Systematics, biodiversity and zoogeography of bryozoans
Even though marine invertebrates such as polychaetes, hydroids, echinoderms, amphipods, decapods, nudibranchs, octocorals and ascidians have been given much attention, experts working on them are unanimous in their opinion that these taxa may be significantly more diverse than those documented. At the same time, other common groups such as nematodes, protists, porifera and bryozoans have been poorly studied in South Africa and the available literature on these taxa has become largely outdated and fragmented.
Bryozoans are sessile colonial animals, which may be found in most marine habitats. Many are small, often inconspicuous and easily overlooked. Bryozoans are potential indicators of environmental health, one of the top known groups of fouling organisms globally and a source of biomedical compounds.
The global bryozoan fauna is largely unknown. Furthermore, the oft-quoted figure of 4000 species appears to be unrealistic, as approximately 1000 new species of bryozoans were described in the second half of the twentieth century and the rate of discovery exhibits no signs of decreasing. The new level of taxonomic accuracy exhibited by modern day bryozoologists, the available technology (e.g., Scanning Electron Microscopy) and the increased number of unexamined habitats being examined, explain these leaps of discovery. The known South African bryozoan fauna constitutes approximately 269 species.
My current research thus aims to document the taxonomy, diversity and biogeography of South African Bryozoans. More specifically to investigate the:
- taxonomy of the South African shallow water bryozoan fauna.
- taxonomy of the South African deep water bryozoan fauna
- bryozoan fauna associated with pelagic plastics
- alien invasive bryozoan fauna associated with South African Ports
- current diversity and regional zoogeography of South African bryozoans
History of South African bryozoology
George Busk described, very superficially, specimens collected in South Africa by the HMS Challenger in the early 1800’s.
Charles O’Donoghue published five papers on South African Bryozoans and his main work investigated the collection from theSS Pickle which was commissioned by the South African Museum during 1920-1921. However, most of these species were described from the south and east coasts.
More recently Patricia Cook and Peter Hayward produced two reports for the South African Museum, based on east coast specimens collected by the Meiring Naude. In these reports an amazing number of 67 species were described as new accounting for 37% of all specimens. These authors go so far as to state that the few previous studies in this region have failed to reveal more than a fraction of its potential complexity.
There are also numerous other incidental records from South African waters, mainly collected by amateur naturalists.
Research on this group to date
Shallow water bryozoans
My PhD work on shallow water bryozoans collected during diving fieldtrips at various sampling localities along the west coast of South Africa (only accessible by 4X4), yielded 63 species of which 14 species were new to science.
Deep water bryozoans
During 1997-1999, De Beers Marine commissioned the Jago, a marine submersible for the collection of specimens to establish baseline benthic diversity data of their offshore mining areas. In excess of 20 collections of bryozoans and several hours of video footage were used to determine the preliminary diversity and distribution of bryozoans from the west coast of southern Africa.
Further deep water surveys are planned in collaboration with Marine and Coastal Management, the South African National Biodiversity Institute and various other organisations and universities, with the aim of establishing offshore Marine Protected Areas.
Aggregations of encrusting Bryozoa found on Flotsum (Plastics)
Bryozoans are well-known fouling organisms. They commonly foul the hulls of ships, the insides of seawater inlet pipes and are even found living epizooically on other organisms, eg., marine algae, sea turtles and even sea snakes to name but a few. It is their association with pelagic plastics that intrigues me most. This type of anthropogenic interference may have widespread zoogeographical implications, as increasing waste disposal due to population growth and urbanisation may result in increased bryozoan distributions. I was involved in a survey of bryozoans recorded from beach-cast plastics along the west coast of South Africa and hope to expand on this data set with the aid of a student in the future.
Alien invasive bryozoans
Unladen ships carry ballast water to ensure stability during long voyages. Water is taken on board, along with tiny marine organism, before the voyage begins. While loading their cargo at their port of destination the ballast water is pumped out along with the surviving "stowed" organisms. If these organisms are able to survive and flourish under the prevailing environmental conditions they may replace the indigenous species occurring there and may ultimately cause damage to the ecosystem.
Port Authorities are legally bound to monitor the extent of ballast water introductions of alien invasive species. I have participated in various port surveys in South Africa, linked to the Globallast Project, which aims to evaluate the global extent of these invasions. I was part of the sampling team for the South African pilot survey in Saldanha Bay. I also provided the taxonomic identifications of all the bryozoans for this survey and those from Richards Bay and Port Elizabeth. At least five species of bryozoans have been identified as possibly being introduced to South African waters via shipping. We are now branching out regionally into Africa and I am currently looking at the specimens collected from Mombasa, Kenya.
Diversity and biogeography of bryozoans
Although an impressive volume of literature exists on the diversity and biogeography of South African marine organisms, some faunas have remained neglected in this regard, e.g. bryozoans. Following a compilation of all South African records, a dedicated study of the shallow water (<30m) west coast fauna and an incidental study on some south coast bryozoans, by myself, the South African fauna is considered to comprise 269 valid species, representing three orders (Cyclostomata, Ctenostomata and Cheilostomata), 73 families, and 130 genera.
I have conducted a preliminary biogeographical analysis, but the data set is incomplete and using inferred species ranges reduces the quality of the analysis. I therefore plan to build the data set using the results of the projects listed above and by undertaking fieldtrips both locally and regionally throughout at least Sub-Saharan Africa.
Dr Wayne K. Florence
Curator: Marine Invertebrate Collections Natural History Department
Iziko South African Museum
Box 61, Cape Town 8000
Tel: +27 (0)21 481 3919
Fax: +27 (0)86 636 7156