Have you ever spotted a lacy mesh-like growth on seaweed whilst rockpooling and wondered what it was? These patches are called sea mats and can cover huge sections of the fronds of kelp and seaweed on rocky shores. Sea mats are a colony of individual animals called zooids. If you look closely, you'll see what look a bit like cells - these individual little boxes are each home to one zooid. The zooids filter feed on phytoplankton using special feeding tentacles called a lophophore. They can reproduce asexually to increase the size of the colony - which can grow by several millimetres a day! The name for these colonies is "Bryozoan", a large and diverse array of colonial creatures known as Sea Mosses.
How to identify
A lacy mesh-like growth found on the fronds of seaweeds on the rocky shore, mainly on oarweed (kelp) and on serrated wrack. There are 2 main species of sea mat on UK rocky shores, you can tell them apart by the shape of the zooid boxes. Membranipora membranacea has rectangular boxes whilst Electra pilosa has oval boxes and tall spines giving it a hairy appearance.
Distribution
Found around all UK coasts.
Did you know?
Sea mats are a favourite food of nudibranchs. Look closely and you might well find one of these colourful little sea slugs munching away.
