First 1000 plants harvested 5/13/2001 half-fill recycle bin

Summary

Major milestones are falling fast.

No WC grew this year in Alewife Brook and Little Pond after removing all WC on two dates last year.  Little River and Perch Pond required only one harvest day this year, and numbers and weight were both reduced 90+ %.  Spy Pond and Yates Pond were harvested for the first time this year after scouting located the WC last year.  The last waterbody infested with WC in the Alewife Brook subwatershed should be permitted for harvests beginning next year.  This will be Blacks Nook – a pond on Fresh Pond Reservation.  Water Board, FreshPond Advisory Committee, and Conservation Commission permissions are all being pursued.

Blair Pond was entirely cleared of almost 32,000 WC plants which sprouted there this year.  Pulling began as early as plantlets could be recognized.  Under 800 pounds total was removed, compared to over six TONS last year when a later start allowed only 1/3 of the Pond to be cleared.  In 2000, Blair Pond was the likely source for fragments forming most of the second-pass harvest in Little River, Little Pond, Perch Pond, and Alewife Brook.

The next three maps summarize the locations of plants removed in the two Y2000 sweeps from the Mystic River to Little Pond; followed by the locations of all plants harvested in the Alewife Brook subwatershed in 2001.

Alewife Brook and Little Pond

Outside of Blair Pond, the largest patches of WC scouted in 1999 prior to harvesting in Y2K – were in lower Alewife Brook north of Broadway, and in the south corner of Little Pond.  Remarkably few plants were found in Y2K, and none appeared in 2001!  Natural variability must be playing a large role.  Hopefully, this will prove to be a permanent demise, but a watch must be maintained in case a bank of seed from earlier years should wait multiple years before finally sprouting.

Little River and Perch Pond

At Perch Pond, the Little River is joined by Wellington Brook.  This carries fragments from the Blair Pond infestation and from Blacks Nook in large rain events.  The second harvest in Y2K was composed largely of such fragments and the clustering near Wellington Brook points to the source.  With Blair Pond completely harvested in 2001, a second trip on Little River found NO additional plants this year.  At right is a picture of the 2001 complete harvest here.  It barely filled one corner of a recycling bin!  If Alewife Brook and Little River are indicative, there is a chance for zero plants here next year!

Spy Pond

Spy Pond was first harvested this year.  In Y2K a single patch of WC was found consisting of an estimated 200 plants.  These were tightly confined in one small area by profuse competition from other aquatic vegetation.  This year, Arlington had the pond treated with a variety of chemicals to reduce clogging of large areas in the pond by nuisance vegetation – largely coontail and fibrous algae, with a little Eurasian milfoil.  In May, 2001 over 700 WC plants were removed from this spot.  In June another 83 WC plants were removed – most from this spot, but the reduction in other vegetation had allowed about 20 fragments to spread far along the shoreline.  In July no further WC could be located.  Possibly the chemicals applied finally killed any remaining WC.  Below is a picture of the densest area just prior to harvesting.

Blair Pond

Y2K harvests here of maturing plants now seem a waste of time and efforts!  Six weeks’ full time effort only cleared the south 1/3 of the pond.  An estimated 10,000 plants weighed 12,000 pounds in July and early August!  This year, the worth of an attack early in the year was clear.  In twelve days of part-time effort the pond was totally cleared of over 30,000 plants weighing merely 700 pounds.  Harvesting early, the weight and volume totals are only 2% of mature plants!  A few seeds continue to sprout thru early June, and followup visits are required to re-harvest the few plants where harvesting left behind a root to re-grow.  Geese were identified as the source of numerous floating fragments due to feeding on succulent new tops while ripping the whole plant free to drift.  Nearly all plants pulled came intact with root and even the seed from which each sprouted! 

Little regrowth was found, and the complete harvest led to a non-existent second harvest at points usually beset by fragments downstream of here.  Growth areas and patterns point to Blair Pond as the original source infestation in the Mystic watershed, and eradication if successful here should be possible in other ponds thought lost to the weed.  At right is a picture showing a line of small plants this year before harvesting began.  It follows closely to the line where harvesting ended last year!  The clear area seen by the far shore was not totally empty of WC, but did show much improvement from Y2K.

Yates Pond

This project was expanded to include Yates Pond in 2001.  Extreme eutrophic vegetation has mostly held the infestation to one small area.  However, the high water temperatures generated in this pond resulted in some maturation and drop of a few seeds prior to and during the harvest.  This pond will be harvested earlier next year.  Photos of both years’ WC are available in an earlier monthly report.

Blacks Nook

Approximately the same size as Blair Pond, about 1/3 is covered by a WC infestation.  Luckily it is held partly in check by extreme growth of several other aquatic species.  Preliminary meetings are underway and hopefully harvesting can commence in May, 2002.  If Blair Pond quantities drop as sharply as quantities elsewhere after being harvested 100%; then Blacks Nook may generate ¾ of the total 2002 harvest in the Alewife Brook subwatershed.

Arlington Reservoir

The ‘Rez’ is not part of the Alewife Brook subwatershed, but feeds Mill Brook – which flows into Lower Mystic Lake.  In Y2K, the half in Arlington had WC mechanically harvested.  This year, the entire pond was mechanically harvested.  Some improvement of the Arlington half from the Y2K harvest may have occurred.  More important was the lowering of the water level over the winter, which left large portions of shallows where seeds were deposited to freeze and dry – both of which kill seeds.  A sharp edge to this years’ growth followed the low-water line.  If this WC could be eradicated, the Mystic River watershed might be in the unique position of having completely conquered WC within the watershed bounds.  I estimate this would take three years of initially intensive hand harvests in May and June.  Anyone got a scout troop with extra time???

Arlington DPW allowed the addition of all harvested plants from this year’s locations to the compost pile from Rez harvesting.  In return, I have harvested some WC missed by the machines.  Also, I am testing the viability of WC seeds which have been composted in their pile.  This fall, after less than two months’ composting time, a sample of 22 seeds from within their pile showed all in various stages of rot.  It seems that seeds on the inside rot quickly, and seeds in the outer layer of a pile dry out and die.  Further checking will be done, but I believe composting will reliably kill WC seeds in only 60-90 days. 

Mystic River, Medford

The last unchecked WC infestation I know of in the entire Mystic River watershed is along two miles of the Mystic River in Medford.  Locations of WC plants were mapped during Y2K & 2001.  Infestations are seen to move and intensify with no noticeable reasons.  Natural variability could help the eradication effort if begun next year.  In Y2K quantities appeared to require machine harvesting.  In 2001, only one large patch was found, and even it appeared suitable for hand harvesting!  Many of the WC are contiguous to or mingled with native white water-lily patches.  Possibly WC are losing space to this native species which sprouts leaves and claims surface area earlier than WC. At right is a photo of the densest WC patch seen this year on the Mystic River.

Observations

This year, I received permission from the Cambridge Conservation Commission to use a small hand rake to snag plants even during the herring run.  I had feared not finishing Blair Pond again, and wanted to have every possible advantage.  It turned out the rake could not catch on the tiny tops of young plants, so was not used at all.  However, I still followed my commitment to watch for and record any herring seen, and avoid disturbing them.  Carp and goldfish are the only long-term resident fish in the pond, because sewage frequently diminishes dissolved oxygen below critical levels for more sensitive fish.  However, on May 20^th, I saw 4 to 8 possible herring hanging motionless in a school with goldfish.  The shape was right for Alewives, but the only distinctive marking I saw was a dark spot just forward of each tail fin.  My only other guess is pickerel, but I am far from expert on fish ID.  The same day I sighted one minnow.  On May 25^th, I saw multiple 2” perch, and over 50 juvenile carp schooling.  On August 1^st, I saw 2 or 3 completely different types of fry schooling in the shallows.  My guess at the time was bass and perch, but now believe one type may have been herring fry headed downstream.  On August 14^th, several schools of probable herring fingerlings were seen in Alewife Brook at Mass. Ave, Mystic Parkway, Henderson Street, and downstream of Broadway for 200-300 yards.  One picture is below.

When surveying Mystic River WC infestations this year, I turned a few plants upside-down on the deck of my kayak to examine development.  After replacing the plants, I found several mosquito larvae which were apparently sheltering in the still water trapped near the center of each plant.  This adds a public-health argument to eradicating WC near populated areas with the advent of West Nile virus.

Acknowledgements

MANY people and groups have helped in many ways with this project:

All maps were generated from digital orthophotographs found at ortho.mit.edu .  MIT and MassGIS are responsible for this free resource.  MassGIS also distributes free GIS software from Trimble Corporation called “pathfinder office” which I have found invaluable.

Special kudos this year go to Betty Radwanski for assisting in the harvest at Spy Pond, and to Mark Shea for arranging my disposal site at Arlington Reservoir this year.

Thanks again this year to the Mystic River Watershed Association for putting all these reports on their website at tufts.edu/mystic , and to their webmaster Joshua Davis who makes HTML sense out of my documents.

A pictorial guide to WC growth and development should be done by year’s end.  This will include specific dates and variability noted so far for plant sprouting, maturation, and seed set/drop dates.

It is indeed a pleasure to work on a project which may accomplish its goals versus an invasive plant.

Sincerely,

Roger Frymire
Water Chestnut Project Manager for Mystic River Watershed Association

If I can help with any additional information, or if you have time next May to harvest on  the Mystic River; call, write or e-mail at:

617-492-0180
ramjet@alum.mit.edu
22 Fairmont Avenue
Cambridge 02139-4423