title: Contrasting light spectra constrain the macro and microstructures of scleractinian corals.
abstract: The morphological plasticity of scleractinian corals can be influenced by numerous factors in their natural environment. However, it is difficult to identify in situ the relative influence of a single biotic or abiotic factor, due to potential interactions between them. Light is considered as a major factor affecting coral skeleton morphology, due to their symbiotic relation with photosynthetic zooxanthellae. Nonetheless, most studies addressing the importance of light on coral morphological plasticity have focused on photosynthetically active radiation (PAR) intensity, with the effect of light spectra remaining largely unknown. The present study evaluated how different light spectra affect the skeleton macro- and microstructures in two coral species (Acropora formosa sensu Veron (2000) and Stylophora pistillata) maintained under controlled laboratory conditions. We tested the effect of three light treatments with the same PAR but with a distinct spectral emission: 1) T5 fluorescent lamps with blue emission; 2) Light Emitting Diodes (LED) with predominantly blue emission; and 3) Light Emitting Plasma (LEP) with full spectra emission. To exclude potential bias generated by genetic variability, the experiment was performed with clonal fragments for both species. After 6 months of experiment, it was possible to detect in coral fragments of both species exposed to different light spectra significant differences in morphometry (e.g., distance among corallites, corallite diameter, and theca thickness), as well as in the organization of their skeleton microstructure. The variability found in the skeleton macro- and microstructures of clonal organisms points to the potential pitfalls associated with the exclusive use of morphometry on coral taxonomy. Moreover, the identification of a single factor influencing the morphology of coral skeletons is relevant for coral aquaculture and can allow the optimization of reef restoration efforts.
authors.affiliation: Departamento de Biologia & CESAM, Universidade de Aveiro, Campus Universitário de Santiago, Aveiro, Portugal.
authors.forename: Rui J M
authors.initials: RJ
authors.lastname: Rocha
authors.affiliation: Departamento de Engenharia dos Materiais e Cerâmica/CICECO, Universidade de Aveiro, Aveiro, Portugal.
authors.forename: Ana M B
authors.initials: AM
authors.lastname: Silva
authors.affiliation: Departamento de Engenharia dos Materiais e Cerâmica/CICECO, Universidade de Aveiro, Aveiro, Portugal.
authors.forename: M Helena Vaz
authors.initials: MH
authors.lastname: Fernandes
authors.affiliation: Laboratório de Ecologia Marinha - Instituto de Biologia Roberto Alcântara Gomes - Universidade do Estado do Rio de Janeiro, Rio de Janeiro, Rio de Janeiro, Brasil.
authors.forename: Igor C S
authors.initials: IC
authors.lastname: Cruz
authors.affiliation: Laboratório Marítimo da Guia, Centro de Oceanografia, Faculdade de Ciências da Universidade de Lisboa, Cascais, Portugal.
authors.forename: Rui
authors.initials: R
authors.lastname: Rosa
authors.affiliation: Departamento de Biologia & CESAM, Universidade de Aveiro, Campus Universitário de Santiago, Aveiro, Portugal.
authors.forename: Ricardo
authors.initials: R
authors.lastname: Calado
mesh_terms: D000818:Animals; D037421:Anthozoa / Q000145:classification / Q000528:radiation effects* / Q000648:ultrastructure; D004141:Dinoflagellida / Q000502:physiology / Q000528:radiation effects*; D017753:Ecosystem; D008027:Light; D008855:Microscopy, Electron, Scanning; D010788:Photosynthesis / Q000528:radiation effects; D013045:Species Specificity; D013559:Symbiosis / Q000528:radiation effects*