Nitrate enrichment has lineage specific effects on Pocillopora acuta adults, but no transgenerational effects in planulae

Abstract

Local-scale nutrient pollution can alter coral growth and reproductive output, as well as their resident communities of microorganisms (dinoflagellates in the family Symbiodiniaceae, bacteria). Yet, the ways in which nutrient pollution alters coral interactions with their microorganisms are not fully understood, and no studies have tested for transgenerational impacts of nutrient stress on coral holobionts. To investigate this, colonies of Pocillopora acuta were enriched with nitrate in situ for up to one year and monitored for planulation. Gene expression, resident microbial communities and holobiont traits were characterized in adults, as well as in planulae. Although separated by [ 5 m, clonality and chimerism were observed in the majority of coral colonies. Lineageand treatment-specific effects of nitrate treatment were detected in adults and planulae. Nitrate-enriched adults contained higher densities of Symbiodiniaceae and exhibited downregulation of genes involved in the synthesis of nitrogenous compounds. Planulae harbored higher Symbiodiniaceae and bacteria diversity than adults; this study constitutes the first assessment of these microorganisms from individual planulae. Coral-associated bacteria communities were Endozoicomonas-dominated and were not altered by nutrient treatment. Planula-associated bacteria communities differed from their parents but not from parental exposure to nutrients, and no changes in fecundity or settlement success resulted from enrichment. Taken together, these findings suggest that adult corals acclimate to chronic nutrient pollution by harboring higher Symbiodiniaceae densities, with no observed negative effects on the subsequent generation.

Cophylogeny and specificity between cryptic coral species (Pocillopora spp.) at Mo′orea and their symbionts (Symbiodiniaceae)

“…Pocillopora acuta can also be found at Mo′orea but is only found on the fringing reef, not on the fore reef, and largely hosts Durusdinium in this environment (Rouzé et al, 2019;Strader et al, 2022) and was therefore not included in our analyses. In general, the Cladocopium phylogeny, including multiple clades within species, mirrored the Pocillopora phylogeny (Figure 7).…”

“…The samples contained nine mitochondrial open reading frame (mtORF) haplotypes including haplotype 1a, 2, 3a, 3b, 3f, 3h, 8a, 10, 11. Haplotype 1a contains two species: P. meandrina and P. grandis (Johnston et al, 2017). While colonies of the same genotype are well known in P. acuta (haplotype 5) (e.g., Strader et al, 2022), we did not sample clones. mtORF identification was carried out as described in Johnston et al (2022) with haplotype numbering following Forsman et al (2013) and Pinzón et al (2013).…”

Cophylogeny and specificity between cryptic coral species (Pocilloporaspp.) at Mo’orea and their symbionts (Symbiodiniaceae)

“…Our analyses supported the presence of five co-occurring Pocillopora species on the fore reef of Mo’orea that largely hosted two species of host-specialized algae ( Cladocopium latusorum and C. pacificum). Pocillopora acuta can also be found at Mo’orea but is only found on the fringing reef, not on the fore reef, and largely hosts Durusdinium in this environment (Rouzé et al 2019; Strader et al 2022) and was therefore not included in our analyses. In general, the Cladocopium phylogeny, including multiple clades within species, mirrored the Pocillopora phylogeny (Figure 7).…”

“…The samples contained nine mitochondrial open reading frame (mtORF) haplotypes including haplotype 1a, 2, 3a, 3b, 3f, 3h, 8a, 10, 11. Haplotype 1a contains two species: P. meandrina and P. grandis (Johnston et al 2017). While colonies of the same clone are well known in P. acuta (haplotype 5) (e.g., Strader et al (2022)), we did not sample clones. mtORF identification was carried out as described in Johnston et al (2021) with haplotype numbering following Forsman et al (2013) and Pinzón et al (2013).…”

“…A mixed mode of symbiont transmission may allow juveniles to have greater flexibility in different environments than strictly vertical transmission. Even if symbionts are transmitted vertically, an individual can host a diverse community of ‘background’ symbionts, even when there is often only one taxa detected, that are transitory and may depend on environmental conditions (Lee et al 2016; Rouzé et al 2019; Kriefall et al 2022; Strader et al 2022). As a result, even in species with vertical transmission, the relationships between scleractinian host and symbiont can be dynamic over ecological timescales (Reich et al 2017; Quigley et al 2019).…”