The Phylum Bryozoa is one of the most diverse and common of the invertebrate animal phyla in the sea, and they can be common and conspicuous in fresh water environments, too. The reason that they are not more widely known is probably because people other than biologists commonly mistake them for corals, seaweeds, and sponges. 'Air fern', the so-called everlasting plant that supposedly absorbs from air all the moisture it needs to live, is commonly dried colonies of the bryozoan Bugula that have been artificially coloured.
All bryozoans are colonial, made of asexually proliferated units called zooids, which are generally much less than 1 mm in all directions. There can be millions of zooids within a single colony, which means that colonies can be immense, in some cases much more than a meter in height or width. They are most commonly noticed by non-biologists when they grow in inconvenient places, such as on the hulls of ships or in the intake pipes of water systems or cooling systems of power plants. Bryozoans have a wide variety of shapes, from thread-like growths attached to shells and rocks to elaborate erect bushes made of flattened branches, to simple free-living cones. On top of all this variation in form, the skeletons of bryozoans can be completely organic and therefore flexible, partially mineralized and still flexible, or completely mineralized and therefore rigid.
Within aqueous ecosystems, bryozoans are part of the bottom-dwelling animals that feed from small particles, usually cells of algae, in the water passing immediately above them. By their growth and production of fecal particles, they therefore transfer nutrients from water to the underlying sea floor, lakebed, or streambed. Feeding is done by the basic zooids of the colony. Each feeding zooid has small ciliated tentacles that radiate from around the mouth in a bell or cone shape, and they draw a stream of water from which they take small food particles.
Bryozoans are not as diverse or abundant in tropical regions as they are at mid-latitudes and in polar waters. But even in coral reefs they can be more abundant than they first appear, because they often grow on the undersurfaces of corals.
Bryozoans are fascinating animals that have an abundant fossil record stretching back over 400 million years. Knowledge about living bryozoans has been used to interpret the ecology and environments of ancient bryozoans, which has helped in unraveling many geological problems. The fossils themselves have been used to infer function from form and to illuminate basic patterns and processes of evolution that involve time scales too long for direct human observation.
Still, there are many known and still-unknown scientific questions to be addressed through the study of bryozoans. Bryozoans are aesthetically pleasing, especially when viewed through a microscope, which is another good reason to study them.
The International Bryozoology Association was established so that all who study living and fossil bryozoans can keep abreast of one another's research, and also to promote the study of bryozoans. Membership in the IBA is open to all with an interest in bryozoans, whether it be the use of bryozoans as research animals addressing biological or paleobiological questions or the study of the animals themselves to learn more about their distribution and diversity. We welcome new members and hope, if the animals interest you, that you will thoroughly explore this website, will join, attend the triennial meetings if possible, and contribute to our better understanding of the animals. This brief introductory statement is accompanied by a few illustrations by which you can get a better idea of what bryozoans are. All of the animals illustrated are from the northern Adriatic Sea and have been part of my research interests for the past several years.
Frank K. McKinney
President, IBA, 1998-2001
Last updated Thursday, 11 March 2004