Commercial seaweeds in southern Africa: a review of utilization and research

Anderson, R. J.; Simons, R. H.; Jarman, N. G.

doi:10.2989/02577618909504568

Cited by 56 publications

(26 citation statements)

References 28 publications

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“…Since the 1950s, South Africa has benefited substantially from the export of Gracilaria gracilis that occurs naturally in Saldanha Bay (Anderson et al, 1989). However, the South African Gracilaria industry, which depends solely on the natural G. gracilis resource in Saldanha Bay, has experienced a number of setbacks in the last decade or so.…”

Section: Introductionmentioning

confidence: 99%

“…However, the South African Gracilaria industry, which depends solely on the natural G. gracilis resource in Saldanha Bay, has experienced a number of setbacks in the last decade or so. These setbacks were due to the major collapse experienced by the natural G. gracilis population in Saldanha Bay in 1989, a number of partial die-offs of raft-cultivated G. gracilis during the summer months in Saldanha Bay post-1989 and another substantial collapse of both natural and raft-cultivated G. gracilis during OctoberDecember 1996 (Anderson et al, 1989(Anderson et al, , 1992(Anderson et al, , 1999.…”

Section: Introductionmentioning

confidence: 99%

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Investigation of the role of a β(1–4) agarase produced by Pseudoalteromonas gracilis B9 in eliciting disease symptoms in the red alga Gracilaria gracilis

2003

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Gracilaria species are an important source of agar. The South African Gracilaria industry has experienced a number of setbacks over the last decade in the form of complete or partial die-offs of the agarophyte growing in Saldanha Bay, which may be attributed to bacterial infection. Since a positive correlation was observed between the presence of agarolytic epiphytes and bacterial pathogenicity, we investigated the role of an agarase in the virulence mechanism employed by a bacterium that elicits disease in Gracilaria gracilis. The recombinant plasmid pDA1, isolated from a Pseudoalteromonas gracilis B9 genomic library, was responsible for the agarolytic activity exhibited by Escherichia coli transformants when grown on solid medium. A blast search of the GenBank database showed that an 873 bp ORF (aagA) located on pDA1 had 85 % identity to the β-agarase (dagA) from Pseudoalteromonas atlantica ATCC 19262T (or IAM 12927T) at the amino acid level. AagA was purified from the extracellular medium of an E. coli transformant harbouring pDA1 by using a combination of gel filtration and ion-exchange chromatography. AagA has an M r of 30 000 on SDS-PAGE. TLC of the digestion products of AagA showed that the enzyme cleaves the β-(1,4) linkages of agarose to yield predominately neoagarotetraose. Western hybridization confirmed that the cloned agarase was in fact the extracellular β-agarase of P. gracilis B9. The observed relationship between disease symptoms of G. gracilis and the agarolytic phenotype of P. gracilis B9 was confirmed. Transmission electron microscope examination of cross sections of both healthy G. gracilis and G. gracilis infected with P. gracilis, revealed a weakening of the cell structure in the latter plants. Immunogold-labelled antibodies localized the agarase in situ to the cell walls of bleached G. gracilis. Thus, the weakening observed in the cell structure of G. gracilis infected with P. gracilis can be attributed to degradation of the mucilaginous component of the cell wall of the bleached thalli.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Investigation of the role of a β(1–4) agarase produced by Pseudoalteromonas gracilis B9 in eliciting disease symptoms in the red alga Gracilaria gracilis

2003

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“…Localities where they have been recorded on the west and south coasts include St Helena Bay, Olifants River mouth, Saldanha Bay, Langebaan Lagoon, Hout Bay, Keurbooms River mouth and Swartkops River mouth (Isaac 1956;Simons 1977;Stegenga et al 1997;Iyer et al 2004). In addition, Gracilariopsis funicularis Iyer, unavailable in Britain (Anderson et al 1989). Collection was mainly from beach-cast material (Anderson et al 1989;Rotmann 1990) while very small amounts were harvested from attached populations (Anderson et al 1989).…”

Section: Introductionmentioning

confidence: 99%

The gracilarioids in South Africa: long-term monitoring of a declining resource

Rothman¹,

Anderson

Boothroyd³

et al. 2008

J Appl Phycol

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In South Africa, gracilarioid red algae have been collected as wash-up to be dried and sold for agar extraction for at least 50 years. Despite much research, there is currently no commercial mariculture of the algae locally although this has been carried out in neighboring Namibia for a number of years. The industry is traditionally confined to Saldanha Bay on the west coast, although small wash-ups of Gracilariopsis longissima have been collected in nearby St Helena Bay. In Saldanha Bay, wash-ups of Gracilaria. gracilis have been very sporadic over the last few decades, with human alteration of the bay configuration possibly responsible for an initial major decline in 1974. This unpredictability in the amounts of wash-up has made the industry unstable and increasingly unprofitable. We compiled the results of previous surveys (some unpublished) of gracilariod populations in St Helena Bay and the Saldanha-Langebaan sytem, and re-surveyed these populations to examine long-term fluctuations. In Saldanha Bay and Langebaan Lagoon, standing stock of G. gracilis was estimated at 538 tons fresh weight and 71 tons fresh weight respectively. Less than 4 tons of gracilarioids are estimated to remain in St Helena Bay. We discuss the fluctuations in biomass and distribution of these South African gracilarioid populations.

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“…Anderson & Bolton, 1985;Anderson, Simons & Jarman, 1989). It is unlikely that any of our Gymnogongrus species are present in amounts that would be worth harvesting on a large scale.…”

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confidence: 99%