Cianobactérias de manguezais no estado de Pernambuco

Abstract

Estuaries have great ecological importance, being one of the most productive ecosystems in the world. Associated with these tropical environments, the mangroves are generally characterized by a halotallerant vegetation, essential for the maintenance of the coastal ecosystem. For these reasons, they are environments where there is extensive socioeconomic activity and, therefore, today there are no more mangroves that have not been impacted by anthropogenic factors. Cyanobacteria make up the microbiota of these environments in the most diverse spaces, being free on water column (phytoplankton) and sessile over submerged substrates (periphyton). In all these environments, cyanobacteria contribute to primary production and are essential in carbon and nitrogen fixation, the latter element being naturally scarce in organic form in many environments colonized by cyanobacteria. Despite their great contribution to ecosystem maintenance in mangroves and estuaries, cyanobacteria are commonly left out of taxonomic research involving these habitats and little is known about these prokaryotes in these environments in Brazil. Therefore, the objective of this research was to identify and describe planktonic and periphytic cyanobacteria in mangrove habitats in the state of Pernambuco. The samples were collected at three points (river mouth, middle and amount) in four estuaries (Barra das Jangadas, Rio Una, Rio Formoso and Santa Cruz): 1) for phytoplankton samples (subsurface water at low tide and high tide) and 2) for periphyton (pneumatophore) samples, where freely collected along the mangrove areas in each region equivalent to the phytoplankton collection points. A total of 66 samples were collected (48 phytoplankton and 18 periphyton). All samples collected were analyzed under optical microscopy, observing a minimum of 30 individuals per species, whose morphological identification were made based on specific and updated literature. 69 cyanobacterial taxa were identified (51 spp., 13 sp., 3 cf., 2 aff.) distributed in 32 genera and 19 families, with the most representative family Oscillatoriaceae with 27 infrageneric taxa identified. Among the identified species and considering only records for mangrove areas, 15 are new occurrences for mangroves and estuaries in Brazil, 22 for the Northeast region and 11 for the state of Pernambuco. The number of cyanobacterial species identified in this work, as the new occurrences, demonstrate the large gap in taxonomic studies about cyanobacteria in mangrove areas in tropical regions. In addition, several populations could not be identified at a specific level, which both demonstrates the lack of specific literature for the identification of these taxa, as the possibility of new species, highlighting the importance of producing new taxonomic studies about cyanobacteria in mangrove areas.