Plant Animal Interactions

Oecologia

, Volume 149, Issue 4, pp 604-619

Larval settlement of the common Australian sea urchin Heliocidaris erythrogramma in response to bacteria from the surface of coralline algae

  • Megan J. HuggettAffiliated withCentre for Marine Biofouling and BioInnovation, University of New South WalesSchool of Biological, Earth and Environmental Sciences, University of New South WalesKewalo Marine Laboratory, University of Hawaii Email author 
  • , Jane E. WilliamsonAffiliated withCentre for Marine Biofouling and BioInnovation, University of New South WalesDepartment of Biological Science, Macquarie University
  • , Rocky de NysAffiliated withCentre for Marine Biofouling and BioInnovation, University of New South WalesSchool of Marine Biology and Aquaculture, James Cook University
  • , Staffan KjellebergAffiliated withCentre for Marine Biofouling and BioInnovation, University of New South Wales
  • , Peter D. SteinbergAffiliated withCentre for Marine Biofouling and BioInnovation, University of New South WalesSchool of Biological, Earth and Environmental Sciences, University of New South Wales

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Abstract

Bacterial biofilms are increasingly seen as important for the successful settlement of marine invertebrate larvae. Here we tested the effects of biofilms on settlement of the sea urchin Heliocidaris erythrogramma. Larvae settled on many surfaces including various algal species, rocks, sand and shells. Settlement was reduced by autoclaving rocks and algae, and by treatment of algae with antibiotics. These results, and molecular and culture-based analyses, suggested that the bacterial community on plants was important for settlement. To test this, approximately 250 strains of bacteria were isolated from coralline algae, and larvae were exposed to single-strain biofilms. Many induced rates of settlement comparable to coralline algae. The genus Pseudoalteromonas dominated these highly inductive strains, with representatives from Vibrio, Shewanella, Photobacterium and Pseudomonas also responsible for a high settlement response. The settlement response to different bacteria was species specific, as low inducers were also dominated by species in the genera Pseudoalteromonas and Vibrio. We also, for the first time, assessed settlement of larvae in response to characterised, monospecific biofilms in the field. Larvae metamorphosed in higher numbers on an inducing biofilm, Pseudoalteromonas luteoviolacea, than on either a low-inducing biofilm, Pseudoalteromonas rubra, or an unfilmed control. We conclude that the bacterial community on the surface of coralline algae is important as a settlement cue for H. erythrogramma larvae. This study is also an example of the emerging integration of molecular microbiology and more traditional marine eukaryote ecology.