title: Effects of light attenuation on the sponge holobiont- implications for dredging management.
abstract: Dredging and natural sediment resuspension events can cause high levels of turbidity, reducing the amount of light available for photosynthetic benthic biota. To determine how marine sponges respond to light attenuation, five species were experimentally exposed to a range of light treatments. Tolerance thresholds and capacity for recovery varied markedly amongst species. Whilst light attenuation had no effect on the heterotrophic species Stylissa flabelliformis and Ianthella basta, the phototrophic species Cliona orientalis and Carteriospongia foliascens discoloured (bleached) over a 28 day exposure period to very low light (<0.8 mol photons m-2d-1). In darkness, both species discoloured within a few days, concomitant with reduced fluorescence yields, chlorophyll concentrations and shifts in their associated microbiomes. The phototrophic species Cymbastela coralliophila was less impacted by light reduction. C. orientalis and C. coralliophila exhibited full recovery under normal light conditions, whilst C. foliascens did not recover and showed high levels of mortality. The light treatments used in the study are directly relevant to conditions that can occur in situ during dredging projects, indicating that light attenuation poses a risk to photosynthetic marine sponges. Examining benthic light levels over temporal scales would enable dredging proponents to be aware of conditions that could impact on sponge physiology.
authors.affiliation: Australian Institute of Marine Science, Townsville, QLD, and Perth, WA, Australia.|Western Australian Marine Science Institution, Perth, WA, Australia.
authors.forename: Mari-Carmen
authors.initials: MC
authors.lastname: Pineda
authors.affiliation: Australian Institute of Marine Science, Townsville, QLD, and Perth, WA, Australia.|Western Australian Marine Science Institution, Perth, WA, Australia.|Centre for Microscopy Characterisation and Analysis, UWA Oceans Institute, and School of Plant Biology: University of Western Australia, Crawley, WA, Australia.
authors.forename: Brian
authors.initials: B
authors.lastname: Strehlow
authors.affiliation: Australian Institute of Marine Science, Townsville, QLD, and Perth, WA, Australia.|Western Australian Marine Science Institution, Perth, WA, Australia.
authors.forename: Alan
authors.initials: A
authors.lastname: Duckworth
authors.affiliation: Australian Institute of Marine Science, Townsville, QLD, and Perth, WA, Australia.
authors.forename: Jason
authors.initials: J
authors.lastname: Doyle
authors.affiliation: Australian Institute of Marine Science, Townsville, QLD, and Perth, WA, Australia.|Western Australian Marine Science Institution, Perth, WA, Australia.
authors.forename: Ross
authors.initials: R
authors.lastname: Jones
authors.affiliation: Australian Institute of Marine Science, Townsville, QLD, and Perth, WA, Australia.|Western Australian Marine Science Institution, Perth, WA, Australia.
authors.forename: Nicole S
authors.initials: NS
authors.lastname: Webster
mesh_terms: D000818:Animals; D058448:Biota / Q000502:physiology*; D008027:Light; D011161:Porifera / Q000502:physiology*; D013559:Symbiosis / Q000502:physiology*