Hydrobiologia

, Volume 592, Issue 1, pp 151–173 | Cite as

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

  • Hilde Eggermont
  • James M. Russell
  • Georg Schettler
  • Kay Van Damme
  • Ilse Bessems
  • Dirk Verschuren
Primary Research Paper

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 lakes Afro-alpine zone Climate change East African mountains Limnology Pools Rwenzori Water chemistry 

Notes

Acknowledgements

The fieldwork was conducted under Uganda NCST research clearance NS21 and Uganda Wildlife Authority permit UWA/TBDP/RES/50, with logistic support from Rwenzori Mountaineering Services. We greatly thank Halewijn Missiaen and Bob Rumes for field assistance, Angelica Alcantara for lab assistance, Renaat Dasseville for pigment analyses (at Ghent University, Belgium) and Lei Chou for TP and TN analyses (at the Univerisité Libre de Bruxelles, Belgium). Elie Verleyen is acknowledged for constructive comments on the statistical analyses, and Steven Declerk and two anomymous referees for supportive critique which helped to improve the manuscript. This research was sponsored by the Fund for Scientific Research of Flanders, the Leopold III-fund Belgium (Belgium), the Stichting Ter Bevordering van het Wetenschappelijk Onderzoek in Afrika (Belgium), and the U.S. National Geographic Society (grant 7999-06). H.E. is a postdoctoral fellow with the Fund for Scientific Research of Flanders (FWO-Vlaanderen).

Supplementary material

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ESM (PDF 445 kb)

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Copyright information

© Springer Science+Business Media B.V. 2007

Authors and Affiliations

  • Hilde Eggermont
    • 1
  • James M. Russell
    • 2
  • Georg Schettler
    • 3
  • Kay Van Damme
    • 1
  • Ilse Bessems
    • 1
  • Dirk Verschuren
    • 1
  1. 1.Limnology Unit, Department of BiologyGhent UniversityGentBelgium
  2. 2.Department of Geological SciencesBrown UniversityProvidenceUSA
  3. 3.Section Climate Dynamics and SedimentsGeoForschungsZentrum PotsdamPotsdamGermany

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