Análise de plantas de mangue como bioindicadoras da qualidade ambiental nas Ilhas de Tinharé e Boipeba, município de Cairu, Bahia, Brasil

Abstract

Tinharé and Boipeba islands, located in the southern shore of Bahia, have rich coast and system and ecosystem in special areas of choral reefs e de forest of mangrove, distributed on the coast zone of both islands. These natural attributes, associated to the relevant colonial social historic patrimony, made these islands important tourist destinations, being these activity more consolidated and with a major infrastructure in Morro de São Paulo, in Tinharé. The present study has as principal objective make an analisys about the mangle plant species as bioindicator of the environmental quality in the Tinharé and Boipeba islands. Lately, the Southern Region of Bahia has been the target of interesting to many oil companies, some of them are already working on research and exploration of natural gas and oil. Besides, it is common the transit of ships carrying oil and/or its derivatives in this coast region. In the coast zone of the studied island, 10 sampling stations were chosen with diverse characteristics: 04 in the Tinharé Island and 06 in Boipeba Island. These stations are under direct influence the waves and tides, main hydrodynamic agent of the coast, being stations E5, E8, E9 and E10 (Boipeba) under the influence of the continental Waters, respectively, of Patos Channel, Catu River, Bainema River and Santo River. 60 leaves of sun were collected from the species Rhizophora mangle, Laguncularia racemosa and Avicennia schaueriana and made analisys of biometric parameters and external morphology. These analyses has suggested foliar reduction and alteration in the integrity of the foliar limb, mainly chlorosis, grazing, necrosis and perforations. After dried until constant weigh, these leaves were properly prepared to the determination of heavy metals (Cu, Cd, Pb and Zn), whose opening has ocurred in a microwaves and the reading through spectrometry by atomic absorption with flame, conform adopted methodology. The average content of Cu were toxic to Rhizophora in E2 and to Laguncularia in stations E3 and E9. Lead has showed high level in all stations and toxic in stations E3 and E4 (for all three species), E2 and E9 (Rhizophora and Avicennia), E5 (Laguncularia and Avicennia), E7 (Avicennia) and E10 (Rhizophora). Lead has showed high values for all stations and toxic in stations E3 and E4 (for the three species), E2 and E9 (Rhizophora and Avicennia), E5 (Laguncularia and Avicennia), E7 (Avicennia) and E10 (Rhizophora). In this work, there were various sources of environmental impacts and it was not possible to infer to only one source the contamination with lead. The collected information could not be used in an identification of a principal source of contamination by lead, on the other hand it suggests diffuse sources, what may take us to jump to the conclusion to new studies and the use of more indicators for a longer period of time. It is suggested accomplishment of posterior studies that use other indicators of ambient contaminators, the example of the fauna, waters and sediments. These can complement the information presented in this study and contribute the accurate analysis of the observed sources of contamination in Tinharé Island and Boipeba Island.