Upper Midwest Environmental Sciences Center
Monitoring Activities and Highlights
Water quality monitoring within the LTRMP focused on the UMRS and its major tributaries and included variables, such as physicochemical features, suspended sediment, and major plant nutrients likely to affect aquatic habitats. The sampling design combined quarterly stratified random sampling (SRS) episodes with fixed-site sampling conducted at 2- and 4-week intervals. Stratified random sampling (about 130 sites per study reach quarterly) provided unbiased, seasonal information on water quality across broad areas, such as entire navigation pools, whereas fixed-site sampling (9 to 14 sites per study reach) provided more continuous information over time at specific locations. The stratified random sampling was not conducted in 2003 and resumed in 2004 following the original 1993 design as modified in 2000 (a 30% reduction in sampling effort was implemented in January 2000). There were no additional changes in the water quality monitoring for 2005.
Sediment and major plant nutrient concentrations within the UMRS are an important management concern. Total suspended solids (TSS; mg/L) in the main channel of the northern three pools (4, 8, and 13) generally declined from 1994 through 2002 (Figure 2). Since 2002 main channel TSS concentrations appear to have remained stable or increased slightly. Main channel TSS concentrations in the southern reaches (Pool 26 and Open River Reach) varied substantially from 1994 to 2005. Spring TSS concentrations peaked in 1999 in the Open River Reach when the river was above flood stage; this was followed in 2000 by lower concentrations that coincided with river stages that were about 10 feet below average. The TSS concentrations were quite low in 2004 in the southern reaches (approximately 50 to 80 mg/L), similar to 2000 (approximately 50 to 65 mg/L), and much lower than the high concentrations observed in 2002 (approximately 300 to 330 mg/L; Figure 2). In 2005, spring TSS concentrations in Pool 26 and the Open River were much higher than during the other 2005 sampling episodes. La Grange Pool of the Illinois River exhibited low TSS concentrations for all sampling episodes of 2005 relative to previous years.
Nitrogen and phosphorus are essential plant nutrients required for the growth of algae and aquatic plants. Nutrient inputs from sewage effluent and urban and agricultural runoff can result in excessive nutrient concentrations. Excessive nutrients cause a range of problems in aquatic systems. For example, elevated nutrients can produces algal blooms that can be problematic (U.S. Geological Survey 2003). First, they are unsightly and can impede recreational uses and aesthetics. Second, excessive plant growth can damage habitats for other biota and impair the general ecological health . From 1994 to 2005, mean main channel TN concentrations in the UMRS ranged from approximately 1 to 8 mg/L (Figure 3). In 2005, spring main channel TN concentrations in Pools 4 and 8 were the second highest observed in since 1994 in these pools and mean fall main channel concentrations were the highest yet observed by the monitoring program. For total phosphorus, low concentrations were observed in winter 2005 for the northern three pools (Figure 4). The 2005 winter main channel TP concentrations in Pools 4 and 8 were the second lowest observed since 1994; the lowest concentrations occurred in 2004. In 2005, summer total phosphorus concentrations in La Grange Pool were the highest yet observed by the monitoring program.
Water temperature (°C) affects a wide range of physical, chemical, and biological phenomena. Because it affects the presence or absence of species, growth rates, oxygen solubility, and chemical equilibria, even subtle changes in temperature have the potential to produce many associated changes. Median temperatures in both the southern and northern study reaches were greater during 2002 than any of other monitored winters, but were notably lower in 2004 and 2005 (Figure 5).
Oxygen concentrations (percent dissolved oxygen saturation) in the waters of the Mississippi River in winter are a function of many factors such as water temperature, ice cover, primary production, and oxygen demand. Adequate winter oxygen concentration is needed by a variety biota. For example, Knights et al. 1995 recommended striving for 3 mg/L winter dissolved oxygen concentrations which translates to about about 21 to 23% saturation at winter water temperatures of 0 to 4°C. However along with adequate winter dissolved oxygen concentration, areas also need low flow and adequate temperatures to sustain fish populations. Historically, winter oxygen saturation has been lower in the northern study areas than in the southern study areas, probably because of greater ice and snow cover. Saturation values below 60% are not uncommon in winter in the northern study areas (Figure 6a), but are rare in the southern study areas (Figure 6b). Most years, median winter oxygen saturation in the southern study areas was typically about 100% and was often supersaturated. From 1996 through 2002, saturation values generally increased in both the northern and southern Mississippi River, but within year variability is relatively high and year to year increases do not appear significant (Figure 6). Median values recorded in 2002 exceeded those recorded in the previous eight winters, possibly because of less extensive areas of ice and snow cover resulting in higher levels of primary productivity as evidenced by chlorophyll-a concentrations (Figure 7). Phytoplankton play a vital ecological role in the UMRS in that they provide food for filter-feeders, process nutrients, and generate (and consume) oxygen. Algal blooms, often noted in summer, can also occur in winter when light penetration is not excessively reduced by snow cover. The highest median winter concentrations observed by the monitoring program occurred in 1995 and similar concentrations were seen in 2002. However, 2004 and 2005 median chlorophyll-a concentrations in the northern and southern reaches were much lower than was observed in 2002.
Annual changes in limnological data are strongly influenced by both long-term and episodic changes in weather and hydrology, and limnological response to prevailing conditions are now evident in the LTRMP data. For example, results of recent spring sampling events demonstrate the relation between TSS concentrations and river discharge, much the same as increases in oxygen saturation and chlorophyll-a may reflect relatively mild winter conditions. The LTRMP limnological record is a useful resource for documenting such changes and relations. These data will be critical in the interpretation of associated changes in the biological communities of the Mississippi River and other large rivers. The break that occurred in the sampling record beginning in 2002 was ill-timed given the extended period of drought that prevailed over some areas in 2003. There are a number of differences between 2002 and 2004 including a strong decline in chlorophyll-a concentrations and water temperature. The lack of 2003 data complicates the interpretation of these changes. Unexpected events (e.g., drought, floods, etc.) contribute significantly to our understanding of UMRS functioning, but their effects will only be recorded with a commitment to long-term, uninterrupted data collection.
Aquatic vegetation acts as a filter to clarify water and dampen wave action in the UMRS as well as being important food for migratory waterfowl (Korschgen et al. 1988) and habitat for fish. The construction of a series of locks and dams in the 1930s created vast shallow areas where aquatic plants proliferated for nearly 3 decades before symptoms of deterioration associated with permanent impoundment became apparent (Green 1984). A widespread and sudden decline in the distribution and abundance of American wild celery (Vallisneria americana) from Pools 5 through 19 in 1987–89 elevated concern as to whether or not the UMRS was on the verge of a drastic degradation in the aquatic vegetation resources (Rogers and Theiling 1999).
In 1998, a stratified random sampling protocol was initiated (Yin et al. 2000) to allow for estimation of poolwide means. A programmatic decision was made to discontinue sampling in Pool 26 and La Grange Pool starting in 2005 because vegetation was extremely scarce in these areas and financial resources were limited.
Within-pool distribution patterns of submersed aquatic vegetation in Pools 4, 8, and 13 had remained relatively stable from 1998 to 2004. Lake Pepin, located in the middle of Pool 4, divides the pool into upper and lower sections. In contrast to lower Pool 4, Pool 8 and Pool 13, submersed aquatic vegetation in upper Pool 4 has declined from 1998 to 2004 (21.8 to 7.1, respectively; Figure 8). The frequency of submersed aquatic vegetation increased in Pools 4, 8, and 13 in 2005. In Pools 8 and 13 the frequency is the highest ever since 1998 when the stratified random sampling protocol was initiated. The increase in Pool 8 started in 2002 and in Pool 13 in 2004. American wild celery, an important waterfowl food species, increased in 2005 in all three study areas (Figure 9).
Fish
Fish monitoring within the Program measures long-term trends in species abundance, community composition, and community structure within multiple habitat classes in each of the six study areas using standardized sampling protocols (Gutreuter et al. 1995). Detection of changes in UMRS fish populations will provide evidence for forming and testing hypotheses directed at determining the factors causing the observed changes. Sampling effort was allocated independently and equally across two sampling periods in 2005 versus three periods in previous years. Other changees in sampling effort had also occurred prior to 2005 (see http://www.umesc.usgs.gov/reports_publications/ltrmp/fish/2005/samplinghistory.html.)
In 2005, the number of samples collected ranged from 136 in the Open River Reach to 240 in La Grange Pool, total annual catch ranged from 4,948 fish in the Open River Reach to 18,327 fish in La Grange Pool (see http://www.umesc.usgs.gov/reports_publications/ltrmp/fish/2005/fish-srs.html).
Thirteen species of concern in one or more UMRS states were collected including [e.g., pugnose minnows, shovelnose sturgeon, lake sturgeon, blue sucker--Minnesota species of special concern; pallid shiners (endangered), lake sturgeon (special concern), silver chub (special concern) weed shiners (special concern), pugnose minnows (special concern), river redhorse (threatened), (special concern), mud darters (special concern), Wisconsin listings; weed shiners (endangered), pugnose minnows(special concern), Iowa’s listings and Missouri-listed species of special concern Mississippi silvery minnow, river darter, blue sucker, and mooneye] . Asian carp (Hypopthalmichthys spp.) continued to be collected in Pool 26, the Open River Reach, and La Grange Pool, but no range expansion into the upper pools was observed by the LTRMP in 2005. Six nonnative species were observed in La Grange Pool, the LTRMP study reach with the highest number of nonnative species perennially (see Table 3.6). La Grange Pool also was the only study area reporting new species detected in 2005--lake sturgeon, spotfin shiner, and green sunfish x redear sunfish hybrid.
In 2005, the LTRMP components published the following reports:
Houser, J. N., editor. 2005. Multiyear synthesis of limnological data from 1993 to 2001 for the Long Term Resource Monitoring Program. Final report submitted to the U.S. Army Corps of Engineers from the U.S. Geological Survey, Upper Midwest Environment Sciences Center, La Crosse, Wisconsin, March 2005. LTRMP Technical Report 2005-T003. 59 pp. (NTIS PB2005-105228)
Ickes, B. S., M. C. Bowler, A. D. Bartels, D. J. Kirby, S. DeLain, J. H. Chick, V. A. Barko, K. S. Irons, and M. A. Pegg. 2005. Multiyear synthesis of the fish component from 1993 to 2002 for the Long Term Resource Monitoring Program. U.S. Geological Survey, Upper Midwest Environmental Sciences Center, La Crosse, Wisconsin. LTRMP 2005-T005. 60 pp. + CD-ROM (Appendixes A–E). (NTIS PB2005-107572)
Sauer. J. 2005. Evaluation of the macroinvertebrate component of the Long Term Resource Monitoring Program. U.S. Geological Survey, Upper Midwest Environmental Sciences Center, La Crosse, Wisconsin, December 2005. LTRMP Technical Report 2005-T006. 11 pp. + Appendixes A-D. (NTIS PB2006-108999)
Yin, Y., and H. A. Langrehr. 2005. Multiyear synthesis of the aquatic vegetation component from 1991 to 2002 for the Long Term Resource Monitoring Program. U.S. Geological Survey, Upper Midwest Environmental Sciences Center, La Crosse, Wisconsin. LTRMP 2005-T001. 29 pp. + Appendixes A–F. (NTIS PB2005-102717)
This summary provides a cursory view of the major highlights from the Long Term Resource Monitoring Program in 2005. For more detailed information, we highly recommend the reader review the individual annual updates for fish, aquatic vegetation, and water quality and the individual graphical browsers for fish, aquatic vegetation, and water quality).
Page Last Modified: April 17, 2018