The Spatial and Temporal Dynamics of Deep Chlorophyll Layers in High-Mountain Lakes: Effects of Nutrients, Grazing, and Herbivore Recycling as Growth Determinants

Document Type

Article

Journal/Book Title/Conference

Journal of Plankton Research

Volume

28

Issue

1

Publisher

Oxford University Press

Publication Date

2006

Keywords

spatial, temporal, dynamics, phytoplankton, deep chlorophyll maxima, nutrients, grazing, herbivore recycling, growth determinants

First Page

65

Last Page

86

Abstract

Deep chlorophyll layers (DCL) are a common feature of oligotrophic lakes, yet the mechanisms that form and maintain them are not understood fully. These phytoplankton populations occur in the metalimnia of lakes where light levels are moderate to low, and where nutrient levels and zooplankton grazing pressure are different than in the epilimnion. To test the importance of nutrients and grazing pressure for algal growth in different lake strata, microcosm experiments and monitoring were conducted in two oligotrophic lakes in the Rocky Mountains of North America that contain DCL. In situ microcosm experiments with natural phytoplankton communities from three depth strata were conducted with macronutrient additions and with and without the natural zooplankton grazing communities. Alkaline phosphatase assays and the in situ microcosm experiments indicated less nutrient limitation in the metalimnia than in the epilimnia of both lakes. Zooplankton grazing in the experiments decreased algal population growth rates by as much as 6% day–1, with impacts shifting to progressively deeper strata over the summer. Zooplankton grazing losses, however, were partially offset by nutrient recycling that increased algal growth rates. Depth-differential nutrient deficiency and zooplankton grazing and recycling interacted to maintain the DCL in these lakes.

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Originally published by Oxford University Press. Publisher's PDF and HTML fulltext available through remote link.

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