OpenUCT :: Browsing by Author "Anderson, Robert J"

Browsing by Author "Anderson, Robert J"

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Open Access
An analysis of subtidal seaweed communities on a depth gradient at Sodwana Bay, on the KwaZulu-Natal coast, South Africa
(2002) McKune, Craig; Bolton, John J; Anderson, Robert J
The subtidal seaweed communities of the KwaZulu-Natal coast are poorly understood. A recent collaborative research project between Belgian and South African phycologists, however, is currently investigating the diversity and biogeographical affinities of the marine benthic algal flora of this region. The newest leg of the project is focusing on correlating biogeographic patterns with abiotic factors in the area between the St. Lucia estuary and Sodwana Bay, where it has become evident that there is a huge turnover in species composition. The present study examines seaweed community change along a depth gradient (1-30 m depth) at Sodwana Bay on the KwaZulu-Natal (KZN) coast, South Africa. All seaweed cover within 25 x 25 cm quadrats was collected, identified and weighed. The environmental variables, depth and % sand cover, were also measured. Both biomass and presence/absence data were ordinated to show community differentiation related to the environmental variables. The seaweed communities are largely red turfs, with a total of 82 Rhodophyte, 14 Chlorophyte, and 8 Phaeophyte taxa recorded. These turf communities showed exceptional diversity with 105 taxa (>25 % of recorded KZN flora) occurring in the total sample area of 1.56m². Seaweed communities clearly change with depth, but the biggest change occurs between the shallow subtidal zone (approx 1 m depth) and deeper waters (>5 m depth), mostly likely due to the effects of wave action; thereafter communities do change with depth, but the effects are less pronounced. Biomass (p=0.049, significant) and seaweed diversity (p=0.078, not significant) were both shown to decrease, and % bare (seaweed-free) cover (p=0.002, significant) increased, with increasing depth. It is likely that these changes with increased depth can be attributed to the effects of increased light attenuation on ecological functioning in the subtidal communities. Sand inundation patterns are shown to be important in determining seaweed community structure, but do not appear to be predictable along a depth gradient (p=0.544, not significant).
Open Access
Can the pathway of abalone aquaculture effluent be traced using carbon and nitrogen stable isotope analysis of kelp Ecklonia maxima and mussels Mytilus galloprovincialis?
(2007) Thomas, Alicia; Bolton, John J; Anderson, Robert J; February, Edmund C
Abalone farms are becoming more common along the coast of South Africa. The effects these farms are having on the coastal habitats they occupy are becoming of increasing concern due to the possible negative effects of the effluent discharged from the farm. This study was conducted along the coast of Jacobsbaai (32°58'22.09" Sand 17°53'10.56" E) and Mauritzbaai (32°58'50.75"S and 17°52'59.44"E) near Saldanha on the South African west coast, situated approximately 120 Km from Cape Town. The aim of this study is to determine if the outflow of effluent from the Jacobsbaai Sea Products (pty) Ltd, abalone farm in Jacobsbaai can be traced using stable carbon and nitrogen isotopes. Kelp (Ecklonia maxima) and blue mussels (Mytilus galloprovincialis) along the coast near the farm (in Jacobsbaai) were collected from 8 sites and used as tracers of the farms effluent. A ninth site was sample in another bay (Mauritzbaai) which functioned as our control. We hypothesised that if the kelp and mussels are taking up the nitrogen and carbon from the farm, the amount of nitrogen and carbon taken up would decrease with decreasing distance from the effluent outfall. Using this we could map the geographic distribution of the abalone effluent alone the coast to measure the extent of eutrophication due to abalone effluent. Our results suggest that the effluent from the farm is having a localized effect on both Ecklonia maxima and Mytilus galloprovincialis.
Open Access
A coastal seawater temperature dataset for biogeographical studies: large biases between in situ and remotely-sensed data sets around the Coast of South Africa
(Public Library of Science, 2013) Smit, Albertus J; Roberts, Michael; Anderson, Robert J; Dufois, Francois; Dudley, Sheldon F J; Bornman, Thomas G; Olbers, Jennifer; Bolton, John J
Gridded SST products developed particularly for offshore regions are increasingly being applied close to the coast for biogeographical applications. The purpose of this paper is to demonstrate the dangers of doing so through a comparison of reprocessed MODIS Terra and Pathfinder v5.2 SSTs, both at 4 km resolution, with instrumental in situ temperatures taken within 400 m from the coast. We report large biases of up to +6°C in places between satellite-derived and in situ climatological temperatures for 87 sites spanning the entire ca . 2 700 km of the South African coastline. Although biases are predominantly warm (i.e. the satellite SSTs being higher), smaller or even cold biases also appear in places, especially along the southern and western coasts of the country. We also demonstrate the presence of gradients in temperature biases along shore-normal transects -- generally SSTs extracted close to the shore demonstrate a smaller bias with respect to the in situ temperatures. Contributing towards the magnitude of the biases are factors such as SST data source, proximity to the shore, the presence/absence of upwelling cells or coastal embayments. Despite the generally large biases, from a biogeographical perspective, species distribution retains a correlative relationship with underlying spatial patterns in SST, but in order to arrive at a causal understanding of the determinants of biogeographical patterns we suggest that in shallow, inshore marine habitats, temperature is best measured directly.
Open Access
Distribution and biomass of epiphytic seaweeds on the kelp Ecklonia maxima (Osbeck) Papenfuss, and the potential effects of two kelp-harvesting methods in the Western Cape
(2001) Drummond, Hazel; Anderson, Robert J
The demand for freshly harvested kelp, Ecklonia maxima, in the Western Cape, has greatly increased due to the need for fodder to supply the growing abalone industry. There is evidence suggesting that the present demand may exceed the amount of E. maxima available, if the traditional method of harvesting continues (cutting the whole kelp plant off, just above the holdfast). There is also evidence that, although the kelp beds recover in 2 - 3 years, and are ready for the next harvesting event, the epiphytic seaweed populations have not recovered even 5 years after harvesting. A new method of harvesting has been proposed, where the secondary blades of the E. maxima are cut 30cm from the primary blade. This method would increase the amount of kelp that can be harvested sustainably. This study investigated whether this new method of harvesting would have less impact on the epiphytic seaweed populations, particularly the three obligate epiphyte species; Carpoblepharis flaccida, Polysiphonia virgata and Suhria vittata, and whether there is pattern of distribution of epiphyte populations around the Cape Peninsula. The distribution of the epiphytes on the different portions (stipe; primary blade and first 30cm of secondary blades; rest of the secondary blades) of kelp was investigated. E.maxima was sampled at five sites around the Cape Peninsula, and the epiphytes on each portion were identified and weighed. All the epiphytes except Carpoblepharis flaccida were found predominantly on the portion of kelp that would be left after the new method of harvesting, and would therefore be unaffected. It was found that the mass of C.flaccida removed in the new method was not significantly different from the mass remaining; therefore a large proportion is left untouched. There was no geographic pattern of distribution of C.flaccida in relation to water temperature around the Cape Peninsula. The results suggest that this new method of harvesting would have little impact on the epiphyte populations, which is an added incentive for changing the method of harvesting.
Open Access
Friend or foe? : the invasive potential and aquacultural application of the sporophytic Falkenbergia stage of Asparagopsis armata in South Africa
(2004) Duncan, John A; Bolton, John J; Anderson, Robert J
The presence of the sporophytic 'Falkenbergia rufolanosa' phase of the invasive algal species Asparagopsis armata was first recorded in South Africa 57 years ago. The introduction of this highly invasive alga, of Australian/New Zealand origins, to Europe in the 1920's has since led to a number of recorded invasions by the gametophytic Asparagopsis phase in both the Mediterranean and Atlantic oceans. Recently however, a number of commercial uses for both phases of A. armata have been identified, which have given rise to industrial interest in the species as a candidate for commercial cultivation. Previous studies on European strains of F. rufolanosa and A. armata have identified a number of life history traits, which not only increase A. armata 's invasive ability, but also make it a useful species for commercial tank cultivation. However, different strains are known to have different environmental parameters which regulate their survival, growth and reproduction capabilities. This study investigated the growth of the South African strain of F. rufolanosa in culture, in response to different environmental variables, as well as the conditions necessary for tetrasporogenesis to occur, in order to assess its potential impacts, both as an invasive threat and as a species for commercial cultivation in South Africa.
Open Access
Measuring the growth of the articulated coralline red algae Corrallina officinalis and Arthrocardia corymbosa, (Corallinaceae, Rhodophyta) using a fluorescent brightener
(2010) Soutschka, Nadine; Anderson, Robert J; Bolton, John J
Coralline algae are important components of the coastal marine ecosystem, making it crucial to understand influences on their production and their growth rate in general. A few attempts have been made to quantify coralline growth rate using various methods, however since they have been reported to be slow growers it is difficult to quantify their growth rate accurately. Calcofluor white is an optical brightener that can be used to stain cell walls of plants and has been used to stain articulated corallines in the field, which proved to be a useful and accurate method for measuring coralline growth rate. This study tested the use of Calcofluor white for measuring growth of articulated (geniculate) coralline algae found on the south-west coast of South Africa, and made a series of methodological tests on the use of the stain. The growth rate of Corallina officinalis and Arthrocardia corymbosa were compared by growing them in culture in aerated plastic bags at 15°C and 16 hr light:8hr dark. Only C. officinalis produced measurable growth in culture (0.08-0.09 mm day⁻¹). Further tests were carried out only on C. officina/is. Additionally, an attempt was made to stain C. officinalis in a rock pool, in situ. In culture, the exposure time to the dye was tested for effect on growth rate. Growth rates were similar after 8 days, but after 20 and 28 days thalli stained for 15 min grew significantly slower than those stained for 5 or 30 min. However, this effect seems to be caused by factors other than staining time (e.g. light or water movement in the culture bags). Growth in culture of C. officinalis was strongly effected by salinity: at 60% saltwater (±21 ppt) growth fell to 0.03 mm day⁻¹ , and there was no growth in 30% saltwater (±10 ppt). The effects of 3 preservation methods on staining in C. officinalis were also tested. The stain was unaffected by drying the thalli or preserving them in 5% formalin in seawater. Preservation in 70% alcohol/20% glycerol/IO% freshwater (a common method of preserving coralline for DNA analysis) reduced stain visibility, particularly when thalli had only been stained for 5 min. The study confirms that Calcofluor white is an effective fluorescent dye for staining coralline red algae. Furthermore, staining can be as short as 5 min and thalli can be preserved without affecting the stain, so that thalli can be stained in situ, preserved, and brought to the laboratory for measurement.
Open Access
Molecular systematics of the genus Hypnea (Rhodophyta) in South Africa, with the description of a new genus, Tenebris (Cystocloniaceae, Rhodophyta)
(2018) Johnson, Victoria Jane; Bolton, John J; Anderson, Robert J; Mattio, Lydiane
Hypnea, an economically important genus of red algae (containing κ-carrageenan) found globally on tropical and subtropical shores, is shrouded in taxonomic confusion due to morphological plasticity of species and general lack of clear morphological characters. Of 113 species described worldwide only half of that number is accepted taxonomically. Of the 11-recorded species in South Africa there are currently 8 recognised (Hypnea arenaria, H. ecklonii, H. intricata, H. musciformis, H. rosea, H. spicifera, H. tenuis and H. viridis). Some of these species are difficult to tell apart and appear to differ only in dimensions, which overlap in some species. In addition, some entities do not fit the descriptions currently in existence for these species and some have not been recorded since description. This study aimed to use morphological and molecular techniques to re-examine as many South African Hypnea entities as possible, in order to improve the taxonomic understanding of this group. Collections were done along the coast of South Africa, Mozambique, Madagascar and Europa Island. Samples were pressed as herbarium specimens, preserved in 5% formalin in sea water for morphological and anatomical analysis, and dried in silica gel for sequencing. DNA was extracted from dried samples and mitochondrial (cox1) and plastid (rbcL) DNA sequences were obtained. Sequences were assembled, aligned by eye, and analysed using maximum likelihood, Bayesian analyses, and genetic distance (GD) matrices for molecular analysis. Specimens were sectioned and photographed for morphological analysis. The results uncovered different organisation of the Hypnea genus than previously recorded. Specimens which fitted the description of Hypnea rosea were found to form a complex containing two molecularly distinct morphotypes (1,7% GD in rbcL; 6,8% GD cox1) with a link to H. cervicornis. Hypnea viridis is shown to be closely linked to the tropical Hypnea pannosa (1,7% GD in rbcL), Hypnea spicifera, although very morphologically variable, was found to comprise one species. There is a clade which could represent Hypnea cf. intricata - a species with a very brief type description that matches with the morphology of these specimens. Hypnea musciformis does not exist here, because none of the specimens that fitted the South African description were even closely linked to H. musciformis from close to the type locality (Trieste, Italy). They came out in the H. rosea clades and the H. cf. intricata clade. Hypnea ecklonii could not be recognised among any of the specimens that were studied. There are two new records of Hypnea cf. pannosa and Hypnea cf. cervicornis for South Africa. All of the specimens that fitted the descriptions of H. tenuis were molecularly unrelated to any of the Hypnea species for which DNA sequences were available (rbcL GD >11%). However, they fit in the Cystocloniaceae with their closest relatives being Calliblepharis ciliata, Hypnea viridis and Hypnea pannosa (rbcL GD >8%). These GD values are large enough that these two species form a separate genus. Therefore, I describe a new genus of Cystocloniaceae, Tenebris V. Johnson, J. Bolton, L. Mattio, R. Anderson gen. nov. This appears morphologically very similar to Hypnea, but differs molecularly. The morphological differences include size ratio of central filament to periaxial cells - where present, Hypnea central cells are significantly smaller than pericentral cells while Tenebris pericentral cells are similar in size to the central filament. Tenebris spp. are also much smaller than the Hypnea spp. Hypnea tenuis Kylin is re-assigned to Tenebris tenuis (Kylin) V Johnson, JJ Bolton, L Mattio, RJ Anderson comb. nov. The second species is based on only one specimen, and although it is somewhat similar to the type description of Hypnea arenaria, without more evidence, it is provisionally named Tenebris sp. In total, there are 13 molecular clades of South African sequences in this study: 7 Hypnea clades identified to species level, 2 unidentified Hypnea which cluster with no other Hypnea species, 2 unidentified and distinct sequences which are not Hypnea, and 2 species assigned to a new genus Tenebris. In conclusion, the 7 South African Hypnea are: Hypnea cf. cerviconis, H. cf. intricata, H. cf. pannosa, H. rosea sp. 1, H. rosea sp. 2, H. spicifera, and H. viridis. The unidentified Hypnea spp. are in clades G and I. The unidentified sequences from a different genus are in clade H. There are 2 species Tenebris tenuis and Tenebris sp. assigned to the new genus.
Open Access
Nitrogen environment, ecophysiology and growth of Gracilaria gracilus in Saldanha Bay, South Africa
(1998) Smit, Albertus Jacobus; Bolton, John J; Anderson, Robert J
The growth of Gracilaria gracilis (Stackhouse) Steentoft, Irvine et Farnham was examined by studying the effect of organismic determinants such as thallus length, position along the thallus and branching in a series of in situ and laboratory-based experiments. Knowledge of these factors is essential in order to maximise production from suspended seaweed rafts seeded with vegetative G. gracilis fragments. Seeding netlons with freshly collected material provided up to 30 % higher relative growth rates than seaweed maintained on the netlons for three successive months. Initial seedstock length greatly affected growth rate and yield such that 30 cm thalli fragments resulted in growth rates 14 % higher than for 10 cm fragments. This difference is suggested to be due to higher contribution of growth by lateral branches to overall biomass. Comparisons of the growth of apical and basal fragments suggested that growth takes place over the entire length of the thallus but that the apex contributes more to overall elongation than does the proximal part. The removal of apical meristems resulted in an enhanced branching frequency with production of four times as many branches as intact fragments. Evidence is also provided for severe morphological differentiation following long periods of rapid growth. These thalli have very high frequency of branching, are hollow due to the disintegration of medullary cells and are considered to be completely senescent.
Open Access
The phylogeny, biology and biogeography of the Southern African kelps Ecklonia maxima and Laminaria pallida
(2015) Rothman, Mark Dino; Bolton, John J; Anderson, Robert J
Brown algae of the order Laminariales, commonly referred to as kelps, are the largest and most productive primary producers in the coastal inshore environment. Three genera of kelps are present on the southern African coast: Ecklonia, Laminaria and Macrocystis, of which the first two are ecologically and economically important and the focus of this study. The taxonomy of the genus Ecklonia is investigated. The genus Ecklonia (Phaeophyceae, Lessoniaceae) consists of seven species with four species in the Northern Hemisphere and three in the southern Hemisphere. Ecklonia was recently transferred to the family Lessoniaceae based on phylogenetic analyses of nuclear and chloroplastic markers, though the type of the genus was not included, and its relationship to the allied genera Eckloniopsis and Eisenia remained unresolved. The present study is the first to produce a phylogeny focussed on the genus Ecklonia. It included sequences from nuclear, mitochondrial and chloroplastic DNA, for most of the distribution range of the three current Southern Hemisphere species (E. radiata, E. maxima and a sample of a putative E. brevipes specimen), sequences for East Asiatic species (E. cava, E. kurome and E. stolonifera), as well as the closely related genera Eckloniopsis and Eisenia. Results confirmed E. radiata and E. maxima as two distinct species in South Africa, E. radiata as a single species throughout the Southern Hemisphere (in South Africa, Australia and New Zealand) and East Asiatic species as a distinct lineage from the Southern Hemisphere clade. Results further indicated a close sister relationship between Eckloniopsis radicosa and two Eisenia species (including the type species: Eisenia arborea), and the genus Ecklonia, suggesting that the genera Eckloniopsis and Eisenia are superfluous.
Open Access
The potential for Gracilaria polyculture at Jacobs Bay Sea Products Pty
(2000) Morgan, Derek; Anderson, Robert J; Bolton, John J
This report investigates the potential for the culture of G. gracilis, an indigenous red alga, into the west coast mariculture farm Jacobs Bay Sea Products Pty. Various methods for cultivating Gracilaria as well as environmental parameters, which influence growth of Gracilaria, are disltussed below. From these optimal conditions for the polycultivation of G. gracilis are determined. Cultivation can take place either, in open waters, or on land. Open water systems are generally less intensive than land based operations. Open water systems can be either bottom planted or suspended. Suspended cultivation has the advantage of maintaining the plant thalli in optimal light intensities. Land based systems can make use of ponds, raceways or tanks. Tanks and raceways are more productive than ponds, but require higher ﬂow rates and regulated nutrient regimes.
Open Access
The potential of Grateloupia filicina (Lamouroux) J. Agardh. for mariculture: culture experiments and observations on shore phenology
(1996) Vetter, Susanne; Bolton, John J; Anderson, Robert J
Grateloupia filicina is a carrageenophytic red alga which is in demand as a carrageenan raw material and for use in food. There is therefore interest in developing a technique for mariculturing this species. Since vegetative propagation from thallus fragments has not been successful, the present study was initiated to determine suitable conditions for spore liberation and growth of G. filicina from spores. It was also attempted to propagate G. filicina sporelings from crust and thallus fragments. In addition, the proportions of plants in different life history phases were determined in August and September to test for seasonal differences in shore phenology, and whether G. filicina is monoecious or dioecious, since there is disagreement on this in the literature. Spore release was easy to achieve, even without stressing the parent plant. Growth of crusts was found to be fastest at 50 μM.m⁻².s⁻¹ and at 20°C. Carposporelings (i.e. young tetrasporophytes) grew slightly but significantly faster than tetrasporelings (i.e. young carposporophytes). Crust fragments were able re-attach to the substrate and gave rise to new upright thalli within 1-2 weeks, compared to 4-5 weeks between spore release and thallus initiation. Attachment was weak, however, and only a small proportion of the crust fragments placed into culture regenerated. Thallus regeneration was not successful. There were seasonal differences in shore phenology during the study period: while two thirds of the plants collected in August were carposporophytes, only tetrasporophytes were found in September. No male gametophytes or spermatangia were found. It did not emerge from this study whether G. filicina in an annual, or what phenotypic differences are found throughout the year. Information of this kind is important for mariculture as it affects the supply of parent plants (and therefore spores) and the growth of young plants on ropes if these are released into the sea. The culturing experiments look promising; techniques (seeding ropes directly with spores or using regenerated crust fragments) still need to be refined.
Open Access
Seaweed diversity in Saldanha Bay and the effects of human activities
(2012) Siyanga-Tembo, Fridah; Bolton, John J; Anderson, Robert J
Several accounts have been produced on the seaweeds of the west coast including the Saldanha and Langebaan System, but none has looked at how human activities may have affected the seaweed diversity of Saldanha Bay. The major human activities in the Bay include shipping and mariculture. The major human impacts resulting from these activities are species introductions which often lead to a change in species composition in an area. Six sites were sampled in various visits in autumn and winter 2012. Two of the sites were natural wave exposed rocky shore sites while the rest were sheltered and man-made. Detailed collections of seaweeds were made. The seaweeds were identiﬁed to species level and preserved either as herbarium specimen or in formalin. Specimens that it was not possible to identify using morphological features were preserved in silica gel for DNA analysis. Three samples of the red algal genus Gruteloupia, collected from aquaculture systems, which could not be identified using morphological features, were sent to Ghent University where the rbcL gene region was sequenced. Collected species were compared with species lists from previous studies in the same area. The results from this study showed that most of the species collected were west coast species, with a few species with south coast distributions. The numbers of species in the Bay since the study of Day showed an increase from 23 by Day to 58 by Simons' 1960 collection. His 1976 collection reduced to 47. The most species so far recorded are by Schils' 1997 collection with 72. From this study, 69 species were recorded of which 23 are potentially new records. Of these records, two were south coast species Gelidium reptans and Laurencia peninsularis. They were recorded for the first time in the system and they are range extensions. Furthermore, the results provide molecular evidence that two species of Grateloupia have been introduced into Saldanha Bay. Bayesian analysis showed that one of the species was Grateloupia turuturu, a Japanese species which has spread to a number of world regions which culture the Paciﬁc oyster. The other was distinct from other Grateloupias previously recorded in South Africa, and did not match any species in Genbank. The potential vector of introduction for Grateloupia turuturu, importation of the Pacific oyster Crassostreo gigas, is discussed.
Open Access
A study of the distribution of algae in the Two Oceans Aquarium, Kelp Tank, Cape Town
(2000) Robertson-Andersson, Deborah; Bolton, John J; Anderson, Robert J
Five years have passed since the Two Oceans Aquarium, Cape Town, opened its doors for the first time in November 1995. Since then, a seaweed community has established itself in the Kelp tank. The seaweeds were brought in as either epiphytes on mature macro algae or as epiphytes on boulders that were placed on the floor of the tank. Thus, the community in the tank can be assumed to have established itself naturally. This study looked at the extent of the species diversity, zonation patterns in the tank (with particular reference to wall orientation), depth substrate type, plane (i.e. vertical or horizontal surfaces) and species distribution with depth. This was done by placing quadrats in transects down each wall and noting the percentage cover of each species. Quadrat depth, substrate type, wall orientation, and plane were noted. The percentage cover values as well as the environmental data were entered into CANOCO, an ordination programme for windows. Ordination showed that the tank was essentially a homogeneous environment with no difference in species distribution with regard to wall orientation, depth, substrate type, or plane. It was noted that self-seeded Ecklonia maxima were very unhealthy, small, deformed and had many epiphytes, with the exception of three plants that were growing under the plunger. From this it was concluded that water motion, and not light or nutrients, was limiting in the tank. Schimmelmannia elegans was found growing in the kelp tank. It had never been described as growing in South Africa previously. One theory was that the increased daylight length in the tank, caused by the fact that lights over the tank were often left on for extended periods, triggered a photoperiodic reproductive cue from the crustose phase (which was assumed to be growing unrecorded on the Cape Peninsular) for the sporophyte to grow. However, daylight length in the Kelp tank and Tristan da Cunha (where it was first recorded as growing) were the same so that theory was discarded. Another theory was that the algae was introduced into the tank in some way. This, however requires further investigation. Environmental conditions in the tank were investigated using aquarium records. Light intensity and duration, water temperature, pH, salinity, dissolved oxygen concentration were all found to be optimal for photosynthesis and growth to occur. Water motion was seen as the only limiting factor for photosynthesis and growth as it also has an effect on nutrient uptake. Grazer intensity was also examined. It was found that grazing by fish was stable; however, grazing by invertebrates and particularly mesa-herbivores could be increased, by adding more of them into the tank. It was found that with light being left on for functions there was no real seasonal change in light duration and this may be a problem for seaweeds that experience seasonal growth as they are missing seasonal cues. A management option of having a strictly controlled 11 hours of daylight during a winter month was proposed as a solution. This study is a good reference point for future work to be done on seaweed succession in the Kelp tank.
Open Access
Substrate dependant survivorship of Ecklonia maxima, in southern African kelp communities
(1996) West, Adam; Anderson, Robert J
Several south-western Cape Ecklonia maxima communities were examined to determine their basic demography and the effects of substrate selection. Overall percentage substrate composition, stipe lengths and substrate attachment for all kelps were recorded at four sites off the Cape Peninsula. Strength of attachment to different substrates was measured. Selection for substrate type was analysed using Jacobs' index. A substrate of Pyura stolonifera was the most common for juveniles, whereas substrates of rock and conspecific holdfasts were dominant in the larger individuals. No significant difference in strength of attachment was found for kelps less than 50 cm. An analysis of the frequency of single- and multi-stiped holdfasts indicates that survival on rock is greater than on that of holdfasts. Size-class distributions indicate that E. maxima is a shade-tolerant species showing advanced regeneration. Establishment on rock may occur through episodic recruitment escaping grazing pressure. In areas with low grazing intensity, recovery from catastrophic storms may be limited by competition with understorey algae.
Open Access
Systematics of the Laurencia complex (Rhodomelaceae, Rhodophyta) in southern Africa
(2014) Francis, Caitlynne Melanie; Bolton, John J; Anderson, Robert J; Mattio, Lydiane
The diversity, systematics and distribution of the red algal Laurencia complex (Rhodomelaceae, Rhodophyta) of South Africa were investigated, being generally poorly understood and taxonomically understudied. Prior to this study, ten currently recognised species in the Laurencia complex were recorded from South Africa: all were ascribed to the genus Laurencia J.V. Lamouroux (Laurencia sensu stricto). However, the diversity anddistribution of the complex in South Africa, and the larger South Western Indian Ocean (SWIO), have not yet been reassessed following the numerous taxonomic changes in this group published over the last two decades. The taxonomy, phylogeny and biogeography of the Laurencia complex in South Africa and apart of the SWIO were reassessed by examining external morphology, vegetative anatomy(including corps en cerise counts) and analysing the plastid-encoded rbcL gene sequence data of recent collections. The collection encompassed more than 250 specimens, were primarily from the coastline of South Africa and to a lesser extent from Madagascar, Mozambique, Reunion, Mauritius and the Europa and Glorioso Islands in the SWIO. In addition, a few new collections were included from Western Australia and Japan. The genetic analyses were done under Bayesian inference using the GTR + I + G model, from which phylogenetic hypotheses were deduced and pairwise sequence divergences were calculated.
Open Access
Taxonomy and phylogeny of the South African Plocamium species Rhodophyta, Plocamiaceae
(2009) Francis, Caitlynne Melanie; Bolton, John J; Mandiwana-Neudani, Tshifhiwa Gift; Anderson, Robert J
A number of taxonomic accounts have been produced for species of the red alga Plocamium in South Africa and the rest of the world; yet, the use of phylogenetic analyses to understand relationships within the genus has only been incorporated in the last decade in Japan and Europe. We used morphological and DNA sequence characters (ITSJ-5.8S-ITS2) in both independent and combined Bayesian and parsimony analyses to investigate the relationships within South African Plocamium species and between South African Plocamium species and those from elsewhere. South African Plocamium forms a monophyletic group within the genus, and Plocamium is paraphyletic with respect to Plocamiocolax, the other genus in the family Plocamiaceae. The morphological and molecular phylogenies are incongruent; morphologically relationships resolve poorly toward the tips and several of the sister relationships resolved on the basis of the nuclear ITS marker are questionable. The results of this study revealed that phylogenetic relationships within Plocamium in South Africa are highly complex and particularly when evaluated in the context of the genus worldwide. The worldwide taxonomy of the genus is in need of full revision as this and several recent studies have highlighted incongruencies in the previous morphological taxonomic accounts of the genus.
Open Access
Taxonomy and systematics of the Bangiales (Rhodophyta) in South Africa using an integrative approach
(2018) Reddy, Mageshnee Mayshree; Bolton, John J; Anderson, Robert J
The Bangiales is a globally distributed red algal order that is best known for its economic value in the nori industry. The morphological simplicity of the Bangiales offers limited distinguishing characters for taxonomy and the order was therefore broadly classified into two genera based on morphology: the bladed Porphyra and filamentous Bangia. However, in 2011, a taxonomic revision of the Bangiales based on a two-gene phylogeny identified 15 genera. Since then, an additional bladed genus and numerous species have been added to the order. The Bangiales were first recorded in South Africa in 1843 when Porphyra capensis Kützing was described. Since then several changes have been made to the bangialean flora of South Africa with many new species discovered based on morphological identification. In 2004, a preliminary molecular assessment of Poprhyra along the South African coast revealed far greater species diversity than previously recorded. Following the taxonomic revision by Sutherland et al. (2011), some species from South Africa have been transferred to the genus Pyropia, others remain in Porphyra and many others have not yet been re-assessed. At present, three genera; the filamentous, Bangia and the bladed Porphyra and Pyropia have been recorded in South Africa, and comprise numerous species (based on morphology) and molecular entities. In the present study a comprehensive collection of newly collected and herbarium specimens (collectively ca. 300 specimens from ca. 50 sites) of the Bangiales from South Africa was analysed. A total of 241 sequences were generated for three unlinked loci (nSSU, rbcL & cox1). Taxa were identified or delimited via an integrative taxonomic approach using molecular, morpho-anatomical and ecological data. Species were delimited using three DNA-based species delimitation methods (ABGD, GMYC, PTP) applied to the mitochondrial gene cox1 (n=203) and the plastid gene rbcL (n=80). A multigene phylogeny was also constructed (nSSU, rbcL & cox1) and used to delimit species. Subsequent morpho-anatomical analyses complemented with ecological data and herbarium specimens (South Africa and Namibia) showed that 16 species in three genera (11 Porphyra, four Pyropia and one Bangia) are present along the South African coast. Morpho-anatomical characters of two species with uncertain taxonomic status were consistent with the descriptions of two widespread species, Bangia cf. fuscopurpurea and Py. cf. suborbiculata but remain to be confirmed using a molecular approach. In addition, two new species, Pyropia meridionalis sp. nov. and Porphyra agulhensis sp. nov. were described. Pyropia meridionalis is a kelp-associated species that is commonly found on the kelp limpet, Cymbula compressa, or on the stipes of Ecklonia maxima, and rarely on other species of southern African kelp, Laminaria pallida and E. radiata or other algae. This species occurs along the southwest and west coast of South Africa throughout the year, but may extend to Namibia. Pyropia meridionalis was shown to be previously misidentified as Py. gardneri in South Africa. This species was not closely related to other southern African endemic species of Pyropia, suggesting that species colonized and spread along this coastline independently. Nevertheless, most species shared close genetic affinities to other Southern Hemisphere taxa. This supports the notion of historic connectivity in the Southern Ocean proposed for red algae. Porphyra agulhensis is characterized by delicate laciniate rosette blades and a distinct greenish to pale pinkish-purple colour. This species was shown to be historically misidentified as P. capensis and is restricted to the Agulhas Marine Province on the south coast of South Africa. It includes one cryptic species (RSAj). The remaining eight molecular species of Porphyra formed a monophyletic group and occurred along the Benguela Marine Province on the west coast of South Africa. No single morpho-anatomical or ecological character could distinguish between these molecular species. Despite overlapping conventional morpho-anatomical or ecological characters among cryptic species, all features were within the range of the current description of P. capensis and were therefore referred to as the P. capensis cryptic species complex (PCC). High genetic diversity and several major lineages were identified in the PCC along the Benguela Marine Province. Conversely, the Porphyra agulhensis cryptic species duo along the Agulhas Marine Province presented low levels of genetic variation with ca. 70% of individuals belonging to a single haplotype group. Genetic diversity within Porphyra in South Africa was higher on the west coast of South Africa than on the south coast and the region between Cape Agulhas and Cape Point was identified as a region of major biogeographic change. Historic and contemporary processes, which likely shape present-day genetic patterns in South African Porphyra, are discussed. Similar to Pyropia, species of Porphyra from South Africa shared a close phylogenetic affinity with some Chilean bladed Bangiales, providing further support for historic connectivity in these red algae in the Southern Ocean. South Africa is now home to the second highest number of species of Porphyra in the world and shares three species of Pyropia with Namibia (based on morphological identification). All species identified using molecular sequences appear to be endemic to South Africa or southern Africa. The extensive genetic diversity found along the South African coast compares well with other Southern Hemisphere countries, such as Chile and New Zealand. The Southern Hemisphere has been suggested as the origin and centre of diversity for the Bangiales, but still remains relatively unexplored, and further investigations are likely to yield further species and species links.
Open Access
Tropical intertidal seaweed turf communities of Jesser Point, Sodwana Bay, South Africa
(2010) Innes, Sheona; Bolton, John J; Anderson, Robert J
Algal turfs play an important role in both tropical and temperate reef ecology, supporting a diverse array of macrofauna as well as being primary producers within both intertidal and subtidal ecosystems. Biodiversity and biomass patterns of the intertidal algal turfs at Sodwana Bay, South Africa have not yet been established so this study was undertaken to investigate these. It was hypothesised that both biodiversity and biomass would decrease with increasing height along the shore, as well as that sediment would have an effect on the community composition of the turfs. The community was sampled over a vertical range of 1.2 m and found to be dominated by the red alga Jania intermedia (24.21 % of total algal coverage) followed by Tolypiocladia glomerulata (18.05 %), Dictyota sp. (13.39 %), Jania adhaerens (12.32 %) and Sphacelaria tribuloides. (5.83 %). No significant vertical zonation patterns were found, though certain species showed vertical trends such as Asparagopsis taxiformis and Sphacelaria tribuloides, which occurred in greatest biomass lower down on the shore, while Tolypiocladia glomerulata occurred higher up on the shore. Sand was found to affect certain species more than others, with Tolypiocladia glomerulata, Jania adhaerens and Asparagopsis taxiformis occurring in greatest biomass when the amount of sediment found in the quadrat was low, while Sphacelaria tribuloides. showed the opposite pattern and Jania intermedia showed no distinct pattern. Sampling took place over 1.2 m vertical height along the shore at spring low tide therefore covering 60 % of the intertidal zone vertically (maximum tidal range in South Africa is 2 m). It is therefore possible that the turfs are the cause of a decline in zonation by remaining damp and decreasing desiccation gradients vertically along the shore.
Open Access
Use of stable isotope signatures in the macroalga Ecklonia maxima and the filter feeder Mytilus galloprovincialis to determine the extent of sewage dispersal from the Green Point outfall, South Africa
(2007) Cyrus, Mark Digby; Bolton, John J; Anderson, Robert J; February, Edmund C
Over the last decade natural abundances of stable isotopes ¹³C and ¹⁵N have been used to investigate the transport pathways of nutrients within aquatic ecosystems, and have contributed new understanding and knowledge to many aspects of ecology, which include tracking the spatial extents of nutrient discharges. In order to assess the uptake of nutrients from the Green Point sewage outfall in Cape Town South Africa, we selected a primary producer, the kelp Ecklonia maxima (for dissolved nutrients) and a filter-feeding organism, the blue mussel Mytilus galloprovincialis (for organic particulates). It was hypothesized that biota within close proximity of the outfall would have isotopic values (signatures) which were closer to the values recorded for sewage and that this signature would become weaker (more positive) with increasing distance from the outfall as the sewage would be diluted and dispersed. Results from our study indicated that the stable isotope abundances of biota near the outfall were significantly affected by sewage. Ecklonia maxima situated on the outfall itself had δ¹⁵N of 1.2±2.3‰, which was extremely depleted relative to our control (8.3±1.1‰), collected at Mauritzbaai. The δ¹⁵N recorded for raw sewage (0.4±0.4‰) was very similar to that of Ecklonia maxima situated on the outfall. Mytilus galloprovincialis were also affected by sewage organic matter however although the effects on the stable isotope abundances were less pronounced as they were relying on more than one source of food. The isotopic values recorded in this study demonstrated that sites which were in close proximity to the outfall and even those just within the study area were contaminated by sewage effluent. From this study we conclude that the δ¹⁵N signatures of Ecklonia maxima and Mytilus galloprovincialis in marine environments can provide a useful means of tracing sewage dispersal in well-mixed ocean conditions, where conventional methods may have failed to reveal the extent of dispersal.

Browsing by Author "Anderson, Robert J"

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