Northerly and Southerly Wind Events in the Eastern Bay of Campeche, Mexico

Migratory soaring birds exhibit spatiotemporal variation in their circannual movements. Nevertheless, it remains uncertain how different winter environments affect the circannual movement patterns of migratory soaring birds. Here, we investigated annual movement strategies of American white pelicans Pelecanus erythrorhynchos (hereafter, pelican) from two geographically distinct wintering grounds in the Southern and Northern Gulf of Mexico (GOM). We hypothesized that hourly movement distance and home range size of a soaring bird would differ between different geographic regions because of different thermals and wind conditions and resource availability. We calculated average and maximum hourly movement distances and seasonal home ranges of GPS-tracking pelicans. We then evaluated the effects of hour of the day, seasons, two wintering regions in the Southern and Northern GOM, human footprint index, and relative pelican abundance from Christmas Bird Count data on pelican hourly movement distances and seasonal home ranges using linear mixed models and generalized linear mixed models. American white pelicans moved at greatest hourly distance near 1200 h at breeding grounds and during spring and autumn migrations. Both wintering populations in the Northern and Southern GOM exhibited similar hourly movement distances and seasonal home ranges at the shared breeding grounds and during spring and autumn migrations. However, pelicans wintering in the Southern GOM showed shorter hourly movement distances and smaller seasonal home ranges than those in the Northern GOM. Hourly movement distances and home ranges of pelicans increased with increasing human footprint index. Winter hourly movements and home ranges of pelicans differed between the Northern and Southern GOM; however, the winter difference in pelican movements did not carry over to the shared breeding grounds during summers. Therefore, exogenous factors may be the primary drivers to shape the flying patterns of migratory soaring birds.

Patterns of population structure and historical genetic demography of blacknose sharks in the western North Atlantic Ocean were assessed using variation in nuclear-encoded microsatellites and sequences of mitochondrial (mt)DNA. Significant heterogeneity and/or inferred barriers to gene flow, based on microsatellites and/or mtDNA, revealed the occurrence of five genetic populations localized to five geographic regions: the southeastern U.S Atlantic coast, the eastern Gulf of Mexico, the western Gulf of Mexico, Bay of Campeche in the southern Gulf of Mexico and the Bahamas. Pairwise estimates of genetic divergence between sharks in the Bahamas and those in all other localities were more than an order of magnitude higher than between pairwise comparisons involving the other localities. Demographic modelling indicated that sharks in all five regions diverged after the last glacial maximum and, except for the Bahamas, experienced post-glacial, population expansion. The patterns of genetic variation also suggest that the southern Gulf of Mexico may have served as a glacial refuge and source for the expansion. Results of the study demonstrate that barriers to gene flow and historical genetic demography contributed to contemporary patterns of population structure in a coastal migratory species living in an otherwise continuous marine habitat. The results also indicate that for many marine species, failure to properly characterize barriers in terms of levels of contemporary gene flow could in part be due to inferences based solely on equilibrium assumptions. This could lead to erroneous conclusions regarding levels of connectivity in species of conservation concern.

The dispersion of surface drifters released over a 7-year period from five locations in the southern Gulf of Mexico is described. It is shown that the drifter dispersion is strongly affected by the main mesoscale circulations features frequently observed in this area. Some of them are the anticyclonic eddies shed by the Loop Current at the eastern side of the Gulf of Mexico, and a semi-permanent cyclonic gyre at the Bay of Campeche. The results are examined further in terms of two dominant and contrasting dispersion scenarios: (i) an intense northward advection of drifters, preferentially along the western margin, and (ii) the retention of drifters in the southernmost part of the Gulf of Mexico. The results are discussed from an environmental point of view, by considering particle dispersion from point sources as an approach to study marine pollution problems.

Seasonal and interannual variability of nitrate in the eastern Chukchi Sea: Transport and winter replenishment

Carbon-sulfur signals of methane versus crude oil diagenetic decomposition and U-Th age relationships for authigenic carbonates from asphalt seeps, southern Gulf of Mexico

Abstract. Hydrocarbon seepage is a widespread process at the continental margins of the Gulf of Mexico. We used a multidisciplinary approach, including multibeam mapping and visual seafloor observations with different underwater vehicles to study the extent and character of complex hydrocarbon seepage in the Bay of Campeche, southern Gulf of Mexico. Our observations showed that seafloor asphalt deposits previously only known from the Chapopote Knoll also occur at numerous other knolls and ridges in water depths from 1230 to 3150 m. In particular the deeper sites (Chapopopte and Mictlan knolls) were characterized by asphalt deposits accompanied by extrusion of liquid oil in form of whips or sheets, and in some places (Tsanyao Yang, Mictlan, and Chapopote knolls) by gas emission and the presence of gas hydrates in addition. Molecular and stable carbon isotopic compositions of gaseous hydrocarbons suggest their primarily thermogenic origin. Relatively fresh asphalt structures were settled by chemosynthetic communities including bacterial mats and vestimentiferan tube worms, whereas older flows appeared largely inert and devoid of corals and anemones at the deep sites. The gas hydrates at Tsanyao Yang and Mictlan Knolls were covered by a 5-to-10 cm-thick reaction zone composed of authigenic carbonates, detritus, and microbial mats, and were densely colonized by 1–2 m-long tube worms, bivalves, snails, and shrimps. This study increased knowledge on the occurrences and dimensions of asphalt fields and associated gas hydrates at the Campeche Knolls. The extent of all discovered seepage structure areas indicates that emission of complex hydrocarbons is a widespread, thus important feature of the southern Gulf of Mexico.

The Bay of Campeche, located in the southern Gulf of Mexico (GoM), is characterized by a semi-permanent cyclonic circulation commonly referred to as the Campeche Gyre (CG). Several studies documenting its upper layer structure have suggested a possible relationship between its seasonal variability and the wind stress, and that non-seasonal variability arises mainly from the interaction of the gyre with Loop Current Eddies (LCEs) that arrive in the region. Nevertheless, a partition of the contributions of these forcings to the circulation of the CG in a statistically consistent manner is still needed. This study examines the wind- and eddy-driven circulation with long-term numerical simulations of the GoM using the HYbrid Coordinate Ocean Model. Our results show that, in the absence of LCEs, the wind can sustain a seasonal-modulated circulation in the CG, confined within the upper 600 m. When considering LCEs, high fluctuations on the flow at intraseasonal time scales are imposed. We found that the LCEs influence the western Bay of Campeche circulation through two main mechanisms: (a) by decelerating and inhibiting the CG through a positive vorticity flux out of the bay, leading to reversals in the flow if LCE southward penetration is large, or (b) by strengthening the CG when a big cyclone, accompanying the LCE, enters the region. It is proposed that the second mechanism is responsible for inducing a net weak cyclonic circulation in the Bay in the absence of wind. Furthermore, past studies have shown that the CG behaves as an equivalent-barotropic flow, with topography acting to confine the CG to the west of the bay. In our modeling results, the role of topography manifests similarly among the different numerical experiments, resulting in closed geostrophic contours to the west of the bay that confine an upper-layer, nearly-symmetric, equivalent-barotropic CG.

Calanoid copepods (CC) are key contributors to the biological carbon pump and pelagic trophic dynamics. The deep-water regions of Perdido and the Bay of Campeche in the western and southern Gulf of Mexico (GM), respectively, differ in hydrography and productivity, leading to potential differences in copepod biomass and community structure. Zooplankton (0-200 m) were collected from the shelf edge to the deep-water region during the winter and summer autumn 2016. Calanoids contributed 38-60% of total zooplankton biomass and 55-70% of overall copepod abundance. The Bay of Campeche had the highest total zooplankton biovolume (287±120 ml 1000 m−3) and total mean copepod abundance (CC and non-calanoids ~146,000 ind. 1000 m−3) during summer-autumn, likely resulting from cross-shelf nutrient transport fueling local productivity. Adult females dominated calanoid numerical abundance (43-50%), thus suggesting a high reproductive potential. Cluster analysis showed differences between seasons (~40% dissimilarity) but not regions. Environmental conditions explained 22% of the variability in community composition; the winter assemblage was significantly related to oxygen concentrations, whereas the summer-autumn community was related to warmer conditions and higher integrated chlorophyll-a concentrations. The CC community responded to seasonal changes more than regionally related hydrographic differences, with likely implications for organic matter cycling and export.

Biogeochemical controls on authigenic carbonate formation at the Chapopote “asphalt volcano”, Bay of Campeche

The approach and selected results of a comprehensive study of storm generated waves and associated winds and currents in the southern Gulf of Mexico (Bay of Campeche) are presented in this paper. The study included the hindcast of historical hurricanes as well as winter storms and the statistical analysis of the hindcast data to determine return period estimated of maximum wave heights and associated parameters throughout the OCS of the southern Gulf of Mexico. A detailed description of hurricane Roxanne (1995) (the most severe hurricane that has affected the area during this century) and its impact on the extreme climate descriptions are also presented. Introduction At the beginning of the offshore drilling operations in the Bay of Campeche, platforms and pipelines were designed using rough estimates of the meteorological and oceanographic (metocean) conditions of this area due to the lack of measurements. Several punctual studies based on Bretschneider's techniques were carried out to establish metocean design conditions for specific sites where most of the platforms were to be located. By November 1993 a definitive study of meteorological and oceanographic normal and extreme conditions in the eastern Bay of Campeche based on application of modem hindcast models was performed1 followed by a measurement program in water depths of 150 and 300 m. Although the measurement program lasted only about one year, it was fully operational during the passage of hurricane Gert, and provided data which served to validate the hindcast methodology. In October 1995, hurricane Roxanne, which formed and became a Category 3 storm in the western Caribbean Sea, crossed the Yucatan Peninsula and then entered the Bay of Campeche. Roxanne meandered there for several days causing severe destruction along the coast of Mexico and significant damage to PEMEX's offshore infrastructure. Little scientific measurement systems were in place in the Bay of Campeche during the storm, so a hindcast was performed to assess the forces responsible for the observed damage and to revisit the extremal analysis to update the rare return period design data2. In the next section, we describe hurricane Roxanne, the results of its hindcast and its rank relative to the results of the November, 1993 study. This is followed by a description of the update design study carried out during 1996 to define extreme and normal conditions throughout Bay of Campeche. Hurricane Roxanne Storm History. Fig 1 shows the storm track. Roxanne passed westward across Yucatán and emerged over the Bay of Campeche on October 12 in a considerably weakened state with central pressure of 990 mb. Further weakening occurred in the following 24 hours after which the center turned toward the northwest and slowly strengthened. A cold front followed by a large high pressure system (1027 mb) moved across the US Gulf Coast states on the 13th and 14th, and these extratropical systems evidently forced Roxanne to turn south and execute a clockwise loop during October 15 and 16. At the beginning of this loop, Roxanne reached again hurricane intensity and during the southward leg of this loop, Roxanne intensified to 979 mb with maximum sustained (1-minute) winds of about 70 knots (130 km/h).

The western Gulf Coast and Caribbean coast are regions that are highly vulnerable to precipitation associated with tropical cyclones (TCs). Defining the spatial dimensions of TC rain fields helps determine the timing and duration of rainfall for a given location. Therefore, this study measured the area, dispersion, and displacement of light and moderate rain fields associated with 35 TCs making landfalls in this region and explored conditions contributing to their spatial variability. The spatial patterns of satellite-estimated rain rates are determined through hot spot analysis. Rainfall coverage is largest as TCs approach the western Caribbean coast, and smaller as TCs move over the Gulf of Mexico (GM) after making landfall over the Yucatan Peninsula. The rain fields are displaced eastward and northward over the western and central Caribbean Sea and the central GM. Rainfall fields have more displacement toward the west and south, which is over land, when TCs move over the southern GM, possibly as a result of the influence of Central American gyres. The area and dispersion of rainfall are significantly correlated with storm intensity and total precipitable water. The displacement of rainfall is significantly correlated with vertical wind shear. Over the Bay of Campeche, TC precipitation extends westward, which may be related to the convergence of moisture above the boundary layer from the Pacific Ocean and near-surface convergence enhanced by land. Additionally, half of the storms produce rainfall over land about 48 h before landfall. TCs may produce light rainfall over land for more than 72 h in this region.

Recent ecological studies from the southern Gulf of Mexico (GoM) provided evidence for the presence of several undescribed kinorhynch species. In the present contribution three new species of Echinoderes from these samples are described. Echinoderes dejesusi sp. nov. has a similar pattern of spines/tubes to species of the Echinoderes dujardinii group, but it is easy to distinguish by its long middorsal spines and lack of type 2 glandular cell outlets. Echinoderes veracruzensis sp. nov. is characterized by spines on segments 4, 6, and 8 and its lateroventral spine pattern, with spines only present on segments 7 to 9. These traits, plus the presence of type 2 glandular cell outlets, allow easy recognition of the species. The third species, Echinoderes xtabay sp. nov., showed a trait not shared with other species, i.e. lateroventral spines on segments 6, 8 and 9. Its trunk appearance is almost rectangular, with very well-developed pachycycli along the anterior margins of segments 2–10, and it has middorsal spines on segments 4, 6, and 8 only. Our results increase the number of Echinoderes species known for the southern GoM from nine to 12. Despite a comprehensive survey in the GoM, the three species described here have only been found in the southern part of the region. http://www.zoobank.org/urn:lsid:zoobank.org:pub:BEF25FE3-E07E-42E3-AA49-E246CBBDD818

Luis Alejandro Yáñez‐Arancibia 1944–2016

Although most research focused on the northern Gulf of Mexico for western Atlantic bluefin tuna, the histological records of reproductive activity of this species in the southern Gulf of Mexico (Mexican waters) have been presented for the first time. This work is the first to study oocyte dynamics in Atlantic bluefin tuna caught in the southern Gulf of Mexico by assessing and comparing them with Mediterranean stock (BFT-E) through stereology using two different methods. Regardless of Atlantic bluefin tuna females returning to their respective spawning grounds at different months in the southern Gulf of Mexico and the Mediterranean, both stocks arrived reproductively inactive and remained in these zones during periods of similar length; they were reproductively active until March for the southern Gulf of Mexico and May for the Mediterranean females. The comparison of the size structure between the two stocks examined using kernel density estimators demonstrated a quite remarkable difference in mean fork lengths between stocks. The ovarian oocyte density, that is, the number of oocytes per gram of ovary, for each gonad stage predicted using the Weibel and Gomez and oocyte packing density (OPD) methods did not significantly differ between stocks and showed that advanced vitellogenic oocytes from spawning-capable females are an appropriate indicator to estimate potential fecundity, presenting values of c. 1273 and ~1355 eggs per gram for the southern Gulf of Mexico and Mediterranean females, respectively. Females caught in Mexican waters (southern Gulf of Mexico) were larger than those caught in the Mediterranean; however, it was demonstrated that the length and weight of females did not affect ovarian oocyte density production. In addition, densities estimated for each gonad stage using W&G and OPD methods did not differ between stocks and presented equal patterns in their oocyte dynamics. These findings contribute to a better understanding of the reproductive biology of Atlantic bluefin tuna, especially in the southern Gulf of Mexico, due to the lack of information regarding this zone, and may allow to support strategies for proper assessment, management, and conservation.

To be able to simulate spatial patterns of predator-prey interactions, many spatially-explicit ecosystem modeling platforms, including Atlantis, need to be provided with distribution maps defining the annual or seasonal spatial distributions of functional groups and life stages. We developed a methodology combining extrapolation and interpolation of the predictions made by statistical habitat models to produce distribution maps for the fish and invertebrates represented in the Atlantis model of the Gulf of Mexico (GOM) Large Marine Ecosystem (LME) (“Atlantis-GOM”). This methodology consists of: (1) compiling a large monitoring database, gathering all the fisheries-independent and fisheries-dependent data collected in the northern (U.S.) GOM since 2000; (2) compiling a large environmental database, storing all the environmental parameters known to influence the spatial distribution patterns of fish and invertebrates of the GOM; (3) fitting binomial generalized additive models (GAMs) to the large monitoring and environmental databases, and geostatistical binomial generalized linear mixed models (GLMMs) to the large monitoring database; and (4) employing GAM predictions to infer spatial distributions in the southern GOM, and GLMM predictions to infer spatial distributions in the U.S. GOM. Thus, our methodology allows for reasonable extrapolation in the southern GOM based on a large amount of monitoring and environmental data, and for interpolation in the U.S. GOM accurately reflecting the probability of encountering fish and invertebrates in that region. We used an iterative cross-validation procedure to validate GAMs. When a GAM did not pass the validation test, we employed a GAM for a related functional group/life stage to generate distribution maps for the southern GOM. In addition, no geostatistical GLMMs were fit for the functional groups and life stages whose depth, longitudinal and latitudinal ranges within the U.S. GOM are not entirely covered by the data from the large monitoring database; for those, only GAM predictions were employed to obtain distribution maps for Atlantis-GOM. Pearson residuals were computed to validate geostatistical binomial GLMMs. Ultimately, 53 annual maps and 64 seasonal maps (for 32 different functional groups/life stages) were produced for Atlantis-GOM. Our methodology could serve other world’s regions characterized by a large surface area, particularly LMEs bordered by several countries.