Browsing by Author "Anderson, R J"

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    The abundance and diversity patterns of seaweed communities on natural and artificial substrata at Sodwana Bay, South Africa
    (2014) Gersun, Leanne; Anderson, R J; Bolton, John J
    The high latitude coral communities of southern Africa suffered minimal impacts during mass bleaching events in the recent past. However, during the 2005 warm-water anomaly in the southern Indian Ocean, coral bleaching reached unprecedented levels. There is surprisingly little known about the fate of bleached corals, which may either regain their zooxanthellae and recover, or may die, in which case they generally become overgrown by macroalgae. The nature and dynamics of this algal overgrowth are not well understood. This study was done on Two-Mile Reef, Sodwana Bay, located in the iSimangaliso Wetland Park, a World Heritage Site. The first aim was to investigate the abundance and diversity of benthic algal communities colonising different hard substrata (comprising bleached digitate, brain and plate coral assemblages, and beach rock). The second was to compare the algal communities colonising various artificial hard substrata. The third was to document the species of non-geniculate coralline red algae found on the natural hard substrata during sampling. Fieldwork was carried out during the marine autumn (March) and spring (September) of 2010 using SCUBA. A total of 90 quadrats (10 cm x 10 cm) were sampled and the underlying substratum was recorded and classified. A Braun-Blanquet scale was used to assign cover-abundance values to each species within each quadrat. Additionally, the relative cover of different types of substrata was estimated using line-point intercept methods. Multivariate analysis (detrended correspondence analysis) and cluster analysis (complete linkage Bray-Curtis) were used to show how substrata and season relate with respect to their seaweed flora. Additionally, Kruskal-Wallis nonparametric tests with pairwise Mann-WhitneyU-tests were used to examine differences in macroalgal assemblages among substratum types.
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    The cultivation of Ulva lactuca (chlorophyta) in an integrated aquaculture system, for the production of abalone feed and the bioremediation of aquaculture effluent
    (2003) Robertson-Andersson, Deborah; Bolton, J; Anderson, R J; Probyn, T
    Significant effort has been put into the development of cost-effective abalone cultivation systems in South Africa, but the limited availability of suitable seaweed for abalone food is an obstacle to future development. The aim of this study was to investigate whether land-based integrated aquaculture (tank cultivation) and seaweed culture using Ulva lactuca in aquaculture effluent was feasible. This study was carried out at two abalone farms: Danger Point (I & J) (140 km east of Cape Town) and Jacobsbaai (JSP) (120 km north of Cape Town, South Africa). Both farms want to supplement the abalone feed with Ulva and investigate its potential for recirculation. Ulva is one of the simplest seaweeds to cultivate as it grows vegetatively. It would have a further benefit in its capacity to absorb nutrients and thus improve water quality of the aquaculture effluent. Results show that abalone effluent medium alone is insufficient for seaweed cultivation. Turbot effluent media has far more nutrients for seaweed but turbidity due to incomplete turbot feed pellet assimilation could be a problem. The most effective cultivation media on both farms is a fertilized effluent growth medium. This study established that water exchange rates are important in assuring an optimum nutrient supply for the seaweed. At high water exchange rates (20 Volume Exchanges (VE).d - Specific Growth Rate (SGR) in turbot and seawater treatments were not significantly different despite a significant difference in water nutrient concentration. Maximum nutrient removal occurs at both 12 and 20 volume exchanges per day, using a stocking denSity of 3 kgm-2 on both farms. Approximately 70 % of the ammonium is removed during the day and 60 % at night at JSP in both turbot and abalone treatments, while at I & J in the abalone treatments, 90 % and 80 % of the ammonium is removed during the day and night respectively. The diel fluctuation in dissolved oxygen is above critical levels (6 mg.l) for abalone respiration at night, thus indicating that direct recirculation is possible.
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    Development in culture, ecophysiology and nutritional content of three South African Porphyra (Rhodophyta, Bangiales) species
    (2011) Dlaza, Thembinkosi Steven; Bolton, John J; Anderson, R J
    The first aim of this study was therefore to study the reproductive biology and phenology of three common Porphyra species (Porphyra aeodis Griffin, Bolton et Anderson 1999, Porphyra capensis Katzing 1843 and Porphyra saldanhae Stegenga, Bolton et Anderson 1997), which occur on the west coast of South Africa. The second aim of the study was to investigate, in culture, the ecophysiological responses of the different phases of the life histories of these threes species to various environmental variables. The third aim of this study was to quantify some important aspects of the nutritional composition of these three species and to investigate seasonal variations in these nutrients.
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    Ecological and biogeographical studies on the rocky shore seagrass Thalassodendron ciliatum (Forsskal) den Hartog and its seaweed epiphytes at the southern limit of its distribution in the western Indian Ocean by Catherine Margot Browne.
    (2012) Browne, Catherine Margot; Bolton, John J; Anderson, R J
    The current study aimed to improve knowledge and understanding about the ecology, diversity and biogeography of the South African rocky shore seagrass Thalassodendron ciliatum and its associated macroalgal epiphytes. Seagrass populations were sampled at Jesser Point (Sodwana Bay) and at Maphelane, the former being larger and the southernmost populations observed, and the latter being the site of an isolated small population further south.
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    Effects of commercial kelp extract and plant growth regulators on growth of Gracilaria gracilis in culture
    (2005) Leitao, Daniela; Bolton, John J; Anderson, R J
    The addition of a local commercial seaweed extract (Kelpak®) to crop plants has proven to be beneficial as it improves growth and yields. Its efficiency has been attributed to its production method that involves a cold process, resulting in a product containing significant amounts of plant growth regulators (auxins and cytokinins). The aim of this study was therefore to investigate the effects of this commercial seaweed concentrate (Kelpak®) on the growth of Gracilaria gracilis (Stackhouse) Steentoft, Irvine et Farnham, with a view to the potential in mariculture, especially as this red seaweed is currently under cultivation in South Africa as feed in abalone aquaculture.
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    Experimental cultivation of the red seaweed, Gracilaria gracilis (Rhodophyta) in land-based tank culture systems on abalone farms in the Western Cape, South Africa
    (2006) Njobeni, Asanda; Bolton, John J; Anderson, R J
    The feasibility of growing red seaweed, Gracilaria gracilis (Gigartinales, Rhodophyta) in land-based culture systems was investigated in two Western Cape abalone farms i.e. Jacobsbaai Sea Products (JSP) and Irvin & Johnson (I&J) and large size culture tanks (I&J). All the tanks were stocked with at 2 kg m⁻² supplied with unfiltered seawater (24 and 4 volume exchanges d⁻¹) JSP and I&J, respectively. This study also tested the efficiency of G. gracilis as a biofiltering species as well as investigating the effectivenss and influence of nutrient-enriched seawater i.e. turbot and abalone effluent (JSP) and fertilized seawater and abalone effluent (I&J) on the growht of Gracilaria.
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    Harvest ecology and biodiversity of South African Porphyra
    (2003) Griffin, Neil John; Bolton, John J; Anderson, R J
    Porphyra (Bangiales, Rhodophyta) is the world's most valuable maricultured seaweed, due to its high value as a food crop. The vast majority of Porphyra in South Africa belongs to P. capensis, a morphologically and ecologically plastic taxon apparently endemic to the region. There is no demand for P. capensis as a food crop, as it is unsuitable for the market, and there are no records of its customary use locally. Porphyra capensis is however a potentially highly valuable fodder for the mariculture of abalone (Haliotis midae), and pressure to harvest it has recently increased. This study aims to assess the potential for harvest of Porphyra on the south-western shores of South Africa. There are two main thrusts to this work. The fIrst thrust examines Porphyra as an ecological entity in the region. The second thrust reassesses the taxonomy of Porphyra species in the region.
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    Shallow subtidal seaweed communities of the Agulhas Marine Province of South Africa
    (2009) Wilby, Deborah; Bolton, John J; Anderson, R J
    Several aspects of seaweed ecology are poorly studied and documented in South Africa, especially the subtidal algal communities along the south coast. This study aims to investigate these communities where few other studies have been conducted. Sampling of shallow subtidal seaweed communities was undertaken at eleven sites along the south coast of South Africa from Still Bay to Mzamba. At each site a number of quadrats were placed within the shallow subtidal zone ranging in depth from O.3m to 2.5m. Within these quadrats all algae were destructively sampled (excluding encrusting algae), invertebrate grazers present were counted, and environmental measurements were taken. These environmental measurements included depth and slope, with temperature data supplied from a previous study. The biogeographical communities of this area were investigated using Detrended Correspondence Analysis, Canonical Correspondence Analysis and cluster analysis, in order to compare them with previous studies on the marine biogeography of the area. In the 85 quadrats that were sampled, 97 species of Chlorophyta, Phaeophyta and Rhodophyta were found. Articulated (or geniculate) coralline red algae were very abundant in the samples, with 17 species that contributed over 44 of the biomass. There was a high number of other red algal species (54 species) but they represented only 10 of the total biomass. Green algal species were not very common (there were only 12 species) but they contributed 42 to the biomass. There were a similar number of brown algal species (14), although they only contributed 2 of the total biomass.
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    The systematics, biology and distribution of the Gelidiaceae (Rhodophyta) of South Africa and related taxa
    (2003) Tronchin, Enrico M; Bolton, John J; Anderson, R J
    The diversity, biology and distribution of the red algal family Gelidiaceae (Rhodophyta) of South Africa (and related taxa) were investigated, being relatively poorly understood and taxonomically problematic. Prior to this study, 21 species in 6 genera were reported from South Africa Now there are 29 species in 3 genera (though molecular data indicates that there is possibly a new, undescribed genus) of which 16 are Gelidium species, 5 are Pterocladiella species and 8 are Ptilophora species. The phylogenetic relationships and taxonomic status of the genera Beekerella, Ptilophora, Onikusa and Suhria, and various species within Gelidium and Pterocladiella, were reassessed.
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    The cultivation of Ulva lactuca (chlorophyta) in an integrated aquaculture system, for the production of abalone feed and the bioremediation of aquaculture effluent
    (2003) Robertson-Andersson, Deborah; Bolton, J; Anderson, R J; Probyn, T
    Significant effort has been put into the development of cost-effective abalone cultivation systems in South Africa, but the limited availability of suitable seaweed for abalone food is an obstacle to future development. The aim of this study was to investigate whether land-based integrated aquaculture (tank cultivation) and seaweed culture using Ulva lactuca in aquaculture effluent was feasible. This study was carried out at two abalone farms: Danger Point (I & J) (140 km east of Cape Town) and Jacobsbaai (JSP) (120 km north of Cape Town, South Africa). Both farms want to supplement the abalone feed with Ulva and investigate its potential for recirculation. Ulva is one of the simplest seaweeds to cultivate as it grows vegetatively. It would have a further benefit in its capacity to absorb nutrients and thus improve water quality of the aquaculture effluent. Results show that abalone effluent medium alone is insufficient for seaweed cultivation. Turbot effluent media has far more nutrients for seaweed but turbidity due to incomplete turbot feed pellet assimilation could be a problem. The most effective cultivation media on both farms is a fertilized effluent growth medium. This study established that water exchange rates are important in assuring an optimum nutrient supply for the seaweed. At high water exchange rates (20 Volume Exchanges (VE).d ·1), Specific Growth Rate (SGR) in turbot and seawater treatments were not significantly different despite a significant difference in water nutrient concentration. Maximum nutrient removal occurs at both 12 and 20 volume exchanges per day, using a stocking density of 3 kgm·2 on both farms. Approximately 70 % of the ammonium is removed during the day and 60 % at night at JSP in both turbot and abalone treatments, while at I & J in the abalone treatments, 90 % and 80 % of the ammonium is removed during the day and night respectively. The diel fluctuation in dissolved oxygen is above critical levels (6 mg.I) for abalone respiration at night, thus indicating that direct recirculation is possible. The seaweeds grown at a high water exchange rate at JSP were all phosphate limited except in winter, when background phosphate concentrations increased. Thus, fertilizers like Maxiphos can benefit the alga, especially if the phosphate ratio were to be increased in summer. Maintaining a pH below 9 is important in maintaining seaweed health and should become an integral part of the farm management protocol. Myrionema strangulans is an epiphyte newly recorded for South Africa during this project and has potentially devastating effects for culture of Ulva. Pulse fertilization of culture tanks combined with seasonal shading (late September to early February) using 20 % shade cloth controls epiphytic and fouling algal growth, particularly Myrionema. Shading also improves thallus condition, increases tissue nitrogen and decreases pH. Shading with a 50 % shade cloth however, has a significant reduction on uptake of ammonium and phosphate by the seaweed as well as decreasing the SGR and resulting in a species dominace switch from Ulva lactuca to Ulva capensis. There is a decrease in SGR when scaling up tank sizes, but this decrease can be optimized by cultivating the alga in pulse fertilized effluent water. Growing Ulva in effluent media increases its tissue nitrogen and thus protein content, increasing it above levels found in nature (average protein content in turbot= 49.8 %) and improving it as a source of protein for cultured abalone. A consistent relationship between tissue nitrogen and thallus colour was determined and can be used by mariculture farmers to assess the nutrient quality of Ulva as a food source for abalone which has important benefits for Ulva aquaculture. On the I & J farm the chosen stocking density (2 kg.m"2) produced maximum SGR and yields. At JSP the chosen stocking density {2 kg.m"2) was too high and a stocking density of 1 kg.m·2 would have optimized SGR. Seasonal effects on stocking density were not investigated. Addition of Kelpak ® concentration (commercial kelp extract) of 1: 2 500 pulse fed once a week, increases SGR. This study has shown that Kelpak® in addition to fertilizer may have commercial potential in the seaweed mariculture industry. These results confirm that Ulva is exceptionally suitable for intensive culture in different types of nutrient loaded water, and that its cultivation on an abalone farm could have significant economic benefits. For example, a 50 ton abalone farm feeding protein enriched Ulva could decrease the production time from 5 years to 3.6 year which equates to a savings of between R 800 000 - R1 300 000.
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    Using Geographic Information Systems and remote sensing to improve the management of kelp resources in South Africa
    (2006) Rand, Andrew M; Bolton, John J; Anderson, R J; Butcher, Shirley
    In 2002 the Department of Environmental Affairs and Tourism (DEA&T), Marine and Coastal Management (M&CM) and the Seaweed Unit undertook a program to document the localities and quantities of the standing crop of the economically important kelps, Ecklonia maxima and Laminaria pallida, in the fourteen commercial seaweed Concession Areas that contain commercial quantities of kelps. The primary objective of this study was to establish a coastal kelp resource database for the South African coastline from Cape Agulhas to the Orange River (the international border with Namibia). The method was designed to integrate past and current analysis of multi-year kelp data from commercial harvesting, biomass and kelp bed extent while allowing for the integration of future surveys within the inventories.