Northeast Aquatic Research

Transcription

1 Northeast Aquatic Research 74 Higgins Highway Mansfield Center, CT Crystal Lake Association Ellington, CT March 6, 2013 RE: Aquatic Plant Mapping at Crystal Lake in Dear Mr. Artz: On September 14, 2012 NEAR conducted a comprehensive aquatic plant survey of the shallow near-shore 0 to 5 feet--littoral zone of Crystal Lake. A second visit was made on October 8, 2012 to survey the lake between 5 and 18 feet of water depth. Survey Results: 1) No new invasive species were found during surveys in ) Variable-leaf milfoil (Figure 2), a. No milfoil was found in the center channel of the outlet cove between the sandbar and the dam. i. Some tiny plants were still present along the shore. b. No milfoil was found in the shallow water zone of the lake, that is no milfoil was detected between the shore and about five feet of water. i. Milfoil was still present in both coves, with larger, denser, beds in Aborn Cove. c. Several milfoil plants were found in deeper water, between 5 and 8 feet specifically in the southern area of the lake off-shore of the town beach (see Figure 2). This suggests that plants in Aborn Cove may be seeding the lake with new fragments that are taking root in the lake outside of the cove. 3) Large-leaf pondweed (Figure 3), a. Large-leaf pondweed was found only in the two coves. b. No large-leaf pondweed was found along the shoreline of the lake. c. Beds of large large-leaf pondweed identified during prior years surveys off-shore of the town beach were gone. 4) Red-leaf pondweed (Figure 4), a. Red-leaf pondweed was present off-shore and to the east and west of the mouth of Northeast Cove. b. No red-leaf pondweed was found in other areas of the lake. c. Red-leaf pondweed is present in both coves.

2 Crystal Lake Aquatic Plant Survey March ) The relative abundance, percent cover, and density of aquatic plant species so far observed in Crystal Lake are given in Table 1. Results of each of the 4 recent surveys are shown in the table. CAES is the Connecticut Agricultural Experiment Station. NEAR survey conducted in 2011 was a focused investigation of the coves and the outlet channel, not a comprehensive lake-wide assessment so many of the species were missed. There are 33 species that have been reported on at least 1 of the 4 surveys. However, only nine species were identified in Crystal Lake during a NEAR Survey in 2000 (shaded species in Table 1). Several robust aquatic plants have appeared in the lake since that time including large-leaf and red-leaf pondweed. Table 1 - Aquatic plant species observed in Crystal Lake Common name Percent *** = invasive non-native CAES NEAR * 2012 Sagatteria teres Variable-leaf Milfoil *** Floating Bladderwort 6 ~ 6 23 Red-leaf Pondweed Stonewort / Musk Grass ~ 17 ~ 15 Quillwort 1 16 ~ 14 Water Shield Water Weed 3 10 ~ ~ Spike-rush -submersed 9 9 ~ 2 Yellow Water lily 5 5 ~ 5 Large-leaf Pondweed ~ 4 ~ 6 Green filamentous algae ~ 3 ~ ~ Waterwort 7 3 ~ ~ Arrowhead -submersed ~ 2 ~ ~ Thread-leaved Pondweed ~ 2 ~ ~ Water-purslane ~ 2 ~ ~ Purple Bladderwort 2 2 ~ 9 White Water lily ~ 5 Great Duckweed 3 1 ~ 3 Aquatic Moss ~ 1 ~ ~ Coontail Bladderwort 4 1 ~ 3 Water Meal ~ 1 ~ ~ Duckweed 2 1 ~ ~ Pipewort Mudmat *** ~ 0.5 ~ 0.5 Water Lobelia ~ Floating Burreed ~ ~ ~ 5 Golden pert 3 ~ ~ ~ Brittle Naiad 1 ~ ~ ~ Robbins Pondweed 1.5 ~ ~ ~ Narrow-leaved Pondweed 3 ~ ~ ~ Northeast Aquatic Research 2

3 Crystal Lake Aquatic Plant Survey March ) Of the 33 species shown in Table 1 only about 8 are present at frequencies over 10%, the remainder are either restricted to the coves, or are present at only one or two specific sites in the lake. The chart in Figure 1 shows the same species to be dominant in the lake during the last several years with other species showing similar low occurrence frequencies that appear to be consistent over time. Figure 1 Frequency of occurrence of aquatic plant species in Crystal Lake 7) Recommendations for 2013: a. Focus milfoil removal efforts on residual deep-water plants. i. NEAR will conduct (at no charge) one early season survey probably late May 2013 to generate a new survey map showing locations of isolated plants in water between 5 and 20 feet of water depth, to aid in removal. b. Consider removal of milfoil in the Aborn Cove, and or, assess the likelihood that milfoil is transferred to the lake from Aborn Cove. c. Continue to observe the lake for new beds of large-leaf pondweed and remove as necessary. d. Continue to observe milfoil in the hot zones: the outlet channel and offshore of Northeast Cove, for regrowth and remove as necessary. e. Conduct a comprehensive lake-wide survey in the fall. f. Consider controlling milfoil in off-site ponds that feed to the lake. g. Communicate with CT Agricultural Experiment Station about their aquatic plant survey to be conducted in h. Continue to monitor the growth of red-leaf pondweed. Northeast Aquatic Research 3

4 Crystal Lake Aquatic Plant Survey March 2013 Figure 2 Locations of variable-leaf milfoil in Crystal Lake September 2012 Northeast Aquatic Research 4

5 Crystal Lake Aquatic Plant Survey March 2013 Figure 3 - Locations of large-leaf pondweed in Crystal Lake in September 2012 Northeast Aquatic Research 5

6 Crystal Lake Aquatic Plant Survey March 2013 Figure 4 Location of red-leaf pondweed in Crystal Lake in September 2012 Northeast Aquatic Research 6