Toxigenic V. cholerae, V. parahaemolyticus, and V. vulnificus in oysters from the Gulf of Mexico and sold in Mexico City

Oysters can accumulate potentially pathogenic bacteria, such as Vibrio cholerae, V. parahaemolyticus, and V. vulnificus. The aim of this study was to detect the presence of these Vibrio species and their toxigenic variants in oysters from the Gulf of Mexico sold in Mexico City. Oyster samples were studied using traditional culture and molecular polymerase chain reaction analysis. V. cholerae was present in 30.4% of the samples and its toxigenic variant chxA+ in 26.1%. It was isolated only in deshelled oysters, mainly in the dry season. V. parahaemolyticus was present in 95.7% of the samples and the toxigenic variant was found in 17.4%. V. vulnificus was identified in 60.9% of the samples, 38% of which corresponded to the environmental genotype and 21.7% to the clinical genotype, mainly in the cold season. Consumption of the oysters analyzed poses health risks due to the presence of Vibrio species, especially in deshelled oysters.

Analysis and Tendencies of Metals and POPs in a Sediment Core from the Alvarado Lagoon System (ALS), Veracruz, Mexico

This study focused on dating of a sediment core from the Alvarado Lagoon System, Veracruz, Mexico, calculating the sedimentation rate by using ²¹⁰Pb to determine the tendency towards pollution by polycyclic aromatic hydrocarbons, organochlorides, the metals Cd, Cr, Cu, Hg, Ni, Pb, and V, and organic matter content. The activity of total Pb and supported Pb in the samples was 83.1 and 29.5 Bq kg^-1, respectively, whereas the average estimated sedimentation rate was 0.48 ± 0.09 cm per year^-1. The organic matter values exhibited linear behavior throughout the historical profile, with values under 2.5%. Metal concentrations followed the order V > Cr > Ni > Cu > Pb > Hg > Cd. Variations found in Cr, Ni, Pb, and V concentrations are basically due to three meteorological phenomena that hit the region: hurricanes Gladys, Hilda, and Janet in September of 1955. V, Ni, and Hg input comes from anthropogenic and lithogenic sources. The presence of individual polycyclic aromatic hydrocarbons showed no ascending accumulation pattern over time, nor did it show any significant statistical correlation to OM. As for the organochlorine pesticides, 63.61% of the total sum of these compounds were from the ciclodienics family. Concentration of p,p'-DDT was observed only in the earliest profile, from 1929.

Quantification of Vibrio species in oysters from the Gulf of Mexico with two procedures based on MPN and PCR

Oysters can accumulate potentially pathogenic water bacteria. The objective of this study was to compare two procedures to quantify Vibrio species present in oysters to determine the most sensitive method. We analyzed oyster samples from the Gulf of Mexico, commercialized in Mexico City. The samples were inoculated in tubes with alkaline peptone water (APW), based on three tubes and four dilutions (10^-1 to 10^-4). From these tubes, the first quantification of Vibrio species was performed (most probable number (MPN) from tubes) and bacteria were inoculated by streaking on thiosulfate-citrate-bile salts-sucrose (TCBS) petri dishes. Colonies were isolated for a second quantification (MPN from dishes). Polymerase chain reaction (PCR) was used to determine species with specific primers: ompW for Vibrio cholerae, tlh for Vibrio parahaemolyticus, and VvhA for Vibrio vulnificus. Simultaneously, the sanitary quality of oysters was determined. The quantification of V. parahaemolyticus was significantly higher in APW tubes than in TCBS dishes. Regarding V. vulnificus counts, the differences among both approaches were not significant. In contrast, the MPNs of V. cholerae obtained from dishes were higher than from tubes. The quantification of MPNs through PCR of V. parahaemolyticus and V. vulnificus obtained from APW was sensitive and recommendable for the detection of both species. In contrast, to quantify V. cholerae, it was necessary to isolate colonies on TCBS prior PCR. Culturing in APW at 42 °C could be an alternative to avoid colony isolation. The MPNs of V. cholerae from dishes was associated with the bad sanitary quality of the samples.

A chemical status predictor. A methodology based on World-Wide sediment samples

As a consequence of the limited resources of underdeveloped countries and the limited interest of the developed ones, the assessment of the chemical quality of entire water bodies around the world is a utopia in the near future. The methodology described here may serve as a first approach for the fast identification of water bodies that do not meet the good chemical status demanded by the European Water Framework Directive (WFD). It also allows estimating the natural background (or reference values of concentration) of the areas under study using a simple criterion. The starting point is the calculation the World-Wide Natural Background Levels (WWNBLs) and World-Wide Threshold Values (WWTVs), two indexes that depend on the concentration of seven elements present in sediments. These elements, As, Cd, Cr, Cu, Ni, Pb and Zn, have been selected taking into account the recommendations of the UNEP (United Nations Environment Programme) and USEPA (United States Environmental Protection Agency), that describe them as elements of concern with respect to environmental toxicity. The methodology has been exemplified in a case study that includes 134 sediment samples collected in 11 transitional water bodies from 7 different countries and 4 different continents. Six of the water bodies considered met the good chemical status demanded by the WFD. The rest of them exceeded the reference WWTVs, at least for one of the elements. The estuaries of the Nerbioi-Ibaizabal (Basque Country) and Cavado (Portugal), the sea inlet of Río San Pedro (Spain), the Sepetiba Bay (Brazil) and the Yucateco lagoon (Mexico) belong to that group.

Pesticides distribution in sediments of a tropical coastal lagoon adjacent to an irrigation district in northwest Mexico

This work presents the content of organochlorine (OCs) pesticides in sediments of both, agricultural drains from the Irrigation District 076, El Carrizo, Sinaloa, and of the adjacent coastal lagoon ecosystem of Agiabampo-Bacorehuis-Jitzamuri, located in northwest Mexico. A questionnaire was applied to the farmers of this irrigation district, to evaluate the usage of pesticides and to determine if banned OCs are still used. Around 31 tons of active ingredients were applied in the autumn-winter cycle (1997-1998). There were eighteen different pesticides; of them 61% are insecticides, 28% herbicides, 6% fungicides and 6% other compounds. Around 73% of the pesticides applied are organophosphorus, carbamates and sulfur, OCs are still applied and represent 4% of the total. All the pesticides applied in the irrigation district are authorized in the Official Pesticide Catalog, nevertheless forbidden and restricted compounds were detected in the sediment samples. The presence of heptachlor, heptachlor epoxide, alpha-endosulfan, beta-endosulfan, endosulfan sulfate, alpha-HCH, beta-HCH, lindane, delta-HCH, aldrin, dieldrin p,p'-DDT, p,p'-DDE and p,p'-DDD was recorded in the sediment sample. The analysis of the sediments suggest that the principal pesticides input to the coastal ecosystem is mainly through three of the seven agricultural drains, that collect the excess irrigation water and runoff from the district surface. A gradient of pesticide residues in sediments exists from the agricultural drains (52 ng OCs g(-1) dry weight) to the Jitzamuri bay (32 ng OCs g(-1) dry weight).

Metal pollution in coastal areas of Mexico

Metals are natural constituents of the earth core and can be widespread in all environments, forming part of sediments, rocks, animal and plant tissues, crude oil, hemoglobin, pigments, proteins, and enzymes. However, some of these metals, such as lead, chromium, and mercury, have been widely used in industrial and human activities, thus provoking an alteration in their geochemical balance and causing high concentrations, frequently three to four orders of magnitude higher than their natural concentrations. The aggressive industrialization and urbanization of coastal areas in Mexico have given rise to singular pollution problems in which such metals play an important role. Thus, this review identifies the main sources and quantifies the concentration levels of metals in the water, sediments, and organisms of coastal ecosystems (rivers, estuaries, coastal lagoons, Continental Shelf) in the Gulf of Mexico as well as the Mexican Pacific. The results show high concentrations of lead, chromium, and nickel in sediments and animal tissues from coastal states (Tamaulipas, Veracruz, Tabasco, and Campeche) in the Gulf of Mexico, especially in areas close to industrialized towns such as Tampico, Veracruz City, and Villahermosa. On the other hand, studies conducted on Mexican Pacific coasts indicate low levels of metals in sediments and organisms, an indication that the metal pollution here is closely tied to human, industrial, and oil activities.

Petroleum pollution in the Gulf of Mexico and Caribbean Sea

In 1976, IOC-UNESCO and UNEP convened a meeting in Port of Spain to analyze the marine pollution problems in the region, noting that petroleum pollution was of regionwide concern and recommended initiating a research and monitoring program to determine the severity of the problem and monitor its effects. The Wider Caribbean is potentially one of the largest oil-producing areas in the world. Major production sites include Louisiana and Texas in the U.S.; the Bay of Campeche, Mexico; Lake Maracaibo, Venezuela; and the Gulf of Paria, Trinidad. All these are classified as high-risk production accident zones. Main sources of petroleum pollution in the Wider Caribbean are production, exploitation, transportation, urban and municipal discharges, refining and chemical wastes, normal loading and unloading operations, and accidental spills. About 5 million barrels of crude oil are transported daily in the Caribbean, thus generating an intense tanker traffic. It has been estimated that oil discharges from tank washings within the Wider Caribbean could be as high as 7 million barrels/yr. The results of the Caribbean Pollution Regional Program (CARIPOL) conducted between 1980 and 1987 pointed out that significant levels of petroleum pollution exist throughout the Wider Caribbean, including serious tar contamination of windward exposed beaches, high levels of floating tar within the major current systems, and very high levels of dissolved and dispersed hydrocarbons in surface waters. Major adverse effects of this type of pollution include: high tar levels on many beaches that either prevent their recreational use or require very expensive cleanup operations, distress and death for marine life, and responses in the enzyme systems of marine organisms that have been correlated with declines in reproductive success. Finally, the presence of polycyclic aromatic hydrocarbons (PAHs) in tissues of important economic species has been reported, creating a risk for public health because of the potential carcinogenic effects.