Iron and carbon interactions and biogeochemical cycling in subglacial ecosystems
Glaciers have been conventionally viewed as lifeless bodies that have little impact on biogeochemical cycles. It is now known that liquid water is present under all large ice masses. In Antarctica, subglacial lakes and rivers have been discovered. One of these subglacial lakes, Subglacial Lake Whillans, was accessed in 2013, and supports a diverse and metabolically active microbial ecosystem. This raises questions about biogeochemical cycling within these ecosystems. Specifically, the sources, concentrations, flows, modifications and interactions between life essential nutrients. The nutrients sourced from these environments might have an impact on downstream ecosystem productivity. This is of particular importance as the Southern Ocean, which surrounds Antarctica, is the world’s largest high nutrient low chlorophyll region, where iron is the primary limiting element for life. Organic matter is thought to play a major role in regulating the flux and bioavailability of iron, and may also be an important source of bioavailable carbon.
The main objective of ICICLES is to investigate the cycling and interactions between iron and carbon (as organic matter) in these unique environments. Iron and organic matter in waters and sediment samples from three sites at the bottom of the Antarctic Ice Sheet will be characterised using state-of-the-art spectroscopic and microscopic techniques. Diatom culturing using these samples will be used to determine potential iron bioavailability to downstream marine organisms, and the effects of organic matter complexation. A new budget of iron and organic matter export, and associated bioavailability, from the Antarctic Ice Sheet will be constructed and utilised with a global ocean model to postulate the impact of subglacial meltwaters on marine productivity. This combination of techniques will provide unprecedented insight into nutrient cycling in unique subglacial ecosystems, and the potential of ice sheets to fertilise surrounding oceans.