365 Urban Species. #260: Freshwater Bryozoan

[urbpan]

Photos by urbpan. A small colony attached to a stick is pulled out of the water to be examined. Location: Ward's Pond, Boston.

Urban species #260: Freshwater bryozoan Pectinatella magnifica

A football-sized clump of gelatinous material in a pond may not be an egg mass. You may encounter a colony of animals called bryozoans, or as that obsolete scientific name translates, "moss animals". Bryozoans make cockroaches look like spring chickens: their fossil record extends back 500 million years. The vast majority of the thousands of species in this group live in salt water, with only 50 or so found in fresh water. This one, Pectinatella magnifica (with no good common name but sometimes referred to as "blobs") is the one most often seen in urban waterways. I have seen it in Spectacle Pond at Mt. Auburn Cemetery in Cambridge Mass., and recently found it in Ward's Pond in Boston. It also apparently occurs in the waters of the Connecticut and Potomoc rivers. Bryozoans have a similar ecology to corals. Hundreds of thousands of individual animals (or "zooids" in zoological jargon) live together, secreting a jelly-like matrix, growing quickly in favorable conditions. Favorable conditions include water temperatures of 68 degrees or more (20 degrees or more celcius) and large amounts of food: single-celled algae, bacteria, and other microorganisms, conditions not uncommon in urban ponds in summer. Each zooid has tiny tentacles with which it grabs food particles. Rapidly growing bryozoan colonies are alarming to some people, and may create problems when they form on intake pipes and other structures. However, it seems that their presence and growth may potentially be a good indicator of water quality.




Found in Pleasure Bay, South Boston. Photos by cottonmanifesto.

Comments

Bryozoan in Florida Pond

[(Anonymous)]

I was researching this jelly-like mass, and its name. I ran across your site and thank you for the name and brief info you gave on the bryozoan. Would love more info if you have any. My pond is a spring fed pond with just the right temps. aparently. This bryozoan has multiplied tremendously in the last 2 years. It does not seem to affect the fish population from what i can tell. Honestly I would like it to disappear if you know what i mean. I have a hard time enjoying the sight of it. Thanks Wj

Re: Bryozoan in Florida Pond

[urbpan.livejournal.com]

Sorry, I don't really know any more than what I've written here. If it bothers you, you may want to look in to whether the pond is getting an excess of nutrients, from fertilizer runoff, Canada geese, or some other source.

It's a harmless colony of animals, if that makes you feel any better!