On the functional significance of molecular variation in Symbiodinium, the symbiotic algae of Cnidaria: photosynthetic response to irradiance

Abstract

The photosynthetic response to irradiance (PI response) of dinoflagellate algae of the genus Symbiodinium was quantified immediately after isolation from symbiosis with 9 species of corals and allied taxa on Bermuda. Significant variation in PI parameters was identified among the algal isolates, but no consistent differences between representatives of different Symbiodinium phylotypes were obtained. In a parallel analysis of Montastraea franksi, a dominant Bermudian coral species, colonies from 4 to 16 m (all bearing Symbiodinium of Phylotype B) were acclimated to high light conditions. The photoacclimatory response was slight. It included an increase in the dark respiration rate by algae from all collection depths, increased light use efficiency and decreased saturating irradiance of algae from 4 m, and increased maximal photosynthetic rate per unit chlorophyll (chl), but not per cell, for algae from 8 and 16 m. We conclude that generalisations about differences between the photosynthetic traits between Symbiodinium phylotypes are not valid, and that the wide depth distribution of M. franksi cannot be attributed to either depth-dependent association with multiple Symbiodinium phylotypes with different photosynthetic properties or strong photoacclimatory capabilities of its complement of Symbiodinium. These data suggest that Symbiodinium phylotype is not generally an important determinant of the abundance and distribution of symbioses on coral reefs. KEY WORDS: Symbiosis · Symbiodinium · Zooxanthellae · PI response · Molecular diversity Resale or republication not permitted without written consent of the publisher

Variation in photosynthesis and respiration in ­geographically distinct populations of two reef‑building coral species

“…Partitioning of genetically distinct Symbiodinium communities in conspecific coral populations has been found to correlate with latitude , Rodriguez-Lanetty et al 2001, Savage et al 2002, Ulstrup et al 2006a) as well as with coral bleaching susceptibilities (Glynn et al 2001, Berkelmans & van Oppen 2006, Ulstrup et al 2006a). This suggests that thermal tolerance is controlled by local environmental conditions that corals have adapted to (West & Salm 2003) or that have caused the expression of distinct phenotypes.…”

Changes in the Number of Symbionts and Symbiodinium Cell Pigmentation Modulate Differentially Coral Light Absorption and Photosynthetic Performance

“…However, although species that present low variation in the dominant Symbiodinium type, do display large changes in coral pigmentation and symbiont content, little attention has received the analysis of this variation and its functional meaning for coral performance. By contrast, a significant effort has been invested in the analysis of changes in the dominant symbiont type and coral susceptibility to bleach (e.g., Savage et al, 2002;Baker, 2004;Tchernov et al, 2004;Berkelmans and van Oppen, 2006;Kemp et al, 2006;Robison and Warner, 2006;Warner et al, 2006;Suggett et al, 2008;Fitt et al, 2009;Pettay et al, 2015). Interestingly, species that have shown low mortality rates during massive bleaching events, also had higher symbiont content per area (Stimson et al, 2002).…”

Long-term monitoring of algal symbiont communities in corals reveals stability is taxon dependent and driven by site-specific thermal regime

“…For this reason we analyzed samples to the clade level only to test hypotheses regarding the persistence and distribution of Symbiodinium in clade D. We used known patterns of D1a (LaJeunesse 2002), also referred to as D-1-4 (LaJeunesse et al 2010), as our reference for all clade D assignments; no other D-types were detected in our dataset. Since substantial phenotypic variability may exist within clades (Savage et al 2002, Tchernov et al 2004, Baird et al 2007, this approach undoubtedly ob scures some emergent patterns at finer taxonomic scales within clade C (e.g. LaJeunesse et al 2010).…”