Perdido Fold Belt Research Articles

Fish community structure along a depth gradient at the Western Gulf of Mexico

The Perdido Fold Belt, located in the Western region of the Gulf of Mexico presents great interest due to its potential oil production, which poses great risks to its marine biodiversity. The objective of this study was to record fish diversity, evaluate its variations along a depth gradient from 43.3 m to 3608.0 m, and determine species assemblages, as a baseline prior to natural or anthropogenic impacts. This information is basic for the evaluation and monitoring of the health of the Gulf of Mexico, which will be linked to the anthropogenic influence caused by hydrocarbon extractive processes and overfishing.A total of 63 sampling collections were made at 20 stations during four oceanographic campaigns (May 2016, September-October 2016, June 2017, September-October 2017). Trawling was conducted with a benthic sled on a stratified depth gradient design. A total of 170 fish species within 69 families and 26 orders were recorded. Multivariate analysis revealed three fish assemblages through the depth gradient, shelf (<300 m), upper slope (400–600 m), and the deep zone (>800 m). Both, fish abundance and species richness were highest on the shelf and decreased to the deep regions, where species were scarce and rare. However, considering the benthodemersal community two assemblages were determined at depths < 300 m and from 400 to 1423 m, where specific differences in species abundance were found. The most abundant species recorded on the shelf was Syacium gunteri, on the upper slope Trichopsetta ventralis and Serrranus atrobranchus, and in the deep zone Cyclothone alba and Cyclothone pseudopallida. Some of the recorded fish species are in the Vulnerable category and others are in the Data Deficient category. Our study will contribute to the management and protection of this region where hydrocarbon exploration activities are recently taking place.

Spatiotemporal dynamics of benthic bacterial communities in the Perdido Fold Belt, Northwestern Gulf of Mexico

This study analyzed the spatiotemporal dynamics of surficial benthic microbial communities in a bathymetric gradient (44 - 3573 m) across four oceanographic campaigns at the Perdido Fold Belt (PFB) in the northwestern Gulf of Mexico (nwGoM). Bioinformatic analysis of 16S rRNA gene amplicons grouped the 27 samples into three clusters according to a longitudinal bathymetric gradient. Differences in community structure among clusters, based on PERMANOVA analysis, were partially explained by cruise, water depth, temperature, salinity, nitrate plus nitrite, silicate, redox potential, Ni, Cd, Pb, and Al, as well by aliphatic and aromatic hydrocarbon concentrations. Into microbial community composition, Gemmatimonadaceae, Planctomycetaceae, and the JTB255 were detected at all depths across the four campaigns. Members of Anaerolinaceae and specific sulfate-reducing bacteria were more abundant in sites located between 43 and 1200 m, and Rhodospirillaceae, wb1-A12, OM1 clade, Desulfurellaceae, Gemmatimonadetes, Nitrospinaceae, and Clostridiaceae 1 were better represented in deeper sites. Alpha diversity was similar between the three groups and remained stable; however, 10 samples presented changes in the community structure across the four campaigns. Finally, a multivariable association analysis revealed 25 bacterial genera positively related with physicochemical parameters that characterized the environment from shallow to deep sea sites. Taken together, these results yield insights into the temporal stability of 17 of 27 sites in the PFB and revealed signature taxa with putatively ecological relevance in sedimentary environments.

Exploring the use of Transition Path Theory in building an oil spill prediction scheme

The Transition Path Theory (TPT) of complex systems has proven to be a robust means to statistically characterize the ensemble of trajectories that connect any two preset flow regions, say 𝒜 and ℬ, directly. More specifically, transition paths are such that they start in 𝒜 and then go to ℬ without detouring back to 𝒜 or ℬ. This way, they make an effective contribution to the transport from 𝒜 to ℬ. Here, we explore its use for building a scheme that enables predicting the evolution of an oil spill in the ocean. This involves appropriately adapting TPT such that it includes a reservoir that pumps oil into a typically open domain. Additionally, we lift up the restriction of the oil not to return to the spill site en route to a region that is targeted to be protected. TPT is applied on oil trajectories available up to the present, e.g., as integrated using velocities produced by a data assimilative system or as inferred from high-frequency radars, to make a prediction of transition oil paths beyond, without relying on forecasted oil trajectories. As a proof of concept, we consider a hypothetical oil spill in the Trion oil field, under development within the Perdido Foldbelt in the northwestern Gulf of Mexico, and the Deepwater Horizon oil spill. This is done using trajectories integrated from climatological and hindcast surface velocity and winds as well as produced by satellite-tracked surface drifting buoys, in each case discretized into a Markov chain that provides a framework for the TPT-based prediction.

Dissolved/dispersed polycyclic aromatic hydrocarbon spatial and temporal changes in the Western Gulf of Mexico

Oil extraction and transport activities in the Gulf of Mexico (GoM), along with major marine oil spills and riverine inputs, are exerting environmental pressure on this system by increasing the concentration of oil-related pollutants such as polycyclic aromatic hydrocarbons (PAHs). To fully identify these changes related to oil activities, current PAH levels should be established. Here, we present the PAH concentration and the low molecular weight/high molecular weight (LMW/HMW) ratios obtained in the Perdido Fold Belt area in surface and bottom water at four cruises from May 2016 to September 2017. The Perdido 1 (P1) cruise was conducted in May 2016, the Perdido 2 (P2) cruise in September–October 2016, the Perdido 3 (P3) cruise in June 2017, and the Perdido 4 (P4) cruise in September 2017. Samples were taken during each cruise at up to 3,500-m depth, the deepest ever recorded for the GoM. Results show that the highest concentrations of PAH, LMW PAHs, and HMW PAHs were found in the P4 cruise (1.15, 1.05, and 0.10 µg/L, respectively), well below the 300 µg/L guideline for acute exposure. LMW/HMW ratios show that only the P1 cruise indicates pyrogenic hydrocarbons, while P2, P3, and P4 were petrogenic. The spatial distribution of total PAH, LMW, and HMW showed higher values in the southern and northeastern areas, except for P4, which showed high values related to riverine inputs. The complex hydrodynamic in the region was found to have a significant effect on PAH seasonal changes, river contributions, eddy circulation, and fronts to promote their dispersion.

Community structure of megabenthos of Perdido Fold Belt (Tamaulipas, Mexico) and its relationship with the oceanographic and sediment parameters including potential pollutants

ABSTRACT Various ecosystems of the Gulf of Mexico (GoM) may be impacted by the present increase in offshore oil exploitation. To identify future changes caused by this activity, we assessed the structure of the megabenthos community in the Perdido Fold Belt (PFB) and its relationships with environmental variables, hydrocarbons, and heavy metals. To achieve this, biological and sediment samples were obtained during the surveys Perdido II (PII) and Perdido III (PIII). 325.75 103 ind km−2 and 582.34 kg AFDW km−2 were collected, distributed in 110 species. Crustaceans and echinoderms comprised more than 70% of the total abundance and biomass. The most abundant species were Astropecten cingulatus Sladen, 1883, Callinectes sapidus Rathbun, 1896, Astropecten duplicatus Gray, 1840, and Penaeus aztecus (Ives, 1891) (12.2 103 ≤ ind Km−2 ≤ 59.4 103). They also had the greatest biomass contribution (16.8 ≤ kg AFDW km−2 ≤ 192.2). BIOENV test showed the influence of depth (Z), salinity, dissolved oxygen (DO), Acenaphthylene (Acy), Fluoranthene (Flu), n-C12, n-C37, and nickel (Ni) on the community structure. Recruitment and trawling also influenced the abundance and biomass values. Despite Z defines the environmental gradient, the hydrocarbon concentration gradient within the shelf areas makes it a good candidate for developing monitoring programmes.

Two new genera (Paraeperopeus and Dentimelita) and four new deep-sea amphipod crustacean species of little-known genera (Neohela, Pardaliscella, Pardaliscoides and Tosilus) from the Perdido Fold Belt, Gulf of Mexico

AbstractTwo new genera and six new species of benthic amphipods from the soft sediments of the Perdido Fold Belt region, western Gulf of Mexico, are described. Morphological comparisons of the new species with description of their congeners resulted in the determination of one new genus and one new species of the family Melitidae as Dentimelita lecroyae gen. nov., sp. nov., one new genus and four new species of the family Pardaliscidae as Pardaliscella perdido sp. nov., Paraeperopeus longirostris gen. nov., sp. nov., Pardaliscoides ecosur sp. nov. and Tosilus cigomensis sp. nov., and one new species of the family Unciolidae as Neohela winfieldi sp. nov. The occurrence of the newly described amphipods in the Perdido Fold Belt region represented new geographic range extensions for the genera, including new records of Neohela in the Gulf of Mexico, Pardaliscella and Pardaliscoides in the western Atlantic and Tosilus in the Atlantic.

Comparison of the fish functional arrangement of two contrasting localities in the Gulf of Mexico

AbstractA central objective of ecological research is to understand the causes and links of diversity. Trophic and morphological variation has been recognized as the baseline to determine communities’ functional arrangement; however, few morphological structures have been explored. In the present study, the fish assemblage of two contrasting localities within the Gulf of Mexico, the Campeche Bank (CB) and the Perdido Fold Belt (PFB), was examined to (1) analyse and compare the size, weight, trophic, and morphological (fish body and otolith) variation and (2) test if the otoliths morphological variation can be used to estimate the fish‐body variation. Fish and otolith size, fish and stomach–intestine weight, and stomach content were determined and geometric morphometric methods were applied to the fish body and otoliths. The fish body shows a relationship with the weight measurement and the otolith size, no differences in these variables were found between the two localities. In both localities Annelida, Mollusca, Osteichthyes, and Crustacean are the most common preys; however, the CB assemblage was more diverse in both diet and morphology and six trophic groups and 18 ecomorphological groups were determined, while in PFB, four trophic groups and 13 ecomorphological groups were determined. Finally, according to the morphological comparison in both localities, the otolith variation can be used to estimate the fish‐body morphological diversity. This study reports important information in the understanding of the links between morphological structures and highlights the importance of the otoliths as a morphological variable that reflects a wide range of ecomorphological variation of the fish body.

Bivalve Diversity on the Continental Shelf and Deep Sea of the Perdido Fold Belt, Northwest Gulf of Mexico, Mexico

Mollusk diversity in coastal areas of the Gulf of Mexico (GOM) has been studied extensively, but this is not the case for deep-water habitats. We present the first quantitative characterization of mollusks in shallow and deep waters of the Perdido Fold Belt. The data came from two research cruises completed in 2017. Sediment samples were collected from 56 sites using a 0.25-m2 box corer. We tested hypotheses about spatial patterns of α, β, and γ-diversity of bivalves in two water-depth zones, the continental shelf (43–200 m) and bathyal zone (375–3563 m). A total of 301 bivalves belonging to 39 species were identified. The two zones display similar levels of γ-diversity, but host different bivalve assemblages. In general, α-diversity was higher on the continental shelf, whereas β-diversity was higher in the bathyal zone. These patterns can be explained by the higher input of carbon (energy) to the near-coast shelf zone, as well as by the greater topographic complexity of habitats in the bathyal zone. These results enabled us to propose redirection of sampling efforts for environmental characterization from continental zones to the deep-water zone, especially in the context of environmental assessments during oil and gas exploration and production.

Red Blood Cell Cytotoxicity Associated to Heavy Metals and Hydrocarbons Exposure in Flounder Fish from Two Regions of the Gulf of Mexico.

In this study, the genotoxic effect of contaminants was assessed through detection of DNA damage using the micronucleus (MNs) test in erythrocytes from 149 flounder fish collected in two regions of the Gulf of Mexico (GoM). The frequency of microcytes (MCs) was also evaluated in the same group of fish collected from the Perdido Foldbelt (PF) and the Yucatan Platform (YP). The MCs frequency was different among locations of the YP (p = 0.011), while MNs frequency varied among locations of PF (p = 0.024). MCs and MNs values correlated with heavy metals from fish muscle, fish species and localities. Mean number, prevalence, and intensity of MCs and MNs correlated with Al, PAHs, depth, and locality. MNs frequency showed a species-specific association (p = 0.004). MNs and MCs were associated with heavy metals and PAHs from fish muscle and sediments, and the MNs frequency was species dependent.

Bacteria From the Southern Gulf of Mexico: Baseline, Diversity, Hydrocarbon-Degrading Potential and Future Applications

The Gulf of Mexico Research Consortium (Consorcio de Investigación del Golfo de México (CIGoM), 2020) was founded in 2015 as a consortium of scientific research and consulting services, specializing in multidisciplinary projects related to the potential environmental impacts of natural and human-induced oil spills in marine ecosystems, to understand and act in the case of possible large-scale oil spills in the Gulf of Mexico. CIGoM comprises more than 300 specialized researchers trained at the most recognized Mexican institutions. Among the main interests of CIGoM are developing the first baseline of the bacterial community inhabiting the southern Gulf of Mexico, investigating the natural degradation of hydrocarbons by bacterial communities and microbial consortia and identifying and characterizing industrially relevant enzymes. In this review, using third-generation sequencing methodologies coupled to function screening methodologies, we report the bacterial profile found in samples of water and sediments in Mexican regions that include the Perdido Fold Belt (northwest of Mexico), Campeche Knolls (in the southeast) and Southwest region of the Gulf of Mexico. We also highlight some examples of novel lipases and dioxygenases with high biotechnological potential and some culturable hydrocarbon-degrading strains used in diverse bioremediation processes.

Microbial prospection of communities that produce biosurfactants from the water column and sediments of the Gulf of Mexico.

Microbial communities capable of hydrocarbon degradation linked to biosurfactant (BS) and bioemulsifier (BE) production are basically unexplored in the Gulf of México (GOM). In this work, the BS and BE production of culturable marine bacterial hydrocarbonoclasts consortia isolated from two sites (the Perdido Fold Belt and Coatzacoalcos area) was investigated. The prospection at different locations and depths led to the screening and isolation of a wide variety of bacterial consortia with BS and BE activities, after culture enrichment with crude oil and glycerol as the carbon sources. At least 55 isolated consortia presented reduction in surface tension (ST) and emulsifying activity (EI24 ). After colony purification, bacteria were submitted to polyphasic analysis assays that resulted in the identification of different strains of cultivable Gammaproteobacteria Gram (-) Citrobacter, Enterobacter, Erwinia, Pseudomonas, Vibrio, Shewanella, Thalassospira, Idiomarina, Pseudoalteromonas, Photobacterium, and Gram (+) Staphylococcus, Bacillus, and Microbacterium. Overall, the best results for ST reduction and EI24 were obtained with consortia. Individually, Pseudomonas, Bacillus, and Enterobacter strains showed the best results for the reduction of ST after 6 days, while Thalassospira and Idiomarina strains showed the best results for EI24 (above 68% after 9 days). Consortia isolates from the GOM had the ability to degrade crude oil by up to 40-80% after 24 and 36 months, respectively. In all cases, biodegradation of crude oil was related to the reduction in ST and bioemulsifying activity and was independent from the depth in the water column.

Origin, migration, and characterization of petroleum in the Perdido Fold Belt, Gulf of Mexico basin

Herein, the characteristics and origin of petroleum in the Perdido Fold Belt (PFB) were studied and the petroleum migration processes and system elements are discussed. The molecular compositions and stable carbon isotopes indicate that natural gases in the PFB are mainly organic and have similar origins. Further, they are mainly sapropel type gases and originated from kerogen cracking. The oil in this region has a high API gravity and contains a relatively high sulfur content. The light hydrocarbon values indicate that most of the oil samples are sapropel type oil. Based on the geochemical characteristics of petroleum, Tithonian is considered to be the dominant source rock in the PFB. Various parameters regarding petroleum maturity suggest that the natural gases and oil are mature. The calculated temperature and vitrinite reflectance of the oil samples indicate that petroleum charging occurred from the Middle to Late Eocene. API gravity and sulfur content are related to maturity and herein, indicate that the Tithonian source rocks are mainly type II-S kerogen and the associated high API gravity of petroleum can be primarily attributed to this kerogen. Petroleum migration in the PFB was jointly controlled by salt activity and petroleum generation, wherein. The active faults and the Wilcox sandstones acted as petroleum migration pathways, allowing large petroleum reservoirs to form from the Middle to Late Eocene.

Implications of the depth profile on the functional structure of the fish community of the Perdido Fold Belt, Northwestern Gulf of Mexico

Studies have demonstrated that environmental conditions affect the richness, diversity, and abundance of fish communities. Depth is an important variable with many species showing preferences for specific depth ranges. Here, we present a functional analysis of the fish community in the Perdido Fold Belt (PFB), Gulf of Mexico. The sampling design was structured across a depth range of 40–3500 m, using 20 oceanographic stations. The aims of our study were: (1) to determine the functional arrangement of the fish community in the PFB; and (2) to describe the effect of the environmental variables on fish richness and functional diversity. A total of 232 species were identified; 195 were grouped into 42 functional groups (FGs). Thirty-seven species did not group with any others and are referred to as “functionally independent species” (FIS). According to our results, depth changes in physicochemical variables allow us to segregate three vertically stratified zones: shelf, slope, and deep. Temperature was the most important environmental variable constraining functional distribution of fishes. The highest FG diversity, species diversity, and biomass were found in the shelf/slope zone (SSo), while the highest diversity of FIS was found in the shelf zone. As the SSo displays its highest diversity, and since greater diversity has been linked with greater resilience and stability of fish communities, the SSo may be the most resilient zone of the PFB. Our study provides the first description of the diversity and resilience of the PFB fish community and helps our understanding of the factors constraining the distribution and functional diversity of fishes across depth gradients.

Metagenomic Profiling and Microbial Metabolic Potential of Perdido Fold Belt (NW) and Campeche Knolls (SE) in the Gulf of Mexico.

The Gulf of Mexico (GoM) is a particular environment that is continuously exposed to hydrocarbon compounds that may influence the microbial community composition. We carried out a metagenomic assessment of the bacterial community to get an overall view of this geographical zone. We analyzed both taxonomic and metabolic markers profiles to explain how the indigenous GoM microorganims participate in the biogeochemical cycling. Two geographically distant regions in the GoM, one in the north-west (NW) and one in the south-east (SE) of the GoM were analyzed and showed differences in their microbial composition and metabolic potential. These differences provide evidence the delicate equilibrium that sustains microbial communities and biogeochemical cycles. Based on the taxonomy and gene groups, the NW are more oxic sediments than SE ones, which have anaerobic conditions. Both water and sediments show the expected sulfur, nitrogen, and hydrocarbon metabolism genes, with particularly high diversity of the hydrocarbon-degrading ones. Accordingly, many of the assigned genera were associated with hydrocarbon degradation processes, Nitrospira and Sva0081 were the most abundant in sediments, while Vibrio, Alteromonas, and Alcanivorax were mostly detected in water samples. This basal-state analysis presents the GoM as a potential source of aerobic and anaerobic hydrocarbon degradation genes important for the ecological dynamics of hydrocarbons and the potential use for water and sediment bioremediation processes.

First records of marine tardigrades of the genus Coronarctus (Tardigrada, Heterotardigrada, Arthrotardigrada) from Mexico

Deep-water sampling in the Perdido Fold Belt, Gulf of Mexico, Mexican Economic Exclusive Zone yielded five specimens of tardigrades belonging to the genus Coronarctus Renaud-Mornant, 1974. The specimens represent the first records of the genus for Mexico. Two two-clawed larvae and two four-clawed larvae of Coronarctus mexicus Romano, Gallo, D&amp;rsquo;Addabbo, Accogli, Baguley &amp;amp; Montagna, 2011 and a single four-clawed larval specimen of an undescribed Coronarctus species were identified. Taxonomic analysis of the specimens contributed to the knowledge of deep-sea and Mexican marine tardigrades, two data-poor areas of study.

Clustered BSRs: Evidence for gas hydrate-bearing turbidite complexes in folded regions, example from the Perdido Fold Belt, northern Gulf of Mexico

We describe previously undocumented but extensive gas hydrate accumulations in the mouth of Perdido Canyon in the northern Gulf of Mexico. The accumulations are located within central parts of structural domes (four-way closures) and are characterized by stacked, high-amplitude bottom simulating reflections (BSRs) that we call clustered BSRs. Seismic data from Perdido Canyon show two clustered BSRs associated with turbidite sequences within two dome folds formed from tectonic folding and salt diapir rise. The northwestern (NW) and southeastern (SE) clustered BSRs have aerial extents of ∼25 km2 and 50 km2, respectively. Well log data confirm gas hydrate occurs above the NW clustered BSR, within a 225 m-thick consistently high-resistivity interval that we interpret as gas hydrate in near-vertical fractures and turbidite sands. The SE dome is only drilled at the edge of the BSR; nevertheless, the well log data indicate that a 30 m-thick gas hydrate accumulation is present. Gas chromatographic logs in both domes suggest a gradual transition from predominantly microbial gas below the BSR (500–1000 m below seafloor (mbsf)) to thermogenic gas at 1000–2000 mbsf. Based on the well log data and seismic stratigraphic analysis, we find gas hydrate is concentrated in fractures in marine mud, as well as in the pores of submarine fan turbidities, where saturations reach as high as 75%. An estimate of the total gas hydrate-bound gas volume at standard temperature and pressure is between 0.04 and 0.17 trillion cubic meters (TCM) assuming average hydrate saturation of 5-20% in a ∼45 m thick turbidite sand unit above the Perdido Canyon BSR area. Measured BSR extent and gas volume estimates indicate that the NW and SE reservoirs are among the largest gas hydrate occurrences known in the Gulf of Mexico.

Analogue model of gravity driven deformation in the salt tectonics zone of northeastern Mexico

In the deep seated gravity-driven deformation systems of the Gulf of Mexico contemporaneous extension and contraction of the overburden is favored by mechanical decoupling from the basement along thick salt sequences (up to 4 km). The updip extension is located inland, on the continental shelf of northeast Mexico, and is characterized by extensional listric faults and roll-overs; the downdip shortening zone is located at the deep waters and is characterized by a fold and thrust belt detached above the salt layer. Two physical experiments are used to discuss some aspects of these gravity-driven systems. The experimental setup includes a motor-driven experimental table, an inclined brittle basement (1°), a silicone layer simulating the salt sequences, and sand layers simulating the pre-kinematic Jurassic-Cretaceous strata before Laramide shortening. Deformation resulted in further tilting of the basement (3° to 4°). After the onset of deformation, thin sand layers were added at regular time intervals simulating the syntectonic sedimentation. The experiments reproduced the geometry of the deformation at the frontal ramp characterized by a seaward vergent thrust and its associated deformed region (the Perdido fold belt). The fold and thrust belt localization was favored by the change in basement inclination (a built-in slope change). Key elements interpreted in one available section of the area were reproduced in the model: a) the presence of an antithethic roll-over in the extensional zone and, b) the basinward vergence of folds and thrusts observed in the downdip shortening zone in the mexican Perdido fold belt.

Invertebrate Megafauna in the Perdido Fold Belt Polygon, Gulf of Mexico, Mexico

Four oceanographic campaigns were done in the Perdido Fold Belt zone of the Gulf of Mexico during 2016 and 2017 to generate baseline data on several macrodescriptors to characterize the region and establish existing biological-ecological conditions before hydrocarbon exploitation begins in the area. General megafauna invertebrate data were collected by trawling with a sled net (2.4m2aperture). Seven Phyla were recorded in 66 trawls in a 274,593m2 area at depths ranging from 44 to 3609 m. Species richness was 299, abundance was 37,024org/hectare, and biomass was 305.5kg/hectare. Total ecological diversity for invertebrate megafauna in the study area as represented by the Shannon-Wiener index, was 5.35bits/ind.Megafauna in this area of the Gulf is very diverse, with the highest abundances of Phyla and species recorded nearest the coast.

Assessment of the bacterial community structure in shallow and deep sediments of the Perdido Fold Belt region in the Gulf of Mexico.

The Mexican region of the Perdido Fold Belt (PFB), in northwestern Gulf of Mexico (GoM), is a geological province with important oil reservoirs that will be subjected to forthcoming oil exploration and extraction activities. To date, little is known about the native microbial communities of this region, and how these change relative to water depth. In this study we assessed the bacterial community structure of surficial sediments by high-throughput sequencing of the 16S rRNA gene at 11 sites in the PFB, along a water column depth gradient from 20 to 3,700 m, including five shallow (20–600 m) and six deep (2,800–3,700 m) samples. The results indicated that OTUs richness and diversity were higher for shallow sites (OTUs = 2,888.2 ± 567.88; H′ = 9.6 ± 0.85) than for deep sites (OTUs = 1,884.7 ± 464.2; H′ = 7.74 ± 1.02). Nonmetric multidimensional scaling (NMDS) ordination revealed that shallow microbial communities grouped separately from deep samples. Additionally, the shallow sites plotted further from each other on the NMDS whereas samples from the deeper sites (abyssal plains) plotted much more closely to each other. These differences were related to depth, redox potential, sulfur concentration, and grain size (lime and clay), based on the environmental variables fitted with the axis of the NMDS ordination. In addition, differential abundance analysis identified 147 OTUs with significant fold changes among the zones (107 from shallow and 40 from deep sites), which constituted 10 to 40% of the total relative abundances of the microbial communities. The most abundant OTUs with significant fold changes in shallow samples corresponded to Kordiimonadales, Rhodospirillales, Desulfobacterales (Desulfococcus), Syntrophobacterales and Nitrospirales (GOUTA 19, BD2-6, LCP-6), whilst Chromatiales, Oceanospirillales (Amphritea, Alcanivorax), Methylococcales, Flavobacteriales, Alteromonadales (Shewanella, ZD0117) and Rhodobacterales were the better represented taxa in deep samples. Several of the OTUs detected in both deep and shallow sites have been previously related to hydrocarbons consumption. Thus, this metabolism seems to be well represented in the studied sites, and it could abate future hydrocarbon contamination in this ecosystem. The results presented herein, along with biological and physicochemical data, constitute an available reference for further monitoring of the bacterial communities in this economically important region in the GoM.

Mexico’s Second Deepwater Auction Successful

Mexico’s second deepwater bid round failed to disappoint as 19 of 29 blocks were awarded, including nine to Anglo-Dutch supermajor and Mexican offshore newcomer Shell. Eleven international firms from 10 countries bidding individually and in consortia won blocks—thought to be mostly oil-rich—in the Perdido Fold Belt, Cordilleras Mexicanas basin, and Salina basin of the Gulf of Mexico. Nineteen firms from 15 countries placed 39 bids overall. The winning bids comprised 44,178 sq km, 23 well commitments, and $525 million in tiebreak payments. Mexico’s National Hydrocarbons Commission (CNH) announced the results 31 January in Mexico City. Benjamin Torres-Barron, partner at multinational law firm Baker &amp; McKenzie, which represented four of the companies that participated in the round, said the auction was “very successful” with results “better than everybody expected.” Estimates prior to the event, including those of the government, had approximately 7–10 blocks being awarded. Instead, about two-thirds of all available blocks were awarded, making Round 2.4 “a great success for the Mexican government,” said Eduardo Corzo Ramos, counsel with international corporate law firm Haynes &amp; Boone. “Very important companies participated and in the bid values you can see how interested these companies are in Mexico’s energy sector.” Ramos said he was impressed by the strength of the bids and high-dollar tie-breakers placed by the participating firms. “If you look at the winners, everyone was hitting the maximum [royalty of 20%] with a maximum investment factor.” Competition was particularly fierce for Salina basin Blocks 29 and 21, respectively won by Shell and a consortium led by Repsol with tiebreak bonuses of $110 million and $151 million. Shell’s haul comprised four blocks won on its own, four in a consortium with Qatar Petroleum, and one more in a consortium with Pemex. Five were in the Perdido Fold Belt just south of the Mexico-US maritime border, and four were in the Salina basin to the southeast in the Bay of Campeche. “We saw a vast, overwhelming victory by Shell,” said Torres-Barron. “I think Shell was very aggressive based on its prior experience” in Mexico’s first deepwater auction, Round 1.4 held in December 2016, in which the firm’s participation comprised a single failed bid alongside Atlantic Rim Mexico for Block 5 in the Salina basin. Shell learned that “you cannot have all the eggs in one basket,” and therefore diversified its bids through a number of blocks this time around, he said. Shell concurrently announced on 31 January that it made “one of its largest US Gulf of Mexico exploration finds in the past decade” near Perdido in perhaps a signal that a comeback is under way for offshore exploration and development. Chevron and Total, two other majors who have actively participated in Mexico’s deepwater rounds, also reported a US gulf discovery on 31 January.