Complex habitat generated by marine bryozoans: a review of its distribution, structure, diversity, threats and conservation

Abstract

1. Habitat-forming bryozoans are here defined as extant, heavily-calcified species which regularly attain sizes over 50 mm in three-dimensions and which contribute significantly to benthic habitat structure as living colonies.2. Records of habitat-forming bryozoans were collated and mapped, together with information about the location, environment, habitat-forming species, the nature and size of the habitat formed, any associated fauna, and relevant threats and/or conservation measures.3. Records collated here indicated that habitat-forming bryozoans occurred from~59 N to 77 S, but that they did not occur frequently in the tropics, being found most commonly in temperate continental shelf environments, on stable substrata in places where water movement was relatively fast and consistent.4. Habitat-forming bryozoans are particularly abundant and diverse in New Zealand, where 27 species, a quarter of which are cyclostomes, provide habitat over hundreds of square kilometres of sea floor. Other areas where they are particularly rich and/or abundant include Antarctica (Weddell, Lazarev and Ross Seas), the North Pacific around Japan, the northern Mediterranean and Adriatic, and along the southern edge of the North Sea, through the English Channel and around the United Kingdom.5. Large bryozoans provide habitat for diverse associated assemblages, particularly for other bryozoans, molluscs, annelids, arthropods, cnidarians, sponges, echinoderms and macroalgae.6. Protected areas which include habitat-forming bryozoans occur throughout the distribution of this frequently unrecognized habitat type, but despite this they are prone to damage by anthropogenic impacts including pollution and bottom fishing.

Compositional Differences in the Habitat-Forming Bryozoan Communities of the Antarctic Shelf

“…However, bryozoan-rich communities (including sponges and soft corals) were found in imaging surveys of the George V Ice Shelf (Post et al, 2011). In general, habitat-forming bryozoan communities are more expansive in Antarctic regions than in other sites worldwide (Wood et al, 2012), albeit only a subset of the Antarctic regions accessible for remote imaging have been explored in detail.…”

“…The species compositional differences observed among Antarctic sites and depths are likely influenced by the spatial and temporal variability inherent in seasonal ice scour, carbonate chemistry, and primary productivity. How these specialized communities will respond to the combined forces of future global warming and ocean acidification remains an open question (although see Ashton et al, 2017), but considering the overall species diversity characteristic of habitat-forming bryozoan communities, these habitats should be protected ( Wood et al, 2012). Marine protection areas are designated in the Ross Sea and the sub-Antarctic Island of South Georgia (Hogg et al, 2018;Nyman, 2018), however surrounding Antarctic regions remain unprotected and, in particular, shelf communities of the eastern Weddell Sea should be given careful consideration.…”

“…Within these clades bryozoan species tend to converge on different kinds of encrusting and erect colonial forms that can make significant secondary structures or reef-like habitats. Although some habitat-forming bryozoan communities have been documented worldwide (Wood et al, 2012), little is known about the species assemblages that create these unique habitats and their importance to Antarctic shelf communities as a whole.…”

Reducing the data-deficiency of threatened European habitats: Spatial variation of sabellariid worm reefs and associated fauna in the Sicily Channel, Mediterranean Sea

“…Besides the most notable case represented by cnidarians, such as hermatypic corals (Sheppard et al, 2009), several other animal taxa have such an ability, including sponges (Bell et al, 2013), molluscs (Guti errez et al, 2003), polychaetes (Naylor and Viles, 2000) and bryozoans (Wood et al, 2012). Gregarious tube-dwelling worms of the Sabellaridae family (Annelida), such as for example Phragmatopoma californica in California and Gunnarea capensis in South Africa, can form, provided suitable environmental conditions, extensive reefs (Achary, 1974).…”

A new species of the cheilostome bryozoan Chiastosella in the Southern Ocean, past and present

“…Bryozoans comprise a phylum of benthic colonial invertebrates that are widely 46 distributed throughout the world's oceans (Hayward and Ryland 1999;Wood et et al 2012). …”