Recent observations supporting the hypothesis of the colonization of thrombolite platforms by mangroves

Resumo

Background. Thrombolites are sedimentary structures formed by precipitation, consolidation, and lithification of sediments generated by the evolution of cyanophyte mats that are responsible for coastal ground formation. Mangroves, however, are opportunist that colonize said substratum, in this case thrombolite platforms. Goals. To provide recent evidence of mangrove colonization of thrombolite platforms. Methods. Photographic images were taken of specimens of mangroves found fixed on the first thrombolite platform described in 2005. The platform was examined and samples were collected to analyze their mineralogical composition. Results. Evidence was gathered of two mangrove species colonizing a thrombolite platform. Specimens that had reached significant heights, indicating healthy juveniles, were found fixed on the first thrombolite platform. Collected platform structures were identified as rhizoliths belonging to mangrove trees. Conclusions. Evidence is presented that, besides this colonizing event, an earlier colonization on a thrombolite platform occurred at an inferior level. A secondary hypothesis that micrite would be a significant component of the rhizolith structure was proven through the mineralogical analysis of rhizolith fragments.