CalcZooidW_closeupBrenda Fisch of Brady Road started noticing large groups of jelly-like creatures living on the side of her dock this summer. Thinking they might be cluster of frog eggs, she pulled one out with a net and examined it. Googling: “What are the strange slimy blobs attached to my dock?”, Brenda came up with an answer.
“Lake residents occasionally find blobs of jelly-like material attached to their dock, reeled in on a hook or washed up on shore in the summer. The strange slimy mass, that may range from clear to green or yellow to dark brown is actually a harmless colony called a bryozoan. The mass may attain the size of a basketball. The colony will not sting. Bryozoans are found in ponds, lakes and slow streams and attach themselves to vegetation or the undersides of logs and docks to avoid strong sunlight. They generally cannot survive in polluted or muddy waters. The colony starts in spring as a single microscopic individual, but grows by budding throughout the summer to attain a larger size by late summer. The ball is made of thousands of individuals that strain tiny plants and animals from the water.” (from the Fish & Wildlife website)

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Brenda Fisch pulling a bryozoan colony up from the sea wall.                         A bryozoan colony attached to one of the dock lines.

Bryozoan_webPhoto by Brenda Fisch
“Colonies of bryozoans have lived in the lake for years”, according to Paul Cooper, senior environmental scientist at Princeton Hydro, a consulting firm that works with the Lake Hopatcong Commisssion helping to monitor water quality. “They are just a part of the natural ecology of the lake, and because they don’t have a high tolerance for pollution, if they are spreading it may be a good sign.”
For those of you living near the canals or on the smaller coves on Lake Hopatcong, bryozoans your dock are nothing to worry about. They are harmless, definitely don’t sting like a jellyfish and can actually be beneficial to the lake. Paul Cooper, indicates “You should probably leave them be, but it is OK to remove them if they are perceived as a nuisance.”
From the New Hampshire Department of Environmental Services fact sheet: “A large colony can filter a significant amount of water in a day. This can be very good for a lake with too much algal growth.You should consider yourself lucky if you find bryozoans in your lake. Not only are they unique and one of nature's oldest animals, they may actually be beneficial by helping to clean the water of the lake."


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