The effect of Symbiodinium spp. symbiont diversity on coral host performance

Open Access
Author:
Abidi, Nadia Yasmin
Area of Honors:
Biology
Degree:
Bachelor of Science
Document Type:
Thesis
Thesis Supervisors:
  • Iliana Brigitta Baums, Thesis Supervisor
  • Bernhard Luscher, Honors Advisor
Keywords:
  • Acropora palmata
  • zooxanthellae
  • symbiosis
Abstract:
Scleractinian corals such as Acropora palmata, a threatened Caribbean coral, form obligate symbioses with single-celled algae of the genus Symbiodinium. Differences in the symbiont clade harbored have been linked to coral performance variation. The objective of this research was to measure variations in the survival and growth of larval settlers dependant on the clade harbored. We hypothesized that endogenous A. palmata symbiont exposure would result in the greatest settler growth. Acropora palmata larvae, collected in the field, were sent to Aquaria (n=6) across the US and settled on tiles. Larvae were either exposed to the native A. palmata symbiont (clade A3), isolated from adults, or left to take up algal symbionts from Caribbean and Pacific corals in their rearing tanks (n= 4-8 tanks per aquaria). Settlement tiles (n =44) were sent from aquaria at two time points (1 and 4 months) and DNA was extracted from all settlers (n=160). The internal transcribed spacer 1 (ITS1) regions of the large ribosomal subunit rDNA of zooxanthellae was isolated, run on acrylamide denaturing gels, and sequenced to differentiate between Symbiodinium clades. Settlers were also photographed for size. Performance of the coral-algal symbiosis was analyzed by correlating the symbiont clades present in the juveniles with polyp lengths measured. Our results revealed an aquarium effect on settlers at one month and four months with Omaha aquarium leading all others in settler performance. Interestingly, at four months, we found that a dominance of the native clade A3 did not result in better larval performance. Opportunistic clade D, and mixed A/C/D symbioses resulted in settlers with the largest sizes. Most importantly, the low specificity of initial symbiont acquisition seen in juvenile A. palmata may be adaptive, allowing for the establishment of an advantageous multi-clade symbioses during early juvenile growth that can then be further specified when requirements change during adulthood.