Biotic interactions and biological mechanisms of metal remediation by natural wetlands (NERC EAO Doctoral Training Partnership)

Pollution from abandoned mine sites is a major environmental problem that has deleterious consequences on both aquatic and terrestrial ecosystems throughout the world. Freshwater resources have been negatively impacted by mining contamination reducing the value of the water for agricultural, recreational or industrial uses, rendering it unsafe for humans, and having a negative effect on biota [1- 3]. Natural wetlands have long been known to play an important role in pollutant remediation, such as in the removal of acid mine drainage (AMD) from abandoned mine sites [1]. However, many aspects of the biological mechanisms underlying AMD remediation by wetlands are unclear, including the role of associated rhizosphere microbial communities. Improved knowledge is important for enhancing fundamental understanding of these biotic interactions but can also direct research and development of constructed wetlands.

The abandoned Parys Mountain copper mine in Anglesey, North Wales discharges significant volumes of AMD into two rivers, one of which is without surrounding plants while the second river flows through a large natural wetland. At its source, dissolved metals and acidity heavily pollute the river but there have been improvements to water quality further downstream due in part to remediation by the wetland [1, 4]. This AMD impacted river system provides an ideal study site to quantify and contrast biological mechanisms and the microbial community composition in river water and sediment without wetland vegetation compared to a river with a substantial natural wetland. Recent unpublished data from our labs have used bacterial 16S rDNA sequencing to identify variation in bacterial community structure and species diversity on the basis of water/sediment chemistry parameters and on the basis of wetland plant presence [5]. Our hypothesis is that the wetland plants play a critical role in maintaining and directing microbial metabolic activities.

This PhD project will further extend upon these earlier studies in order to examine the mechanisms involved in the reduction in metal load by the wetland from a holistic examination of metal behaviour and processes. The objectives are to further identify and quantify the role of bacterial communities through the use of next generation sequencing of DNA and RNA isolated from sediment cores throughout both sites.

Molecular and bioinformatics approaches will be used to predict the metabolic activities of the communities through the use of metabolic reconstruction analysis plus validation by transcriptomic microbiology analysis. Alongside field analysis, laboratory-based mesocosm experiments will further examine mechanisms by dissecting the role of associated bacteria and plants under controlled conditions.

Together these observations will provide an in-depth understanding of metal remediation processes in wetland systems subject to long-term metal pollution. The assessment of the degree to which metal removal is enhanced due to the selection for tolerant microorganisms and macrophytes will also facilitate the development of wetlands as a bioremediation strategy. The student will receive training in a range of physiological, analytical, and molecular biology techniques, including metal analysis and bioinformatics. The research team has an excellent track record in environmental pollution analysis, microbial ecology and plant physiology. Jon Pittman (primary supervisor) has experience examining responses of metal pollution and bioremediation by plants and microorganisms. He will provide training in plant growth, physiology, molecular biology and some analytical techniques. Co-supervisors Keith White and Andrew Dean will provide aquatic biology, water chemistry, microbiology and analytical techniques. Access to genome sequencing and spectroscopy analysis core facilities will also be available from collaboration with both universities. The supervisor’s labs have MSc, PhD students and postdoctoral scientists working on related projects and using relevant techniques, and together the labs will provide an excellent training environment for the student to gain a unique set of cutting edge, multidisciplinary skills.