Phosphorus biogeochemistry in meltwater ponds of Victoria Land, Antarctica

• Main Author: Christenson, H. K.
• Format: Other/Unknown Material
• Language: English
• Published: University of Canterbury 2015
• Subjects: Victoria Land; Antarc*; Antarctica
• Online Access: http://hdl.handle.net/10092/11957; https://doi.org/10.26021/6498

Phosphorus plays an essential role in the biochemistry of all living organisms, and understanding factors controlling its availability in an ecosystem can provide insight into how the ecosystem will respond to change. Freshwater ecosystems in Antarctica are important biodiversity elements, containing vibrant microbial communities dominated by benthic cyanobacterial mats. Productivity in meltwater ponds can become limited by nutrient availability, and inland aquatic systems are typically P deficient. In order to understand phosphorus (P) biogeochemistry in meltwater ponds in Victoria Land, the distribution and speciation of P was determined in ponds at 7 locations, and processes which influence P concentration in the water column were investigated. The biogeochemical cycle concept has been applied to the results as a tool to interpret P behaviour. This involved identification of the key reservoirs that hold P within the pond ecosystem, and the processes which can transfer P between these reservoirs. Sediment, soil, water and benthic microbial mats were identified as important reservoirs in the ponds. Microbial mats can accumulate P to concentrations over 2 g/kg, and often had higher concentrations of P than soils and sediments. Soils consistently had higher P concentrations than sediments, and comparatively little P was present in pond waters. Concentration and pond structure data were used to create a conceptual model of P distribution in meltwater ponds, which revealed sediments are the major reservoir of P in these systems. Saturated soils are the next largest reservoir of P, followed by microbial mats then the pond water. Sediments are the major source of P to meltwater ponds. This is demonstrated by low total P concentrations in sediments relative to adjacent soils. Transects from pond shorelines reveal that both reactive and apatite P fractions in sediments are transported into ponds, and that soils within 2 m from pond edges can also act as a P source. It is not clear whether P from marginal soils is ...