Histopathology reveals environmental stress in dusky flounder Syacium papillosum of the Yucatan Peninsula continental shelf.

The histological changes in the liver, kidney, spleen, and gills of Syacium papillosum from the continental shelf of the Yucatan Peninsula, Gulf of Mexico, and their statistical associations with environmental conditions and pollutants were assessed in 2010, 2011, and 2012. We evaluated the extension and severity of the lesions through a degree of tissue change (DTC), and, with the sum of the number of lesion types within each of their DTC stages, we determined the histological alteration index (HAI). The liver and kidney were the most affected organs, with HAI values > 100. Fish with the most severe damage were observed on the Campeche Bank and the Caribbean Sea, contrasting with those collected from the northern Yucatan continental shelf. The presence of foci cellular alteration and abundant melanomacrophage centers indicated that these flatfishes were chronically exposed to environmental stress factors. Redundancy analyses showed strong associations between HAI values and hydrocarbon and heavy metal concentrations in muscle. Our results provide evidence for the first time of a differential health condition of the Yucatan shelf through the histopathology shown in S. papillosum, establishing the baseline for future monitoring programs in the region.

Optimization of the Biodegradation of Aliphatic, Aromatic, and UCM Hydrocarbons from Light Crude Oil in Marine Sediment Using Response Surface Methodology (RSM).

This study describes the optimization of the biodegradation of total aliphatic (tAHCs), total aromatic (tPAHs), and unresolved complex mixture (UCM) hydrocarbons from light crude oil in marine sediment. The response surface methodology (RSM), with a Box-Behnken design, was used to optimize the hydrocarbon fraction degradation, reported as degradation efficiency (E (%)), using four independent variables (inoculum, dispersant, light oil concentration, and carbon/nitrogen ratio), all at three levels. Analysis of variance (ANOVA) showed R2 values of 0.976, 0.974, and 0.975 for tAHCs, tPAHs, and UCM, respectively. All fractions exhibited a statistically significant effect (P < 0.05) in the second-order quadratic regression model for degradation. According to the models, the optimal degradation prediction was: 81.03% for tAHCs, 85.96% for tPAHs, and 92.86% for UCM. This work highlights the possibility of carrying out efficient biodegradation, of more than 80%, through an optimization process using different light oil concentrations, opening up possibilities of multiple response optimization.

Assessing the Effect of Chemical Dispersant Nokomis 3-F4 on the Degradation of a Heavy Crude Oil in Water by a Marine Microbial Consortium.

Degradation efficiency of a heavy crude oil by a marine microbial consortium was evaluated in this study, with and without the addition of a chemical dispersant (Nokomis 3-F4). 15.50% of total petroleum hydrocarbons (TPH) were removed after 15 days of incubation without dispersant, with a degradation rate of 2.39 ± 0.22 mg L-1 day-1. In contrast, the addition of Nokomis 3-F4 increased TPH degradation up to 30.81% with a degradation rate of 5.07 ± 0.37 mg L-1 day-1. 16S rRNA gene sequencing indicated a dominance of the consortium by Achromobacter and Alcanivorax. Nonetheless, significant increases in the relative abundance of Martelella and Ochrobactrum were observed with the addition of Nokomis 3-F4. These results will contribute to further environmental studies of the Gulf of Mexico, where Nokomis 3-F4 can be used as chemical dispersant.

Metazoan Parasite Infracommunities of the Tomtate Grunt (Haemulon aurolineatum) as Potential Bioindicators of Environmental Conditions in the Yucatan Continental Shelf, Mexico.

Metazoan parasites and their hosts experience the environmental influence of the seasonal presence of Western and Eastern subzones with different oceanographic conditions on the Yucatan continental shelf (YS). In addition, natural seeps and oil transport in the area lead to the presence of hydrocarbons. We hypothesized that the parasite infrapopulations and infracommunities of Haemulon aurolineatum will respond to environmental variability related with ongoing oceanographic subzone conditions of the YS. Spatial and multivariate statistical analyses were used to test this hypothesis. For 17 sampling sites along the YS, 55 parasite morphospecies were recovered from 146 fishes. There were significant differences in the number of parasite species between Western and Eastern subzones, but not in the number of parasite individuals. Spatial autocorrelation on environmental variables as a consequence of the Yucatan current was found. Overall, the parasite metrics suggested a region with a good ecosystem health condition naturally influenced by oceanographic processes.

Acute Exposure to Crude Oil Induces Epigenetic, Transcriptional and Metabolic Changes in Juvenile Sciaenops ocellatus.

In this study, we report molecular and metabolic responses of Sciaenops ocellatus during an acute oil exposure bioassay (100, 800 and 8000 mg 1-1 of crude oil). The global DNA methylation and expression profiles of key genes of the xenobiotic biotransformation system (cytochrome P450 1A [cyp1a] and glutathione S-tranferase [gst]), oxidative stress system (glutathione peroxidase [gpx], catalase [cat], aldehyde dehydrogenase [aldh]) and reproductive system (vitellogenin [vtg]) were evaluated. At the metabolic level, we evaluated the concentration of four polycyclic aromatic hydrocarbon (PAH) metabolites -hydroxybenzo[a]pyrene, hydroxypyrene, hydroxynaphthalene and hydroxyphenanthrene- in fish bile. The results of this study revealed that fish exposed to crude oil exhibited hypomethylation of DNA, up-regulation of cyp1a and gst and down-regulation of gpx, cat, aldh and vtg and high concentrations of PAH metabolites with respect to the control.

Functional Groups of Metazoan Parasites of the Dusky Flounder (Syacium papillosum) as Bioindicators of Environmental Health of the Yucatan Shelf.

We aimed to compare the percentage of explained variance given by the relationship of species and functional groups of metazoan parasites of the dusky flounder Syacium papillosum and environmental variables from water and sediments in the Yucatan shelf (YS). Parasite data were obtained from 127 S. papillosum specimens collected from 17 of 67 stations. At each station, 46 environmental variables were measured, including hydrocarbons, heavy metals, and physicochemical variables from water and sediments. Fifteen functional groups were defined based on biological characteristics of 48 parasite species. Our multivariate statistical analyses showed that species and functional groups produced similar explained variance values (47.3% and 50% respectively). However, using functional groups the time and financial resources were minimal compared with those used for morphological and molecular identification to produce the species composition matrix. Thus, functional groups are the best choice from the point of view of saving time and money.

Histological Effects of Light Crude Oil on Sciaenops ocellatus Under Experimental Conditions.

The health status of Sciaenops ocellatus was studied by qualitative and quantitative histopathological analysis through histological damage prevalence and degree of tissue change (DTC) in response to 96 h and 9 days of exposure to 0.1, 0.8, and 8 g/L of light crude oil in seawater. The histology of the liver, spleen, kidney, and gills of the fish were analyzed and compared between treatments. Our results showed that the exposed fish developed lesions associated with degenerative and necrotic changes. The highest frequency of damage and DTC scores were observed in the liver and kidney from 96 h to 9-days post-exposure. Generalized additive models of location, scale, and shape, showed that the DTC was strongly associated with crude oil compounds such as napthalene, Cd, Ni, Pb, and bile polycyclic aromatic hydrocarbon metabolites. Our findings suggest that exposure to crude oil affects fish health, producing irreversible histological damage.

Effects of a Light Crude Oil Spill on a Tropical Coastal Phytoplankton Community.

Oiling scenarios following spills vary in concentration and usually can affect large coastal areas. Consequently, this research evaluated different crude oil concentrations (10, 40, and 80 mg L-1) on the nearshore phytoplanktonic community in the southern Gulf of Mexico. This experiment was carried out for ten days using eight units of 2500 L each; factors monitored included shifts in phytoplankton composition, physicochemical parameters and the culturable bacterial abundance of heterotrophic and hydrocarbonoclastic groups. The temperature, salinity, and nutrient concentrations measured were within the ranges previously reported for Yucatan Peninsula waters. The total hydrocarbon concentration (TPH) in the control at T0 indicated the presence of hydrocarbons (PAHs 0.80 µg L-1, aliphatics 7.83 µg L-1 and UCM 184.09 µg L-1). At T0, the phytoplankton community showed a similar assemblage structure and composition in all treatments. At T10, the community composition remained heterogeneous in the control, in agreement with previous reports for the area. However, for oiled treatments, Bacillariophyceae dominated at T10. Hydrocarbonoclastic bacteria were associated with oiled treatments throughout the experiment, while heterotrophic bacteria were associated with control conditions. Our results agreed with previous works at the taxonomic level showing the presence of Bacillariophyceae and Dinophyceae in oil-related treatments, where these groups showed the major interactions in co-occurrence networks. In contrast, Chlorophyceae showed the key node in the co-occurrence network for the control. This study aims to contribute to knowledge on phytoplankton community shifts during a crude oil spill in subtropical oligotrophic regions.

Octopus maya parasites off the Yucatán Peninsula, Mexico. I. Faunal assemblages.

The red octopus Octopus maya Voss et Solís-Ramírez, 1966 is an endemic species found exclusively off the coast of the Yucatán Peninsula, Mexico; its fishery is one of the most important along the Atlantic coast of Mexico and the Caribbean Sea. To date, the parasite fauna of Octopus spp. in southern Mexico remains unknown. In this study, we present the parasite fauna of O. maya from 8 localities along the Yucatán Peninsula. From August 2009 to June 2010, a total of 1202 specimens of O. maya were caught by artisanal fisheries and examined. Twenty parasite taxa were recorded from all octopus examined: 7 cestodes, 8 digeneans, 3 nematodes, 1 copepod and 1 coccidian. All taxa are new records for this host species, and the sampled locations represent new records of the geographic distribution of these parasite taxa. The gills and the intestine were the micro-habitats in which the highest number of taxa were found. More than half of the parasites (13 taxa) that we found infected O. maya via its feeding habits, although a high number of taxa (n = 9) colonized via active transmission. Cestoda and Digenea were the taxonomic groups with the highest number of taxa. Prochristianella sp. showed the highest prevalence and mean abundance values in the localities where it was present. This work represents the first study on the parasite fauna of any cephalopod species in Mexico.

Two new species of dicyemid mesozoans (Dicyemida: Dicyemidae) from Octopus maya Voss & Solis-Ramirez (Octopodidae) off Yucatan, Mexico.

Two new dicyemid species are described from the endemic cephalopod Octopus maya Voss & Solis-Ramirez collected off Yucatan, Mexico. The renal sacs of 40 juvenile and adult octopuses from four localities were examined. Dicyema hochbergi n. sp. is a medium-sized species that reaches 2,245 µm in length. The vermiform stages consist of 18-24 peripheral cells, a conical calotte and the extension of the axial cell between the base and middle of the metapolar cells. Infusoriform embryos consist of 39 cells with urn cell containing one germinal cell, two nuclei and solid refringent bodies. Dicyema mexcayae n. sp. is a relatively small species that reaches 1,114 µm in length. The vermiform stages are constituted by 14-16 peripheral cells, an elongate calotte and the axial cell extending forward to the middle of the metapolar cells. The infusoriform embryos consist of 37 cells, two solid refringent bodies and urn cells with two nuclei each. The present study represents the first description of a dicyemid species from O. maya and increases the number of described species from Mexican waters to 11.