title: Combined thermal and herbicide stress in functionally diverse coral symbionts.
abstract: Most reef building corals rely on symbiotic microalgae (genus Symbiodinium) to supply a substantial proportion of their energy requirements. Functional diversity of different Symbiodinium genotypes, endorsing the host with physiological advantages, has been widely reported. Yet, the influence of genotypic specificity on the symbiont's susceptibility to contaminants or cumulative stressors is unknown. Cultured Symbiodinium of presumed thermal-tolerant clade D tested especially vulnerable to the widespread herbicide diuron, suggesting important free-living populations may be at risk in areas subjected to terrestrial runoff. Co-exposure experiments where cultured Symbiodinium were exposed to diuron over a thermal stress gradient demonstrated how fast-growing clade C1 better maintained photosynthetic capability than clade D. The mixture toxicity model of Independent Action, considering combined thermal stress and herbicide contamination, revealed response additivity for inhibition of photosynthetic yield in both tested cultures, emphasizing the need to account for cumulative stressor impacts in ecological risk assessment and resource management.
authors.affiliation: Australian Institute of Marine Science, PO Box 41775, Casuarina, NT 0811, Australia; The University of Queensland, School of Biological Sciences, St. Lucia, QLD 4072, Australia; Australian Institute of Marine Science, PMB 3, Townsville MC, Townsville, QLD 4810, Australia. Electronic address: j.vandam@aims.gov.au.
authors.forename: J W
authors.initials: JW
authors.lastname: van Dam
authors.affiliation: Australian Institute of Marine Science, PMB 3, Townsville MC, Townsville, QLD 4810, Australia. Electronic address: s.uthicke@aims.gov.au.
authors.forename: S
authors.initials: S
authors.lastname: Uthicke
authors.affiliation: Australian Institute of Marine Science, PMB 3, Townsville MC, Townsville, QLD 4810, Australia. Electronic address: v.beltran@aims.gov.au.
authors.forename: V H
authors.initials: VH
authors.lastname: Beltran
authors.affiliation: The University of Queensland, National Research Centre for Environmental Toxicology, 39 Kessels Road, Coopers Plains, QLD 4108, Australia. Electronic address: j.mueller@uq.edu.au.
authors.forename: J F
authors.initials: JF
authors.lastname: Mueller
authors.affiliation: Australian Institute of Marine Science, PMB 3, Townsville MC, Townsville, QLD 4810, Australia. Electronic address: a.negri@aims.gov.au.
authors.forename: A P
authors.initials: AP
authors.lastname: Negri
mesh_terms: D000818:Animals; D037421:Anthozoa / Q000502:physiology; D057894:Coral Reefs; D004141:Dinoflagellida / Q000187:drug effects* / Q000502:physiology; D004237:Diuron / Q000633:toxicity*; D005838:Genotype; D006540:Herbicides / Q000633:toxicity*; D006358:Hot Temperature / Q000009:adverse effects*; D010788:Photosynthesis / Q000187:drug effects; D013312:Stress, Physiological; D013559:Symbiosis; D014874:Water Pollutants, Chemical / Q000633:toxicity*
chemical_list: D006540:Herbicides; D014874:Water Pollutants, Chemical; D004237:Diuron
keywords: Combined stress; Diuron; Photoinhibition; Symbiodinium; Thermal stress