Monitoring ecosystem health of the Terminos Lagoon region using heavy metals as environmental indicators

Abstract

The Terminos Lagoon region is one of the most important biodiversity hotspots of Mexico and Mesoamerica. However, this high biodiversity is threatened by the activities of the Mexican oil industry, urban development, and land use change in the watersheds of the rivers that drain into it. This study presents the results of a monitoring program undertaken from 2006 to the present using heavy metals (Cd, Pb, Hg, Cu, Zn, As, Al, V and Cr) as environmental indicators. Heavy metals were measured in water, sediments and oysters as sentinel organisms, three times a year for 15 different sites. Eventually, metals concentration has been measured on selected marine-estuarine organisms (shrimp, fishes, sea turtles, dolphins, and manatees) to see the effect of bioaccumulation. Although heavy metals levels remained in low concentrations in water, some samples of oysters and mammals presented contamination levels above Mexican Legislation, suggesting effects of bioaccumulation.

Functional diversity and redundancy across fish gut, sediment and water bacterial communities

“…Besides, these communities display a highly diversified array of functional genes involved in the resistance to environmental stress. We observed genes involved in the resistance to general stressors such as oxygen limitation and antibiotics (Tetracycline, Vancomycin), but more importantly to stressors directly observed in this lagoon, such as osmotic stress (Medina‐Gómez et al ., ), heavy metals (Vazquez et al ., ; Benitez et al ., ) and numerous pollutants such as PAH (e.g., Fluorene, Chlorocyclohexane; Norena‐Barroso et al ., ) or PCBs (Gold‐Bouchot et al ., ; Diaz‐Gonzalez et al ., ; Carvalho et al ., ). Altogether, this suggests that the microbial metacommunity has the functional potential to realize important ecological processes and maintain them within a naturally changing environment (i.e., a lagoon) under strong and multiple anthropogenic pressures.…”

“…These three sets of communities are composed of organisms adapted to the aquatic environment. In addition, the presence of numerous organic and chemical pollutants (polynuclear aromatic hydrocarbons: Norena‐Barroso et al ., ; pesticides and PCBs: Carvalho et al ., ; heavy metals: Benitez et al ., ), which have accumulated in the Terminos lagoon since the 1970s could have acted as selective forces, leading to the detection in the communities metagenome of genes related to the degradation of these compounds or the resistance to their harmful effects. It was recently reported using a similar tool (i.e., Geochip 5) that functional gene richness increases in heavy metal contaminated sediments (Jie et al ., ), which could be also the case in the Terminos lagoon, leading to the observed functional similarity across habitats.…”

“…The study area was located in the southern part of the Gulf of Mexico in the Terminos lagoon, which has experienced high anthropogenic pressures since the last three decades (see Supporting Information Appendix S1 for further details). This includes domestic and industrial pollution by compounds such as polynuclear aromatic hydrocarbons (Norena-Barroso et al, 1999), pesticides, chlorinated compounds (Carvalho et al, 2009a,b) and heavy metals (Benitez et al, 2012). In addition, recent studies showed that anthropogenic pressure and environmental change have impacted the biomass of fish communities along with their taxonomic and functional diversity (Ramos Miranda et al, 2005;Vill eger et al, 2010).…”

Effects of pollutant discharges on the aquatic mammal populations of Terminos Lagoon, Campeche, Mexico

“…Values of both heavy metals and pesticides in biopsies were low compared to those recorded in other studies. In the Terminos Lagoon area, high Cadmium has not been found in fish and sea turtles egg samples, but in shrimp, bottlenose dolphins (blubber) and manatee (blubber) the mean concentrations were 0.1027, 0.3069 and 0.0159 ppm, respectively (Benítez et al [9]). Delgado-Estrella et al [10] reported low levels in cadmium and no traces of lead, however zinc concentrations were very high.…”

“…Benítez et al [9] reported that cadmium, lead and chrome highest levels were found in sediments and some crustaceans near Ciudad del Carmen, Campeche when they performed a heavy metals spatial analysis at the Terminos Lagoon, suggesting an anthropogenic source for these pollutants.…”