A PROFILE OF SUBMERSED AQUATIC VEGETATION ON NAVIGATION POOL  4  OF
THE UPPER MISSISSIPPI RIVER SYSTEM

Megan Moore.
Minnesota Department of Natural Resources, Mississippi River Monitoring Office, 
1801 South Oak Street, Lake City, MN 55041.

In 1998, the Long Term Resource Monitoring Program initiated a stratified random 
sampling protocol to monitor submersed aquatic vegetation (SAV) of the Upper 
Mississippi River System (UMRS).  The primary objective of the monitoring is to 
determine the status and trends of SAV within target pools of the UMRS.  During 
each summer in 1998 and 1999, SAV data were collected in Pool 4 at 550 randomly 
distributed sites within shallow aquatic areas (<= 3 m in 1998 and <= 2.5 m in 
1999).  The shallow aquatic areas were classified into seven habitat strata including 
isolated backwaters, main channel border, side channel border, upper Lake Pepin (a 
tributary delta lake), lower Lake Pepin, contiguous backwaters above Lake Pepin and 
contiguous backwaters below Lake Pepin.  The data enable us to construct a profile 
of SAV in each habitat stratum and in the entire Pool 4.

Pool 4 showed a slight decrease in the overall relative abundance of SAV between 
1998 and 1999; however, the number of sites where SAV occurred remained stable. 
Isolated backwaters contained the greatest abundance of SAV in both years.  The 
most frequently encountered species among all strata in Pool 4 in both years was 
coontail (Ceratophyllum demersum L.).  In general, strata above Lake Pepin (upper 
Pool 4) were sparsely vegetated and had low species richness, with sago pondweed 
(Potamogeton pectinatus L.) as the predominate species; whereas strata below Lake 
Pepin (lower Pool 4) were more abundantly vegetated and had high species richness. 
A total of 16 species were found in 1998 and 15 species in 1999, with the largest 
number recorded in the contiguous backwaters of lower Pool 4 (13 and 13 in 1998 
and 1999, respectively).  Pool 4 species richness is similar to that of Pools 8 and 13, 
and higher than that of Pool 26 and La Grange on the Illinois River.  Overall frequency 
of occurrence of SAV in Pool 4 is slightly lower than Pools 8 and 13, but higher than 
Pool 26 and La Grange.

Keywords:  submersed vegetation, aquatic plants, Mississippi River, trend analysis, 
stratified random sample
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