The Influence of Iron and Manganese on Nutrient Cycling in Shallow Freshwater Antarctic Lakes

• Main Author: Gallagher, JB
• Format: Book Part
• Language: English
• Published: Springer-Verlag Berlin Heidelberg 1985
• Subjects: Earth Sciences; Oceanography; Chemical Oceanography; Antarctic; Signy Island; Heywood; Heywood Lake; Antarc*
• Online Access: https://www.springer.com/gp/book/9783642822773; https://doi.org/10.1007/9783642822759; http://ecite.utas.edu.au/136970

Two lakes, mesotrophic Heywood Lake and oligotrophicSombre Lake, at Signy Island, have been studied over 1 full yr(1980-1981). The development of deep water anoxia in SombreLake is accompanied by release, from the sediments, of nitrogen,silicon, phosphorus, iron, and manganese. Iron is released fromanoxic sediments in massive amounts, but is quickly returnedthrough oxidation to iron oxides, near the anoxic-<>xic boundaryand through possible ferrous carbonate precipitation, within theanoxic region. Phosphorus is also quickly returned to sediments, atthe oxic-anoxic boundary, which suggests efficient co-precipitation-sorptionby the recently oxidized ferrous. Phosphorus is thereforeunable to enter the main waterbody. Melt water inflows are thesource of P supply to the surface waters. Nitrogen and Si appear tohave little association with axides and, therefore, freely pass into theoxic main water-body of the oligotrophic system. There are strongseasonal correlations between the vertical profiles of Fe and P,under the ice cover in Heywood Lake. Nitrogen profiles appearindependent of the other determinants, Si, P, Fe, and Mn. Towardsthe end of the period of bottom-water anoxia, during the springmelt, high concentrations of ferrous, released from the anoxicsediments, have been detected in oxygenated waters. This apparentstability, in the presence of oxygen, may be attributable to a combinationof low pH and the possible influence of high concentrationsof humic acids from the melt inflows. Sulphide concentrations maybecome sufficiently high to influence Fe transport significantly,probably through ferrous sulphide precipitation, within the anoxicregion.