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Mollusk death assemblages are formed by shell remnants deposited in the surficial mixed layer of the seabed. Diversity patterns in tropical marine habitats still are understudied; therefore, we aimed to investigate the taxonomic, phylogenetic, and functional diversity of mollusk death assemblages at regional and local scales in coral reef sands and seagrass meadows. We collected sediment samples at 11 sites within two shallow gulfs in the Northwestern Caribbean Sea and Southeastern Gulf of Mexico. All the shells were counted and identified to species level and classified into biological traits. We identified 7113 individuals belonging to 393 species (290 gastropods, 94 bivalves, and nine scaphopods). Diversity and assemblage structure showed many similarities between gulfs given their geological and biogeographical commonalities. Reef sands had higher richness than seagrasses likely because of a more favorable balance productivity-disturbance. Reef sands were dominated by epifaunal herbivores likely feeding on microphytobenthos and bysally attached bivalves adapted to intense hydrodynamic regime. In seagrass meadows, suspension feeders dominated in exposed sites and chemosynthetic infaunal bivalves dominated where oxygen replenishment was limited. Time averaging of death assemblages was likely in the order of 100 years, with stronger effects in reef sands compared to seagrass meadows. Our research provides evidence of the high taxonomic, phylogenetic, and functional diversity of mollusk death assemblages in tropical coastal sediments as result of the influence of scale-related processes and habitat type. Our study highlights the convenience of including phylogenetic and functional traits, as well as dead shells, for a more complete assessment of mollusk biodiversity.

The environmental ubiquity of plastic materials generates global concern, pollution, and health problems. Microorganisms and enzymes with plastic biodegradation potential are considered as environmentally friendly alternatives to address these issues. Interestingly, polluted environments exert selective pressure on native microbial communities that have the metabolic capacity to tolerate and transform different contaminants, including plastics. A number of enzymes have been described as polyurethane degraders. However, some of them do not possess complete characterization or efficient degradation rates. Hence, there is still a need to identify and characterize efficient enzymes for application in green processes for plastic recycling. Here, we used an environmental DNA sample isolated from the sediments of a polluted river in Mexico (Apatlaco River), which was used to construct a metagenomic fosmid library to explore the metabolic potential of microbial communities for polyurethane biodegradation. Functional screenings were performed on agar media containing the polyester polyurethane Impranil DLN (Impranil), and positively selected fosmid DNA was identified and sequenced by Illumina. Bioinformatic analyses identified two Acinetobacter genes ( epux1 and epux2) encoding alpha/beta hydrolases. The genes were heterologously expressed to determine the capacity of their encoded proteins for Impranil clearing. Both Epux1 and Epux2 enzymes exhibited Impranil cleavage at 30 °C and 15 °C and ester group modifications were validated by infrared spectroscopy. Furthermore, the release of building blocks of the polymer was determined by GC-MS analysis, thus indicating their esterase/polyurethanase activity. Overall, our results demonstrate the potential of these novel bacterial enzymes for the hydrolysis of polyurethane with potential applications in the circular plastics economy.

Diversity of free-living marine nematode assemblages in the Southwestern Gulf of Mexico (SW GoM) is scarcely studied. Here, we aimed (1) to analyze the influence of a water depth gradient on the species richness, feeding type and taxonomic composition of assemblages; and (2) to document the regional diversity of free-living nematodes in the SW GoM. We sampled 63 sites along a water depth gradient from 186 to 3774 m during four oceanographic cruises. We found clear variations along the depth gradient of bottom water (temperature, salinity, and dissolved oxygen) and sediment variables (grain size and organic content). We identified 1881 nematodes belonging to 108 genera, 33 families, ten orders, and two classes. The abundance and species richness decreased with water depth. However, the expected number of species for a same level of abundance did not change along the depth gradient likely because the scarcity of food was compensated by reduced environmental stress (e.g., higher oxygen content and physical stability). Microbial sucker was the most abundant feeding type indicating the important role of sediment bacteria in the nematode’s diet. Species composition varied along the depth gradient with dominance in the upper slope sites of species of Comesomatidae tolerant to reduced sediments (e.g., Dorylaimopsis sp., Sabatieria spp., and Setosabatieria hilarula ). Many congeneric species typical of deep sea were restricted to the deepest sites such as Acantholaimus spp., Ledovitia spp., Desmoscolex spp., and Halalaimus spp. The nematode regional diversity of SW GoM was 154 species, but the Chao 1 estimator indicated a richness of about 194 species and a highest limit of 246 species. The accumulation curves of richness were non-asymptotic suggesting a substantial fraction of undiscovered richness. Our study increased the free-living nematode fauna of GoM in 144 species (76%) respect to Hope’s list (2009). The large diversity of nematodes stands out the necessity of further studies to unravel the environmental drivers of α- and β-diversities and highlights the potential of this taxon for monitoring the deep sea of the Gulf of Mexico.

Holopelagic Sargassum spp. (sargassum) are the founding species of diverse communities in the Sargasso Sea. Since 2011, a new area of concentration of these algae was formed in the equatorial North Atlantic and Caribbean Sea. We analyzed elemental composition, and the small mobile fauna associated with sargassum collected at 41 stations, during two expeditions in the Caribbean Sea in 2018 and 2019, that covered open-sea stations in two marine ecoregions, and coastal stations (< 20 km from the shore) in one of them. Metal(loid) concentrations generally followed the order As > Zn > Cu > Cd > Se > Pb > Hg, and contents of As (195.5 ± 13.7 µg g −1 ), Cd (0.59 ± 0.02 µg g −1 ), and Hg (0.22 ± 0.09 µg g −1 ) were highest in S. fluitans III in the South-Western-Caribbean ecoregion. Mean [Ctot] per ecoregion varied between 26.1 and 30.1 mg g −1 , and variation was mainly accounted for by higher [Cinorg] (likely produced by calcifying epibionts) in the South-Western Caribbean (10.12) compared to the Western Caribbean (8.92 and 7.19); this tendency that was also found for [Ntot] (between 1.06 and 1.27), and these contents were positively correlated with seawater chlorophyll concentrations. Sixty-six taxa of mobile fauna were identified, with the phylum Arthropoda being most abundant and diverse. The faunal community composition was similar in both open-sea regions, but differed in the coastal stations, which was mostly explained by differential relative abundance of Latreutes fucorum, Carpias minutus , Litiopa melanostoma, and some fish species. The Caribbean open-sea rafts harbor a diverse fauna comparable to that found in the Sargasso Sea, and likely provide similar ecosystem services, and thus merit similar protective efforts as those directed towards sargassum in the Sargasso Sea.

The diversity and distribution of macrofaunal communities in the deep-sea bottoms of Gulf of Mexico (GoM) Mexican waters are poorly known compared to the northern GoM. This study was designed to contribute to the knowledge of macrofauna communities through (i) evaluate the taxonomic composition of macrofauna communities at major taxa level, and (ii) analyze the spatial distribution patterns in the deep sea of the southwestern GoM. Benthic macrofauna composition was analyzed in a large geographical area (92.67°–96.70° W 18.74°–23.04° N) and bathymetric gradient (185-3740 m depth). Samples were collected on board the R/V Justo Sierra (Universidad Nacional Autónoma de México) with a Reineck-type box corer during the oceanographic cruises SOGOM-3 and SOGOM-4 carried out on April 21–May 15, 2017, and on August 29–September 20, 2018, respectively. Thirteen environmental parameters were measured (among them, depth, salinity, temperature, O2, sediment grain size, hydrocarbons, and organic matter). Twenty-five taxa were registered in SOGOM 3 (2315 individuals) all of which were observed in SOGOM 4 (1721 individuals) with exception of the mollusk Class Solenogastres. The average abundance (ind. m -2 ) registered was 517 (range: 150-1388 ind. m -2 ), and 347 (range: 38-1088 ind. m -2 ) for SOGOM 3, and SOGOM 4, respectively. In SOGOM 3 Polychaeta, Nematoda, Amphipoda, Tanaidacea, and Bivalvia contributed with 75% of the total abundance, which were also the most abundant in SOGOM 4 representing 82% of total macrofauna abundance. Highest abundance was registered to the south of the study area near the coast, and the lowest one was found in deeper areas. Macrofauna abundance decreased with depth in both cruises. High diversity values were registered at intermediate depths in the south and west zones of the study area. Both cruises separated in a nMDS analysis. During SOGOM 3 dissolved oxygen, aromatic hydrocarbons, and organic matter (%) were the environmental variables related to macrofauna whereas, in SOGOM 4, depth was the most important one. This study fills a gap in the knowledge of diversity and distribution of macrofaunal communities of the deep-sea bottoms of a large area covering the whole bathymetric range of southern Gulf of Mexico and provides a baseline useful to compare with polluted areas and for assessing the impact of chronic pollution and/or potential oil spill accidents.

This study examines the vertical assemblages of the holoplanktonic mollusks (Pteropoda and Pterotracheoidea) in the Campeche Canyon, southern Gulf of Mexico, during a “Nortes” season (February 21–28, 2011) and explores their relationship with the hydrography and the geostrophic circulation pattern. High-resolution hydrographic data were acquired during a multidisciplinary research cruise of 48 hydrographic stations. Zooplankton samples were collected at 24 stations from four depths (10, 50, 100, and 200 m) using a multiple open/closed net system. The results revealed a deep thermocline at a depth of 90 m and a circulation pattern dominated by cyclonic and anticyclonic eddies that induced cold and warm cores. Thirty-three Pteropoda and three Pterotracheoidea species were identified, with the highest richness at a depth of 100 m (just below the thermocline). The highest organism densities were observed at a depth of 10 m. The diversity index ( H ’) showed variations depending on the sampling depth, with the highest values (1.9 bits ind −1 ) at 100 and 200 m, while at 10 m depth the lowest values (1.45 bits ind −1 ) were observed. Multivariate analyses showed that dissolved oxygen, and temperature were the main environmental factors determining organism density.

The southern Gulf of Mexico (sGoM) is home to an extensive oil recovery and development infrastructure. In addition, the basin harbors sites of submarine hydrocarbon seepage and receives terrestrial inputs from bordering rivers. We used stable carbon, nitrogen, and radiocarbon analyses of bulk sediment organic matter to define the current baseline isoscapes of surface sediments in the sGoM and determined which factors might influence them. These baseline surface isoscapes will be useful for accessing future environmental impacts. We also examined the region for influence of hydrocarbon deposition in the sedimentary record that might be associated with hydrocarbon recovery, spillage and seepage, as was found in the northern Gulf of Mexico (nGoM) following the Deepwater Horizon (DWH) oil spill in 2010. In 1979, the sGoM experienced a major oil spill, Ixtoc 1. Surface sediment δ13C values ranged from -22.4‰ to -19.9‰, while Δ14C values ranged from -337.1‰ to -69.2‰. Sediment δ15N values ranged from 2.8‰ to 7.2‰, while the %C on a carbonate-free basis ranged in value of 0.65% to 3.89% and %N ranged in value of 0.09% to 0.49%. Spatial trends for δ13C and Δ14C were driven by water depth and distance from the coastline, while spatial trends for δ15N were driven by location (latitude and longitude). Location and distance from the coastline were significantly correlated with %C and %N. At depth in two of twenty (10%) core profiles, we found negative δ13C and Δ14C excursions from baseline values in bulk sedimentary organic material, consistent with either oil-residue deposition or terrestrial inputs, but likely the latter. We then used 210Pb dating on those two profiles to determine the time in which the excursion-containing horizons were deposited. Despite the large spill in 1979, no evidence of hydrocarbon residue remained in the sediments from this specific time period.

We describe an assembled marine bacterial consortium designed for bioremediation of oil-contaminated seawater, based on a statistical method using a Plackett-Burman (PB) experimental approach. The final consortium consists of four bacteria isolated from the Gulf of Mexico, from four genera: Pseudomonas, Halopseudomonas, Paenarthrobacter , and Alcanivorax . Individually, bacterial oil removal by these microorganisms was evaluated by gravimetry, reaching 39% at maximum after 75 days, whereas in consortium it was ~62%. We also measured biodegradation levels by Gas Chromatography/Mass Spectrometry (GC-MS) observing 12 polyaromatic hydrocarbons (PAHs) degradation analyzed and n -alkanes degradation with a preference for specific chain length. Consortium population analysis using the V3-V4 region of 16S rRNA showed a stable community, suggesting that the metabolic load was distributed among bacteria and that stable dynamic interactions were achieved. In this work, we show that the use of a factorial method for synthetic consortium design offers the possibility of improving oil degradation efficiency with stable bacterial populations.

This study reports four new records of gymnosome pteropods (Pteropoda, Gymnosomata): Pneumodermopsis macrochira Meisenheimer, 1905, Spongiobranchaea intermedia Pruvot-Fol, 1926, Schizobrachium cf. polycotylum Meisenheimer, 1903, and Cliopsis krohnii Troschel, 1854, collected at different depths in the Campeche Canyon, southern Gulf of Mexico, during the winter storm season in 2011 (\"Nortes\"). These species are illustrated and described, increasing the knowledge of this group in the region. We also present hydrographic conditions of the stations and depths where the organisms were collected.

Four oceanographic cruises were carried out between April 2011 and May 2013 on the continental slope of the southern Gulf of Mexico (GoM) in a depth range of 290 to 1200 m on board the R/V JUSTO SIERRA. A total of 91 trawls covered a total swept area of 170.49 hectares. We recorded 177 fish species belonging to 80 families. Fifteen species extended their distribution into the south of the gulf and 37 increased their depth ranges. Five species could have commercial importance: Aphanopuscarbo Lowe, 1839; Hydrolagusmirabilis (Collett, 1904); Helicolenusdactylopterus (Delaroche, 1809); Lophiusgastrophysus Miranda Ribeiro, 1915, and Merlucciusalbidus (Mitchill, 1818). The most abundant species were Polymixialowei Günther, 1859; Parasudistruculenta (Goode & Bean, 1896); M.albidus , Chlorophthalmusagassizi Bonaparte, 1840; Dibranchusatlanticus Peters, 1876; Nezumiaaequalis (Günther, 1878); Yarrellablackfordi Goode & Bean, 1896; and Laemonemabarbatulum Goode & Bean, 1883. High values of fish species richness, diversity, and evenness were registered throughout the study area. A high percentage of the fish species (97%) collected during this project are distributed in the entire GoM. Most of the species showed a wide depth distribution; however, a vertical zonation of species can be observed.