Flowering Rush Hand Removal. Lake Minnetonka Pilot Program

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1 Flowering Rush Hand Lake Minnetonka Pilot Program Spring 2012 Survey Report Provided For the Minnehaha Creek Watershed District By Waterfront Restoration LLC & Blue Water Science May 31, Waterfront Restoration, LLC Ph: Page 1 of 18

2 Summary: In May 2012, aquatic plant surveys were conducted on all flowering rush (Butomus umbellatus) sites where the invasive species was hand removed by Waterfront Restoration in fall of. Steve McComas (Blue Water Science) performed an independent aquatic plant assessment (Exhibit 1) to enable quantitative comparison to pre-extraction surveys. Also present in this report, Waterfront Restoration LLC performed underwater surveys to acquire GPS-coordinated observations and photographs in a sample of the previously extracted areas. These underwater observations help to provide further detail and an early indication of any submerged flowering rush growth. As detailed in the Completion Report: Flowering Rush Hand, Lake Minnetonka Pilot Program provided to the MCWD in December, there is a broad difference in limnologic characteristics the three test sites where extraction took place in the fall of. All three sites were found to have different substrates, depths, density, available light, boat traffic, and wave action. Such differences appear to influence the wide range of efficacy that is evident in these surveys. An outline of the quantitative and qualitative observations of each test site is provided in this report. Manual extraction was found to be most effective in Smith Bay where there has been a dramatic reduction in the population of flowering rush. Blue Water Science assessments show this reduction to be approximately 98%. These results suggest that a uniquely comprehensive and carefullycontained manual extraction (hand-removal) process may be capable of dramatically outperforming the poor results achieved in previous hand-removal studies. Some such studies may have utilized less comprehensive extraction and containment techniques. The hand-removal was found to be least effective in the Maxwell Channel where the population of flowering rush has returned to approximately the same level as. These results suggest a number of specific factors at play in this site may contribute to lower efficacy of hand-removal in this instance. Among many potential factors, a few are notable. First, the cobble/gravel substrate presents the challenge for technicians of being unable to find, follow, and extract some portions of flowering rush rhizomes. Second, the timing of removal (Oct ) was such that it is possible a large portion of the flowering rush had senesced due to different characteristics in Maxwell bay than Smith bay. Third, lower water levels and warmer temperatures may have promoted root development, leaf sprouting and rapid growth of rhizome fragments. The summary of the Blue Water Science assessments is provided on page 3. All other data from these assessments are present in the appendix. Waterfront Restoration will provide cost estimates and discuss recommendations for removal of flowering rush re-population in all three test sites. These will be provided by June 5 th, Waterfront Restoration, LLC Ph: Page 2 of 18

3 Table 1. Summary of flowering rush stem counts for the flowering rush assessments. Approximate flowering rush stem counts are for a transect parallel to the shoreline in 2 to 3 feet of water. *first number represents stems along the rocky rip-rapped channel. The second number represents the estimated number of stems in the nearshore area of the open lake. Site 1: Heritage Lane, Smith Bay (415 meters along shore) Pre- Sept 29, Oct 31,, Year 1 May 18, 2012 Site 2: Maxwell Bay (176 meters along shore) Pre- Sept 29, flowering rush 18, (channel) 4,000 (shore)* Oct 31, May 18, (channel) 4,800 (shore)* Site 2A: Crystal Bay (124 meters along shore) Pre- Sept 29, Oct 31,, Year 1, May 18, 2012 Site 3: Smiths Bay, Year 1, May 18, 2012 (no pre survey) Waterfront Restoration, LLC Ph: Page 3 of 18

Smith Bay- Site 1: In Smith Bay Site 1, flowering rush was found to exist, although in dramatically lower populations.

Some of the patches in low and medium depth waters were still found to contain some flowering rush, but the density of the invasive plant and the number of

The characteristics of flowering rush growth were most radically changed in Smith Bay in relation to the other test sites.

From Blue Water Science survey results, along with Waterfront Restoration, LLC observations and photographic comparisons, we estimate there has been a 95-98%

4 Smith Bay- Site 1: In Smith Bay Site 1, flowering rush was found to exist, although in dramatically lower populations. Many of the patches that were removed in no longer exist. Some of the patches in low and medium depth waters were still found to contain some flowering rush, but the density of the invasive plant and the number of stalks was much lower than what was documented in the fall of. It is now rare to find emergent plants at this site. The characteristics of flowering rush growth were most radically changed in Smith Bay in relation to the other test sites. Here, where many large, dense, and highly visible patches were found in, now only a few plants remain in the spring of From Blue Water Science survey results, along with Waterfront Restoration, LLC observations and photographic comparisons, we estimate there has been a 95-98% reduction in flowering rush at this site. Photos: In patches where pre-extraction flowering rush grew at a high-density of stems per square meter, growth has been reduced to 0 to 5 stems per square meter. This reduction is evident in the below photos, now showing bare sediment that was previously infested with FLR. Waterfront Restoration, LLC Ph: Page 4 of 18

Smith Bay- Site 3 At Smith Bay Site 3, flowering rush was found to exist, although in much lower

In the fall of six different patches of flowering rush were discovered and removed.

Where patches currently exist, the plants are more clustered than before.

5 Smith Bay- Site 3 At Smith Bay Site 3, flowering rush was found to exist, although in much lower concentrations than in. In the fall of six different patches of flowering rush were discovered and removed. In the spring of 2012 only three small patches were found with dramatically lower density, and stem counts per plant. The patches that are growing this year are roughly 1/2 to 1/3 of their original size last year. Where patches currently exist, the plants are more clustered than before. Last year the plants were evenly distributed in high density throughout an entire patch. From the observations and picture comparisons we estimate that there has been a 75-80% reduction in flowering rush at this site. Maxwell Channel Waterfront Restoration, LLC Ph: Page 5 of 18

6 In the Maxwell channel flowering rush was present in the spring of The species was found in relatively all of the areas previously documented in the fall of. It does not appear to have expanded outside of its prior location, however, patches are occurring in the same patterns and sizes as before. These results suggest a number of factors present in this site may contribute to lower efficacy of hand-removal in this instance. First, the cobble/gravel substrate presents removal challenges, as noted in the Completion Report: Flowering Rush Hand, Lake Minnetonka Pilot Program provided to the MCWD in December. Such substrate makes it difficult for technicians to be able to find, follow, and extract some portions of flowering rush rhizomes. This contrasts with Smith Bay, where soft, organic substrate enables one to feel all of a rhizome with one s hands, and thus follow and extract it completely. It is theorized that leaving a small portion of rhizome may allow the flowering rush to grow and re-establish quickly. Another factor that may be involved in the lower efficacy of removal in Maxwell channel is the timing of removal. In August and early September, all of the emergent and submerged growth of flowering rush was visible and healthy. At the time of the pre-extraction surveys by Blue Water Science, it is possible the species had begun to senesce. By the time removal had begun in October, it was evident a significant portion of the flowering rush had senesced or was beginning to do so. Many of the plants that were previously emergent were now submerged below the surface of the water. Many of the plants that were previously submersed were now lying weakened on the lake bottom. This made it more challenging to find all instances of flowering rush and to ascertain if a given submerged plant was flowering rush or a native species. The site was comprehensively searched and all plants discovered were carefully removed. However, it is likely a significant portion of the plants were not discovered because they had senesced. Further, where plants were discovered and rhizomes removed, it is likely some portion of the rhizomes were not able to be removed completely. Especially those rhizomes in the early stages of development and thus small, weak, and difficult to feel with one s hands. A third factor that may be involved in the lower efficacy of removal in Maxwell channel, is the warmer temperatures of drawdown-exposed sediments early this spring, and/or the water/sediment interface at shallow depths. This may have promoted root development, leaf sprouting and rapid growth of rhizome fragments in this channel. Warmer sediment and shallow water column temperatures may have also promoted regrowth from established rhizomes and lead to stand thickening. Strong wave action in the channel from persistent boat wakes may also deposits rhizome fragments along the shoreline. At the time these photos were taken many plant stalks were emergent (reaching above the water level). The stalks in some cases reached 3-6 inches above water level. It has also been reported Waterfront Restoration, LLC Ph: Page 6 of 18

that since the photos were taken (mid-may, one to three weeks prior to the writing of this report), the water level has risen significantly and there are no longer any emergent stalks.

Other plants that have taken root at the end of the channel on the sandy bottom, and may be as large as 2.5 feet tall.

7 that since the photos were taken (mid-may, one to three weeks prior to the writing of this report), the water level has risen significantly and there are no longer any emergent stalks. The flowering rush through the channel is currently seen in many different growth stages. Some plants buried in the rock are as little as a few inches tall. Other plants that have taken root at the end of the channel on the sandy bottom, and may be as large as 2.5 feet tall. From Blue Water Science survey results, along with Waterfront Restoration, LLC observations, and photographic comparisons, we estimate there has been a maximum of 5% reduction of flowering rush at this site. Photos: Underwater and above-water appearance of flowering rush in Maxwell Channel May Waterfront Restoration, LLC Ph: Page 7 of 18

8 Photos continued: Underwater and above-water appearance of flowering rush in Maxwell Channel, May 2012 Waterfront Restoration, LLC Ph: Page 8 of 18

9 Photos continued: Underwater and above-water appearance of flowering rush in Maxwell Channel, May 2012 Waterfront Restoration, LLC Ph: Page 9 of 18

10 Appendix EXHIBIT 1 Flowering rush Summary Tables (Steve McComas) Table 2. Summary of aquatic plant assessments. Numbers indicate the number of occurrences of the aquatic plant species along the transect parallel to the shoreline. Site 1: Heritage Lane, Smith Bay (415 meters along shore) Pre - Sept 29, Oct 31,, Year 1 May 18, 2012 Site 2: Maxwell Bay (176 meters along shore) Pre - Sept 29, Oct 31, May 18, 2012 Site 2A: Crystal Bay (124 meters along shore) Pre - Sept 29, Oct 31,, Year 1, May 18, 2012 Site 3: Smiths Bay, Year 1, May 18, 2012 (no pre survey) White lilies Bladderwort Bushy Chara Claspingleaf Coontail EG Elodea EWM Flatstem Floatingleaf Marsh marigold Naiads Narrowleaf NWM Sago Stringy Water celery Water stargrass Whitestem Waterfront Restoration, LLC Ph: Page 10 of 18

11 Table 3. Aquatic plant assessment of the flowering rush test sites prior to flowering rush removal. Survey conducted on September 29,. Site (GPS Coord) Depth White lilies Bladderwort Bushy Chara Claspingleaf Site 1: Heritage Lane, Smith Bay, Lake Minnetonka Coontail Plants Density for Unshaded Columns (scale 1-5) EG Elodea EWM Flatstem Floatingleaf Flowering rush individual stems flowering rush stems per site Marsh marigold NLPW NWM Sago Water celery stems Water stargrass bunch big patches 22 stems/ 0.1m 2 28 stems/ 0.1m 2 20 stems/ 0.1m 2 continues to , , light stems bunch small patch big patch starts 18 stems/ 0.1 m 2 22 stems/ 0.1 m 2 17 stems/ 0.1 m 2 continues to 400 (20 m) , continues patch ends several small patch Whitestem Waterfront Restoration, LLC Ph: Page 11 of 18

12 downed tree deep patch ends big patch out deep starts 2 1 patch in deeper water couple of patches in deep water patches in toward shore and slightly larger patch in deeper water 13 stems/ 0.1 m 2 25 stems/ 0.1 m 2 23 stems/ 0.1 m 2 patches patches patches in deep water , , big patch ends 2 1 several culvert is the end of area small small Total , Waterfront Restoration, LLC Ph: Page 12 of 18

13 Site 2: Maxwell Bay E N bunch Total Site 2A: Crystal Bay to the end of channel milfoil with density 1-3 to end of channel large patch in nearshore area , / 4, patch Total Waterfront Restoration, LLC Ph: Page 13 of 18

14 Table 4. Aquatic plant assessment of the flowering rush test sites after flowering rush removal. Survey on October 31,. Site (GPS Coord) Depth White lilies Bladderwort Claspingleaf Coontail Site 1: Heritage Lane, Smith Bay, Lake Minnetonka Elodea EWM Plants Density for Unshaded Columns (scale 1-5) Flatstem Floatingleaf flowering rush Marsh marigold Naiads NWM Sago dead downed tree deep patch ends big patch out deep starts big patch ends dead culvert is the end of area 575 not in treatment area Total Water celery Water stargrass Whitestem Waterfront Restoration, LLC Ph: Page 14 of 18

15 Site 2: Maxwell Bay E N E 030 N 250 E 600 N Total Site 2A: Crystal Bay E N E 884 N 064 E 944 N Total Waterfront Restoration, LLC Ph: Page 15 of 18

16 Table 5. Aquatic plant assessment of the flowering rush test sites one growing season after flowering rush was removed in October of. Survey was conducted on May 18, For flowering rush, 1 bunch = 4-8 stems/bunch. Site (GPS Coord) Depth Bushy Chara Claspingleaf Site 1: Heritage Lane, Smith Bay, Lake Minnetonka Coontail EG EWM Flatstem Plant Density for Unshaded Columns (scale 1-5) flowering rush flowering rush stems per site X X X X X X stems stems (4stems/0.1 m 2 ) bunch ft 1 bunch Marsh marigold Narrowleaf pondweed bunch X downed tree 2 X deep patch ends 2 1 bunch (3 feet) bunch big patch out deep starts 2 1 patch 1 m x 1 m bunch big patch ends NWM Sago Stringy pondweed Water celery Water stargrass Whitestem No Plants Waterfront Restoration, LLC Ph: Page 16 of 18

17 culvert is the end of area 575 not in treatment area Total Site 2: Maxwell Bay E N E N N X X X X E 600 N foot deep 25 1 long patch, linear along shoreline 43 milfoil stops at end 12 m x 4 m - 12 stems per 0.1 m 2 mouth of canal open to lake 2 X Total /4, Site 2A: Crystal Bay E N E 880 N 842 E 900 N 832 E 915 N 822 E 940 N 812 E 965 N 802 E 975 N 792 E 990 N X Total ,800 Waterfront Restoration, LLC Ph: Page 17 of 18

18 Site 3: Smiths Bay E N within 2 meters bunch E N within 1 patch 18 1 patch N E 587 N572 E 587 N 576 E 598 N Total Sample Number Table 6. Sediment data for six sites (2-3 feet of water depth) in the nearshore areas along the Smith Bay (Heritage Lane) site. Sediments collected on September 29,. Bulk Density (wt/8.51) Water ph Bray-P Olsen-P NH 4OAc- K LOI OM (%) Zn Fe Cu FL FL FL FL FL FL Mn Ca Mg Boron Pb Ni Cd Cr Fe/Mn Waterfront Restoration, LLC Ph: Page 18 of 18

Northeast Aquatic Research

Northeast Aquatic Research 74 Higgins Highway Mansfield Center, CT 06250 860-456 - 3179 Crystal Lake Association Ellington, CT 06029 March 6, 2013 RE: Aquatic Plant Mapping at Crystal Lake in 2012. Dear