1998 aquatic vegetation in Pools 4, 8, 13, and 26 and La Grange Pool of the UMRS Yin, Y., H. Langrehr, J. Nelson, T. Blackburn, T. Cook, W. Popp, and J. Winkelman. 2000. 1998 annual status report: Status and trend of submersed and floating-leaved aquatic vegetation in thirty-two backwaters in Pools 4, 8, 13, and 26 and La Grange Pool of the Upper Mississippi River System. U.S. Geological Survey, Upper Midwest Environmental Sciences Center, La Crosse, Wisconsin, June 2000. LTRMP 2000-P003. 21 pp. + Appendixes A B. (NTIS # PB2000-107874) ABSTRACT Thirty-two backwaters of the Upper Mississippi and Illinois Rivers were monitored for the eighth consecutive year in 1998 to determine the status and trend of changes of submersed and floating-leaved aquatic vegetation. Aquatic vegetation was sampled at regularly spaced sites along previously established permanent transects. Species compositions, frequencies of individual species, and the frequencies of sites that supported aquatic vegetation in 1998 were calculated and compared with results from previous years. The status and trend of aquatic vegetation in 1998 varied among the thirty-two backwaters. In upper Pool 4 (above Lake Pepin), where aquatic vegetation has declined since 1991, the trend continued in 1998. In lower Pool 4 (below Lake Pepin), where aquatic vegetation declined from 1991 to 1996 and started to rebound in 1997, the rebound continued in 1998. Aquatic vegetation has increased in Pools 8 and 13 since 1994 and is at or near its best (recorded) condition since 1991. In recent years, especially since a devastating flood in 1993 and through 1998, aquatic vegetation has been rare in La Grange Pool (Illinois River) and Pool 26. In Pool 26, however, aquatic vegetation was found in all four backwaters surveyed in 1998 three of the four had no aquatic vegetation in 1997. Similarly, aquatic vegetation was found in three of the four backwaters surveyed in La Grange Pool in 1998 one of the three had no aquatic vegetation in 1997. KEYWORDS Annual report, aquatic, floating-leaved, LTRMP, Mississippi River, submersed, vegetation