Hydrobiologia

, Volume 592, Issue 1, pp 151–173

Physical and chemical limnology of alpine lakes and pools in the Rwenzori Mountains (Uganda–DR Congo)

Authors

    • Limnology Unit, Department of BiologyGhent University
  • James M. Russell
    • Department of Geological SciencesBrown University
  • Georg Schettler
    • Section Climate Dynamics and SedimentsGeoForschungsZentrum Potsdam
  • Kay Van Damme
    • Limnology Unit, Department of BiologyGhent University
  • Ilse Bessems
    • Limnology Unit, Department of BiologyGhent University
  • Dirk Verschuren
    • Limnology Unit, Department of BiologyGhent University
Primary Research Paper

DOI: 10.1007/s10750-007-0741-3

Cite this article as:
Eggermont, H., Russell, J.M., Schettler, G. et al. Hydrobiologia (2007) 592: 151. doi:10.1007/s10750-007-0741-3

Abstract

This study describes the physical and chemical properties of 17 Afroalpine lakes (>2 m deep) and 11 pools (<2 m deep) in the Rwenzori mountains, Uganda-DR Congo, with the aim to establish the baseline conditions against which to evaluate future environmental and biological changes in these unique tropical ecosystems, and to provide the foundation for lake-based paleoenvironmental studies. Most Rwenzori lakes are located above 3,500 m elevation, and dilute (5–52 μS/cm specific conductance at 25°C) open systems with surface in- and outflow. Multivariate ordination and pairwise correlations between environmental variables mainly differentiate between (1) lakes located near or above 4,000 m (3,890–4,487 m), with at least some direct input of glacial meltwater and surrounded by rocky catchments or alpine vegetation; and (2) lakes located mostly below 4,000 m (2,990–4,054 m), remote from glaciers and surrounded by Ericaceous vegetation and/or bogs. The former group are mildly acidic to neutral clear-water lakes (surface pH: 5.80–7.82; Secchi depth: 120–280 cm) with often above-average dissolved ion concentrations (18–52 μS/cm). These lakes are (ultra-) oligotrophic to mesotrophic (TP: 3.1–12.4 μg/l; Chl-a: 0.3–10.9 μg/l) and phosphorus-limited (mass TN/TP: 22.9–81.4). The latter group are mildly to strongly acidic (pH: 4.30–6.69) waters stained by dissolved organic carbon (DOC: 6.8–13.6 mg/l) and more modest transparency (Secchi-disk depth: 60–132 cm). Ratios of particulate carbon, particulate nitrogen and chlorophyll a in these lakes indicate that organic matter in suspension is primarily derived from the lakes’ catchments rather than aquatic primary productivity. Since key features in the Rwenzori lakes’ abiotic environment are strongly tied to temperature and catchment hydrology, these Afroalpine lake ecosystems can be expected to respond sensitively to climate change and glacier melting.

Keywords

Alpine lakesAfro-alpine zoneClimate changeEast African mountainsLimnologyPoolsRwenzoriWater chemistry

Supplementary material

10750_2007_Article_741_ESM.pdf (444 kb)
ESM (PDF 445 kb)

Copyright information

© Springer Science+Business Media B.V. 2007