Kelp Lace Bryozoan

Overview

The kelp lace bryozoan (Membranipora membranacea) is a colonial marine invertebrate that forms thin, white or light-gray, lacy encrustations on the surfaces of kelp and other algae. These colonies are composed of thousands of microscopic, box-like individuals called zooids, which work together to filter-feed and grow across their host substrate.

Appearance

Colonies typically begin as small, circular patches that expand outward, eventually forming extensive, flexible sheets that can cover large areas of algal fronds. Each individual zooid is rectangular and features a calcified frame with a flexible, uncalcified frontal membrane. While generally smooth, colonies may develop small tubercles or spines at the corners of the zooids, sometimes in response to the presence of predators like nudibranchs.

Distribution & habitat

This species is widely distributed throughout temperate waters in both the Atlantic and Pacific Oceans. It is commonly found in shallow, subtidal environments, particularly on the blades of large kelps such as Laminaria and Macrocystis. It thrives in areas with fast-flowing water, which helps deliver the plankton necessary for its growth, and can occasionally be found on other firm surfaces like rocks, buoys, or boat hulls.

Biology & behavior

Membranipora membranacea is a fast-growing organism, capable of expanding its colony by several millimeters per day. It reproduces both asexually, through the budding of new zooids, and sexually, by releasing eggs into the water column. These eggs develop into planktonic, triangular-shaped larvae known as cyphonautes, which drift in the ocean before settling on a suitable substrate to begin a new colony. In some regions, this bryozoan is considered an invasive species, as heavy encrustation can make kelp blades brittle and prone to breaking during storms.