American Wild Celery (Vallisneria americana) Population Dynamics Within Lake Onalaska from 1980 – 2003 Amy M Seitz 1,2 1Department of Resource Analysis, Saint Mary’s University of Minnesota, Winona, MN 55987; 2United States Fish and Wildlife Service, Upper Mississippi River National Wildlife and Fish Refuge – La Crosse District, Onalaska, WI 54650 Keywords: Vallisneria americana, American wild celery, submersed aquatic vegetation, Upper Mississippi River National Wildlife and Fish Refuge, Analysis of Variance (ANOVA), Spearman rank correlation, Tukey’s test, Geographical Information Systems (GIS), Aythya valisineria, canvasback duck Abstract The United States Fish and Wildlife Service surveys submersed aquatic vegetation annually to measure American wild celery (Vallisneria americana) population density and frequency of occurrence, in Lake Onalaska, Navigation Pool 7 of the Upper Mississippi River National Wildlife and Fish Refuge. Since 1980, sampling continues to be conducted in August during peak vegetation growth along fixed transects. There has been significant change in density and frequency of occurrence since 1980. Statistically significant correlations have been found between American wild celery density and water depth. After a population decline in the late 1980’s American wild celery continues to recover. Introduction long (Muenscher 1944). It is a dioecious, vascular perennial typically American wild celery is a critical and found in shallow lakes and streams increasingly important component of throughout eastern North America, quality waterfowl staging areas ranging from Nova Scotia west to South (Korschgen et al. 1988). Temporal Dakota and then south to the Gulf of change in American wild celery Mexico (Fassett 1957). It is a common populations of Lake Onalaska is an species in Mississippi River backwaters. important consideration for resource American wild celery occurs in water management. As these populations are depths of 0.3-5.0 meters; totally extensively dynamic, extreme submersed or with the upper portion of fluctuations in density and frequency of leaves floating (Korschgen and Green occurrence take place. 1988). These plants predominately reproduce via tuberous tipped rhizomes, Natural History which like the fruit and other parts of the plant, are relished by canvasbacks Vallisneria americana is a submersed, (Aythya valisneria). aquatic macrophyte with long, ribbon- Healthy stands of submersed like leaves approximately 3-11 aquatic vegetation, particularly millimeters wide and 2 meters or more American wild celery, have historically 1 attracted fall migrating waterfowl to provides nursery areas for young fish Lake Onalaska (Korschgen et al. 1988). and serves as spawning habitat (Engel Food of canvasbacks during fall 1990). Food resource management on migration generally is comprised of canvasback staging areas must vegetative matter. A major component emphasize American wild celery and of this food is American wild celery and other tuber producing plants e.g. it is an excellent source of arrowhead (Sagittaria spp.) and carbohydrates. Bellrose (1980) affirms pondweeds (Potamogeton spp.) canvasbacks’ preference of American (Korschgen et al. 1988). wild celery. Approximately 75 percent, Flooding, lock and dam of North American canvasbacks use the construction and sedimentation have Upper Mississippi River during fall resulted in dramatic effects to the river migration (Korschgen and Green 1988). ecosystem. First, flooding has had Staging areas are locations along dramatic effects on aquatic macrophytes. waterfowl migration routes where birds Complex interactions of date, duration refuel and rest. In the 1950s, Lake and magnitude of floodwater inundation Onalaska became an important all collaborate to stress plants (Spink and waterfowl staging area for diving ducks, Rogers 1996). Second, American wild particularly canvasbacks. This is due in celery distribution and density has been large part to the excellent food source impacted by the development of the available and the disappearance of many Upper Mississippi River Navigation smaller traditional wetland staging areas System. The navigation system outside the river corridor. With the implemented a complex of Lock and increase in importance to preserve these Dam structures designed to maintain a 9- areas, the majority of Lake Onalaska foot navigation channel. Because of was designated a closed area to this, much of the original floodplain waterfowl hunting in 1957. This forest, marsh and agricultural lands designation means that the area is off adjacent to the Mississippi River were limits to migratory bird hunting and inundated with permanent water trapping. Closed Areas provide (Korschgen et al. 1987). The dams that migrating waterfowl with refueling and control water levels created 90,000 acres resting locations. of marshland in the Upper Mississippi American wild celery improves River National Wildlife and Fish water quality by stabilizing sediments Refuge. Soon after inundation, water and filtering suspended materials levels stabilized and submersed aquatic (Korschgen et al. 1988). It also absorbs vegetation thrived. This magnificent nutrients such as phosphorus and makes waterfowl habitat was only temporary. them unavailable for algal absorption The lack of seasonal water level (Korschgen et al. 1987; Barko et al. fluctuations eventually transformed this 1991). The roots, rhizomes, and stolons superb waterfowl marshland habitat into reduce erosion and facilitate colonization open water. Third, the trapping of aquatic invertebrates. American wild efficiency of fine sediments in off- celery foliage offers shelter, support, and channel areas has greatly increased locally enriched oxygen supply for a (Peck and Smart 1986). The resultant variety of aquatic invertebrate accumulation of fine sediments has led populations. American wild celery to a wide range of problems for aquatic 2 macrophytes (Sparks et al. 1990). The annual sample size consisted of 120 quadrats (0.33 meter2) per year. These Materials and Methods 120 data points are distributed 10 per each of the 12 transects. In 1989, Lake Onalaska is a ~7,700-acre transect 11 was cut short with the impounded lake like area immediately construction of a dredge spoil island. above Lock and Dam 7 within the Upper Twelve samples were taken at shorter Mississippi River National Wildlife and intervals. These twelve transects were Fish Refuge. Lock and Dam 7, sampled in 1980, 1983 and 1989-2003. constructed by the United States Army Transect end points were entered into a Corps of Engineers, was completed in PLGR+96 (Rockwell Precise 1937. Lightweight GPS Receiver) which In 1980, twelve 800 meter utilizes the Precise Positioning Service transects (Figure 1) were established in (PPS) of the Department of Defense areas of historically dense vegetative Global Positioning System. Using the cover to measure American wild celery Navigation feature of the PLGR, buoys population density. Monitoring was were placed to mark these end points. employed to increase understanding of PLGRs were not used prior to the mid- observed population fluctuations. 1990s to lay out transects; the Biologists surveyed submersed aquatic technology used from 1980 thru 1995 vegetation in Lake Onalaska annually was LORAN. Each three-person boat through 1984 and stopped the survey. It crew was given a map to locate their was restarted in 1989 following a crash assigned transects. Quadrat frame in submersed aquatics (Kenow 2004). spacing of 70 to 80 meters along any Figure 1. American wild celery sampling transects, the characters not in parenthesis were the original name for transects. The numbers within parenthesis were assigned to simplify the transects’ identity. 3 given transect varies due to uncontrolled multiple comparison test used to factors such as boat drivers’ spatial determine if there are differences judgment and accessibility issues between transect means within relating to sedimentation and dense individual years sampled. According to vegetation. A buoy was attached to each Zar (1999), the critical value used for the quadrat frame. This buoy facilitated Tukey test is q 0.05(60,12) = 4.808. With a ease of location on the lake bottom by a sample size of 120 points, the error diver. At each quadrat drop point all degree of freedom (DF) for the analysis American wild celery plants found of variance is 108. In the table of critical within the quadrat frame were collected values for the q distribution, v (error DF and counted. Depth readings were for the analysis of variance) jumps from recorded at each quadrat drop point 60 to 120. Since the sample error DF using a three-meter pole numbered with falls within this range the lower v value 0.1-meter increments. Depth data were was used. Twelve represents the number not collected in 1980 and 1983. of groups (transects) annually sampled. When the calculated q value was greater Statistical Analyses than the critical q the null hypothesis was rejected. Statistically significant Four null hypotheses were tested. The correlations do not necessarily imply first two null hypotheses were cause and effect but serve to illustrate discounted based on graphical possible factors (Ambrose and Ambrose illustration. The remaining two null 1995) effecting American wild celery hypotheses were rejected statistically. density. These data were analyzed with SPSSTM Statistical Software and hypotheses were Results statistically tested. Spearman Rank Correlation was used as a nonparametric Overall,