My postdoctoral research work focuses on both aspects of our « Stream and river metabolism » project. In the first part, I am synthesizing a unique multi-decadal bio-physico-chemical dataset from the middle Loire River to understand non-linear regime shifts in primary producer communities resulting from both top-down and bottom-up controls. For the second part, I have helped instrument the headwaters of the Loire River to understand how stream metabolism scales from reaches to networks, with a particular emphasis on non-additive behavior of tributaries, and spatial arrangements of land-use throughout the watershed.
Hanieh Seyedhashemi, PhD student
River thermal regimes play a key role in the distribution of aquatic communities and water quality. However, we have a poor understanding of how human activities and natural processes influence the spatiotemporal variability of stream thermal regimes. To fill these knowledge gaps, my work focuses on the following:
1) Identifying and quantifying the influence of ponds and dams on the thermal regime at regional scale through statistical analyses; 2) Analysis of thermal regime sensitivity to environmental variables such as vegetation, hydraulic geometry, and hydrology. For this focus, I am using a physically-based thermal model, T-NET (Temperature-NETwork), coupled with a semi-distributed hydrological model (EROS) to simulate daily discharge and water temperature at the scale of the Loire River basin in France (Beaufort et al. 2015, Loicq et al, 2018); 3) Reconstruction and detection of stream temperature historical trends using the T-NET model to improve understanding of contemporary and future change of ecologically relevant thermal metrics; 4) Projecting stream temperature under future climate change scenarios using T-NET model and analysis of the subsequent changes to ecologically important thermal metrics.
My doctoral thesis in Florentina’s team (2012-2015) was on the eutrophication processes that occur in the Middle and Lower reaches of the Loire River. To characterize eutrophication causes and consequences in large rivers, I have studied the relationships between nutrient sources, biogeochemical processes, hydrological pathways, and meteorological condition across different temporal scales (daily, seasonal, inter-annual, decadal) and at different locations of the Loire catchment. This was based on long-term but monthly public data, daily measurements collected during my PhD, and a numerical model of eutrophication processes I’ve developed to represent the fine-scale biogeochemical variations in the river network of a 30,000 km2 sub-catchment.
Since my PhD, we’ve worked together on identifying the catchment properties that shape the spatial and temporal variations of nutrient transfers in rivers. I also contributed in Florentina’s work on the uncertainties inherent to the estimation of suspended matter and solute fluxes, as a function of catchment behavior and sampling frequency.
Bio coming soon …
I did my PhD on the modelling of river temperature at the regional scale on the Maine river catchment (tributary of the Loire river at Angers), which is climatically homogeneous. My work mainly focused on the impact of riparian vegetation on the radiative budget at the meter resolution on 270 km of the Loir River, with the T-NET model, developed during the PhD of Aurélien Beaufort.
My project now is to develop an automated solar reflector (or « heliostat »)!