title: Impacts of ocean acidification on early life-history stages and settlement of the coral-eating sea star Acanthaster planci.
abstract: Coral reefs are marine biodiversity hotspots, but their existence is threatened by global change and local pressures such as land-runoff and overfishing. Population explosions of coral-eating crown of thorns sea stars (COTS) are a major contributor to recent decline in coral cover on the Great Barrier Reef. Here, we investigate how projected near-future ocean acidification (OA) conditions can affect early life history stages of COTS, by investigating important milestones including sperm motility, fertilisation rates, and larval development and settlement. OA (increased pCO2 to 900-1200 µatm pCO2) significantly reduced sperm motility and, to a lesser extent, velocity, which strongly reduced fertilization rates at environmentally relevant sperm concentrations. Normal development of 10 d old larvae was significantly lower under elevated pCO2 but larval size was not significantly different between treatments. Settlement of COTS larvae was significantly reduced on crustose coralline algae (known settlement inducers of COTS) that had been exposed to OA conditions for 85 d prior to settlement assays. Effect size analyses illustrated that reduced settlement may be the largest bottleneck for overall juvenile production. Results indicate that reductions in fertilisation and settlement success alone would reduce COTS population replenishment by over 50%. However, it is unlikely that this effect is sufficient to provide respite for corals from other negative anthropogenic impacts and direct stress from OA and warming on corals.
authors.affiliation: Australian Institute of Marine Science, Townsville, Queensland, Australia.
authors.forename: Sven
authors.initials: S
authors.lastname: Uthicke
authors.affiliation: Department of Marine Biology, University of Otago, Dunedin, Otago, New Zealand.
authors.forename: Danilo
authors.initials: D
authors.lastname: Pecorino
authors.affiliation: Australian Institute of Marine Science, Townsville, Queensland, Australia.
authors.forename: Rebecca
authors.initials: R
authors.lastname: Albright
authors.affiliation: Australian Institute of Marine Science, Townsville, Queensland, Australia.
authors.forename: Andrew Peter
authors.initials: AP
authors.lastname: Negri
authors.affiliation: Australian Institute of Marine Science, Townsville, Queensland, Australia.
authors.forename: Neal
authors.initials: N
authors.lastname: Cantin
authors.affiliation: Australian Institute of Marine Science, Townsville, Queensland, Australia.
authors.forename: Michelle
authors.initials: M
authors.lastname: Liddy
authors.affiliation: National Marine Science Centre, Southern Cross University, Coffs Harbour, New South Wales, Australia.
authors.forename: Symon
authors.initials: S
authors.lastname: Dworjanyn
authors.affiliation: National Marine Science Centre, Southern Cross University, Coffs Harbour, New South Wales, Australia.
authors.forename: Pamela
authors.initials: P
authors.lastname: Kamya
authors.affiliation: Schools of Medical and Biological Sciences, University of Sydney, Sydney, New South Wales, Australia.
authors.forename: Maria
authors.initials: M
authors.lastname: Byrne
authors.affiliation: Department of Marine Biology, University of Otago, Dunedin, Otago, New Zealand.
authors.forename: Miles
authors.initials: M
authors.lastname: Lamare
mesh_terms: D000143:Acids / Q000032:analysis* / Q000494:pharmacology; D000818:Animals; D002245:Carbon Dioxide / Q000737:chemistry; D057894:Coral Reefs; D005247:Feeding Behavior / Q000187:drug effects; D005260:Female; D005306:Fertilization; D006863:Hydrogen-Ion Concentration; D008018:Life Cycle Stages / Q000187:drug effects / Q000502:physiology*; D008297:Male; D009792:Oceans and Seas; D012623:Seawater / Q000737:chemistry*; D013081:Sperm Motility; D013215:Starfish / Q000187:drug effects / Q000254:growth & development / Q000502:physiology
chemical_list: D000143:Acids; D002245:Carbon Dioxide