Origin and composition of settling iron aggregates in oligotrophic Sombre Lake, Signy Island, Antarctica

Caulkett, A. P.; Ellis-Evans, J. C.. 1996 Origin and composition of settling iron aggregates in oligotrophic Sombre Lake, Signy Island, Antarctica. Hydrobiologia, 330 (3). 177-187.

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Sediment traps were deployed in an oligotrophic, seasonally anoxic maritime Antarctic lake for 15 months. Immediately after the onset of the inflow in spring many iron oxyhydroxide aggregates were collected in the traps. Image analysis, scanning electron microscopy and energy dispersive X-ray analysis were used to examine the aggregates. The aggregates consisted of primary particles that persisted in the aggregates. The mean diameter of the aggregates was constant with depth. The aggregates consisted predominantly of iron, phosphorus and oxygen but calcium was also an important constituent. Significant concentrations of manganese and sodium were also detected. The molar ratio Fe:P remained constant at 4:1 as did the ratio Fe:Ca at 52:1. The concentration of iron, phosphorus and calcium in the aggregates increased with depth, whilst the concentration of manganese decreased with depth in parallel with a gradient of increasing anoxia. The stable water column formed under ice cover and the temporal and spatial data provide evidence that the Fe:P and Fe:Ca ratios are constant and characteristic of the aggregates, whilst the overall composition of the aggregates is more dynamic and dependant on redox conditions and water chemistry.

Item Type: Publication - Article
Digital Object Identifier (DOI):
Programmes: BAS Programmes > Pre 2000 programme
ISSN: 0018-8158
Additional Keywords: imaga analysis, electron microscopy, nutrient cycling, sediment traps, iron particles
Date made live: 26 Oct 2016 08:36 +0 (UTC)

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