Dissolved Oxygen and Thermal Regimes of a Ugandan Crater Lake

Lauran J. Chapman, Colin A. Chapman, Thomas L. Crisman, Frank G. Nordlie

Research output: Contribution to journalArticlepeer-review

Abstract

This paper quantifies the temporal pattern of thermal stratification and deoxygenation in Lake Nkuruba, a small (3 ha), deep (maximum depth = 38 m) crater lake in western Uganda. Dissolved oxygen penetrated to an average depth of 9 m and a maximum depth of 15 m below which the lake was permanently anoxic over the 2 years of study. Although surface oxygen levels were correlated with both surface water temperature and rainfall, seasonal cycles of dissolved oxygen were not well-defined and may have been obscured by the high frequency of short-term fluctuations and by inter-annual variations caused by shifts in rainfall. Surface water temperature averaged 23.3±0.7°C (S.D.) and varied directly with air temperature. Both diurnal changes and top-bottom temperature differentials were small averaging 1.7±0.7 °C and 1.6±0.8°C, respectively. Thermal stability ranged from 101.3 to 499.9 g-cm cm -2 and was positively related to surface water temperature suggesting that this small protected lake responds rapidly to short-term meteorological changes. Because contribution to the annual heat exchange cycle was confined to upper waters, the lake's annual heat budget was low, 1,073.8 cal cm -2 yr -1 . However, net primary productivity was relatively high averaging 1.3 g C m -2 d -1 . The region where Lake Nkuruba is situated experienced a very strong earthquake (6.2 on the Richter scale) on 4 February, 1994. Subsequently, water levels dropped markedly in the lake, falling 3.14 m over a 5-month period.

Original languageAmerican English
JournalHydrobiologia
Volume385
DOIs
StatePublished - Jan 1 1998

Keywords

  • Anoxic hypolimnion
  • Heat budget
  • Hypoxia
  • Productivity
  • Stability
  • Stratification
  • Volcanic crater lake

Disciplines

  • Earth Sciences

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