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New Hampshire Department of Environmental Services

Ideas for a Cleaner Environment
Published monthly by the NH Department of Environmental Services Watershed Assistance Program, Concord, NH (603) 271-7889

August, 2007

Invading New Hampshire Waters

New Hampshire waters are being invaded by plants that are not welcome. The latest invasion, an invasive freshwater alga, "Didymosphenia geminata" also known as "rock snot" or "didymo," was recently found in Vermont and New Hampshire. For rivers and streams, didymo is a very scary alga. Forming extensive "blooms" on the bottoms of rocky river beds, didymo essentially smothers aquatic life forms such as aquatic insects, native algae, and other organisms.

Didymo is the most recent and alarming in a list of aquatic plant invasions in New Hampshire waters. If you spend time fishing, swimming, or boating in New Hampshire lakes or rivers, you might have noticed one or two species of invasive plants as a thick vegetation in the water that is difficult to boat through or turning your favorite pond into a swamp.

In New Hampshire waters, as transient boat registrations have increased over the last decade, the spread of aquatic invasive plants like Variable milfoil, fanwort, water chestnut, and Eurasian milfoil, to other uninfected waterbodies by boat traffic has increased. Over 60 New Hampshire waterbodies are now impacted by aquatic invasive plants. If accidentally introduced into a lake, they grow at explosive rates. When these plants grow without natural controls they encroach into and replace the native aquatic plants, disrupting the food chain, stunting fish growth, and degrading wildlife habitat and water quality. Water recreation activities are also impacted while property values on the water decrease.

New Hampshire is taking this invasion seriously. Rules implemented in 2004 state that "no person shall knowingly collect, transport, sell, distribute, propagate or transplant" any of the 34 plants on the New Hampshire Prohibited Invasive Species List. Included in this list are the 14 aquatic species that are regulated by the NH Department of Environmental Services’ (NHDES) Aquatics Program. Certain species of aquatic plants have been prohibited since 1999, and with the passage of new regulations in 2006, 29 exotic aquatic plants are now prohibited in New Hampshire.

Unfortunately, invasive plants are already here taking over by the minute. Other states are also faced with the problem, and no one has yet found a practical, environmentally sound means to eradicate these plants. Education, vigilance, and early detection are key components in keeping these invaders in check. You can help.

  • Verify that the plants you are buying for your yard, garden, water garden, and aquarium are not invasive. Replace invasive plants with non-invasive alternatives. Ask your local nursery staff for help in identifying invasive plants and for alternative plantings.
  • When boating, clean your boat, motors, trailers, vehicles, fishing lures, bait buckets, and any other equipment of all plant fragments. Dispose of all plants away from waterbodies.
  • Rinse your boat and equipment thoroughly before and after entering any waterbody. For possible didymo exposure, use HOT tap water and lots of soap: Scrub boats and other "hard" items thoroughly; Soak clothes, felt-sole waders and other "soft" items for 30 minutes!
  • Don’t release aquarium or water garden plants into the wild. Never put plants in a natural waterbody.
  • Learn more about invasive plant species so you can identify them and help educate others about the threat.
  • Volunteer to become a Weed Watcher. Visit the NHDES Web site to learn more about invasive aquatic plants. To volunteer to help monitor for invasives or to educate others about invasive species, contact the NHDES Exotic Species Program below.

For more information on aquatic invasive plants, visit the NHDES Exotic Species Program Web site or contact the program coordinator, Amy Smagula, at (603) 271-2248 or For information on the Invasive Species Committee or invasive terrestrial plants, visit the New Hampshire Department of Agriculture, Markets and Food Web site. To learn more about all invasive species, visit The Nature Conservancy Invasive Species Initiative. For information on invasive aquatic animals, visit the NH Fish and Game Web site.



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NH Department of Environmental Services | 29 Hazen Drive | PO Box 95 | Concord, NH 03302-0095
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