Bryozoans’ role in the ecosystem
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In the Northern Hemisphere, bryozoans are often described as a relatively unimportant, minor phylum. In this video, Associate Professor Abby Smith, from the University of Otago, talks about the very important role played by bryozoans here on the mid-continental shelf in New Zealand.
Point of interest
What types of animals might be affected if bryozoans are no longer able to make a shell and form structures on the mid-shelf?
ASSOC PROF ABBY SMITH
I think if you were to read an invertebrate zoology text book, you would discover that bryozoans – along with, say, brachiopods and a few of the worm classes – are among the minor phyla that are considered not to be particularly important, and partly that’s because these textbooks are written in the Northern Hemisphere, where bryozoans are very infrequently found, and when they are, they are teeny. But in New Zealand and Australia, out on the shelf, they can grow to be quite large and they can be quite important. The thickets that are on the shelf here and in Australia serve as important pieces of structure in a place that is often very flat and sandy. They let other animals live inside something. They do just what a coral reef does in more shallow water. They provide a location for biodiversity. And so particularly we think that, in New Zealand’s mid-shelf waters, that they are providing a nursery ground for fish and that the baby fish can hide somewhere, and it would be a bad idea to lose them. So bryozoans are important in a kind of ecosystem way. Experiments have shown that some corals, at least, if you lower the pH in which they live, they thrive just fine. They live, they grow, they reproduce – they just don’t make a skeleton. They turn into a jelly instead of a reef. Whether people want to go snorkel on coral jellies is an interesting question and we will have to see, but if the bryozoans do the same thing and collapse into non-mineralised colonies, it’s fine but the structure won’t be there any more. So the little fish and all the little echinoids and all the sea stars and everybody else that’s using this structure as a place for shelter or a food source or whatever, they won’t have it any more. So I think there is substantial impact to be had if bryozoans are lost on the mid-shelf.