Efectos de los metales pesados a lo largo del gradiente mareal en cinco especies de plantas halófitas en el Paraje Natural Marismas del Odiel, Huelva

Abstract

Heavy metals are considered a threat to ecosystems due to their high toxicity, their persistence and their bioaccumulative behavior, since they accumulate in organisms and concentrate at each jump in the trophic level. In this thesis, it is intended, first, to know how some heavy metals affect the germination rate, germination speed and seedling development in five species from different habitats of the marshes: Sarcocornia perennis, S. fruticosa, Salicornia ramosissima, Salsola vermiculata and Atriplex halimus. The results indicate that in concentrations up to 2000 μM of Mn, Cu, Zn and Ni no effects were observed on the germination rate in A. halimus, S. vermiculata, S. fruticosa and S. perennis, while in the case of S ramosissima germination was reduced in the presence of Ni. In Salsola vermiculata Cu and Zn reduced the germination rate only at concentrations of 4000 μM. Regarding the mean germination time (T50), in Atriplex halimus, Sarcocornia fruticosa, S. perennis and Salicornia ramosissima it was not affected by the studied concentrations of these metals, but it was observed in Salsola vermiculata exposed to Zn concentrations of 4000 μM. Regarding the effects of metals on seedling development, Mn did not produce negative effects in any case. Cu and Ni reduced root, hypocotyl, and cotyledon growth in all species except Sarcocornia ramosissima and S. perennis, where it had no effect on cotyledons and hypocotyls. Zn only affected the radicle of all species, except in Sarcocornia fruticosa, in which it also affected the cotyledons and hypocotyls. In addition, the metal accumulation capacity in Salsola vermiculata was analyzed in order to evaluate its use as a bioremediator of soils contaminated by heavy metals. The accumulation of Cu in the tissues increases exponentially with the increase of the metal in the medium, and the plants accumulate 154 mg kg 1 dry weight in media with 100 μM without presenting damage. The accumulation of Mn increases arithmetically up to 2000 μM in the medium, accumulating 4676 mg kg 1 dry weight, and from this concentration it stabilizes, without presenting damage at 4000 μM. The accumulation of Ni in the tissues increases arithmetically with the increase of the metal in the medium, and the plants accumulate 1537 mg kg 1 dry weight at 1000 μM without presenting damage. The accumulation of Zn increases arithmetically up to 2000 μM in the medium and from this concentration it stabilizes, accumulating levels of up to 3990 mg kg 1 dry weight at this concentration without negative effects on the plants. In the case of Salicornia ramosissima, a study was carried out on the bioaccumulation and transport of heavy metals between different organs of the plant, in populations developed on highly contaminated soils, in order to see its impact on its edibility. A large heterogeneity was observed in metal concentrations both in soils and in different plant parts in the 14 locations studied, and no significant correlations were observed between metal concentration in different plant parts and metal concentration. on the floor. The roots of S. ramosissima seem to exclude the absorption of Cr, Mn, Co, Ni, Cu, Zn, As and Cd, but the plants act as accumulators of Al and Fe. As a result, the consumption of this species in populations is discouraged. of the Huelva estuary, since in many cases the limits established in the regulations are exceeded, regarding the concentrations of Cd, Pb and Tl in leaves.