Common Name 
Lacy Crust Bryozoan  

• Forms large, outward-growing, encrusting colonies which appear lacy or net-like
• Colonies are composed of individual zooids
• Zooids (< 1mm in size) are rectangular or box-shaped with short spines in each corner
• Each "box" is transparent on the top, so light still penetrates the blade of colonized seaweed
• For excellent pictures of a colony and individual zooids, please click here to see the Salem Sound Coastwatch ID card
• They filter feed by using a lophophore (feeding tentacles) 
• Pale grayish-white in color
• not to be confused with a native bryozoan, Electra pilosa, which has ovoid zooids surrounded by 4-12 spines including one larger central spine

 

 

Habitat 

Bryozoans typically live attached to firm substrates, such as the blades of kelp or other seaweeds, rocks, or the hulls of boats or docks. Bryozoans settle out of the water column as larvae, metamorphose, and then spread across and algal frond by budding off new zooids (asexual reproduction). Optimal growth is obtained in fast flowing water which provides food and oxygen. Colonies may vary in size, and several colonies may be found on a single blade of seaweed. The lacy crust bryozoan grows quickly, up to several millimeters per day. There are some natural predators of lacy crust bryozoans, and they include varying species of nudibranchs, or sea slugs.

 

Invasion History 

The lacy crust bryozoan has a native range in temperate waters of Europe and the Pacific coast of North America. This bryozoan was first introduced to the east coast of the North America in the Isles of Shoal in the Gulf of Maine in 1987. Since then lacy crust bryozoan has spread both north and south, and within three years of its introduction, this bryozoan became the dominant kelp epiphyte off the coasts of New Hampshire and Maine. It has also recently invaded Atlantic Canada. The introduction of lacy crust bryozoan to the eastern coast of North America was likely through ship fouling and ballast water.

 

Regional Sightings 

Lacy crust bryozoan has invaded Cape Breton!  This invasive bryozoan has traveled from Maine northward, up the eastern coast of Canada and has been recently detected in Nova Scotia and Cape Breton Island.  It may be difficult to detect lacy crust bryozoan since there are also several other species of native bryozoans to Cape Breton which may also grow on kelp.  However, these species do not have rectangular-shaped zooids nor do they exhibit such rapid growth patterns as lacy crust bryozoans.

 

Potential Impacts 

Under ideal growing conditions, lacy crust bryozoan can have long-term effects on subtidal ecosystems.  Kelp blades which are heavily encrusted by lacy crust bryozoan are susceptible to breakage, this is especially evident during storm events.  In some cases, outbreaks of lacy crust bryozoan can lead to the loss of entire kelp beds.  While kelp will eventually return to the area, in some cases in Nova Scotia, the affected area may become established with the non-native green algae known as oyster thief, also called dead man's fingers or Codium.  The establishment of Codium will then prevent the return of kelp to their former locations. 

 

• What is a bryozoan? - Details about Bryozoa from the Smithsonian Marine Station at Fort Pierce, Florida, USA
• Marine invasive species in Nova Scotia: Membranipora membranacea - website of Dr. Robert Scheibling, Dalhousie University, Nova Scotia
• Identification card for lacy crust bryozoan - from Salem Sound Coastwatch and the Massachusetts Executive Office of Environmental Affairs, Office of Coastal Zone Management
• Detailed information about Membranipora membranacea - A key to identifying marine invertebrates found at or near Rosario Beach Marine Laboratory (a campus of Walla Walla University, Washington, USA)