Elemental Cycles

The overarching interesting in the Penn BiCycles Lab is the biogeochemical cycling of elements through the Earth System. Understanding the mobilization, transportation and fate of various elements ultimately links to impacts on the carbon cycle, biology and earth’s climate.

Our research encompasses aquatic geochemistry, with a focus on the mobilization, cycling and transport of nutrients, contaminants and solute between the lithosphere, hydrosphere and biosphere. Understanding the behavior of elements essential for primary and secondary production, particularly their movement through the downstream cascade, is important for predicting the response of aquatic ecosystems to environmental change and anthropogenic disturbance, and for providing the foundation for ecosystem services.

Polar and Alpine Biogeochemistry

Glaciers and ice sheets cover ~10 % (up to 30 % during recent glaciations) of global land surface area yet our knowledge of their role in global biogeochemical cycles is still limited. The regions downstream of significant glacial freshwater inputs are home to productive ecosystems and there is an emerging body of evidence to suggest that glacier melt plays a role in sustaining these by directly and indirectly providing essential nutrients. Far from being frozen, sterile and static blocks of ice, glaciers are diverse biomes (the largest freshwater ecosystems on Earth by volume) that play a role in the global carbon cycle. Glacially derived nutrients sustain in situ aquatic ecosystems (e.g., active microbial ecosystems exist in subglacial lakes more than 1000 m beneath the Antarctic Ice Sheet) and help to sustain and drive complex and economically important marine ecosystems. Understanding the evolution and behavior of these elemental cycles and ecosystems is important as regions containing components of the cryosphere are amongst the most vulnerable on Earth yet remain among the least understood.

A primary interest of our lab is to understanding the flow and flux of elements in glaciated landscapes, with a view to understanding how the cryosphere interacts with other Earth sub-systems. Our current research focuses on the role of glacial meltwater in downstream biogeochemical cycles. We take particular interest in the potential of glacial meltwater to influence the structure and productivity of ecosystems, subglacial biogeochemical weathering processes, and the mobilization and export of nutrients and toxic elements from glaciated envrionments.

Toxic Elements in the Environment

Elements such as mercury, chromium (especially in its hexavalent form) and arsenic are toxic to organisms. As such they can prove detrimental to ecosystems and human health when present in environmentally elevated concentrations. Understanding how they are mobilized, transported and cycled in the natural environment is therefore of great importance.

In the Penn BiCycles Lab we are most interested in how concentrations of toxic elements become elevated in aquatic systems and how toxic elements are transported through pristine systems. As mobilization of toxic elements is usually a result of anthropogenic activity (even in pristine systems) we are also interested in how their impact can be minimized or mitigated, and their behavior predicted. We apply elemental speciation techniques (e.g., gas and liquid chromatography) to determine how the most toxic forms of these elements (e.g., methylmercury, hexavalent chromium and arsenite) are produced and cycled.

Changing Aquatic Critical Zones

Rapid and expansive change to the environment has occured due to human activity, which has led to scientists declaring a new period in Earth history – the Anthropocene. Human activity has and is profounding impacting aquatic critical zones – interface zones where biologically important geological, physical and geochemical processes are taking place to maintain function of aquatic environments and the ecosystems they maintain.

The aquatic critical zones we’re most interested in include dynamic interfaces in terrestrial environments (e.g., rivers and glacier surfaces) and land-ocean interface transition zones (e.g., fjords and estauries), where steep biogeochemical gradients occur. The function and associated ecosystem health in these systems is in constant flux due to external influences. We look to investigate the importance of these critical zones, quantify the internal and external influences, and reduce uncertainties in future predictions of change.