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Vanvoorstia bennettiana

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Taxonomy [top]

Kingdom Phylum Class Order Family
PLANTAE RHODOPHYTA FLORIDEOPHYCEAE CERAMIALES DELESSERIACEAE

Scientific Name: Vanvoorstia bennettiana
Species Authority: (Harv.) Papenf.
Common Name(s):
English Bennett's Seaweed
Synonym(s):
Claudea bennettiana Harvey, 1859
Sonderia bennettiana (Harvey) Müller ex J.Agardh, 1890
Taxonomic Notes: The genus Vanvoorstia contains three species. Vanvoorstia spectabilis and V. coccinea are common tropical (Indo-Pacific, including GBR) species, with the former also recorded from Lord Howe Island. While some confusion exists as to the exact differences between these two species (Price and Scott 1992), both are easily distinguished and considered very different from V. bennettiana, a very much smaller- and finer-meshed species in which the tetrasporangial stichidia are also easily defined.

There are now four species. Eric Coppejans (pers. comm.) indicates that there is a new species he described from East Africa which is probably Critically Endangered: Vanvoorstia incipiens De Clerck, Wynne & Coppejans (Phycologia 38 (1999): 394-400). This newly described species occurs massively in a single (rather small) bay along the east coast of Zanzibar, at about low tide level (large amounts drifting or entangled to other seaweeds in intertidal pools). Coppejans carried out over 200 collecting excursions along the Kenyan, Tanzanian (incl. Zanzibar) coast and NEVER found a single specimen anywhere else than the type locality, where we find it again year after year. It doesn't occur in the neighbouring bays, which look "identical" to this one! If that bay would be disturbed (harbour, oil pollution, etc.) the only known (type) locality would disappear and we would have a similar story there within the same genus!! Apparently some representatives do not succeed in colonizing larger areas!

Assessment Information [top]

Red List Category & Criteria: Extinct ver 3.1
Year Published: 2003
Date Assessed: 2003-04-30
Annotations:
Needs updating
Assessor(s): Millar, A.J.K. (Royal Botanic Gardens Sydney, Australia)
Reviewer(s): Paxton, J. (Australian Museum) & Coppejans, E. (University of Gent, Belgium)
Justification:
The red alga Vanvoorstia bennettiana has only ever been collected from two sites (in the world). The initial discovery, the type locality, was from the seabed at the eastern end of Spectacle Island in Parramatta River sometime between the 1st and the 16th May in 1855. This site is now operated by the Royal Australian Navy as an explosives storage (barge), administrative offices and a mooring site for destroyers and other large Naval vessels. The shoreline has been altered and strengthened and the seabed is regularly dredged to allow ample draught for large ships. This site was first surveyed by myself and colleague Mr Peter Richards in December 1988. Since then, seven dives during all seasons up until 23 April 2001, have been undertaken at that site. No specimens have been discovered, and the only alga found there was a species of the genus Sargassum, that appears to tolerate low light, high nutrient, regularly disturbed conditions.

The only other site known to have harbored this species was on the seabed between Point Piper and Shark Island in Port Jackson (Sydney Harbour). This was collected by Dr Ramsay of the Australian Museum in October 1886. This site was also surveyed by myself and colleague Mr Peter Richards firstly in December 1988 then numerous times (approx 10) since. The seabed in this area now has no solid rocky substrata to which any seaweed could attach, the sediment is approximately 1 m thick (a divers arm disappears to the shoulder) and is easily stirred up by divers and passing ferry traffic. The surrounding rocky foreshore of both Point Piper and Shark Island have only small amounts of the kelp Ecklonia radiata and the green alga Caulerpa filiformis growing on them. Both are known to tolerate heavily disturbed conditions. No specimens of Vanvoorstia bennettiana have been discovered.

Within Parramatta River and Port Jackson proper, I have logged some 50 dives from 12 different sites, all of which have reasonable coverage of a few marine algal species typical of the NSW coastline. Based on knowledge of two other species in the genus Vanvoorstia, in addition to known growth strategies and environmental preferences of other genera and species of the red algal family Delesseriaceae, to which Vanvoorstia bennettiana belongs, such areas should harbor this species. In 1913, the then Curator of Algae at the Royal Botanic Gardens Sydney, Arthur Lucas, published a paper in the Proceedings of the Linnaean Society of NSW in which he states "I have never obtained it [Vanvoorstia bennettiana] either cast up or by dredging." He was an active collector of algae along the NSW coast up until his death in 1936. The next Curator of Algae was Ms Valerie May who was also an active collector until her retirement in 1988, when I took over the position. She was also unable to rediscover this species.

Since 1980, I have logged in excess of 540 dives along the NSW coast as part of a state government research priority to document the entire marine algal flora of the coast. Our collections have come from Cape Howe in the very south of the state, to Cook Island on the Queensland/NSW border, with approximately 100 sites scattered in between. The red algal species Vanvoorstia bennettiana has not been discovered during any of these dives.

Several colleagues of mine from the universities of Southern Cross, New England, NSW, Sydney, and Wollongong, plus the Solitary Island Underwater Research Group (SURG), and the operators of every commercial dive shop I have worked through in NSW, have all been briefed on the identification of this and several other rare species of marine algae. None has reported a sighting during the 12 years I have been based at the Royal Botanic Gardens Sydney. The genus is known to have an isomorphic alternation of generations. This means that the haploid male and female macrophytic gametophytes are morphologically identical to the diploid macrophytic tetrasporophytes which they ultimately produce. There is no crustose or resting stage in the life cycle of the species, which may have allowed it to lie dormant for many years until environmental conditions were favourable. In short, both life stages are susceptible to the same environmental parameters.

The Extinct category is used 'when there is no reasonable doubt that the last individual has died.' With negative data there can always be some doubt. And new species continue to be found in Australian marine waters, even in Sydney Harbour (J.R. Paxton in litt.). The presence of 15 individuals in one collection indicates that the species was relatively common in at least one portion of Sydney Harbour at that time. Given the isomorphic alternation of generations, it seems most unlikely that the species would remain in existence and remain undetected for more than 100 years. Therefore as no specimens have been seen or collected in the intervening 116 years, despite numerous collections made by algologists in that period, the species can be considered truly Extinct.

Geographic Range [top]

Range Description: First collected/discovered (1855) by crude dredging as a single individual plant from the east end of Spectacle Island, in the Parramatta River, Port Jackson, Sydney Harbour, New South Wales, Australia. Second and last collection (1886) by dredging of approximately 15 individual plants from between Shark Island and Point Piper, Port Jackson, Sydney Harbour, New South Wales, Australia (8 kilometres east of Spectacle Island). Presently unknown.
Countries:
Regionally extinct:
Australia (New South Wales)
FAO Marine Fishing Areas:
Regionally extinct:
Pacific – southwest
Range Map: Click here to open the map viewer and explore range.

Habitat and Ecology [top]

Habitat and Ecology: Unknown at time of collection in 1855 and 1886. The two sites, and much of Sydney Harbour, presently has soft sediment seabed with scattered rocky reef and rocky intertidal shores. Scattered shells and solid waste products (cans, bottles etc.) also lie on the seabed.
Systems: Marine

Threats [top]

Major Threat(s): Sydney Harbour is in the middle of the city of Sydney, the largest metropolis in Australia with more than 4 million people. In the 200+ years since settlement, the harbour has been seriously degraded by the population explosion. Use of the harbour as recreational facility, port, source of food, and sewer has seriously impacted on the native flora and fauna. Even by 1880, the harbour was found to be overfished by a Royal Commission. The Major Threats that may have caused the extinction of this alga include large and small scale fisheries particularly trawling, infrastructure development including industry, human settlement, tourism/recreation, water transport [including dredging for ship passage], fisheries- related bycatch by netting, and water pollution from agriculture, domestic, commercial/ industrial, oil, sedimentation, and sewage. The water quality of the harbour has improved since the 1972 passage of the New South Wales Clean Waters Act and the more recent removal of sewage outfalls some kilometers offshore. More fish species have moved to the upper estuarine portions of the Parramatta River and whales have returned to the outer harbour. However, for sessile species of limited distribution like Bennetts seaweed, swimming out of the harbour was not an option and the damage was done, permanently. As we do not even know in which decade the extinction occurred, we will never know which of the major threats was causative; a combination of a number of those listed is likely. [Threats information provided by J.R. Paxton in litt.].

Conservation Actions [top]

Conservation Actions: Listed as a "Species Presumed Extinct" in section 4 of Schedule 4 of the Fisheries Management Act 1994, in the state of New South Wales, Australia. Listed as "Extinct" under the Environment Protection and Biodiversity Conservation Act 1999, by the Commonwealth of Australia.

Citation: Millar, A.J.K. (Royal Botanic Gardens Sydney, Australia) 2003. Vanvoorstia bennettiana. The IUCN Red List of Threatened Species. Version 2014.3. <www.iucnredlist.org>. Downloaded on 18 December 2014.
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