title: Effects of dissolved organic carbon on the toxicity of copper to the developing embryos of the Pacific oyster (Crassostrea gigas).
abstract: The effects of humic acid (HA) on copper speciation and its subsequent toxicity to the sensitive early life stages of the Pacific oyster (Crassostrea gigas) are presented. Differential pulse anodic stripping voltammetry with a hanging mercury drop electrode was used to measure the copper species as labile copper (LCu; free ion and inorganic copper complexes) and total copper (TCu) with respect to increasing HA concentration. The TCu and LCu 50% effect concentrations (EC50s) in the absence of HA were 20.77 microg/L (95% confidence interval [CI], 24.02-19.97 microg/L) and 8.05 microg/L (95% CI, 9.6-5.92 microg/L) respectively. A corrected dissolved organic carbon (DOC) concentration (HA only) of 1.02 mg/L was required to significantly increase the TCu EC50 to approximately 41.09 microg/L (95% CI, 44.27-37.52 microg/L; p < 0.05), almost doubling that recorded when DOC (as HA) was absent from the test media. In contrast, the LCu EC50 was unaffected by changes in DOC concentration and was stable throughout the corrected DOC concentration range. The absence of change in the LCu EC50, despite increased HA concentration, suggests that the LCu fraction, not TCu, was responsible for the observed toxicity to the oyster embryo. This corresponds with the current understanding of copper toxicity and supports the free-ion activity model for copper toxicity.
authors: Centre for Environment Fisheries and Aquaculture Science, Burnham Laboratory, Remembrance Avenue, Burnham-on-Crouch, Essex CMO 8HA, United Kingdom. steven.brooks@cefas.co.uk
authors: Steven J
authors: SJ
authors: Brooks
authors: Thi
authors: T
authors: Bolam
authors: Laura
authors: L
authors: Tolhurst
authors: Janice
authors: J
authors: Bassett
authors: Jay
authors: J
authors: La Roche
authors: Mike
authors: M
authors: Waldock
authors: Jon
authors: J
authors: Barry
authors: Kevin V
authors: KV
authors: Thomas
mesh_terms: D000818:Animals; D002244:Carbon / Q000032:analysis / Q000737:chemistry / Q000633:toxicity*; D003300:Copper / Q000032:analysis / Q000633:toxicity*; D049896:Crassostrea / Q000187:drug effects* / Q000196:embryology / Q000254:growth & development; D004305:Dose-Response Relationship, Drug; D004563:Electrochemistry; D004566:Electrodes; D006812:Humic Substances / Q000032:analysis / Q000633:toxicity*; D012995:Solubility; D018675:Toxicity Tests; D014874:Water Pollutants, Chemical / Q000032:analysis / Q000633:toxicity*
chemical_list: D006812:Humic Substances; D014874:Water Pollutants, Chemical; D002244:Carbon; D003300:Copper