Potencial biotecnológico de spartina maritima e inoculantes bacterianos para la recuperación de estuarios andaluces contaminados con metales pesados

Abstract

Heavy metal pollution is a growing environmental problem with a major detrimental impact on ecosystems and living organisms’ health. The joint estuary of the Tinto and Odiel rivers in Huelva (Spain) is known as one of the most polluted areas by heavy metals in the world. Phytoremediation strategies have been proposed as a cheaper and eco-friendly alternative to physicochemical remediation procedures. In this context, halophyte cordgrasses in the genus Spartina come under the spotlight due to their heavy metal bioaccumulation capacity. In occidental Andalusian salt marshes, S. maritima and S. densiflora grow naturally. Nonetheless, S. densiflora is an invasive species that is gradually affecting coasts, flora and fauna dynamics. Accordingly, in this Doctoral Thesis the use of autochthonous plant growth promoting bacteria is proposed to enhance the phytoremediation potential of native S. maritima as a biotool to rehabilitate degraded salt marshes. Soil heavy metal concentration in Tinto and Odiel estuaries was determined to outreach the threshold intervention values settled by state laws. These high pollution levels dictated soil microbial dynamics in estuarine soils over S. maritima rhizosphere or seasonal changes. Cultivable bacteria were isolated from S. maritima rhizosphere and inner tissues and, based on their plant growth promoting properties and multiresistance to heavy metals, two bacterial consortia (rhizospheric and endophytic) with potential use to facilitate phytoremediation were designed. Under greenhouse conditions, bioaugmentation treatments with both consortia improved S. maritima growth and physiological parameters. However, whereas endophytic inoculation lessened metal accumulation in above and belowground tissues, bioaugmentation with rhizobacteria stimulated S. maritima root metal uptake. On the whole, this thesis supports that bioaugmentation treatments with autochthonous bacteria may be claimed as a biotool to enhance native S. maritima adaptation and metal rhizoaccumulation in Andalusian salt marshes.