Limnology of the Green Lakes Valley: phytoplankton ecology and dissolved organic matter biogeochemistry at a long-term ecological research site

ABSTRACT

Background: Surface waters are the lowest points in the landscape, and therefore serve as excellent integrators and indicators of changes taking place in the surrounding terrestrial and atmospheric environment.

Aims: Here we synthesise the findings of limnological studies conducted during the past 15 years in streams and lakes in the Green Lakes Valley, which is part of the Niwot Ridge Long Term Ecological Research (LTER) Site.

Methods: The importance of these studies is discussed in the context of aquatic ecosystems as indicators, integrators, and regulators of environmental change. Specifically, investigations into climatic, hydrologic, and nutrient controls on present-day phytoplankton, and historical diatom, community composition in the alpine lake, Green Lake 4, are reviewed. In addition, studies of spatial and temporal patterns in dissolved organic matter (DOM) biogeochemistry and reactive transport modelling that have taken place in the Green Lakes Valley are highlighted.

Results and conclusions: The findings of these studies identify specific shifts in algal community composition and DOM biogeochemistry that are indicative of changing environmental conditions and provide a framework for detecting future environmental change in the Green Lakes Valley and in other alpine watersheds. Moreover, the studies summarised here demonstrate the importance of long-term monitoring programmes such as the LTER programme.

KEYWORDS:

• atmospheric nitrogen deposition
• dissolved organic matter
• drought
• Green Lakes Valley
• hyporheic zone
• limnology
• Niwot Ridge
• phytoplankton
• reactive transport modelling

Acknowledgements

Reviews by E. Gardner and three anonymous reviewers provided many helpful suggestions that greatly improved this manuscript.

Additional information

Notes on contributors

Matthew P. Miller

Matthew Miller is an aquatic ecologist; his research addresses abiotic controls on the structure of aquatic communities and transport of nutrients and organic matter in stream and lake ecosystems.

Diane M. McKnight

Diane McKnight is a professor of Civil, Environmental, and Architectural Engineering. Her research focuses on interactions between hydrologic, chemical and biological processes in controlling the dynamics in aquatic ecosystems.