HR: 14:10h
AN: OS23B-03    [Abstracts]
TI: Doughnut In The Desert: Vertical Structure Of A Winter Production Pulse
AU: * Green, S A
EM: sgreen@mtu.edu
AF: Department of Chemistry, Michigan Technological University, 1400 Townsend Drive, Houghton, MI 49931 United States
AU: Budd, J W
EM: jrbudd@mtu.edu
AF: Geological and Mining Engineering and Sciences, Michigan Technological University, 1400 Townsend Drive, Houghton, MI 49931 United States
AU: Kerfoot, W C
EM: wkerfoot@mtu.edu
AF: Department of Biological Sciences, Michigan Technological University, 1400 Townsend Drive, Houghton, MI 49931 United States
AB: SeaWiFS imagery has revealed a spatially complex, annually reoccurring pattern of chl a in the open waters of Southern Lake Michigan during late winter to early spring (March-April). The circular ring (doughnut) persists for weeks and occurs every year. A cross-lake survey in April 2001 confirmed the doughnut pattern and demonstrated that the gyre structure penetrated throughout the well-mixed water column. Spatial images suggest the feature may be related to the transport of phosphorus-rich coastal sediments which are entrained along gyre convergence zones and moved into the southern central region, enhancing deep-water production. Vertical reconstructions from two separate profiling instruments (CTD vertical casts, horizontal tows with an optical plankton counter) uncovered columnar patterns of Chl a, temperature, and other variables consistent with a spatially complex, rotating gyre structure. The horizontal surface patterns and vertical profiles suggest a heretofore unrecognized coupling between winter gyre formation, sediment resuspension, and deep-water productivity. The Chl a pattern is superimposed upon a spatially heterogeneous late-winter phytoplankton and zooplankton distribution pattern. The winter productivity pulse marked by the doughnut may explain how certain zooplankton species characteristic of the Great Lakes fauna can successfully over-winter through what was previously perceived as a very unproductive and resource-stressful period.
DE: 0458 Limnology (1845, 4239, 4942)
DE: 0793 Biogeochemistry (0412, 0414, 1615, 4805, 4912)
DE: 0933 Remote sensing
DE: 4273 Physical and biogeochemical interactions
SC: Ocean Sciences [OS]
MN: Fall Meeting 2005