How does mineral dust derived from glacial melting affect phosphorus cycling in different types of fjords in Greenland?

Details

Supervisors

Opfergelt, Sophie ; Bonneville, Steeve

Faculty

Faculté des bioingénieurs

Degree label

Master [120] : bioingénieur en sciences et technologies de l'environnement, à finalité spécialisée

Abstract

enFjords, at the interface between terrestrial ecosystems and the open ocean, are facing dramatic changes with the acceleration of the melting of the Greenland Ice Sheet. The shift from marine-terminating (MT) to land-terminating (LT) glaciers directly influences the ecosystem in downstream fjords, reducing primary production and nutrient processes in fjords located downstream of LT glaciers compared to fjords downstream of MT glaciers. The melting of the Greenland Ice Sheet exposes glaciogenic sediments which can be deflated by winds onto the ice sheet to sustain algal blooms by releasing phosphorus (P) or transported downstream by glacier-fed rivers into fjord waters. At the base of the food web, microbial communities consume inorganic phosphorus (especially orthophosphate) and may therefore be the primary concern in this ecological shift. Yet, our understanding of how the shift from fjords with MT to LT glaciers impacts mineral dust input and the biogeochemistry and productivity of coastal waters is currently limited. First, water was collected from a supraglacial lake system in Greenland. P concentrations in supraglacial lakes have shown that particulate organic phosphorus (POP) is present in higher concentrations since particulate inorganic phosphorus (PIP) has directly been consumed upstream. Second, surface water sampling, direct biological, chemical and physical measurements as well as identification of the microbial communities have been carried out in fjords with MT and LT glaciers in Greenland. Findings revealed that dissolved phosphorus concentrations are more elevated in fjords from MT glaciers compared to fjords from LT glaciers, in line with their respective hydrobiological processes and microbial communities. By the end of the productive season, orthophosphate concentrations are at their lowest, indicating a deep consumption within the water column. These insights explore the spatial and seasonal dynamics of P and microbial communities in glacial and marine systems, with a view to investigating the potential impact of climate change on fjord ecosystems.