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Within-Bed Distribution of Myriophyllumspicatum L. in Lake Onalaska, UpperMississippi RiverStanley A. Nichols a & Sara J. Rogers ba Wisconsin Geological and Natural History Survey , Madison, WI,53705b National Biological Service, Environmental Management TechnicalCenter , Onalaska, WI, 54650Published online: 06 Jan 2011.

To cite this article: Stanley A. Nichols & Sara J. Rogers (1997) Within-Bed Distribution ofMyriophyllum spicatum L. in Lake Onalaska, Upper Mississippi River, Journal of Freshwater Ecology,12:2, 183-191, DOI: 10.1080/02705060.1997.9663525

To link to this article: http://dx.doi.org/10.1080/02705060.1997.9663525

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Within-Bed Distribution of Myriophyllum spicatum L. in Lake Onalaska, Upper Mississippi River

Stanley A. Nichols Wisconsin Geological and Natural History Survey

Madison, WI 53705

and Sara J. Rogers

National Biological Service Environmental Management Technical Center

Onalaska, WI 54650

ABSTRACT

The exotic species Myriophyllum spicaluni L. has become a recent member of the submersed aquatic plant community within the upper Mississippi River system (UMRS). Notable for nuisance growth in many North American locations, its potential for creating problems in the river system is not known. To better understand its nuisance potential, within-bed-plant pattern and the relationship between plant biomass, water depth, sediment moisture, and sediment organic content were studied in Lake Onalaska, a backwater lake of UMRS Pool 7. These results were compared with studies of biomass distribution of M. spicatum in Lake Wingra, Wisconsin. Within-bed biomass fiom Lake Onalaska was not significantly correlated with depth, organic matter, or sediment moisture. Lake Onalaska ~nilioil beds produced biomass similar to other lakes in the region but were restricted to much shallower water depths. The shallow maximum growth depth is probably related to poor water clarity but the maximum growth depth could v a y significantly fiom year to year because of the dynamic nature of water clarity in the UMRS. Because Mississippi River pools are shallow, the area occupied by milfoil could also vary considerably from year to year.

INTRODUCTION

The exotic Myriophyllum spicarum L. (Eurasian watennilfoil) grows in the pools and backwaters of the upper Mississippi River system (UMRS), and large beds have appeared in recent years in areas where native species such as wildcelely (VaNisneria americana Michx.) have declined. Although M. spicatunl is not considered a nuisance at present, the niche definition and productivity of the species in the UMRS is poorly understood. Because the UMRS region is of such high fishery, wildlife, recreational, and aesthetic value, and because the main channel of the Mississippi River is also a major commerical transportation route for barge traffic, river managers and scientists are concerned about the species' ability to prosper and spread.

To better assess its nuisance potential and better define its habitat preferences, we studied the within-bed distribution of milfoil. That is, given that M. spicatum is present, what causes differences in distribution of plants and biomass within the bed? Specific parameters studied were plant distribution patterns and the relationship between plant biomass and water depth, sediment moisture, and sediment organic content.

Joumal of Freshwater Ecology, Volume 12, Number 2 - June 1997

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METHODS

A single bed, located along the eastern edge of Lake Onalaska was sampled during the late summer of 1993 to study the relationship between plant biomass, water depth, sediment moisture, and sediment organic content. Starting from a random point, a sampling grid was established with transects going across the narrow dimension of the bed. The transects were located every 20 In, starting at tlie upstream end of the bed and proceeding toward the downstream end. Sampling points were located at 10-m intervals along each transect and extended at least one sampling point (10 m) into the nonvegetated area on both sides of the bed (Figure 1). In this bed, the shallowest depths were near the center and water depth increased toward the edges. At each sampling site, water depth was measured and a sediment core was collected using a Wildco sediment sampler (Wildlife Supply Company, Saginaw, MI). The toy 10 cm of each core was placed in a plastic bag and returned to the laboratory. Sediment moisture and density were evaluated after oven-drying sediment at 105°C for approximately 12 11. Dried samples were combusted at 550°C for estimates of organic matter content from loss of mass following ignition (Allen et al. 1974). Biomass was determined by removing all plant shoots and easily removed root structures from two adjacent 0.1 m2 quadrats. The quadrats were placed on opposite sides of the sedllnerit core location. All plant material was washed clean, placed in paper bags, and returned to the laboratory. Plant samples were dried at 80 "C for 48 hr and weighed to the nearest 0.1 g. Values for the two quadrats were averaged to estimate biomass at the sampling point.

Depth

Figure 1. Depth (cm) across 1993 study site 111 Lake Onalaska. Line outlines the Myriophyllzrrn spicalzrn~ bed.

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For analyzing 1993 data, each sampling point was coded as being outside the plant bed, within 30 m of the edge of the bed (edge), or greater than 30 m from the edge of the plant bed (interior). Selection of the 30 m distance to divide bed edge from interior was arbitrary. In total, 54 sampling locations were outside the bed, 71 were within 30 m of the edge of the bed, and 38 were in the interior of the bed. Descriptive statistics and the non-parametric Mood's median test (Minitab 1994) were used to compare biomass and habitat differences at outside bed, edge, and interior locations. Pearson's correlation coefficient was used to investigate relationships between biomass, depth, organic matter, and sediment moisture.

Five plant beds located within the vicinity of the 1993 bed and in the southwest comer of the lake were selected during the late summer of 1994 to study the spatial pattern of plant distribution. A 100-m transect line was run from a random starting point approximately down tlie center of the long axis of the bed. The transect line was divided into 0.1-m segments; the presence of M. spicatztnl was recorded in a segment if the line crossed any part of a M. spicaluni plant. The technique was very similar to that used by Lind and Cottarn (1969), except our sampling unit was smaller and, because of water depth, plant density, and poor water clarity, our transect was run on the water surface instead of on the substrate. Six similar transects, two each following the 0.5 m, 1.0 m, and 1.5 m depth contours, were done on Lake Wingra, Wisconsin, during the summer of 1994 to compare the spatial pattern in Lake Onalaska with that of a natural lake.

To test the null hypothesis that the pattern of plant occurrence was random, a runs test (Davis 1986) was done on each of the 1994 transects from Lake Onalaska and Lake Wingra. The 0. I-m sampling units were summed to score rnilfoil occurrence from 0 to 5 in successive 0.5 m line segtnents (200 for each transect). These 0.5-m units were analyzed using the paired quadrat variance (PQV) technique (Ludwig and Reynolds 1988).

RESULTS

The single bed studied in 1993 was nearly a monotypic stand of M. spicatum. The mean biomass was 382 + 52 g.mS2 for vegetated quadrats. Eight percent of the quadrats within the bed contained no vegetation (Figure 2). Edge sampling points had a significant (p<0.05) and somewhat higher median biomass (375 g.m-' vs. 3 10 g.m-') than did interior sampling points.

Areas outside the plant bed were deeper (Figure 1) and had higher median moisture and organic matter values than points within the bed (Table 1). The points at the edge of the bed were deeper than interior points, but moisture and organic values did not differ significantly between edge and interior areas. Biomass was not significantly correlated with depth, organic matter, or sediment moisture; but depth, organic matter, and sediment moisture were significantly correlated with each other.

The number of runs (i.e., one or more contiguous sampling units with milfoil) in all 1994 transects was significantly less than expected from a random distribution, indicating a clumped plant distribution in the beds (Table 2). The PQV analysis (Figure 3) also indicates a clumped distribution. We interpreted the clumping is at a

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Myriophyllum Biomass

Granis/Square Meter

t METERS

10 0 10 '20 30 40 v

Figure 2. Myriophyllunl spicarum biomass point data (gem") at 1993 study site in Lake Onalaska. Line outlines the Myriophyllum spicafunt bed.

Table 1. Medians, 95% confidence intervals, and number of samples (n) for Mood's Median Tests (Minitab 1994) for depth, percentage moisture, and percentage organic matter in Lake Onalaska Myriophylllrr~t bed, 1993. Edge = < 30 m from edge of bed; Interior = > 30 m from edge.

95% Confidence

Location Median Interval N

Outside Depth (cm) 105.5 99- 111 54 Moisture (Oh) 28.9 25.6 - 37.3 46 Organic (Oh) 3.06 1.96 - 3.46 46

Edge Deptli (cm) 94 91 - 97 7 1 Moisture (Oh) 24.4 23 - 25.4 59 Organic (Oh) 1.55 1.27 - 1.84 59

Interior Depth (cm) 87 83.6 - 91 38 Moisture (ON 23.9 22.5 - 25.4 32 Organic (Oh) 1.23 1.01 - 1.76 32

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Table 2. Comparison of Lake Onalaska Transects

Transect Y 7 Y 8 Y 9 Y 10 Y11

Freq. (%)" 62.2 64.5 83.6 63.4 71.1

Runs 68 40 22 103 53 (number)

Runs 47 1 229 274 464 41 1 (expected)

Length (m) 0.9 1.6 3.8 0.4 0.5

595% 0.2 0.6 0.3 0.1 0.2 C.I.(m)

" Percentage of 0.1 m line segments that crossed a M. spicalum plant Significant atp<0.05

block-sizelspacing of about 1 to 4 units, and these clumps are regularly spaced. This block-sizelspacing indicates that the diameter of the clumps are about 1 to 4 m (Ludwig and Reynolds 1988), which is similar to the average run length of 0.4 to 3.8 m for Transects Y7 to Y 11 (Table 2). Lake Wingra data also indicated that the plants were clumped and the average run length for the six Lake Wingra transects was 0.650.1 m.

DISCUSSION

The mean biomass of 382 g.m-2 for vegetated quadrats in Lake Onalaska is very similar to the 383538 g.mS2 (ash-free dry weights were increased by 22% to make Lake Wingra data comparable to Lake Onalaska data) found during the height of the milfoil invasion in Lake Wingra, Wisconsin (Nichols 1971), and the approximately 390 g.m-2 found in Devils Lake, Wisconsin (Lillie and Barko 1990). Lake Onalaska milfoil biomass also falls within the 283 to 555 g.m-2range found for milfoil in vegetated quadrats in Fish Lake, Wisconsin, for 1991-1994 (R.A. Lillie pers. comm.) Individual sampling locations in Lake Onalaska contained more than 1000 g.m-' of milfoil biomass, as did areas of Lake Wingra (Nichols 1971) and Devils Lake (Lillie 1990).

The frequency of nonvegetated quadrats within the beds was 13.7% in Lake Wingra during the height of the milfoil invasion (Nichols 197 1) and 3% to 5% for Fish Lake (Lillie, personal communication), so the frequency of plant occurrence within the beds (based on 1993 Lake Onalaska data) is similar for all three lakes. The 1994 line transect data for Lake Onalaska indicated a higher percentage of nonvegetated area. There are no comparative data to determine whether the increased open area is real or the result of different sampling techniques.

The deeper water, higher organic matter content, and higher sediment moisture content outside the 1993 Lake Onalaska plant bed should not have limited

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M. spicatzrr?i growth. The 6% maximum value for organic matter in Lake Onalaska sediment is low for Lake Wingra (5.8% to 20%, Nichols 1971) and Fish Lake (29% to 53%, Lillie pers. comm.) sediments that supported milfoil growth. Devils Lake sediments ranged from only 1.1% to 2.3% organic matter in areas of milfoil growth (Lillie and Barko 1990). Similarly, the median depth of 106 cm for depth outside the bed is at the bottom of the depth range that supported high milfoil biomass in Lake Wingra (Nichols 1994), and the milfoil beds in Devils Lake were not found in water depths less than 1.5 m (Lillie 1990). The maximum depth of a vegetated quadrat in Lake Onalaska was 134 cm compared to about 270 cm in Lake Wingra (Nichols and Mori 1971), 4 m in Fish Lake (Budd et al. 1995), and 9 m in Devils Lake (Lillie 1990).

The shallow maximum depth of milfoil growth 111 Lake Onalaska is likely related to poor water clarity. Newman and Perry (1993) found maximum growth depth of M. spicatunr positively correlated with Secchi depth. They also found that Lake Onalaska had the shallowest Secchi reading (0.3 m) and the highest turbidity reading (3 1.0 NTU) of any of the 21 milfoil lakes they sampled in Wisconsin and Minnesota. However, summer chlorophyll a readings were moderate to low (8.5 mg.m4 compared to a range of 2.9 to 66.9 mg.m4), so high turbidity appeared related to high suspended sediment rather than algal turbidity. Lake Onalaska has a large surface area, shallow water depths, and is part of a large riverine system. Water clarity in large, shallow, backwater lakes is strongly affected by wind- and weather-related events and is highly variable during the season and between years. For example, the water depth where 10% of surface photosynthetically active radiation, was found ranged from 0.3m to 1.6m during the 1992 growing season in Lake Onalaska (Rogers et al., 1995), and Sullivan (pers. comm.) found that a 10 mph increase in average wind speed in Weaver Bottoms, a backwater lake in Pool 5 of the upper Mississippi River, decreased light penetration by about 0.4m.

-+- transect Y7 -+- transect Y8 + transect Y9 --+ transect Y10 --r- transect Y11

Figure 3. Paired quadrat variance of 1994 transect data in Lake Onalaska 188

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Myriophyllunl spicalur?z appears to have a competitive advantage over many native species because it begins growth earlier in the spring (Nichols and Shaw 1986). In Lake Onalaska, this could be a disadvantage during years when spring water clarity is poor, but may promote successful growth during years when water clarity is relatively good early in the season. This compares to V. americana, which was formerly abundant in Lake Onalaska (Rogers et al. 1995). It is a late season strategist (Titus and Adams 1979) and could take advantage of midsummer water clarity.

It is not clear how influential sediment characteristics are for determining milfoil biomass. Organic matter content in Lake Onalaska, which also relates to sediment density and water-holding capacity, varied from 0.4% to 9.0% and seemed to have little influence on biomass. However, higher organic matter areas were in deeper water that did not support milfoil growth probably because of poor water clarity. Likewise, there was no apparent relationship between sediment characteristics and milfoil biomass in Lake Wingra (Nichols 1994). hi Devils Lake, however, there was an association between milfoil biomass and sediment characteristics. Areas of higher organic matter and moisture content supported higher milfoil biomass (Lillie and Barko 1990).

The decrease in biomass toward the center of the bed is probably related to water depth, although turbidity (Engel and Nichols 1994, Schiemer 1979) or some factor such as nutrients supplied by current or wave action that does not penetrate the milfoil bed are possible explanations. The interior bed median depth was 87 cm, compared to 94 cm for points near the edge of the bed. Shallow water cannot support tall plants that have high biomass. Mechanical damage to milfoil from wave action and ice scouring limits growth in shallow water. Negligible milfoil biomass was found in Lake Wingra in water depths less than 40 cm and biomass never reached 1000 g.m-2 in water less than 1 tn deep (Nichols 1994).

Budd et al. (1995) defined a clump of lnilfoil as all plant s t em originating from a single root crown. On the basis of a circular geometry, they found an average clump diameter of 0.34 m in Fish Lake. It appears the distribution pattern seen in Lake Onalaska reflects this clumped growth form and the clumps are uniformly distributed. The clump size (i.e., run length) was larger in Lake Onalaska than in Lake Wingra and in Fish Lake. The difference in size from Fish Lake could be explained by the location of the measurement. The sizes of plant clumps in Fish Lake were based on measurement at the substrate and in Lake Onalaska at the water surface. The spreading canopy of milfoil occupies more area than stem bases occupy.

Lake Wingra plants also displayed clumping at a small block-sizelspacing and a uniform distribution of clumps, so this growth pattern is not unique to Lake Onalaska. Uniform dispersion is relatively uncommon in natural plant stands and usually results from a negative interaction between individuals such as competition for resources or space (Ludwig and Reynolds 1988). However, detecting the uniform pattern and explaining its causes are separate problems. This study or previous studies in Lake Wingra (Nichols. 1994) do not adequately explain the cause of the uniform distribution.

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From the information collected in this study and the comparisons to other lakes, it appears that M. spicatum biomass in Lake Onalaska is in the same range as some natural lakes of the region, but the depth zone it grows in is more restricted. The depth zone it occupies in Lake Onalaska is narrow and shallow. Milfoil does not commonly grow in water depths less than 0.5 m in northern climates, and the beds we studied in Lake Onalaska stopped in water depths a little over 1 m deep. The reason for this depth limitation is probably poor water clarity. Sediments in milfoil beds have low organic matter and hence low water-holding capacity and high density when compared to sediments in some other lakes, but data from Devils Lake show that milfoil can thrive on low organic matter sediments. The range of sediments conditions that support milfoil growth is wide enough that it could probably grow in most conditions found in the Mississippi River pools.

Limited depth distribution does not mean that milfoil cannot or will not produce nuisance problems. Many areas within the upper Mississippi River pools are approximately 1 m deep. In Lake Onalaska, nearly 47% of the surface area is between the 0.5 m and 1.5 m deep. If our interpretation that maximum depth of milfoil growth in Lake Onalaska is controlled by water clarity, then the area where milfoil can grow will probably be highly dynamic. Conditions that allow for clear water, especially early in the growing season, could allow milfoil to expand, and more turbid conditions would restrict growth. A canopy of stems spreading out over the surface of the water is the typical milfoil growth form in turbid water. This growth form causes a nuisance to some recreational users even when high biomass is not produced.

ACKNOWLEDGMENTS

John Barko, the Environmental Technical Management Center, Onalaska, WI and U.S. Army Engineers, Waterways Experiment Station, Vicksburg, MS; Richard Lillie, the Wisconsin Department of Natural Resources; and Brian Yandell, University of Wisconsin-Madison, are all gratefully acknowledged for providing critical review and suggestions on prelimitmy drafts of this manuscript.

LITERATURE CITED

Allen, S. E., H.M. Grimshaw, J.A. Parkinson, and C. Quarmby. 1974. Cheniical Analysis of Ecological Malerials. Wiley, New York.

Budd, J., R.A. Lillie, and P. Rasmussen. 1995. Morphological characteristics of the aquatic macrophyte, M. spicalunz, in Fish Lake, Wisconsin. J. Freshwater Ecol. 10: 19-3 1.

Davis, J.C. 1986. Statistics and Data Analysis in Geology (second edition). John Wiley & Sons, New York. 646 pp.

Engel, S, and S.A. Nichols. 1994. Restoring Rice Lake at Milltown, Wisconsin. Tech. Bull. No. 186, Wisconsin Department of Natural Resources, Madison. 42 PP.

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Lillie, R.A. 1990. A quantitative survey of the submersed macrophytes in Devils Lake, Sauk County, with a historical review of the invasion of Eurasian watermilfoil, Myriophyllum spicalum, L. Trans. Wis. Acad. Sci. h t s Letts. 78: 1-20.

Lillie, R.A., and J.W. Barko. 1990. Influence of sediment and groundwater on the distribution and biomass of Myriophylltrnt .spicafttr~l L. in Devils Lake, Wisconsin. J. Freshwater Ecol. 5:4 17-426.

Lind, C.T. and G. Cottam. 1969. The submerged aquatics of University Bay: A study in eutrophication. Am. Midl. Natr. 8 1 :353-369.

Ludwig, J.A. and J.F. Reynolds. 1988. Statistical Ecology. John Wiley & Sons, New York. 337 pp.

Minitab 1994. Minitab Reference Manual, release 10 for Windows. State College, PA.

Newman, R.M. and J.A. Perry. 1993. The potential for biological control of Myriophyllunt spicalum L. in Minnesota with native and naturalized invertebrates. Final Report to the Minnesota Department of Natural Resources, St. Paul. 5 1 pp.

Nichols, S.A. 1971. The distribution and control of macrophyte biomass in Lake Wingra. Tech. Rept. OWRR-B-019-WIS, Univ. Wis.-Madison, Water Resources Center. Madison, WI. 132 pp.

Nichols, S.A. 1994. Factors influencing the distribution of Myriophyllunl spicarttnt L. in Lake Wingra, Wisconsin. J. Freshwater Ecol. 9: 145- 15 I .

Nichols, S.A. and S. Mori. 1971. The littoral macrophyte vegetation of Lake Wingra. Trans. Wis. Acad. Sci. Atts Letts. 59: 107-1 17.

Nichols, S.A. and B. Shaw. 1986. Ecological life histories of tluee aquatic nuisance plants, Myriophyllunt spicatunt, Potantogeton crispus, and Elodea canadensis. Hydrobiologia 13 1 :3-2 1.

Rogers, S.J., D. G. McFarland, and J.W. Barko. 1995. Evaluation of tlie growth of Vallisneria americana Michx. in relation to sediment nutrient availability. Lake and Reservoir Management 1 1(1):57-65.

Schiemer, F. 1979. Submerged macrophytes in tlie open lake. Distribution patterns, production, and long term changes. In: Loffler, H. (ed.). Neusiedlersee: tlie limnology of the shallow lake in central Europe. Monogr. Biol. 37, Dr. W. Junk Publ., The Hague, Netherlands. 235-250 p.

Titus, J.E. and M.S. Adams. 1979. Coexistence and Comparative Light Relations of the Submersed Macrophyte Myriophylllrni spicaltrnt L. and Valisneria anlericana Michx. Oecologia 40: 273-286

Received: 24 June 1996 Accepted. 7 November 1996

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