HomeMy WebLinkAbout2024.08.13 - Report on macrophyte harvesting with photos August 13, 2024Red Lily Pond Project Association Inc.
Report Summarizing Cutting and Removal of Macrophytes
In Lake Elizabeth and Red Lily Pond
July 11, 12, 14, 15, and 16, 2024
Order of Conditions SE3-5862
Pursuant to Order of Conditions SE3-5862, issued on October 12, 2022, to the Red
Lily Pond Project Association, Inc. (“RLPPA”), 23 volunteers and one paid contractor
cut and removed an estimated 15 tons (more than 30,000 pounds) of vegetation
macrophytes), roots, and muck from Lake Elizabeth and Red Lily Pond over five days in
July 2024. The removal was performed under an Order of Conditions issued by the
Barnstable Conservation Commission in areas cleared with the Conservation
Commission Administrator and the Herring Warden in advance. Cutters, loaders,
transporters, and loaders working in the ponds and on the shore performed about 300
hours of labor.
This is the third annual campaign under the Order of Conditions. We will shortly
be seeking a three-year extension for the OOC because of the success of the campaigns:
substantial areas of Lake Elizabeth and Red Lily Pond have been cleared of choking
vegetation, improving habitat for wildlife (birds, mammals, and fish) and enabling much
better passage for kayaks and canoes. Although areas cleared of dense vegetation
generally revegetate in the following growing season, the growth is much less dense the
following year, and, where a benthic barrier has been installed, the lake surface has
remained clear, obviating the need to cut and clear vegetation in the same area. The Red
Lily Pond Project will be installing more benthic barriers this fall over some of the areas
where macrophytes were removed (we will provide the Conservation Commission and
the Herring Warden with advance notification of our plans), and is investigating
equipment (called a Water Bug) that would mechanize the cutting and gathering of the
macrophytes next year. We are also considering the use of herbicides, as discussed more
fully later in this submission.
More wildlife was encountered this year than in years past. A turtle was raised on
a cutting tool in Lake Elizabeth (it was unharmed), and we saw more than 20 fish nesting
sites, apparently for striped bass, and numerous eels in the water, as well as seeing a grey
heron, swans, a freshwater clam, and jumping fish. The onsite storage, launching, and
access areas were not disrupted by our operations.
This document will summarize the operation and the water quality conditions
based on samples collected before and after the operation.
1.Method of Cutting and Removal
The materials were cut and removed following the methods proposed to the
Conservation Commission and the Herring Warden on June 19, 2024, except that part of
the operation was postponed by a day due to weather conditions, and an extra day was
added to complete the operation.
a.Red Lily Pond
In past campaigns, the cutting of the macrophytes was primarily performed by
volunteers in waders, in the water, with a minimal amount of cutting performed from a
nonmotorized 15’ platform boat (the boat was pushed, rowed, or poled through the
water). In this year’s campaign, after notifying the Conservation Commission and
Herring Warden of our plans, we purchased and mounted a small propane-powered motor
on the stern of the same boat (a new 5hp Mercury) to push the boat slowly through
designated areas, with volunteers guiding and stabilizing the boat using the motor, long
poles and oars, and other volunteers using 28” Weed Cutters, pushing them forward to
cut vegetation, and then pulling them back. In the past, to collect the cuttings, individuals
either standing in the water or sitting on boards (usually paddle boards) collected the
cuttings out of the water with rakes or pitchforks, and placed the cuttings on other boards,
which were then towed by kayak back to shore, where the cuttings were placed on
tarpaulins. This year, while some of the cuttings were gathered by people on the boat or
in kayaks, most of the cuttings were gathered by two individuals standing or kneeling on
the mucky bottom and either gathering them into nets (two so-called “Deskuzzers” linked
here https://www.deskuzzer.com/), or collecting them and transferring them onto the boat
or onto kayaks. The cuttings were then towed to shore by kayak, where they were placed
on tarpaulins. After being permitted to dry for about ten days, the cuttings were
transported to the Barnstable Recycling Center, where they were deposited in the lawn
waste recycling area.
Composite drone photographs attached show the conditions before and after the
operation, with a red outline roughly around the area where clearing was conducted.
Although the Order of Conditions permits harvesting in up to 25% of the pond, we had
proposed to perform clearing operations in about 34,200 square feet in Red Lily Pond out
of about 202,000 square feet of lake surface area (about 17%). We ended up clearing
vegetation in about 14,100 square feet of the Red Lily Pond (about 7%). The materials
harvested were nearly all white water lilies and roots.
b.Lake Elizabeth
The same weed cutter tools were used in Lake Elizabeth by operators standing on
the relatively solid sandy bottom. We had proposed to perform clearing operations in
about 11% of the pond (approximately 27,000 square feet out of 245,000 square feet), but
we ended up clearing vegetation in only about 8% of the pond (approximately 18,500
square feet). Composite drone photos showing conditions before and after the operation
are included on the following pages. Vegetation removed was nearly entirely white and
yellow water lilies, but included some sedges and some swamp loosestrife that was
extending into shallow water from shore and creating nuisance conditions.
2.Names of participants in campaign (volunteers, except as noted)
Kathleen Caldera Steve Haig Roger Hansen
Stephen Carpenter (paid) Doug Farquhar Jim Lane
Dale Oates Greg Winkler Steve Brown
Tom Coyle Ed Deyton Jayden Beal
Pam Danforth Jack Kay Michael Lyons
Fran Lahey Barney Beal Georgeann Oates
Nelson “Ship” Orr Peter Caldera Sam Carpenter
Larry Owen Smith Cécile Mauré Dave (LNU, from Trade
Winds)
3.Pre- and Post-Operation Water Quality Monitoring
Water quality stations were established at two locations in each of Lake Elizabeth
and Red Lily Pond (Figure 1). RL-1 and LE-1 are in areas targeted for harvesting in any
given year while RL-2 and LE-2 are in areas where no harvesting occurred in the year of
monitoring. As the areas harvested are not identical in each year, the location of
monitoring stations shifts among years, and a harvested area one year may be monitored
as a non-harvested area in a subsequent year. A suite of water quality features was
measured in the field with a Hach Hydrolab DS5 multiprobe sonde with sensors for
depth, temperature, oxygen, pH, conductivity, turbidity, and chlorophyll-a, with the probe
array set roughly halfway between the surface and bottom at each site. Water samples
were collected roughly halfway between the surface and bottom of the pond at each
location as well, with most depths being <1 m (3.3 ft) and samples collected between 0.3
and 0.5 m below the surface.
Samples sent to Microbac Laboratories in Dayville, CT were analyzed for total
phosphorus, nitrate nitrogen, and total Kjeldahl nitrogen. The sum of nitrate nitrogen and
TKN equals total nitrogen. The water quality assessment was conducted before and after
each harvesting event, with sampling on October 7 and 28, 2022, June 29 and July 11,
2023, and June 28 and July 30, 2024. Secchi transparency readings were also made, but
the disk reached the bottom at all stations on all dates, negating any value to those
measurements.
Water quality data (Table 1) indicated few issues in 2022, with only elevated
nitrate nitrogen in Red Lily Pond raising any concern (shaded values in Table 1). Values
in excess 0.6 mg/L are considered high and values >1.0 mg/L are rarely natural and often
indicate wastewater or agricultural impacts, the former more likely in this case.
Phosphorus was low at all stations in 2022.
In 2023 the same nitrate nitrogen issue was again apparent and the phosphorus
concentrations were elevated in both ponds but not at all stations. Phosphorus values
higher than 20 ug/L often support algal blooms, although no blooms were observed in
either pond at any time. The difference between phosphorus in 2022 and 2023 is likely a
function of much greater rainfall and runoff generation during the monitoring period in
2023. The harvesting operation could release some phosphorus, but the pattern is not
indicative of that source. Rainfall was substantial between the two samplings in 2023 and
the increase in downstream Lake Elizabeth was characteristic of stormwater impacts.
Phosphorus was elevated prior to harvesting in 2024 at the same two stations
where it was elevated prior to harvesting in 2023, but all values after harvesting were
low. Nitrate nitrogen values were high at both Red Lily stations before harvesting but
only at RL-1 (harvested area) after harvesting. TKN was moderate at all stations in 2024,
but total nitrogen was elevated at the Red Lily stations on both sampling dates.
Table 1. Water quality results for Lake Elizabeth and Red Lily Pond
Oxygen was an issue in 2023. All oxygen values were acceptable during the June
sampling, but three values were slightly below the state standard of 5 mg/L during the
July sampling, with just the non-harvested Red Lily site having higher oxygen in July
2023. The harvesting could have stirred up enough organic material to cause some
oxygen demand, but the widespread nature of the low oxygen is more indicative of
weather pattern. The temperature rose substantially in less than 2 weeks and considerable
inputs from the watershed would be expected during the storms that occurred.
Additionally, the dense assemblage of plants, while adding oxygen by day, will respire
and remove oxygen by night, leading to oxygen fluctuations. Harvesting acted on only a
small area in each waterbody, while the weather and plants act on the entirety of both.
One oxygen value was below the state standard (4.9 at LE-2 before harvesting vs
standard of 5.0 mg/L) in 2024. Time of day of the measurements will also matter, with
earlier morning values likely to be lower after a night of no photosynthesis but continued
respiration. Later afternoon measurements are likely to be higher after a day of
photosynthesis and this pattern was evident in 2024 with early sampling before
Date Time Depth Temp DO DO Sp.Cond pH CHL a Turbidity Total PNitrateNTKN TotalN
Station MM.DD.YY HH:MM:SS meters °C mg/l %Sat µS/cm Units µg/l NTU ug/L mg/L mg/L mg/L
LE 1 10.07.22 15:00:50 0.3 17.2 7.9 86.6 299 6.9 2.2 1.2 10.6 0.26 0.32 0.59
LE 2 10.07.22 15:11:03 0.5 17.2 7.9 83.1 300 6.8 2.3 1.8 10.6 0.29 0.31 0.60
RL 1 10.07.22 15:46:25 0.4 17.4 7.9 83.4 276 6.1 6.1 1.1 13.8 1.13 0.56 1.69
RL 2 10.07.22 15:55:58 0.3 17.2 7.2 75.6 298 6.3 13.8 1.8 10.6 0.89 0.42 1.30
LE 1 10.28.22 13:23:20 0.3 15.2 6.8 68.2 227 6.7 3.0 2.3 10.6 0.31 0.42 0.73
LE 2 10.28.22 13:16:03 0.5 14.9 6.7 67.4 230 7.0 2.6 1.8 10.6 0.37 0.50 0.86
RL 1 10.28.22 13:36:05 0.4 13.8 8.4 82.0 242 6.4 3.1 2.3 10.6 1.82 0.30 2.12
RL 2 10.28.22 13:40:23 0.3 13.9 6.5 64.1 234 6.3 4.4 1.1 10.6 1.02 0.49 1.51
LE 1 06.29.23 11:54:13 0.5 23.9 6.6 79.8 287 6.7 11.6 3.3 18.1 0.15 0.34 0.49
LE 2 06.29.23 12:00:06 0.4 23.9 6.8 81.5 275 6.6 4.7 1.6 20.2 0.20 0.41 0.61
RL 1 06.29.23 12:47:27 0.4 22.4 7.3 85.3 236 5.8 4.5 0.9 22.3 0.76 0.64 1.40
RL 2 06.29.23 12:33:44 0.3 22.9 8.9 104.5 265 6.5 7.0 0.8 15.9 1.38 0.55 1.93
LE 1 07.11.23 10:00:34 0.3 26.0 3.7 47 282 6.5 4.0 3.8 30.8 0.05 0.64 0.69
LE 2 07.11.23 10:15:44 0.3 28.8 4.8 63 285 6.7 4.0 1.8 25.5 0.14 0.61 0.75
RL 1 07.11.23 11:02:00 0.3 23.1 4.2 50 300 5.9 1.9 2.9 17.0 0.96 0.39 1.35
RL 2 07.11.23 11:20:23 0.3 19.8 6.8 77 301 5.9 2.9 1.7 11.7 1.32 0.47 1.79
LE 1 06.28.24 7:10:30 0.3 22.2 7.3 88 314 6.5 3.2 0.9 14.9 0.15 0.38 0.53
LE 2 06.28.24 7:24:15 0.3 22.8 4.9 56 310 6.2 2.7 0.9 22.3 0.13 0.47 0.60
RL 1 06.28.24 8:15:23 0.3 20.6 7.2 80 294 6.3 21.5 1.1 23.4 1.01 0.39 1.40
RL 2 06.28.24 8:28:17 0.3 21.3 6.6 76 310 6.2 18.6 3.4 11.7 0.81 0.32 1.13
LE 1 07.30.24 16:47:28 0.3 29.0 7.6 99.6 231 6.9 2.0 1.0 10.6 0.05 0.37 0.42
LE 2 07.30.24 16:40:15 0.3 31.3 9.0 123.1 236 7.6 2.9 1.0 11.7 0.05 0.60 0.65
RL 1 07.30.24 17:14:58 0.3 28.1 7.4 96.5 234 6.4 1.4 0.5 10.6 1.11 0.49 1.60
RL 2 07.30.24 17:19:25 0.3 29.1 7.2 95.8 230 6.5 2.7 0.5 10.6 0.48 0.63 1.11
harvesting and late sampling after harvesting. Yet the oxygen values at all stations and
dates were not particularly low and the pattern does not represent an obvious threat to
pond ecology.
Other water quality data indicate mostly acidic pH and low to moderate levels of
conductivity and turbidity. Chlorophyll-a (an algal pigment) values were variable. Four
chlorophyll-a values were >10 ug/L, normally regarded as a threshold concentration, but
water clarity was high and no visible algae were observed in the water column other than
growths of filamentous greens in association with rooted plants. Elevated chlorophyll-a
values may have been related to fluorescence of dead organic matter and not actual
chlorophyll-a.
For the purposes of the harvesting program, sampling was intended to facilitate
pre- and post-harvesting water quality comparison and detection of any adverse impacts
of the harvesting program between harvested and unharvested areas. The small changes
in water quality variables before vs. after harvesting and between harvested and
unharvested areas were not ecologically significant and did not indicate any negative
influence of harvesting on water quality in either pond in autumn 2022. The lower
oxygen and higher phosphorus observed after harvesting in 2023 might be related to that
harvesting but are more likely a function of weather, including heat and storms with
inputs of runoff. The small areas harvested and limited disturbance by harvesting
activities would not be expected to be detectable on a pondwide basis. There was no
indication of any negative influence of harvesting on water quality in 2024, although
elevated nitrates in Red Lily Pond remains an issue independent of harvesting.
4.Pond Management Expert discussion of management options
Manual harvesting has been conducted three times so far, in October of 2022 and
July of 2023 and 2024. Considerable plant material was removed, yet both ponds still
have excessive vegetation over most of their areas. Shallowness prevents effective use of
a standard mechanical harvester and herbicides on a whole lake or repetitious basis may
be an option for the RLPPA. Continued manual effort may eventually open some areas
on a more sustained basis, but ongoing effort will be needed and may not be sustainable
with volunteers. Much has been learned by the group over the last three years and
operational efficiency has been enhanced; it just does not address as much area as would
be preferred and has been permitted.
Another option is the use of benthic barriers, sheet materials that cover the bottom
and both kill plants and prevent regrowth, and one area was covered in 2024 under a
modified Order of Conditions as an experiment (Figure 2). Large areas are not addressed
by this approach, but shoreline access points and travel lanes can be maintained. The
benthic barrier applied along the west shore of Lake Elizabeth just north of the dock area
is Lake Bottom Blanket, a thin but solid sheet material with vent holes to avoid gas
buildup. Panels were aligned linearly along shore to create a kayak/canoe lane and have
prevented significant plant growth where applied. Additional benthic barrier application
would make sense in other areas where access to open water through dense plant growths
is desired.
Figure 2. Benthic barrier zone on east side of Lake Elizabeth.
Use of herbicides does not have to be a lakewide or annual event. There are a
dozen active ingredients accepted for use in Massachusetts, subject to approval under the
Wetlands Protection Act and a License to Apply Chemicals (WM04) issued by the DEP.
Of those, herbicides with glyphosate are most appropriate for the many floating leaved
and emergent forms that create excessive plant density in Red Lily and Lake Elizabeth
e.g., Phragmites, swamp loosestrife, white and yellow water lilies, watershield), but will
not have any major impact on submergent forms (most pondweeds, spikerush,
filamentous algae).
Glyphosate herbicides are applied directly to plants, not dissolved in the water
column, and can be used in a delineated area to create open water channels. For use by
canoes and kayaks, control of the dense surface growths should be adequate. Glyphosate
is a systemic herbicide, affecting the whole plant, including roots, but not killing seeds or
other reproductive propagules (e.g., winter buds, turions). Treated areas of lilies should
not regrow to nuisance densities for several years. Use to control Phragmites is usually
the recommended approach to that invasive species. The cost per unit area is less than for
benthic barrier and less application and maintenance effort is needed. “Aquascaping”
parts of the pond with a glyphosate-based herbicide could be permitted within the
constraints already applied to the physical techniques. A separate permit from Barnstable
Conservation Commission than that covering the current physical control program would
likely be needed.
Getting consensus among both RLPPA members and town officials on the use of
herbicides will present challenges. Glyphosate has been implicated in human health
issues by association in the herbicide Round Up, but it is the additives in that terrestrial
formulation that represent the bigger threat and large agricultural programs are very
different than targeted aquatic applications. Glyphosate is routinely used on the Cape and
the nearby islands for Phragmites control. Occasional (i.e., every few years) use does not
represent a significant human or ecological health threat; registration in Massachusetts
would not be possible if it was. Getting nuisance vegetation under control with herbicides
is highly applicable in cases like Red Lily and Lake Elizabeth and would allow the
physical removal efforts to be more targeted and efficient in maintaining desired
conditions.
5.Long-term Management of Lake Elizabeth and Red Lily Pond
As noted above, excessive vegetation continues to exist over most of Lake
Elizabeth and Red Lily Pond. Shallowness prevents effective use of a large mechanical
harvester and, while there is concern about herbicides, RLPPA is discussing their use
with our lake management consultant. Continued manual effort may eventually open
some areas on a more sustained basis, but ongoing effort will be needed.
Aside from direct control of rooted plants, installation of the proposed pool and
boulder herring run to raise the water level in the pond would be desirable. The Town of
Barnstable has received a sizable federal grant to design and construct the new herring
run, and to enlarge the culverts that currently inhibit passage of herring. Deeper water
will inhibit some plant growth and provide more water volume to support aquatic life.
The ponds are very shallow and subject to dense plant growth over most of their area.
The lack of open water will limit some populations, notably river herring which may use
the pond as a nursery area.
6.Photographs
Photographs of some of the operations are included below.
Respectfully submitted,
Douglas B. Farquhar,
Vice President, Red Lily Pond Project Association, Inc.
Project supervisor
Input and review provided by Dr. Kenneth J. Wagner, Pond
Manager
Dated: August 13, 2024
COMPARISON OF LAKE ELIZABETH
BEFORE AND AFTER CUTTING AND REMOVAL OF MACROPHYTES
Photo on left is montage of June 2024 drone photos; on right is of photos taken on 7/18/24. Colored circles surround areas
where macrophyte cutting and removal was performed, with colors in photo on left matching areas in photo on right.
Before
After
Before
Before
AfterAfter
After
Before
Lake Elizabeth before
macrophyte cuttingoperation in
July 2024, and insets showing
areas cleared, before and after
operation
Tr adewinds dock
Causeway
The montage of drone photos on the
left shows Red Lily Pond in June 2024,
just before the July operations to cut
and remove macrophytes. The
montage on the right shows Red Lily
Pond after theoperation. On the left,
red outlines the areas where we
proposed to cut and remove the
macrophytes. On the right, we outline
in red the areas where the macrophytes
were harvested. Insets of these photos
are included on the next page to
provide a more detailed comparison.
Red Lily Pond
Before and After
Operations