title: The metazoan parasite communities of the shoal flounder (Syacium gunteri) as bioindicators of chemical contamination in the southern Gulf of Mexico.
abstract: BACKGROUND
  Because agriculture and offshore oil extraction are significant economic activities in the southern Gulf of Mexico, high concentrations of nutrients and hydrocarbons are expected. As parasite communities are sensitive to environmental impacts, these contaminants should have an effect on metrics such as species richness, relative abundance and similarity. Consequently, these community metrics can be used as indicators of aquatic environmental health. Our objectives were to describe the parasite communities of the shoal flounder Syacium gunteri and to determine potential thresholds above which environmental contaminants become major controlling factors of parasite community metrics.
  
  
  METHODS
  The study area included 33 sampling sites in the southern Gulf of Mexico, where benthic sediments, water and shoal flounder individuals were collected. Data on ecto- and endo-parasites from flounder and nutrients, contaminants and physicochemical variables from the water and sediments were obtained. The statistical associations of the parasite community metrics at the component and infracommunity levels and the environmental data were analysed using redundancy analysis (RDA).
  
  
  RESULTS
  Overall, 203 shoal flounder were examined for parasites, recovering 13 metazoan parasite species, and 48 physicochemical (e.g. temperature, nutrients) and contaminant (e.g. hydrocarbons, heavy metals) variables were obtained. The larval stages of the cestode Oncomegas wageneri and the nematodes Pseudoterranova decipiens and Hysterothylacium sp. were numerically dominant at the component and infracommunity levels. The parasite community metrics had significant negative statistical associations with both nitrate and total PAHs. With the exception of these two chemicals, which exceeded the threshold effect levels (TELs), no other environmental variable exceeded the range considered safe for marine organisms.
  
  
  CONCLUSIONS
  The community metrics chosen generally had robust statistically significant associations with both physicochemical and contaminant variables, which supports the ecological relevance of these parameters as indicators of aquatic environmental health. Within the study area, the shoal flounder and their parasites live in a polluted environment with relatively high levels of hydrocarbons and nitrate. Regarding nitrate, we emphasise that if uncontrolled sewage discharge continues in the southern Gulf of Mexico, hypoxic conditions similar to those caused by the Mississippi river can be expected in the near future.
authors.affiliation: Laboratorios de Parasitología y Geoquímica, Centro de Investigación y de Estudios Avanzados del Instituto Politécnico Nacional, Unidad Mérida, Km 6 Carretera Antigua a Progreso, Cordemex, Mérida, Yucatán, 97310, México. vvidal@mda.cinvestav.mx.
authors.forename: Víctor Manuel
authors.initials: VM
authors.lastname: Vidal-Martínez
authors.affiliation: Laboratorios de Parasitología y Geoquímica, Centro de Investigación y de Estudios Avanzados del Instituto Politécnico Nacional, Unidad Mérida, Km 6 Carretera Antigua a Progreso, Cordemex, Mérida, Yucatán, 97310, México. poseidon_184@hotmail.com.
authors.forename: Oscar A
authors.initials: OA
authors.lastname: Centeno-Chalé
authors.affiliation: Laboratorios de Parasitología y Geoquímica, Centro de Investigación y de Estudios Avanzados del Instituto Politécnico Nacional, Unidad Mérida, Km 6 Carretera Antigua a Progreso, Cordemex, Mérida, Yucatán, 97310, México. edgar.torres@mda.cinvestav.mx.
authors.forename: Edgar
authors.initials: E
authors.lastname: Torres-Irineo
authors.affiliation: Laboratorios de Parasitología y Geoquímica, Centro de Investigación y de Estudios Avanzados del Instituto Politécnico Nacional, Unidad Mérida, Km 6 Carretera Antigua a Progreso, Cordemex, Mérida, Yucatán, 97310, México. isanchez@cicese.mx.
authors.forename: Juan
authors.initials: J
authors.lastname: Sánchez-Ávila
authors.affiliation: Laboratorios de Parasitología y Geoquímica, Centro de Investigación y de Estudios Avanzados del Instituto Politécnico Nacional, Unidad Mérida, Km 6 Carretera Antigua a Progreso, Cordemex, Mérida, Yucatán, 97310, México. ggold@mda.cinvestav.mx.
authors.forename: Gerardo
authors.initials: G
authors.lastname: Gold-Bouchot
authors.affiliation: Laboratorios de Parasitología y Geoquímica, Centro de Investigación y de Estudios Avanzados del Instituto Politécnico Nacional, Unidad Mérida, Km 6 Carretera Antigua a Progreso, Cordemex, Mérida, Yucatán, 97310, México. leo@mda.cinvestav.mx.
authors.forename: M Leopoldina
authors.initials: ML
authors.lastname: Aguirre-Macedo
mesh_terms: D000818:Animals; D005393:Fish Diseases / Q000453:epidemiology / Q000469:parasitology*; D005432:Flounder; D060851:Gulf of America / Q000453:epidemiology; D010273:Parasitic Diseases, Animal / Q000453:epidemiology / Q000469:parasitology*; D015995:Prevalence; D014874:Water Pollutants, Chemical / Q000737:chemistry*
chemical_list: D014874:Water Pollutants, Chemical