Studies of dissolved species and suspended particulate matter in the freshwater systems of Signy Island, Maritime Antarctic.

Caulkett, Andrew Paul (2000). Studies of dissolved species and suspended particulate matter in the freshwater systems of Signy Island, Maritime Antarctic. PhD thesis The Open University.

DOI: https://doi.org/10.21954/ou.ro.0000ff8d

Abstract

The freshwater lakes and streams of Signy Island, maritime Antarctic were studied during two periods of field work (Jan 1992 - Mar 1993, Nov 1994 - Feb 1995). This work examined the dynamics of both dissolved and particulate phases. Due to the complex nature of catchment, stream and lake interactions only qualitative conclusions could be made.

The sources of the major dissolved ions in the streams were identified. Ions derived from precipitation and sea spray (Na⁺, K⁺, Mg²⁺, Ca²⁺, Cl^-, NH₄⁺, NO₂^-, Mn²⁺) were supplied to the streams as a pulse at the beginning of the season. Areas of permanent ice were an important source of NO₃^- . Dissolved reactive silica, Ca²⁺, and Mg²⁺ were derived from crustal weathering. Whilst ortho-phosphate (o-P) and Mn²⁺ were products of crustal weathering, these ions were released as a pulse probably related to thawing of the fellfield soils.

Geochemical cycles in a seasonally ice-covered lake were studied. It was demonstrated that ice-cover and the onset of inflow have profound influences on the chemistry of the lake. At the onset of inflow it was demonstrated that oxygen can penetrate deep into the lake without disruption of the stratification and this caused the rapid oxidation of Fe²⁺. It was shown that there was a dynamic link between the inorganic forms of nitrogen (NH₄⁺, NO₃^-, NO₂^-).

The suspended particulate material (SPM) in the lake was examined using an electron microscope and the affects of ice-cover on SPM were identified. The endogenic particulates formed on oxidation of Fe²⁺ were examined in detail and it was demonstrated that this process exerts controls on the concentrations of the o-P and Ca²⁺ in the lake waters.

These conclusions were discussed in the context of nutrient limitation of the lake and the retreat of areas of permanent ice and snow at Signy Island.