Multiyear Synthesis of the Aquatic Vegetation Component from 1991 to 2002 for the Long Term Resource Monitoring Program
GEOLOGICAL SURVEY LA CROSSE WI UPPER MIDWEST ENVIRONMENTAL SCIENCES CENTER
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Aquatic vegetation data were collected in the Upper Mississippi River System UMRS under the Long Term Resource Monitoring Program LTRMP. From 1991 to 2002, five reaches were surveyed every year key pools, and another five reaches were surveyed once outpools. The study design changed from a protocol involving sampling along transects 1991-2000 to a protocol incorporating stratified random sampling 1998-2002 with concurrent sampling under both protocols in 1998-2000. The frequency of occurrence of plants revealed no synchronous trends among three key pools Pools 4, 8, and 13 supporting sizable submersed aquatic vegetation beds. Submersed aquatic vegetation in upper Pool 4 declined steadily between 1991 and 2002. Submersed aquatic vegetation in lower Pool 4 declined between 1991 and 1996 and thereafter recovered moderately. Submersed aquatic vegetation in Pool 8 increased between 1991 and 1999, which probably was a recovery process from a reported sudden collapse after the 1987-1989 drought. Submersed aquatic vegetation in Pool 13 demonstrated a high degree of stability during the period of monitoring despite drastic fluctuations between spring and summer sampling in some years. Water turbidity and water level fluctuation were strongly correlated with the longitudinal pattern of submersed aquatic vegetation distribution in the UMRS. Pools with clearer water and less fluctuating water levels supported more submersed aquatic vegetation. The LTRMP key pools represented a wide spectrum of the UMRS habitats. The habitat rehabilitation and enhancement project HREP at Stoddard Bay in Pool 8 effectively stimulated colonization by aquatic vegetation.
- Biological Oceanography