more directed movements. Spring migrations most frequently terminated at Mobile Bay, Alabama, and several manatees quickly and directly migrated from Florida to nGoM stopover sites. Migrations ranged from 10 to 133 days in length, and variation in duration was primarily driven by use of stopover sites and directedness of travel. These data confirm partial migration as an important component of manatee migratory behavior that has already enabled range shifts for manatees on the U.S.A. Gulf of Mexico coast and has potential to facilitate future responses to climate change. As the most common type of migration across the animal kingdom, partial migration may provide a global mechanism for a diverse variety of species to resist the range limiting effects of climate change.

Observation and modeling of the historic “Godzilla” African dust intrusion into the Caribbean Basin and the southern US in June 2020

Abstract. This study characterizes a massive African dust intrusion into the Caribbean Basin and southern US in June 2020, which is nicknamed the “Godzilla” dust plume, using a comprehensive set of satellite and ground-based observations (including MODIS, CALIOP, SEVIRI, AERONET, and EPA Air Quality network) and the NASA GEOS global aerosol transport model. The MODIS data record registered this massive dust intrusion event as the most intense episode over the past 2 decades. During this event, the aerosol optical depth (AOD) observed by AERONET and MODIS peaked at 3.5 off the coast of West Africa and 1.8 in the Caribbean Basin. CALIOP observations show that the top of the dust plume reached altitudes of 6–8 km in West Africa and descended to about 4 km altitude over the Caribbean Basin and 2 km over the US Gulf of Mexico coast. The dust intrusion event degraded the air quality in Puerto Rico to a hazardous level, with maximum daily PM10 concentration of 453 µg m−3 recorded on 23 June. The dust intrusion into the US raised the PM2.5 concentration on 27 June to a level exceeding the EPA air quality standard in about 40 % of the stations in the southern US. Satellite observations reveal that dust emissions from convection-generated haboobs and other sources in West Africa were large albeit not extreme on a daily basis. However, the anomalous strength and northern shift of the North Atlantic Subtropical High (NASH) together with the Azores low formed a closed circulation pattern that allowed for accumulation of the dust near the African coast for about 4 d. When the NASH was weakened and wandered back to the south, the dust outflow region was dominated by a strong African easterly jet that rapidly transported the accumulated dust from the coastal region toward the Caribbean Basin, resulting in the record-breaking African dust intrusion. In comparison to satellite observations, the GEOS model reproduced the MODIS observed tracks of the meandering dust plume well as it was carried by the wind systems. However, the model substantially underestimated dust emissions from haboobs and did not lift up enough dust to the middle troposphere for ensuing long-range transport. Consequently, the model largely missed the satellite-observed elevated dust plume along the cross-ocean track and underestimated the dust intrusion into the Caribbean Basin by a factor of more than 4. Modeling improvements need to focus on developing more realistic representations of moist convection, haboobs, and the vertical transport of dust.

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.

Late Quaternary paleosols and landscape evolution in dune systems of Veracruz at the Gulf of Mexico coast

The Gulf of Mexico coastal plain contains one of the largest dune systems in Mexico. These dunes and particularly their paleosols contain valuable paleoenvironmental information, however this aspect has been poorly studied. Here, we present the preliminary results obtained from buried paleosols of coastal dune ridges in Veracruz with the aim to reconstruct the environmental conditions during their formation as well as the phases of stability (pedogenesis) and instability (sedimentation) of the landscape. Three profiles were studied in the areas of Punta Delgada, PD (in the north), Palma Sola, PS, and La Mancha, LM (in the south). The chronological frame was constructed by radiocarbon dating of paleosols organic matter and pedogenic carbonates, and by Optical Stimulated Luminiscence (OSL) dating for the dune sediments. For each section several paleosols levels were identified whose properties permitted the differentiation of pedogenetic trends as well as their periods of formation. Nevertheless, the three sections did not provide for a continuous record of pedogenesis and sedimentation, as most of the paleosols are truncated by erosion. PS is the most complete profile which is formed from Marine Isotope Stage (MIS) 5c to MIS 1, with especially well-developed Holocene paleosols. LM includes only paleosols developed during MIS 4 and MIS 3, and PD shows only one paleosol originated during MIS 2. Although, the chronology is not complete as it has been constructed with a few dates, we consider each section contains information from different chronological windows. The results demonstrate that the oldest paleosols formed under more humid conditions during MIS 5c to 5a and probably MIS 4. As the MIS 4 to MIS 2 paleosols contain pedogenic carbonates, we interpret drier climates or with higher evapotranspiration rates. Paleosols from the early Holocene exhibit vertic properties probably formed by seasonal climates. Soils from the Middle-Late Holocene are less developed, due to the activation of the dune sedimentation. The results found here are compared at a regional scale with the dune system in the northern Gulf of Mexico and Yucatan peninsula, revealing both synchronous and asynchronous systems of eolian dynamics. The major asynchrony relates to the Wisconsinian stage (MIS 4 to MIS 2) for which high intensity of dune development is documented in the Veracruz and northern coasts whereas no dunes of that age are found in the Yucatan peninsula.

Genetic diversity of the blue land crab Cardisoma guanhumi (Latreille 1825) in the Alvarado Lagoon System in Veracruz, gulf coast of Mexico

In the Alvarado Lagoon System (ALS) in south-central Veracruz on Mexico's gulf coast, the blue land crab, Cardisoma guanhumi, a semi-terrestrial crustacean species, represents an important fishery resource, but one that is subject to overexploitation and habitat destruction. Identifying genetic diversity and the genetic unit are required to establish efficient conservation strategies. The present study's goal was to assess the genetic structure and degree of genetic diversity of C. guanhumi populations along the ALS. A fragment of the D-loop region of the mtDNA (750 bp) and a partial sequence of the COI gene (580 pb) was sequenced for 120 specimens collected at four sites in the ALS. Genetic diversity indices were estimated for each marker. The study sites' gene flow was estimated, as was the effective population size and the mutational rate for each locality. A haplotype network was built to estimate the gene genealogies of the populations. A Tajima's neutrality test, Fu tests, and mismatch analysis were performed to detect demographic expansion. Results show that this C. guanhumi population has high genetic diversity with a large gene flow among the localities studied and expanded during the recent evolutionary past. All haplotypes from both markers are novel for the species, according to the NCBI GenBank. The high genetic diversity and genetic connectivity among sites suggests that the size of blue crab populations in the ALS has not been drastically affected by past exploitation. Finally, management strategies are proposed to protect the species.