title: Relationship between mRNA biomarker candidates and location near a marine municipal wastewater outfall in the benthic indicator species Modiolus modiolus (L.).
abstract: The deep-sea horse mussel Modiolus modiolus (L.) is a sentinel bivalve species used for the assessment of potential biological exposure to anthropogenic contaminants in benthic environments. Using a combination of endpoints that included gross biological metrics, reproductive status, tissue contaminant load, and mRNA abundance profiles, we characterized variation in the local M. modiolus population situated in different spatial zones relative to a municipal wastewater outfall. Significant differences were observed in reproductive indicators, growth parameters, and abundance of four specific mRNA transcripts representative of stress response or membrane transport (CAT, NET/SCF6, ABCA4 and HSP70) in adductor muscle tissue of animals adjacent to the wastewater outfall. Concentrations of metals and organic chemicals in M. modiolus tissue were generally highest directly at the outfall site with much lower levels at 100-800 m from the outfall. This general pattern did not match the mRNA profiles. HSP70 and ABCA4 mRNA showed increased abundance in all regions adjacent to the municipal outfall compared to the reference site. One site group located within 100-200 m south/south-easterly of the outfall had increased levels of all four transcripts. Some mRNAs showed significant correlations with nickel, arsenic, lead, selenium, copper, and one of thirteen polycyclic aromatic hydrocarbons measured (dibenzo(a,h)-anthracene). Three mRNAs (CAT, NET/SCF6, and ABCA4) were negatively correlated with bis(2-ethylhexyl)phthalate. The data suggest that these benthic organisms are exhibiting biological responses to the outfall and support an alternate interpretation regarding dispersal of contaminants. The potential effects of emerging chemicals of concern entering the receiving environment merits further assessment.
authors.affiliation: Department of Biochemistry and Microbiology, University of Victoria, STN CSC, Victoria, British Columbia, Canada V8W 3P6.
authors.forename: Nik
authors.initials: N
authors.lastname: Veldhoen
authors.forename: Marek
authors.initials: M
authors.lastname: Kobylarz
authors.forename: Christopher J
authors.initials: CJ
authors.lastname: Lowe
authors.forename: Lizanne
authors.initials: L
authors.lastname: Meloche
authors.forename: Adrian M H
authors.initials: AM
authors.lastname: deBruyn
authors.forename: Caren C
authors.initials: CC
authors.lastname: Helbing
mesh_terms: D018528:ATP-Binding Cassette Transporters / Q000235:genetics / Q000378:metabolism; D000818:Animals; D015415:Biomarkers / Q000378:metabolism; D002374:Catalase / Q000235:genetics / Q000378:metabolism; D002947:Cities; D004784:Environmental Monitoring / Q000379:methods*; D018840:HSP70 Heat-Shock Proteins / Q000235:genetics / Q000378:metabolism; D049879:Mytilidae / Q000187:drug effects* / Q000235:genetics / Q000378:metabolism; D050484:Norepinephrine Plasma Membrane Transport Proteins / Q000235:genetics / Q000378:metabolism; D012333:RNA, Messenger / Q000378:metabolism; D012623:Seawater / Q000737:chemistry; D014865:Waste Disposal, Fluid; D014874:Water Pollutants, Chemical / Q000032:analysis / Q000633:toxicity*
chemical_list: D018528:ATP-Binding Cassette Transporters; D015415:Biomarkers; D018840:HSP70 Heat-Shock Proteins; D050484:Norepinephrine Plasma Membrane Transport Proteins; D012333:RNA, Messenger; D014874:Water Pollutants, Chemical; D002374:Catalase