Introdução
The mangrove forest function as an integrated unit between terrestrial and marine environments and play a key role in the maintenance of coastal ecological balance and species diversity (Du et al., 2013). However, it has been reported that coastal habitats have been faced with severe metallic contaminant input, which has become a problem of increasing concern when in excess of natural loads. The bioavailability and toxicity of metals in sediment are associated with pH, redox potential, mineral and organic content, resident biota, and the complicated synergistic interactions between these variables (Morrissey and Guerinot 2009). Thus, the accumulation of metals in plant tissues is determined by the bioavailability of these elements in the soil and the plant efficiency to absorb and translocate it in roots and vascular tissues (Qian et al. 2012). The aim was investigate the effects of a potentially contaminated environmental in a mangrove plant to provide a better understanding of metal tolerance and translocation mechanisms.
Metodologia
This study was conducted in two neotropical estuaries located in the State of Espírito Santo, Brazil: Vitória Bay and Santa Cruz which were selected because they represent areas affected by different pollution sources and ocean influence. The analysis of metals and metalloids (Al, Cr, Mn, Fe, Ni, Cu, Zn, As, Se, Ag, Cd, Hg and Pb) in both abiotic and biotic digested samples was performed with a Mass Spectrometer Inductively Coupled Plasma (ICP-MS). The thickness of cortex, air gap area and vascular cylinder of pneumatophores and absorption roots were measured (30 measurements/root section) and the cortex/vascular cylinder ratio was calculated. In pneumatophores the thickness of the periderm was also measured. Multivariate statistical methods were applied to different datasets (physical parameters, chemical parameters, anatomical parameters, combined parameters): lineal discriminant analysis (LDA), factor analysis (FA), generalized procrustes analysis (GPA) and Spearman's rank correlation coefficient. Multivariate statistical methods evidenced the contribution of diverse variables to the model, and their capacity to discriminate one category from another.
Resultados e Discussão
Studied estuaries can be primarily differentiated on the basis of anatomical biomarkers of plant and physical and chemical parameters of the environment. The dissolved oxygen and organic matter content evidence the spatial difference between areas, affecting the cortex/vascular cylinder ratio and the pneumatophore cortex thickness, indicating a strong anthropic influence on the sites from Vitória bay. The influence of activities of steel industry through the metals uptake used in the siderurgical process on environments was also evidenced by nickel and chrome values in sediment, with higher concentrations in Serra, which showed the highest values for most contaminants in this study. GPA confirms spatial differences between studied areas by an independent statistical calculation.
Conclusão
The evaluation of phenotypic plasticity of A. schaueriana demonstrated that anatomical root and metal uptake analysis are efficient biomarkers to contrast different pollution scenarios. In addition, the use of multivariate statistics contributes to extrapolate results from field and laboratory measurements, highlighting parameters that help to differentiate sites with different contamination sources and, consequently, different risks for the aquatic biota. Furthermore, statistical methods like LDA and GPA contribute to integrating the knowledge coming from different scientific disciplines, such as biology and chemistry, producing more complete results complementing both field and laboratory efforts.
Referências Bibliográficas
DU J, YAN C, LI Z (2013b) Formation of iron plaque on mangrove Kandalar. Obovata (S.L.) root surfaces and its role in cadmium uptake and translocation. Mar Pollut Bull 74: 105-109. doi: 0.1016/j.marpolbul.2013.07.023
MORRISSEY J, GUERINOT M (2009) Iron uptake and transport in plants: the good, the bad, and the ionome. Chem Rev 109: 4553-4567. doi: 10.1021/cr900112r Fonte Financiadora
