Multilayer biological structure and mixing in the upper water column of Lake Biwa during summer 2008

• Published in: Limnology Vol. 11; no. 1; pp. 63 - 70
• Main Authors: Yamazaki, Hidekatsu, Honma, Hikaru, Nagai, Takeyoshi, Doubell, Mark J, Amakasu, Kazuo, Kumagai, Michio
• Format: Journal Article
• Language: English
• Published: Japan Japan : Springer Japan 01-04-2010; Springer Japan; Springer Nature B.V
• Subjects: Acoustics; Aquatic environment; Biomedical and Life Sciences; Ecology; Environment; Freshwater & Marine Ecology; Hydrology; Lakes; Life Sciences; Research methodology; Research Paper; Turbulence; Water column; Zooplankton; Lake Biwa; Japan, Honshu, Shiga Prefect., Biwa L; Phytoplankton; Oxygen; Mixing; Turbulence; Stratification
• ISSN: 1439-8621; 1439-863X
• DOI: 10.1007/s10201-009-0288-2

We carried out a 24-h station experiment at Lake Biwa (Japan) to measure mixing events and concurrent biological signals using a free-fall microstructure profiler (TurboMAP-L), conventional hydrographic measurement device (F-probe), and the Tracker acoustic profiling system (TAPS). A clearly defined three-layer physical system was observed. Two layers were actively mixed: the surface-mixed layer and the subsurface-mixed layer. Both winds and night-time convection create the surface-mixed layer, and vertical shear due to a counterclockwise gyre maintains turbulence in the subsurface mixing layer. A strongly stratified layer between these two mixing layers is almost turbulence free, so no material flux is expected. A local oxygen maximum layer, a local oxygen minimum layer, and layers of increased chlorophyll and zooplankton abundance are all located in this strongly stratified layer. The data show the intricate influence of physical processes on the structure of biological systems and their combined influence on biogeochemical and trophic transfers in aquatic systems.