Master's Thesis Defense - Timothy Thomson

Jun 26 2019 10:00 AM - Jun 26 2019 12:30 PM

TITLE: Investigating Spatial Patterns of Variability in Bacterial Communities Inhabiting Soils of Arid Avicennia Marina Forests

ADVISOR: Professor Burt Jones

DATE: Wednesday, June 26, 2019

TIME: 10:00 a.m. – 12:30 p.m.

LOCATION: Building 3 - Level 5 - Room 5209


Abstract: Mangrove forests provide a suite of critical ecosystem services ranging from local to global scales. Soil conditions and associated micro-organisms play a fundamental role in maintaining these services, such as nutrient cycling, carbon sequestration, and plant growth-promoting properties. Despite its importance, the microbial abundance and function of mangrove soil have received little effort in current research. On the ecotone between the land and the sea, mangrove soils are subject to the high variability of geomorphological and ecological conditions that imply a strong distinction of ecological niches. These conditions can diversify the structure and function of the prevalent microbiome. To identify the structure of bacterial communities of mangrove soils, 16S rRNA gene sequencing techniques were applied on samples from arid Avicennia marina forests across different spatial scales: (i) at different depths of the soil profile (surface/subsurface); (ii) between two distinct zones within a given forest (seaward/landward); (iii) among forests with varying local hydrodynamic conditions (exposed/sheltered); and (iiii) among forests in different geographic regions (Saudi Arabia and  Australia). This study found that the bacterial soil community varied more within each forest than between forests in different countries. Notably, differences between countries became more apparent at the finest taxonomic resolution (ASVs). Bacterial communities from the landward zone of the mangrove forest are more conserved across countries than those from the dynamic seaward zone. Theoretically assigned functions showed high levels of sulfate respiration and chemoheterotrophy as major metabolic pathways. Differences across local factors in the functional traits reflect within forest variability.  The distinct microbial assemblages from the landward zone were associated with high salinity and phosphorus, and nitrogen and larger grain size were associated with the seaward samples. Understanding patterns of microbial communities in mangrove soils is important to predict changes and mitigate anthropogenic pressures on the ecosystem.

Bio: Timothy began his scientific journey in Bremen, Germany, where he completed his BSc with a thesis on the effect of turbidity on seagrass productivity and morphology in Hainan, China. After a short internship, he moved to KAUST to pursue a masters degree in marine science. He has been working under Prof. Burt Jones in the IOP lab. ​Timothy is interested in the biogeochemical fluxes of marine coastal ecosystems. Over the course of his masters, he has gained an increased curiosity for the community metabolism of microbial assemblages and their contributions to global and local system services. Timothy also loves frisbee, which is the best community group at KAUST and he plays it every Sunday and Wednesday with his friends.