Live colonies are whitish pink in colour and roughly circular (5-7mm wide). Colonies are a single sheet of many connected, oval-shaped “cells.” These cells are filter feeding individuals, known as “zooids.” The appearance of these zooids varies, with some having many ribs (more common) to looking like a sieve with many pores. A colony can have a mix of both types.
Whitish pink colour and roughly circular (5-7mm wide). R- and I-type zooids appear ribbed. S-type zooids appear sieve-like
This species inhabits shallow waters and commonly encrusts eelgrass. It occasionally encrusts kelp and other brown seaweeds, such as knotted wrack. It grows best in areas sheltered from strong currents and waves.
The ribbed bryozoan adds to the fouling of eelgrass, which provides a habitat for shelter, reproduction and feeding for fish, molluscs, and crustaceans. The buildup of fouling organisms increases the chances of blade breakage and damage to the eelgrass habitat. The encrusting colonies also reduce light available for photosynthesis, and compete with native species for space.
This species was first reported in the southern Gulf of Maine in 2018. That same year, it was discovered in the Gulf of St. Lawrence (Prince Edward Island). It was discovered in Nova Scotia (Cape Breton) in 2020, and may be established throughout the Canadian Maritimes.
Ribbed bryozoan has been detected using environmental DNA throughout Nova Scotia, but physical specimens have been found in Cape Breton and Prince Edward Island.
Ensure boats and boating gear are regularly cleaned and inspected to prevent the movement of unwanted organisms. Avoid moving water between locations. Report any sightings to Fisheries and Oceans Canada