Abstract
Previous studies of symbiotic associations between scleractinians corals and Symbiodinium have demonstrated that the consortium of symbionts can change in response to environmental conditions. However, less is known about symbiont shuffling during early coral development, particularly in brooding species. This study examined whether Symbiodinium consortia (1) varied in Porites astreoides on shallow (10m) and upper mesophotic (30m) reefs, (2) changed during coral development, and (3) influenced growth of juveniles in different environments. Symbiodinium ITS2 sequences were amplified using universal primers and analyzed using phylotype-specific primers designed for phylotypes A, B, and C. Adults from both depths were found to host only phylotype A, phylotypes A and B, or phylotypes A, B, and C and the frequency of the phylotype composition did not vary with depth. However, phylotype A was the dominant symbiont that was vertically transmitted to the planulae. The presence of phylotypes B and C was detected in the majority of juveniles when transplanted onto the shallow and upper mesophotic reefs whereas only phylotype A was detected in the majority of juveniles reared in outdoor aquaria. In addition, growth of juvenile P. astreoides harboring different combinations of Symbiodinium phylotypes did not vary when transplanted to different reef zones. However, juveniles reared in in situ reef environments grew faster than those reared in ex situ outdoor aquaria. These results show that Symbiodinium consortia change during development of P. astreoides and are influenced by environmental conditions.
Highlights
In recent decades, shallow coral reef communities have experienced large-scale declines driven by anthropogenic and environmental stressors [1,2,3]
The combination of Symbiodinium phylotypes A and B was detected at the highest frequency in adults from both shallow and upper mesophotic reefs and the distribution of phylotypes did not vary with depth (χ2 = 0.42, d.f. = 2, p = 0.81)
This study examined Symbiodinium consortia in Porites astreoides adults over a depth gradient where environmental factors such as temperature, nutrients, and light vary with depth
Summary
Shallow coral reef communities have experienced large-scale declines driven by anthropogenic and environmental stressors [1,2,3]. Coral recovery is influenced by the frequency and magnitude of ongoing disturbances as well as the dynamics of population maintenance, recruitment, structure, and size [4]. Population maintenance and recruitment can occur through horizontal connectivity and vertical mixing, allowing for the increase in coral cover during both processes. These processes are shaped by patterns of dispersal and genetic connectivity, which vary with coral reproductive life histories. PLOS ONE | DOI:10.1371/journal.pone.0171768 February 9, 2017
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