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Introduction

The objective of the Long Term Resource Monitoring Program (LTRMP) macroinvertebrate component is to annually monitor and report trends in the status and distribution of key macroinvertebrate populations. Mayflies, fingernail clams, and midges, part of the soft-sediment substrate fauna, were chosen as target organisms for the LTRMP because of their important ecological role in the UMRS. For example, Thompson (1973) found that in fall, lesser scaup (Aythya affinis) gizzard contents contained 76% sphaeriids and about 13% mayflies. Thompson also found the target organisms to be important to canvasbacks (A. valisneria), ring-necked ducks (A. collaris), and American coots (Fulica americana) feeding in open water. A number of fish, including commercial and recreational species, eat the target organisms (Hoopes 1960; Jude 1968; Ranthum 1969).

Mayflies, fingernail clams, and midges have been historically used as indicators of river water quality (Fremling 1964, 1973, 1989; Steingraber and Wiener 1995). An indicator species can be defined as a species that has particular requirements about a known set of physical or chemical variables. Macroinvertebrates also perform an important ecological function by digesting organic material and recycling nutrients (Reice and Wohlenberg 1992). Asiatic clams and zebra mussels were chosen for sampling because of their potential adverse effects on the economy and biology of the UMRS (Tucker 1995a,b).

The ultimate goal of the LTRMP is to improve the understanding and management of the UMRS. That goal can best be achieved by the integration of routine monitoring with experimental research directed at identifying the causes of and solutions to specific problems. Future LTRMP studies will integrate focused analyses of data from all LTRMP monitoring components (limnology, bathymetry, sediments, aquatic plants, and fisheries) with results of experimental studies to identify causes of problems and opportunities for improved management.

In 2005, a 5-year plan was developed for the LTRMP assuming a static budget of about $5 million per year over the period. Within this plan, the data collection portion of the Program was reduced to a level that could be accomplished annually over the 5-year period given the budget constraint. This effort, called the "minimum sustainable program," required about $3.7 million in 2005, which will inflate (based on a projected 4.1 % annual inflation rate) to about $4.3 million in 5 years. As part of this restructuring, which was based on guidance from the LTRMP Analysis Team and Environmental Management Program Coordinating Committee, the macroinvertebrate component was dropped from the minimum sustainable program. Future work on invertebrates within LTRMP will be funded as focused research projects to address specific issues of interest to the Partnership.

The present update summarizes macroinvertebrate monitoring at each of the LTRMP field stations from 2000 to the present. Tables and figures include all years of sampling for comparison purposes. Beginning in year 2000, these annual status updates are only published online. Hard-copy reports have been published annually for the years 1992–1999. These reports are available, for a fee, in hard-copy format, from National Technical Information Service, 5285 Port Royal Road, Springfield, VA 22161. Electronic copies of the reports are available for the years 1993–1999 at http://www.umesc.usgs.gov/
reports_publications/ annual_status_reports/macro/asr_macroinvertebrate.html.

Sauer, J. 2005. Macroinvertebrate sampling in the Upper Mississippi River System: Annual update. U.S. Geological Survey, Upper Midwest Environmental Sciences Center, La Crosse, Wisconsin. An LTRMP Web-based report available online at http://www.umesc.usgs.gov/reports_publications/ltrmp/macro.html. (Revised and accessed April 2005.)

Content manager: Jennie Sauer