12 Plant Community Restoration 12.1 INTRODUCTION Because of the vital role plants play in the aquatic ecosystem there is a growing interest in restoring aquatic plant communities. Aquatic plant restoration may: (1) improve fish and wildlife habitat; (2) reduce shoreline erosion and bottom turbulence; (3) buffer nutrient fluxes; (4) shade shorelines; (5) reduce nuisance macrophyte and algae growth; (6) treat stormwater and wastewater effluent; (7) replace exotic invaders with native species; (8) improve aesthetics; and (9) generally moderate environmental disturbance. Although there is some debate about the proper term(s) — enhance, restore, rehabilitate, develop, restructure — for these efforts (Haslam, 1996; Moss et al., 1996; Munrow, 1999) the essence is to return aquatic plants to areas where they were previously found, to develop areas where they should be found, or to restructure present plant populations to provide the ecological assets of a healthy macrophyte community. For purposes of this discussion, resto- ration is broadly and loosely defined. It can mean planting a single species where plants were previously extirpated. It can mean changing habitat conditions so revegetation occurs naturally. It can mean restoring diversity to a monotypic, exotic plant community. It can mean doing nothing and letting nature take its course. In few, if any, cases is an aquatic plant community restored or rehabilitated in the strictest, ecological definition of the terms (Haslam, 1996; Moss et al., 1996; Munrow, 1999; Chapter 1). Various techniques have been used to restore saline and fresh water marshes, swamps, sea- grasses, and fresh water plants in lakes and streams (Kadlec and Wentz, 1974; Johnston et al., 1983; Orth and Moore, 1983; Marshall, 1986; Storch et al., 1986; Moss et al., 1996). The technology for aquatic plant community restoration is quickly developing but presently it is still as much of an art as it is a science. Much more is known about restoring wetlands, which includes shoreline emergent plants, than is known about restoring submergent communities. Table 12.1 lists decision items for estimating the potential for success or the amount of work involved in a plant restoration. If the habitat for restoration has most of the items in the right or “increase success” side of the table, little or nothing other than patience may be needed to restore plants. If most items are in the “decrease success” column, anticipate more work, expense, and potential for failure. The suggested remedies are broad categories. They may not be suitable because of cost, physical limitations, environmental impact, or regulatory or political realities at any specific location. For instance, drawdown may be physically impossible, prohibitively expensive, or not approved by regulatory agencies on a natural lake without a control structure. Some techniques are untested. Would algicide treatments, a selective plant management technique, temporarily increase water clarity for macrophyte establishment? Most restoration areas need some remediation or a desirable plant community would be present. Remediation and restoration should not be viewed as a single effort. For example, after macrophytes are planted, they may need protection from predators and waves before they become successfully established and spread. Careful selection of plant material can overcome some habitat limitations. Some species are more tolerant of turbidity or fluctuating water levels, or are able to grow in deeper water than are other species. Many of the suggested remedies are discussed in other sections of this book (e.g., nutrient limitation and inactivation to increase water clarity, drawdown, dredging) or are discussed more thoroughly in the following sections and in the case histories. Copyright © 2005 by Taylor & Francis Some tests needed to enhance restoration success are simple. Secchi depths explain a lot about water clarity and whether algal blooms, benthivorous fish, wind and waves, or heavy powerboat use causes turbidity. Aquarium tests determine sediment seed banks, sediment suitability for plant growth, and propagule viability. Wind and wave impacts are estimated from local weather summa- ries, a lake map, and observation of plant distribution. Simple observation is used to determine animal and human use (e.g., carp (Cyprinus carpio) spawning, powerboating, bank fishing). Plant collections determine species occurrence and distribution. These tests may not be all that are needed but they will answer some of the basic questions needed for a successful restoration. Aquatic plant restoration is discussed based on the level of effort needed to complete a project. The least effort method is “doing nothing,” followed by habitat protection and alteration, and finally by active establishment. In reality all three might be needed in a single project. Habitat may need to be altered before any plants will grow. After alteration, doing nothing for a growing season or two determines if natural revegetation will occur. If natural revegetation occurs, the additional cost and time-consuming effort of planting may not be needed. If this is not the case, planting is needed to increase desirable species, diversity, or to revegetate difficult areas. Even after successful plant establishment, further efforts are usually needed to protect the plant community. For instance, herbivory may be a problem or other aquatic plant management techniques may be needed to control nuisance macrophytes. 12.2 THE “DO NOTHING” APPROACH There is evidence that aquatic plant management techniques such as harvesting and herbicidal treatment favor rapidly reproducing, aggressively growing species — the weeds (Cottam and Nichols, 1970; Nicholson, 1981; Bowman and Mantai, 1993; Doyle and Smart, 1993; Nichols and TABLE 12.1 Decision Items for Assessing Plant Restoration Potential and Suggested Remediation Techniques Factors for Assessing Plant Restoration Potential Decrease Success Increase Success Remedies a Water clarity Turbid water Clear water during most of growing season 1, 2, 3, 4, 12 Sediment characteristics Density Low density Moderate to high density 2, 6, 7 Organic matter content High Moderate to low 2, 6, 7 Toxicity Toxic Non-toxic 5, 6, 7 Predator population High Low 3, 4, 8 Environmental energy (current, waves, etc.) High Low 4, 9 Water Depth Deep Shallow 2 Stability Fluctuating Stable water level 4, 10 Plant population Residual plants Few or none Abundant 11 Sediment seed bank Few or none Abundant 11 Plant population in area Few or none Abundant 11 Non-desirable species Abundant Few or none 11, 12, 13 a Types of remedies: (1) nutrient limitation, (2) drawdown, (3) fish population manipulation, (4) physical barriers, (5) aeration, (6) shallow dredging, (7) sand blanket, (8) predator population control, (9) slow-no-wake or no-motor regulations, (10) stabilize water level, (11) macrophyte planting, (12) selective plant management, (13) do nothing. Copyright © 2005 by Taylor & Francis Lathrop, 1994). Plant succession is continually “set back.” So what can be done? — “do nothing” and hope that natural successional trends will re-establish a diverse community of non-weedy, native species. The advantages of doing nothing are that the developing plants are from local sources and they are adapted to local conditions so they may have the best chance for survival. The technique is inexpensive and plant succession is not continually “set back” so the community that develops may be the most stable for existing conditions. The disadvantages are that it may take a long time for a plant community to develop or change, especially if the area was not previously vegetated and/or if there is no natural source of propagules in the area (Smart and Dick, 1999; Nichols, 2001). Little is known about the dynamics of aquatic plant community change so the results are unpre- dictable and doing nothing may be politically unpalatable. There is also evidence that plant communities can change from a diverse native community to one dominated by exotics without cause or manipulation. For example, the plant community in the Cassadaga Lakes, New York, with little or no management, changed from one dominated primarily by native pondweeds to one dominated by curly-leaf pondweed and Eurasian watermilfoil — an obvious case where doing nothing did not work (Bowman and Mantai, 1993). In some locations the “do nothing” approach is codified by designating areas as critical habitat, which is a regulatory approach to protect areas so restoration is not needed or can occur naturally. 12.2.1 CASE HISTORY: LAKE WINGRA, “DOING NOTHING” Lake Wingra is a 137-ha, shallow (mean depth of 2.4 m), urban lake located in Madison, Wisconsin. The University of Wisconsin Arboretum and city parkland surrounds it so, unlike many urban lakes, the shoreline is not heavily developed. Around 1900, Equisetum spp., Zizania sp., Typha latifolia, T. angustifolia, and Scirpus validus were common species of the broad marshes surrounding the lake. Dense growths of Chara spp. were interspersed between the emergents. Wild celery (Vallis- neria americana) was particularly abundant. There were at least 34 species of aquatic plants in Lake Wingra at this time and the lake bottom was completely vegetated (Bauman et al., 1974). During the first half of the 20th century dredging, filling, water-level fluctuation, and the introduc- tion of carp decimated the aquatic vegetation. Macrophytes were sparse from the late 1920s through 1955 (Bauman et al., 1974). Eurasian watermilfoil (Myriophyllum spicatum) invaded Lake Wingra in the early 1960s and by 1966 it was dominant and replaced the remaining native species. From the mid-1960s to the early 1970s M. spicatum was present in dense stands in shallow areas of the lake. The milfoil stands declined in 1977 (Carpenter, 1980). Except for some minor plant harvesting around a public boat livery and a swimming beach, there was little or no management on Lake Wingra after the early 1950s when carp were seined to low levels. The reason for the milfoil decline was never adequately determined. Between 1969 and 1996 species number increased slightly, Simpson’s (1949) diversity increased dramatically from 0.52 to 0.88, the relative frequency of exotic species (M. spicatum and Potamogeton crispus) dropped from 68.9% to 35.9%, and the relative frequency of species sensitive to disturbance (Nichols et al., 2000) increased from 0.1% to 19.1% (Table 12.2). The maximum depth of plant growth increased from 2.7 m to 3.5 m. Wild celery and Potamogeton illinoensis returned — they were last reported in the lake in 1929. The vegetation recovery in Lake Wingra was more dramatic than in the other Madison, Wisconsin area lakes that had a similar history of an Eurasian watermilfoil invasion (Nichols and Lathrop, 1994) but are more heavily managed. The vegetation recovery in Lake Wingra was neither planned nor predicted so why did the vegetation recover? No reason can be given with absolute certainty because the results are obser- vational and were not part of an experimental program. Historically Lake Wingra had a rich aquatic flora and even at the height of the milfoil invasion there were more than 15 species of plants in the lake. Dane County, Wisconsin also has 24 lakes greater than 30 ha in size so there is an abundant supply of aquatic plant propagules in the vicinity for invasion and there is probably a seed (propagule) bank in the sediment, although this was never tested. After the abundant carp population Copyright © 2005 by Taylor & Francis was seined to low levels in the early 1950s they never regained their former abundance. The lake is shallow, with fine, moderately organic, and moderately nutrient rich sediments. There has been no major disturbance of the plant beds due to management activities and there is a “slow-no-wake” boating ordinance on the lake. In total, Lake Wingra is an ideal location for aquatic plant growth and given the chance, they returned. Eurasian watermilfoil declines occurred in other lakes and native species are returning (Smith and Barko, 1992; Nichols, 1994; Helsel et al., 1999;) so the Lake Wingra experience is not unusual. 12.3 THE HABITAT ALTERATION APPROACH The degradation or decimation of aquatic plant communities often resulted from major habitat alterations. Plant communities were lost because of water level increases; wind and wave erosion; actions of benthivorous fish or plant predators; and cultural eutrophication, aquatic plant manage- ment, or other human activities. Often a combination of these factors led to the demise of macrophyte communities (Nichols and Lathrop, 1994). The end result is turbid water and/or high-energy environments that are unsuitable for aquatic plant growth. Reversing unsuitable habitat conditions allows vegetation to return. Both regulatory and more active approaches involving engineering or biomanipulation are used to alter habitat. The disadvantages to these approaches are that there is no way of predicting the results and they may be politically unpalatable, especially regulatory approaches. Restoration may take a long time but experience indicates that revegetation occurs TABLE 12.2 Comparison of Species Relative Frequencies in Lake Wingra, Wisconsin between 1969 and 1996 a Plant Species Rel. Freq. (%) 1969 b Rel. Freq. (%) 1996 Myriophyllum spicatum 68.4 27.4 Potamogeton pectinatus 8.1 6.6 Potamogeton natans 6.2 1.3 Nuphar variegatum 4.8 0.4 Potamogeton nodosus 3.0 — Ceratophyllum demersum 2.9 8.4 Nymphaea tuberosa 2.6 3.5 Chara sp. — 7.1 Najas flexilis 0.3 2.2 Potamogeton crispus 0.5 8.4 Potamogeton foliosus 0.1 5.8 Potamogeton richardsonii 0.2 6.6 Potamogeton zosteriformis 0.5 9.3 Vallisneria americana —5.3 Potamogeton sp. c —4.0 Other species d 2.4 3.7 Simpson diversity e 0.52 0.88 a Does not include emergent species. b After Nichols, S.A. and S. Mori. 1971. Trans. Wis. Acad. Sci. Art Lett. 59: 107–119. c Probably Pota mogeton illinoensis. d Species with less than 1.0% relative frequency in either or both sampling periods; includes Elodea canadensis, Zosterella dubia, and Ranunculus longirostris. e A modification of Simpson, W. 1949. Nature 163: 688. Copyright © 2005 by Taylor & Francis rapidly once limiting habitat factors are removed. An advantage is the plant community that develops is from local sources so it should be adapted to local conditions. Costs and environmental impacts are highly variable, depending on the technique. Regulatory approaches like establishing no-motor or slow-no-wake zones are inexpensive and environmentally benign or beneficial. Fencing “founder” colonies of remaining plants to protect them from predation is of moderate cost. Con- structing islands and breakwalls to protect plants from wind and waves, large-scale fish removal projects, and nutrient reduction techniques are expensive, some costing in the millions of dollars; and they may have moderate to severe environmental impacts, at least over the short-term. 12.3.1 CASE HISTORY: NO-MOTOR, SLOW-NO-WAKE REGULATIONS 12.3.1.1 Long and Big Green Lakes: Heavily Used Recreational Lakes in Southeastern Wisconsin 12.3.1.1.1 Long Lake Long Lake has a surface area of 169 ha and a maximum depth of 14.3 m. A dam installed in 1855 raised the natural level of this glacial lake by 2 m. This created an extensive littoral zone extending from shore by as much as 120 m before dropping sharply into deep water. The Long Lake State Recreation Area occupies the east shore of the lake and the west shore is developed with permanent and seasonal homes. A 1989 survey found that Long Lake had 7,088 boating days of annual use, which corresponds to 41 boating days per hectare per year (Asplund and Cook, 1999). Peak boating activity occurs in July, with as many as 60 boats present on some weekends. The lake is long and narrow in a north-south direction, which makes it ideal for water-skiing and inner tubing. The lake has at least 22 species of floating and submerged plants with Chara sp. being the most abundant species. Local property owners wanted to protect aquatic vegetation for fish habitat. They were also worried about water quality problems from the exposed sediments and that disturbed areas might be colonized by Eurasian watermilfoil. Aerial photos showed major areas of the shallow littoral zone that were devoid of plant growth. The worst area was along the eastern shore. In May 1997 the Long Lake Fishing Club placed slow-no-wake buoys for approximately 1,500 m along the east shore of the lake. The buoys were placed approximately 120 m out from the shore so the slow-no-wake zone extended from the buoys into the shoreline. Two no-motor zones of about 125 m each were placed within the slow-no-wake zone. Although the restrictions were technically voluntary, a concerted effort was made to educate lake users about the importance of respecting the special boat-use zones. Asplund and Cook (1999) assessed the submerged macrophyte community in late August of 1997. They found that the large scour (non-vegetated) areas seen in 1995 were almost completely covered with Chara. Scour areas were reduced to as little as 1.5% of the area (Table 12.3). Boat tracks were still evident in the no-wake area, but at a much lower frequency. This suggests that boats still uproot plants or cut off stems at no-wake speeds. Alternative explanations are that boaters occasionally traveled through the area at faster speeds or anchors were dragged along the bottom. No boat tracks were observed in the no-motor plots. Sampling found very little vegetational difference between management areas in terms of overall stand density and canopy height. One can only speculate on the reason, but unprotected comparison areas may have historically received less boat use and were in fact protected because boaters avoided the east side of the lake that was largely a no-wake zone. In 1998 the local town board permanently established a no-wake zone along the eastern side of the lake, but the buoys were placed closer to the shoreline so that about one-third to one-half the area protected in 1997 was outside the no-wake zone. Aerial photography revealed that boat scour and tracks eliminated much of the Chara that grew in 1997 in this newly unprotected area. Copyright © 2005 by Taylor & Francis 12.3.1.1.2 Big Green Lake Big Green Lake is large (surface area 2,974 ha) and deep (maximum depth 72 m). However, it has shallow bays where hardstem bulrush (Scirpus acutus) was an important part of the emergent vegetation. Historical accounts identified five bulrush stands in the lake ranging in size from 3,500 to 255,000 m 2 (Asplund and Cook, 1999). The largest remaining stand was about 1,840 m 2 in size in 1997 and appeared to be shrinking. Motorboat activity was thought to be a major factor in the decline of this remaining stand. The sandbar area adjacent to the stand is a popular place for mooring boats and wading. To address this concern the local town board enacted an ordinance in 1997 to place no-motor buoys around the stand. The extent of the stand was divided into three sections and mapped in 1997, 1998, and 2002 using GPS. Stem densities were also determined for those years. In 1998 the stand size and stem densities appeared to be somewhat greater or at least not shrinking (Table 12.4; Asplund and Cook, 1999). By 2002 stand size and stem densities have not increased and may have decreased slightly (Table 12.4). After 5 years of protection, it appears, at best, that restricting motorboat traffic has slowed the decline of the bulrush bed. 12.3.1.2 Active Habitat Manipulation: Engineering and Biomanipulation Case Studies 12.3.1.2.1 Lake Ripley, Wisconsin: Boat Exclosures Lake Ripley has a surface area of 169 ha, a maximum depth of 13.4 m, and an extensive littoral area less than 2 m deep. Littoral sediments are very flocculent and easily resuspended due to a high percentage of marl. Homes ring the lake, there are more than 300 boats docked around the TABLE 12.3 Comparison of the Percentage of Unvegetated Area in Protected and Unprotected Areas of Long Lake, Wisconsin between 1995 and 1997 a Area 1995 (before protection) (%) 1997 (during protection) (%) No-motor 2.7 1.5 No-wake 17.4 2.0 Unprotected 12.0 2.2 a Vegetation consisted primarily of Chara sp. and native milfoils. Source: After Asplund, T. and C.E. Cook. 1999. LakeLine 19(1): 16. TABLE 12.4 Bulrush Density and Bed Size in Big Green Lake, Wisconsin Bed location Bed Area (m 2 ) Bulrush stem density (stems/m 2 ) 1997 1998 2002 1997 1998 2002 Southwest 114 94 77 8 45.3 12.5 Center 1223 1268 1157 20.9 26.3 19.3 Northeast 505 662 432 24.3 25.3 23.2 Total 1842 2024 1666 Source: Data supplied by Chad Cook, Wis. Dept. Nat. Res. Personal communications, 2002. Copyright © 2005 by Taylor & Francis lake, and on weekends boat use approaches 50 boats on the lake at one time (Asplund and Cook, 1997). Historically, Lake Ripley had a diverse plant community dominated by wild celery, pond- weeds (primarily P. illinoensis and P. pectinatus), and water lilies (Nuphar variegata and Nymphaea odorata). Eurasian watermilfoil dominated the vegetation in the 1980s but has since declined. Native species were slow to recolonize areas suitable for plant growth. Motorboats had a major impact on aquatic plants. Boat “tracks” or scour lines through the remaining plant beds were visible from aerial photos in areas of high boat traffic (Asplund and Cook, 1997). It was not known whether the impact was due to increased turbidity caused by resuspension of bottom sediments, turbulence from boat wakes and prop wash, direct scouring of the sediment, direct cutting by motor propellers, or breakage from contact with boat hulls. Asplund and Cook (1997) examined the impact of motorboating on the aquatic plant community by constructing two solid plastic and two mesh fencing exclosures in the lake that excluded boat access. After a single growing season, species composition was similar between the plots with Chara sp. and Najas marina being the predominant species. However, plant growth between the areas varied considerably. The plant growth in the protected areas was not significantly different between those areas protected with mesh or solid fencing. The protected areas had about one and one-half times as much area covered, about one and one-half to two times the maximum plant height, and two to two and one-half times the biomass as the unprotected areas (Table 12.5). Through additional water chemistry testing they concluded that motorboats reduced plant biomass by sediment scouring and direct cutting of the plants, but not by turbidity generation. Similar exclosures of varying sizes and designs were needed to protect remaining plants from herbivorous fish, wading or aquatic mammals, and waterfowl in other restoration efforts (Moss et al, 1996; van Donk and Otte, 1996). 12.3.1.2.2 Big Muskego and Delavan Lakes, Wisconsin: Drawdown, Benthivorous Fish Removal, and Nutrient Reduction Big Muskego Lake has a surface area of 840 ha and is very shallow (mean depth is 0.75 m). A dam built in the 1800s flooded this former deep-water marsh. The lake is eutrophic and drains a predominantly agricultural watershed of 7,600 ha. Before the treatment the submersed plant com- munity was dominated by Eurasian watermilfoil and common carp dominated the fishery. Although the lake was well vegetated, with approximately 95% of the area containing vegetation; soft, flocculent and highly organic sediments, carp, wind and wave action, and turbidity limited the growth of desirable, native aquatic plants. Besides increasing plant diversity, wildlife managers were interested in increasing the extent of the emergent zone. Before treatment cattails were found at 9.9% of the sampling points and all other emergent species were found at less than 1% of the sampling points. Drawdown (Chapter 13) of Big Muskego Lake started in October 1995 and the water level was lowered by about 0.5 m between December 1995 and July 1996. A channel was excavated to promote further drawdown in mid-July 1996. This caused an additional 0.5 to 0.6 m drawdown TABLE 12.5 Average Plant Growth in Protected and Unprotected Areas in Lake Ripley, Wisconsin Location Percent Cover (%) Max. Plant Height (cm) Biomass (g/m 2) Unprotected area 58 46 434 Protected area — mesh fencing 84 82 823 Protected area — solid fencing 82 61 1063 Source: After Asplund, T. and C.E. Cook. 1997. Lake and Reservoir Manage. 13: 1–12. Copyright © 2005 by Taylor & Francis between July 1996 and January 1997. The lake was allowed to refill during late winter and early spring 1997. Normal water levels returned by April 1997. Overall, about 13% of the sediment area was exposed for approximately 1 year, while over 80% of the sediment area was exposed for about 6 months (James et al., 2001a, b). In addition, drawdown concentrated undesirable fish so they were more easily removed with a piscicide. Prior to drawdown Muskego Lake sediments were very fluid. Surface sediments were over 90% water, sediment density was low, and organic content of the sediment was very high (more than 40%) (James et al., 2001a, b). Hopefully, desiccation would consolidate sediments, reducing resuspension potential and turbidity. A concern was the effect oxidation of aerially exposed sedi- ments might have on mobilizing sediment organic nitrogen and phosphorus. Internal nutrient loading after reflooding exposed sediments could stimulate excessive algal blooms that would be counter- productive to macrophyte growth. Lake drawdown effectively consolidated sediments (e.g., increased sediment density) and decreased organic matter content. Mean porewater concentrations of soluble reactive phosphorus and NH 4 –N initially increased after reflooding but declined markedly 1 year later (James et al., 2001a, b). Macrophyte growth responded to the new habitat conditions. Mean macrophyte biomass increased from pretreatment levels of 150 g/m 2 in 1995 to post-treatment levels of 1,400 g/m 2 in 1998. This high biomass may have played a role in depleting sediment phosphorus reserves (James et al., 2001a, b). The plant community also changed dramatically (Table 12.6). Species number increased from 18 to 25 taxa. The relative frequency of emergent species increased from 14.2% to 35.3%. The TABLE 12.6 The Vegetation of Big Muskego Lake before and after Drawdown and Carp Removal Species Rel. Freq. (%) Pre-treatment (1995) Rel. Freq. (%) Post-treatment (1997) Ceratophyllum demersum 2.9 0.6 Chara sp. — 15.5 Lemna minor —12.2 Lythrum salicaria 6.5 2.8 Myriophyllum sibiricum 3.8 1.0 Myriophyllum spicatum 61.6 8.3 Najas marina 1.3 4.2 Nuphar variegata 4.2 0.1 Nymphaea odorata 3.6 2.8 Potamogeton amplifolius 2.3 0.1 Potamogeton crispus 0.6 1.7 Potamogeton illinoensis —1.3 Potamogeton pectinatus 1.6 11.9 Ranunculus longirostris 0.6 3.8 Scirpus spp. 0.3 14.2 Typha latifolia 6.8 18.1 Other species a 3.9 1.4 a Other species include: Carex spp., Ceratophyllum echinatum, Elodea canadensis, Zosterella dubia, Najas flexilis, Potamogeton nodosus, P. pusillus, Sagittaria latifolia, and Zizania aquatica. They had a relative frequency of less than 1% in both sampling periods. Source: Data from John Madsen, Department of Biology, Minnesota State University, Mankato. Personal communications, 2002. Copyright © 2005 by Taylor & Francis relative frequency of exotic species decreased from 70% to 17%. Simpson’s (1949) diversity increased from 0.61 to 0.88. The areal extent of the plant community changed very little between pre- and post-treatment. This was not surprising since there was little room for plant community expansion. Before treatment only about 1% of the area was not vegetated. After treatment only about 0.5% was not vegetated. From a wildlife management perspective the treatment was very successful. The desired increase in emergent coverage was achieved and there was a substantial increase in sago pondweed (Pota- mogeton pectinatus), a prime waterfowl food. Success needs to be carefully defined when planning restorations since results are unpredictable and riparian property owners may not appreciate increased aquatic vegetation. An example is Delavan Lake in southeastern Wisconsin. It has a surface area of 725 ha, a maximum depth of 16.5 m, and a mean depth of 7.6 m. A major rehabilitation in the late 1980s and early 1990s included efforts to reduce internal and external phosphorus loading; eradicate benthivorous fish, primarily carp and buffalo (Ictiobus cyprinellus); restock predatory game fish; and temporarily draw down lake levels. Historically Delavan Lake had a rich aquatic flora. Surveys done between 1948 and 1975 identified 25 macrophyte taxa (not all in the same survey), but vegetation was declining by the 1950s. In 1955, the Izaak Walton League planted a number of desirable species in the southwest end of the lake because of a concern over the loss of aquatic vegetation. In the early 1960s only seven species were reported and by 1968 only four species remained. The aquatic vegetation for several years before rehabilitation consisted of a single pondweed species (Potamogeton sp.) and white water lily (N. odorata). As expected the diversity and abundance of aquatic plants increased because of rehabilitation. The number of species increased to six in 1990 and 20 in 1993. By 1998, however, species number decreased to 13 and Eurasian watermilfoil, curly-leaf pondweed (P. crispus), and coontail (Ceratophyllum demersum) reached nuisance levels in parts of the lake, especially in areas less than 3 m deep in the northern and southern ends of the lake and near the inlet and outlet (Robertson et al., 2000). Additional plant management was anticipated and mac- rophyte harvesting and chemical treatment were part of the original rehabilitation plan; but mac- rophyte growth was much greater than expected. A total of 5,376 m 3 of plant material was harvested during the 1997, 1998, and 1999 growing season. Heavy macrophyte growth near the inlet was partially blamed for remobilizing sediment phosphorus that reduced the success of phosphorus limitation efforts (Robertson et al., 2000). By 2001, 12 submergent or free floating species were found but the relative frequency of exotic species was 36.7% (Table 12.7). 12.3.1.2.3 Breakwaters of All Sizes Breakwaters are used to reduce the impact of wind and wave erosion on aquatic plants (Chapter 5). They are used to protect established plants, new plantings, or to make suitable habitat for plant invasion or community expansion. The simplest breakwaters are wave breaks; V-shaped wave deflectors constructed out of two half-sheets of plywood or other suitably sturdy material (approximately 1.2 m by 1.2 m in size). They are joined at an approximately 90° angle and staked to the bottom on the lakeward side of remaining plants or new plantings (Bartodziej, 1999). Sandbags containing sediment and rhizomes of reeds (Phragmites australis) and burlap bags containing sediment and rhizomes of reeds placed inside old tires filled with sand were used to try to stabilize sediments on Lake Poygan, Wisconsin. These plantings eventually failed (Kahl, 1993). Coir (coconut fiber) geotextile rolls, plant rolls, geotextile mats, branch box breakwaters, brush mattresses, and wattling bundles were used as wave breaks and erosions control devises in some Missouri impoundments (Fischer et al., 1999). Coir rolls were 0.4 m in diameter and placed in shallow trenches. Emergent species were planted on 0.5-m centers on the shoreward side of the roll. A plant roll is similar to a coir roll. It is a cylinder of plant clumps and soil wrapped in burlap and placed in a trench. The ones used in Missouri were 3 m long. Coir geotextile non-woven mats, placed flat and anchored on the reservoir bottom, with emergents planted on 0.3-m centers through- Copyright © 2005 by Taylor & Francis out the mat was another technique used. Brush mattresses and wattling bundles consisted of young willow (Salix sp.) shoots tied in bundles or in a long roll and staked to the bottom. Brush boxes were similar except the willow shoots were woven between and wired to posts driven into the bottom. These techniques are most easily installed in reservoirs under drawdown conditions. The Missouri impoundments project is very recent so the results are inconclusive (Fischer et al., 1999). The Missouri researchers learned that patience is the key. Do not expect lush aquatic vegetation covering the entire littoral zone after one year unless you have a small pond and plenty of time and money. Wave action appeared to be the primary limiting factor to initial plant survival and dispersion. The growth of thick algal mats in the protected areas; fluctuating water levels, especially during cold weather; herbivory; and drifting logs and debris that knocked down protective devises were also problems. Floating booms of logs or old tires have been used to dampen wave action (see Chapter 5). Probably the most interesting floating devises are the Schwimmkampen (Germany) or Ukishima (Japan) — artificially constructed floating wetlands (Hoeger, 1988; Mueller et al., 1996). They are constructed on floating platforms that support wetland vegetation. They move up and down with fluctuating water levels and improve water quality primarily by dissipating wave action thus reducing shoreline and bottom erosion. They provide nursery areas for small fish and crustaceans and in urban areas they have been used for aesthetics by enhancing privacy and dissipating noise. Depending on size, they can be towed to different areas of the lake as needed. One of the larger projects was the Terrell’s Island breakwall constructed on Lake Butte des Morts, Wisconsin. Lake Butte des Morts is a 3,587-ha lake with a mean depth of 1.8 m and a maximum depth of 2.7 m. Originally Lake Butte des Morts and other upriver lakes of the Winnebago Pool were large riverine marshes. Dams constructed in the 1850s raised water levels by about 1 m. Initially they were rich in aquatic vegetation but vegetation decline accelerated from the 1930s through the present because of high water levels, extreme flooding, erosion of shorelines and bottom sediments, lake shore development, plant removal, carp, and accelerated nutrient inputs (Wisconsin Department of Natural Resources (WDNR), 1991). Between 1994 and 1998, 3,245 m of breakwall was constructed connecting the mainland to a series of small islands and enclosing around 243 ha TABLE 12.7 Relative Frequency (%) of Aquatic Plants in Delavan Lake, Wisconsin for 2001 Species Rel. Freq. (%) Ceratophyllum demersum 9.3 Elodea canadensis 2.2 Myriophyllum spicatum 29.0 Potamogeton crispus 7.7 P. foliosus 3.3 P. pectinatus 35.5 P. zosteriformis 2.2 Vallisneria americana 2.2 Zannichellia palustris 1.6 Zosterella dubia 6.0 Other species a 1.0 a Other species were Lemna minor and Chara sp. Source: Data from Kevin MacKinnon, District Admin- istrator, Delavan Lake Sanitary District, Delavan, WI. Personal communications, 2002. Copyright © 2005 by Taylor & Francis [...]... Kadlec, J.A and W.A Wentz 1974 State -of- the Art Survey and Evaluation of Marsh Plant Establishment Techniques: Induced and Natural Contract Rep D-7 4-9 Dredged Materials Research Program, U.S Army Coastal Eng Res Ctr., Fort Belvoir, VI; Trudeau, P.N 1982 Nuisance Aquatic Plants and Aquatic Plant Management Programs in the United States: Vol 3: Northeastern and North-Central Region Rep MTR-82W4 7-0 3, Mitre... Rep MTR-82W4 7-0 3, Mitre Corp., McLean, VI U.S Army Corps of Engineers 1978 Wetland Habitat Development with Dredged Material: Engineering and Plant Propagation Tech Rept DS-7 8-1 6, Office, Chief of Engineers, Washington, DC van Donk, E and A Otte 1996 Effects of grazing by fish and waterfowl on the biomass and species composition of submerged macrophytes Hydrobiologia 340: 285–290 van Donk, E and W.J... islands but detailed results are not available (Janvrin and Langreher, 1999) 12. 4 AQUASCAPING Aquascaping — a term describing the planting of aquatic and wetland plants — is landscaping in and around water (see Chapter 5 for additional discussion) The vision of landscaping may not seem appropriately applied to lakes or reservoirs but natural landscaping is a term that has been used for many years in... plants in a pond with emphasis on growth of American lotus J Aquatic Plant Manage 21: 41–43 Kadlec, J.A and W.A Wentz 1974 State -of- the Art Survey and Evaluation of Marsh Plant Establishment Techniques: Induced and Natural Contract Rep D-7 4-9 Dredged Materials Research Program, U.S Army Coastal Eng Res Ctr., Fort Belvoir, VA Kadono, Y 1982a Distribution and habitat of Japanese Potamogeton Bot Mag Tokyo... Measurement of diversity Nature 163: 688 Smart, R.M and G Dick 1999 Propagation and Establishment of Aquatic Plants: A Handbook for Ecosystem Restoration Projects Tech Rept A-9 9-4 U.S Army Corps of Engineers, Vicksburg, MS Smart, R.M., G.O Dick and R.D Doyle 1998 Techniques for establishing native aquatic plants J Aquatic Plant Manage 36: 44–49 Smith, C.S and J.W Barko 1992 Submersed Macrophyte Invasions and. .. resource for lowtech, low-budget, labor-intensive restoration activities It is also a successful way to raise community awareness and instill a sense of stewardship and collective responsibility for the water resource REFERENCES Asplund, T and C.E Cook 1997 Effects of motor boats on submerged aquatic macrophytes Lake and Reservoir Manage 13: 1 12 Asplund, T and C.E Cook 1999 Can no-wake zones effectively... coastal wetland of Lake Ontario LakeLine 19(1): 12 Cottam, G and S.A Nichols 1970 Changes in Water Environment Resulting from Aquatic Plant Control Water Res Ctr Tech Rept OWRR B-019-Wis University Wisconsin, Madison Crow, G.E and C.B Hellquist 1981 Aquatic vascular plants of New England: Part 2 Typhaceae and Sparganiaceae Station Bull 517 University New Hampshire Agric Exp Sta., Durham Crow, G.E and C.B... (Egeria densa), and Eurasian watermilfoil Tables 12. 9 12. 11 list native North American species Remember, these species are not indigenous to all locations in North America and they could cause serious aquatic nuisance problems if they are transported out of their native range A similar warning is given for non-North America restorations Les and Mehrhoff (1999) reported that 76% of the non-indigenous aquatic... information unknown or unreported Source: Adapted from Nichols, S.A and J.G Vennie 1991 Attributes of Wisconsin Lake Plants Inf Cir 73 Wis Geol Nat Hist Surv., Madison Original data from: Kadlec, J.A and W.A Wentz 1974 State -of- the Art Survey and Evaluation of Marsh Plant Establishment Techniques: Induced and Natural Contract Rep D-7 4-9 Dredged Materials Research Program, U.S Army Coastal Eng Res Ctr.,... Corp., McLean, VI; Carlson, R.A and J.B Moyle 1968 Key to the Common Aquatic Plants of Minnesota Spec Publ 53 Minn Dept Cons., St Paul, MN; U.S Army Corps of Engineers 1978 Wetland Habitat Development with Dredged Material: Engineering and Plant Propagation Tech Rept DS-7 8-1 6, Office, Chief of Engineers, Washington, DC; Fassett, N.C 1969 A Manual of Aquatic Plants University of Wisconsin Press, Madison . millions of dollars; and they may have moderate to severe environmental impacts, at least over the short-term. 12. 3.1 CASE HISTORY: NO-MOTOR, SLOW-NO-WAKE REGULATIONS 12. 3.1.1 Long and Big Green Lakes: . colonies of remaining plants to protect them from predation is of moderate cost. Con- structing islands and breakwalls to protect plants from wind and waves, large-scale fish removal projects, and. about one and one-half times as much area covered, about one and one-half to two times the maximum plant height, and two to two and one-half times the biomass as the unprotected areas (Table 12. 5). Through