Ecklonia maxima

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Mark D Rothman - One of the best experts on this subject based on the ideXlab platform.

  • Geographical variation in morphology of the two dominant kelp species, Ecklonia maxima and Laminaria pallida (Phaeophyceae, Laminariales), on the west coast of Southern Africa
    Journal of Applied Phycology, 2017
    Co-Authors: Mark D Rothman, John J. Bolton, Michael S. Stekoll, Christian J. T. Boothroyd, Frederik A. Kemp, Robert J. Anderson
    Abstract:

    Laminaria pallida and Ecklonia maxima are large, commercially valuable kelps that co-dominate inshore waters of the west coast of Southern Africa in a geographically changing pattern. In the south, E. maxima dominates and forms a canopy in shallow waters (< about 5 m deep), with L. pallida forming a sub-canopy and extending down to 20 m or more. Northward along the Southern African coast and into Namibia, E. maxima is progressively replaced by L. pallida. Corresponding with this change in dominance, L. pallida shows certain morphological changes along the south-to-north geographical gradient. To explain these phenomena, we examined a range of morphological characters in both kelps (stipe length, stipe weight, stipe outer diameter, stipe inner diameter, length of hollow section in the stipe, and frond weight), and various environmental factors (seawater temperature, seawater turbidity, cloud/fog data, daylength, and wave and wind data). Our results, based on measurements at seven sites along 1600 km of coast between Cape Town and Swakopmund (Namibia), quantified and confirmed the change in dominance and the northward increase in stipe hollowness in L. pallida. The morphology of E. maxima did not change with latitude. Water turbidity, wind speed, and wave height differed significantly along the coast. However, only turbidity showed a steady trend, increasing northward in terms of all indicators (chlorophyll a, particulate inorganic carbon, particulate organic carbon) while wind speed and wave height showed a generally decreasing trend. Furthermore, the hollowness of L. pallida was also not related to the flexibility of the stipes. Our results suggest that L. pallida sporophytes may progressively outcompete E. maxima northward, perhaps because they are more low-light tolerant, and we suggest that by developing a hollow stipe, the sporophytes may grow faster in length, potentially increasing their competitive advantage in the shallow water where they must compete with sporophytes of E. maxima.

  • A simple method for rapid estimation of Ecklonia maxima and Laminaria pallida biomass using floating surface quadrats
    African Journal of Marine Science, 2010
    Co-Authors: Mark D Rothman, John J. Bolton, Robert J. Anderson, C Jt Boothroyd, F. A. Kemp
    Abstract:

    In South Africa two species of kelp, Ecklonia maxima and Laminaria pallida, occur in quantities sufficient for commercial use. Currently, the former species is harvested in large quantities (about 5 000 tonnes wet weight per year) as abalone feed. In order to set limits to the amount of kelp that may be harvested, it is necessary to obtain reasonably accurate measurements of kelp biomass. Biomass estimates are traditionally obtained by destructive sampling of kelp sporophytes from quadrats placed on the bottom. Scuba divers harvest the plants and weigh them ashore. This method is slow and labour-intensive, and severely limits the area of kelp bed that can be sampled. This study investigates several alternative methods to determine an easier, quicker method of estimating kelp biomass. First, morphometric data on both species of kelp were collected to investigate if there were easily measurable characters that correlate with the weights of individual sporophytes, which then could be used as proxies for dest...

  • the effects of harvesting of the south african kelp Ecklonia maxima on kelp population structure growth rate and recruitment
    Journal of Applied Phycology, 2006
    Co-Authors: R. J. Anderson, Mark D Rothman, Albertus J Smit
    Abstract:

    Ecklonia maxima is an economically important kelp in South Africa. The harvested kelp is used mainly as feed for cultured Haliotis midae (abalone) on farms all along the South African South and West Coast. The effects that different harvesting methods have on the growth of sub-canopy kelps, kelp population structure and kelp recruitment were tested in a kelp bed at Bordjies Rif near Cape Town. Two 30 × 10 m sites were set up, about 100m apart, in near monoculture stands of E. maxima. Each 30 × 10m area was subdivided into three treatments. In treatment 1 (T1) the whole ‘head’ of each kelp sporophyte that reached the surface was cut off between the bulb and the primary blade (‘lethal’ method). In treatment 2 (T2) (‘non-lethal’ method), the secondary fronds of all sporophytes that reached the surface were cut 20–30 cm from their junction with the primary blade, and removed. In the control plot, the kelp plants were not treated. Harvesting treatments were done approximately every four months, at low spring tide, from 3 March 2003 to 3 November 2003 (three treatments). The effects of harvesting on the kelps depend largely on the size of plant and the time the fronds were removed; however, no seasonal pattern could be observed. The different treatments had no effect on the growth rate, population structure or recruitment of the kelp. This means that factors other than light play an important role in the growth, structure and recruitment of the kelp beds in False Bay. Results are discussed in relation to current commercial harvesting practices.

  • Harvesting of the Kelp Ecklonia maxima in South Africa Affects Its Three Obligate, Red Algal Epiphytes
    Journal of Applied Phycology, 2006
    Co-Authors: Robert J. Anderson, Mark D Rothman, A. Share, H. Drummond
    Abstract:

    In South Africa, more than 7000 t (f wt) of kelp (Ecklonia maxima) fronds are harvested annually to feed cultured abalone. Carpoblepharis flaccida, Gelidium vittatum and Polysiphonia virgata are conspicuous red algal epiphytes on older kelps and provide habitat and food for numerous animals. Over 4.5 y, we examined the effects of one destructive harvest of E. maxima on these 3 epiphytes. Two 20 × 20m plots of kelp with similar epiphyte loads were demarcated. In one, all E. maxima sporophytes with stipes longer than 50 cm were harvested. The other plot served as a control. After 2.5 y the biomass of E. maxima in the harvested plot had recovered to control levels, but the epiphyte load (g epiphytes. kg kelp−1) was statistically lower in the harvested plot after 2.5 and 3.5 y, and only recovered after 4.5 y. While most commercial harvesters cut through the “heads” (primary blades) of the kelp, effectively killing them, a new, non-lethal method removes secondary blades 20–30 cm from their bases, leaving the meristems and primary blades intact. At 5 sites studied, G. vittatum and P. virgata were found almost entirely on stipes and primary blades, and harvesting only distal parts of secondary blades limited losses to about 50% of C. flaccida biomass. To protect epiphytes, non-lethal harvesting is recommended and permanent non-harvest zones have been established in addition to limiting kelp yields and disallowing harvesting in Marine Protected Areas.

Wendy A. Stirk - One of the best experts on this subject based on the ideXlab platform.

  • eckol a new plant growth stimulant from the brown seaweed Ecklonia maxima
    Journal of Applied Phycology, 2015
    Co-Authors: Kannan R.r. Rengasamy, Wendy A. Stirk, M G Kulkarni, Johannes Van Staden
    Abstract:

    The seaweed concentrate Kelpak® made from the brown kelp Ecklonia maxima is used worldwide as a biostimulant for a number of agricultural crops. Plant growth regulators such as auxins, cytokinins, polyamines, gibberellins, abscisic acid, and brassinosteroids were identified from E. maxima and Kelpak®. In this study, we investigated the plant growth stimulating effects of two phlorotannins, i.e., phloroglucinol and eckol that were recently isolated from E. maxima. The activity of isolated eckol was compared with Kelpak® and commercially available phloroglucinol and the auxin indole-3-butyric acid (IBA). The isolated eckol from E. maxima stimulated maize growth in terms of shoot and root elongation and number of seminal roots and exhibited improvement in the biochemical activities of α-amylase compared to Kelpak®, phloroglucinol, and IBA. Furthermore, eckol showed auxin-like activity in the mung bean root assay at 10−5 M with an increased number of roots, shoot elongation, and seedling weight. Eckol can potentially play a significant role in increasing agricultural productivity.

  • abscisic acid gibberellins and brassinosteroids in kelpak a commercial seaweed extract made from Ecklonia maxima
    Journal of Applied Phycology, 2014
    Co-Authors: Wendy A. Stirk, Danuse Tarkowska, Veronika Turecova, Miroslav Strnad, J. Van Staden
    Abstract:

    The seaweed extract Kelpak® made from the kelp Ecklonia maxima is registered as a biostimulant for use in agriculture. It elicits many beneficial responses including improved root and shoot growth, higher yields and greater resistance to abiotic and biotic stresses. Previously, cytokinins, auxins and polyamines were identified in Kelpak®. The aim of the present study was to quantify other groups of plant growth regulators (PGRs)—abscisic acid (ABA), gibberellins (GAs) and brassinosteroids—that may be present in E. maxima and Kelpak®. Kelpak® samples harvested between 2008 and 2010 and stored for up to 26 months were analysed using ultra performance liquid chromatography tandem mass spectrometry. ABA levels were below the limits of detection in E. maxima but were detected in low concentrations in Kelpak®, ranging from 0.31 to 20.70 pg mL−1 Kelpak®. Eighteen GAs were found in E. maxima and Kelpak® with concentrations from 187.54 to 565.96 pg mL−1 Kelpak®. The biologically active GAs (GA1, GA3, GA4, GA5, GA6 and GA7) comprised less than 3 % in Kelpak®. Although GA13 (a final product in the metabolic pathway) was present in low concentrations in E. maxima, very high concentrations were present in Kelpak®. The brassinosteroids brassinolide (BL) and castasterone (CS) were identified in E. maxima and Kelpak®. Concentrations varied with harvest and storage time, ranging from 384.72 to 793.23 pg BL mL−1 Kelpak® and 62.84 to 567.51 pg CS mL−1 Kelpak®. It is likely that this cocktail of natural PGRs present in Kelpak® may act individually or in concert and thus contribute to the numerous favourable physiological responses elicited by Kelpak® application to plants.

  • acetylcholinesterase inhibitory activity of phlorotannins isolated from the brown alga Ecklonia maxima osbeck papenfuss
    Food Research International, 2013
    Co-Authors: Rengasamy Ragupathi Raja Kannan, Wendy A. Stirk, M A Aderogba, A R Ndhlala, Johannes Van Staden
    Abstract:

    Abstract Ecklonia maxima, a brown alga grows abundantly on the west coast of South Africa and is used to produce alginate, animal feed, nutritional supplements and fertilizer. The crude extract, solvent fractions and phlorotannins isolated from E. maxima were evaluated for acetylcholinesterase (AChE) inhibitory activity using the microplate technique. The IC50 values for the solvent fractions ranged from 62.61 to 150.8 μg/mL, with the ethyl acetate fraction having the best inhibitory activity against AChE. Repeated column fractionation of the ethyl acetate fraction on Sephadex LH-20 resulted in isolation of three compounds identified as: 1,3,5-trihydroxybenzene (phloroglucinol) (1), together with two of its derivatives dibenzo [1,4] dioxine-2,4,7,9-tetraol (2) and hexahydroxyphenoxydibenzo [1,4] dioxine (eckol) (3). The spectra data of compound 2 is reported for the first time. Structure elucidation of the isolated compounds was carried out using spectroscopic techniques: mass spectrometry (ESI-TOF-MS), 1H and 13C NMR, DEPT together with 2D experiments (GCOSY, GHSQC and GHMBC). The IC50 values for the compounds ranged from 76.70 to 579.32 μM, with compounds 2 and 3 having the best AChE inhibitory activity. The activity demonstrated by the extracts and the isolated compounds suggests that they could be used as functional food ingredients for the management of neurodegenerative disorders.

  • Potential antiradical and alpha-glucosidase inhibitors from Ecklonia maxima (Osbeck) Papenfuss
    Food chemistry, 2013
    Co-Authors: Kannan R.r. Rengasamy, Wendy A. Stirk, M A Aderogba, Stephen O. Amoo, Johannes Van Staden
    Abstract:

    Alpha-glucosidase inhibitors play a potential role in the treatment of type 2 diabetes by delaying glucose absorption in the small intestine. Ecklonia maxima, a brown alga which grows abundantly on the west coast of South Africa, is used to produce alginate, animal feed, nutritional supplements and fertilizer. The crude aqueous methanol extract, four solvent fractions and three phlorotannins: 1,3,5-trihydroxy- benezene (phloroglucinol) (1), dibenzo (1,4) dioxine-2,4,7,9-tetraol (2) and hexahydroxyphenoxydibenzo (1,4) dioxine (eckol) (3) isolated from E. maxima were evaluated for antiradical and alpha-glucosidase inhibitory activities. All the phlorotannins tested had strong antioxidant activities on DPPH free radicals with EC50 values ranging from 0.008 to 0.128 lM. Compounds 2 and 3 demonstrated stronger antioxidant activity and an alpha-glucosidase inhibitory property than positive controls. These results suggest that E. maxima could be a natural source of potent antioxidants and alpha-glucosidase inhibitors. This study could facilitate effective utilization of E. maxima as an oral antidiabetic drug or functional food ingredient with a promising role in the formulation of medicines and nutrition supplements. Diabetes mellitus (DM) is a complex disorder characterized by hyperglycemia. It is one of the world's most serious health con- cerns, developing increasingly with the increasing obesity and advancing age in the general global population. The world preva- lence of diabetes among adults (aged 20-79 years) is 6.4%, affect- ing 285 million adults, in 2010, and is estimated to increase to 7.7%, affecting 439 million adults by 2030 (Shaw, Sicree, & Zimmet, 2010). The global prevalence of diabetes is 6.4%. It varies from 10.2% in the Western Pacific to 3.8% in the African region. However, the African region is expected to experience the highest increase. According to Levitt (2008), 10.8 million people had diabetes in sub-Saharan Africa in 2006, which could rise to 18.7 million by 2025, which is an increase of 80%, exceeding the globally predicted increase of 55%. In South Africa, the number of adults with diabetes was 1.28 million in 2010 and is expected to reach 1.64 million in 2030, with an annual increment of 18,000 (Shaw, Sicree, & Zimmet, 2010). The disease is primarily classified into insulin dependent DM (type 1 diabetes), non-insulin dependent DM (type 2 diabetes) and gestational diabetes. Type 2 diabetes is responsible for 85-95% of all diabetes in high-income countries and may account for an even higher percentage in low and middle income countries.

  • Seasonal variation in the polyamines of Ecklonia maxima
    Botanica Marina, 2012
    Co-Authors: H.b. Papenfus, Wendy A. Stirk, Jeffery Franklin Finnie, Johannes Van Staden
    Abstract:

    The seaweed concentrate (SWC) Kelpak ® is made from Ecklonia maxima (Osbeck) Papenfuss and is used as a biostimulant in agriculture. Cytokinins and auxins have been identified in Kelpak ® and are partly responsible for the growth-promoting effects observed. Other biologically active compounds such as polyamines (PAs) might also be present in the SWC. A study was carried out to inves- tigate the PA levels in E. maxima and Kelpak ® . The stipes, fronds, and SWC prepared from E. maxima were collected monthly over a 2-year period. Extracts were benzoylated, and endogenous PAs were quantified using high-perfor- mance liquid chromatography. Putrescine concentrations ranged from 6.10 to 40.40 μ g g -1 dry weight (dw), from 15.98 to 54.46 μ g g -1 dw, and from 0.98 to 5.51 μ g ml -1 in the stipe, fronds, and SWC, respectively. Spermine concentrations ranged from 1.02 to 35.44 μ g g -1 dw, from 1.05 to 27.35 μ g g -1 dw, and from 1.27 to 4.95 μ g ml -1 in the stipe, fronds, and SWC, respectively. Spermidine concentrations fell below the detection threshold. This is the first report of PAs being detected in a SWC. The seasonal pattern established for the stipe, frond, and SWC followed the same trend over a biennial cycle, with PAs accumulating in the seaweed tissue during periods of active growth and during periods of rough wave action (stress response).

Johannes Van Staden - One of the best experts on this subject based on the ideXlab platform.

  • Bioactive molecules derived from smoke and seaweed Ecklonia maxima showing phytohormone-like activity in Spinacia oleracea L.
    New biotechnology, 2018
    Co-Authors: Manoj G. Kulkarni, Kannan R.r. Rengasamy, S.c. Pendota, Jiří Grúz, Lenka Plačková, Ondřej Novák, Karel Doležal, Johannes Van Staden
    Abstract:

    Bioactive compounds such as karrikinolide (KAR1 from smoke) and eckol (from the seaweed Ecklonia maxima) show promising effects on several important crop plants. These plant growth-stimulating organic biomolecules, along with crude extracts (smoke-water and Kelpak® product prepared from Ecklonia maxima), were tested on spinach plants. Eckol sprayed at 10-6 M significantly increased all the growth and biochemical parameters examined compared to control spinach plants. All tested plant growth biostimulants significantly increased total chlorophyll, carotenoids and protein content of spinach leaves. The cytokinin profile of spinach plants was also determined. Cis-zeatin, dihydrozeatin and isopentenyladenine types of cytokinins were promoted by both smoke- and seaweed-based biostimulants. In comparison to the control plants, the level of free sinapic acid was greater in all spinach plants treated with these biostimulants. The application of these biostimulants can help spinach crop by improving growth, yield and nutritional quality; moreover, they are organic and cost-effective.

  • Quantification of plant growth biostimulants, phloroglucinol and eckol, in four commercial seaweed liquid fertilizers and some by-products
    Algal Research, 2016
    Co-Authors: Kannan R.r. Rengasamy, Manoj G. Kulkarni, H.b. Papenfus, Johannes Van Staden
    Abstract:

    Abstract Kelp species such as Ecklonia maxima are widely used as sources of liquid fertilizer for many economically important crops. Phloroglucinol and eckol are active biomolecules isolated from the brown seaweed Ecklonia maxima. They have shown root and growth promoting activity in some crop species. Currently there are many seaweed liquid products available in the markets that are sold as plant biostimulants. In some of these products auxins, cytokinins, polyamines, gibberellins, abscisic acid and brassinosteroids have been quantified and their role in plant growth and development has been well established. But, the presence and quantification of phloroglucinol and eckol in these products have not been determined yet. This would be useful for quality control of the products. In this study, four commercially available seaweed liquid fertilizers were analyzed for phloroglucinol and eckol content using High Performance Liquid Chromatography (HPLC). Additionally, a seaweed dry cake product (‘Plant it’ manufactured by Kelpak® from Ecklonia maxima ) and Kelpak® cell wall paste by-product were also assessed for phloroglucinol and eckol content. The liquid seaweed products evaluated in this study were prepared from the seaweeds Ascophyllum nodosum , Durvillaea potatorum and Ecklonia maxima . HPLC analysis of these products showed that eckol content was greater than the known plant growth regulator phloroglucinol in three products. The amount of eckol detected in all the samples ranged from 96 to 860 μg L − 1 . A higher quantity of both phloroglucinol and eckol was recorded for Kelpak® in comparison to the other products. The higher levels of these two plant growth promoting biomolecules in the Kelpak® samples can be attributed to the use of cold cellular-burst technology. More studies are necessary to determine the optimum levels of phloroglucinol and eckol required for plant growth in different liquid seaweed fertilizers.

  • eckol a new plant growth stimulant from the brown seaweed Ecklonia maxima
    Journal of Applied Phycology, 2015
    Co-Authors: Kannan R.r. Rengasamy, Wendy A. Stirk, M G Kulkarni, Johannes Van Staden
    Abstract:

    The seaweed concentrate Kelpak® made from the brown kelp Ecklonia maxima is used worldwide as a biostimulant for a number of agricultural crops. Plant growth regulators such as auxins, cytokinins, polyamines, gibberellins, abscisic acid, and brassinosteroids were identified from E. maxima and Kelpak®. In this study, we investigated the plant growth stimulating effects of two phlorotannins, i.e., phloroglucinol and eckol that were recently isolated from E. maxima. The activity of isolated eckol was compared with Kelpak® and commercially available phloroglucinol and the auxin indole-3-butyric acid (IBA). The isolated eckol from E. maxima stimulated maize growth in terms of shoot and root elongation and number of seminal roots and exhibited improvement in the biochemical activities of α-amylase compared to Kelpak®, phloroglucinol, and IBA. Furthermore, eckol showed auxin-like activity in the mung bean root assay at 10−5 M with an increased number of roots, shoot elongation, and seedling weight. Eckol can potentially play a significant role in increasing agricultural productivity.

  • acetylcholinesterase inhibitory activity of phlorotannins isolated from the brown alga Ecklonia maxima osbeck papenfuss
    Food Research International, 2013
    Co-Authors: Rengasamy Ragupathi Raja Kannan, Wendy A. Stirk, M A Aderogba, A R Ndhlala, Johannes Van Staden
    Abstract:

    Abstract Ecklonia maxima, a brown alga grows abundantly on the west coast of South Africa and is used to produce alginate, animal feed, nutritional supplements and fertilizer. The crude extract, solvent fractions and phlorotannins isolated from E. maxima were evaluated for acetylcholinesterase (AChE) inhibitory activity using the microplate technique. The IC50 values for the solvent fractions ranged from 62.61 to 150.8 μg/mL, with the ethyl acetate fraction having the best inhibitory activity against AChE. Repeated column fractionation of the ethyl acetate fraction on Sephadex LH-20 resulted in isolation of three compounds identified as: 1,3,5-trihydroxybenzene (phloroglucinol) (1), together with two of its derivatives dibenzo [1,4] dioxine-2,4,7,9-tetraol (2) and hexahydroxyphenoxydibenzo [1,4] dioxine (eckol) (3). The spectra data of compound 2 is reported for the first time. Structure elucidation of the isolated compounds was carried out using spectroscopic techniques: mass spectrometry (ESI-TOF-MS), 1H and 13C NMR, DEPT together with 2D experiments (GCOSY, GHSQC and GHMBC). The IC50 values for the compounds ranged from 76.70 to 579.32 μM, with compounds 2 and 3 having the best AChE inhibitory activity. The activity demonstrated by the extracts and the isolated compounds suggests that they could be used as functional food ingredients for the management of neurodegenerative disorders.

  • Potential antiradical and alpha-glucosidase inhibitors from Ecklonia maxima (Osbeck) Papenfuss
    Food chemistry, 2013
    Co-Authors: Kannan R.r. Rengasamy, Wendy A. Stirk, M A Aderogba, Stephen O. Amoo, Johannes Van Staden
    Abstract:

    Alpha-glucosidase inhibitors play a potential role in the treatment of type 2 diabetes by delaying glucose absorption in the small intestine. Ecklonia maxima, a brown alga which grows abundantly on the west coast of South Africa, is used to produce alginate, animal feed, nutritional supplements and fertilizer. The crude aqueous methanol extract, four solvent fractions and three phlorotannins: 1,3,5-trihydroxy- benezene (phloroglucinol) (1), dibenzo (1,4) dioxine-2,4,7,9-tetraol (2) and hexahydroxyphenoxydibenzo (1,4) dioxine (eckol) (3) isolated from E. maxima were evaluated for antiradical and alpha-glucosidase inhibitory activities. All the phlorotannins tested had strong antioxidant activities on DPPH free radicals with EC50 values ranging from 0.008 to 0.128 lM. Compounds 2 and 3 demonstrated stronger antioxidant activity and an alpha-glucosidase inhibitory property than positive controls. These results suggest that E. maxima could be a natural source of potent antioxidants and alpha-glucosidase inhibitors. This study could facilitate effective utilization of E. maxima as an oral antidiabetic drug or functional food ingredient with a promising role in the formulation of medicines and nutrition supplements. Diabetes mellitus (DM) is a complex disorder characterized by hyperglycemia. It is one of the world's most serious health con- cerns, developing increasingly with the increasing obesity and advancing age in the general global population. The world preva- lence of diabetes among adults (aged 20-79 years) is 6.4%, affect- ing 285 million adults, in 2010, and is estimated to increase to 7.7%, affecting 439 million adults by 2030 (Shaw, Sicree, & Zimmet, 2010). The global prevalence of diabetes is 6.4%. It varies from 10.2% in the Western Pacific to 3.8% in the African region. However, the African region is expected to experience the highest increase. According to Levitt (2008), 10.8 million people had diabetes in sub-Saharan Africa in 2006, which could rise to 18.7 million by 2025, which is an increase of 80%, exceeding the globally predicted increase of 55%. In South Africa, the number of adults with diabetes was 1.28 million in 2010 and is expected to reach 1.64 million in 2030, with an annual increment of 18,000 (Shaw, Sicree, & Zimmet, 2010). The disease is primarily classified into insulin dependent DM (type 1 diabetes), non-insulin dependent DM (type 2 diabetes) and gestational diabetes. Type 2 diabetes is responsible for 85-95% of all diabetes in high-income countries and may account for an even higher percentage in low and middle income countries.

Robert J. Anderson - One of the best experts on this subject based on the ideXlab platform.

  • Geographical variation in morphology of the two dominant kelp species, Ecklonia maxima and Laminaria pallida (Phaeophyceae, Laminariales), on the west coast of Southern Africa
    Journal of Applied Phycology, 2017
    Co-Authors: Mark D Rothman, John J. Bolton, Michael S. Stekoll, Christian J. T. Boothroyd, Frederik A. Kemp, Robert J. Anderson
    Abstract:

    Laminaria pallida and Ecklonia maxima are large, commercially valuable kelps that co-dominate inshore waters of the west coast of Southern Africa in a geographically changing pattern. In the south, E. maxima dominates and forms a canopy in shallow waters (< about 5 m deep), with L. pallida forming a sub-canopy and extending down to 20 m or more. Northward along the Southern African coast and into Namibia, E. maxima is progressively replaced by L. pallida. Corresponding with this change in dominance, L. pallida shows certain morphological changes along the south-to-north geographical gradient. To explain these phenomena, we examined a range of morphological characters in both kelps (stipe length, stipe weight, stipe outer diameter, stipe inner diameter, length of hollow section in the stipe, and frond weight), and various environmental factors (seawater temperature, seawater turbidity, cloud/fog data, daylength, and wave and wind data). Our results, based on measurements at seven sites along 1600 km of coast between Cape Town and Swakopmund (Namibia), quantified and confirmed the change in dominance and the northward increase in stipe hollowness in L. pallida. The morphology of E. maxima did not change with latitude. Water turbidity, wind speed, and wave height differed significantly along the coast. However, only turbidity showed a steady trend, increasing northward in terms of all indicators (chlorophyll a, particulate inorganic carbon, particulate organic carbon) while wind speed and wave height showed a generally decreasing trend. Furthermore, the hollowness of L. pallida was also not related to the flexibility of the stipes. Our results suggest that L. pallida sporophytes may progressively outcompete E. maxima northward, perhaps because they are more low-light tolerant, and we suggest that by developing a hollow stipe, the sporophytes may grow faster in length, potentially increasing their competitive advantage in the shallow water where they must compete with sporophytes of E. maxima.

  • A simple method for rapid estimation of Ecklonia maxima and Laminaria pallida biomass using floating surface quadrats
    African Journal of Marine Science, 2010
    Co-Authors: Mark D Rothman, John J. Bolton, Robert J. Anderson, C Jt Boothroyd, F. A. Kemp
    Abstract:

    In South Africa two species of kelp, Ecklonia maxima and Laminaria pallida, occur in quantities sufficient for commercial use. Currently, the former species is harvested in large quantities (about 5 000 tonnes wet weight per year) as abalone feed. In order to set limits to the amount of kelp that may be harvested, it is necessary to obtain reasonably accurate measurements of kelp biomass. Biomass estimates are traditionally obtained by destructive sampling of kelp sporophytes from quadrats placed on the bottom. Scuba divers harvest the plants and weigh them ashore. This method is slow and labour-intensive, and severely limits the area of kelp bed that can be sampled. This study investigates several alternative methods to determine an easier, quicker method of estimating kelp biomass. First, morphometric data on both species of kelp were collected to investigate if there were easily measurable characters that correlate with the weights of individual sporophytes, which then could be used as proxies for dest...

  • Mapping and quantifying the South African kelp resource
    African Journal of Marine Science, 2007
    Co-Authors: Robert J. Anderson, A. Share, Rothman, A. Rand, John J. Bolton
    Abstract:

    Two species of kelp are exploited commercially in South Africa. Use of beach-cast Laminaria pallida is limited, although it comprises the bulk of the biomass on the northern West Coast. Ecklonia maxima dominates the southern West Coast and provides most of the material for the South African kelp industry. Harvests of E. maxima fronds for abalone feed have reached 3 000–5 000 tonnes fresh weight (t f wt) y –1 , whereas beachcast material of both species (about 1 000t dry wt y –1 ) is collected mainly for alginate extraction. For the first time, a South African kelp inventory has been compiled using all available data for the 900km-long West Coast (Cape Agulhas to the Orange River), although a few gaps remain. Beds of E. maxima and L. pallida reaching the surface at low spring tides were mapped using one or several methods: infrared aerial photography, digital multispectral aerial imagery, Landsat satellite imagery, and physical mapping with a hand-held GPS. The data are on a GIS database. Landsat 5 TM imagery could identify the presence of kelp beds, but only infrared aerial imagery and multispectral imaging at low spring tides accurately quantified surface areas of kelp beds. Biomass of the main kelp ( E. maxima ) is variable in space (between 3kg f wt m –2 and 24kg f wt m –2 ) and time (changes of up to 50%), making estimates for management difficult. Using an average biomass value of 12kg m –2 , the total biomass of surface-reaching kelp beds on the West Coast is estimated to exceed 593 000t f wt, but extensive subsurface beds remain unquantified. Results are discussed in relation to sustainable limits to harvesting, gaps in knowledge, and the improved management of kelp resources. Keywords: Aerial infrared, Ecklonia maxima, GIS, kelp mapping, South Africa African Journal of Marine Science 2007, 29(3): 369–378

  • Harvesting of the Kelp Ecklonia maxima in South Africa Affects Its Three Obligate, Red Algal Epiphytes
    Journal of Applied Phycology, 2006
    Co-Authors: Robert J. Anderson, Mark D Rothman, A. Share, H. Drummond
    Abstract:

    In South Africa, more than 7000 t (f wt) of kelp (Ecklonia maxima) fronds are harvested annually to feed cultured abalone. Carpoblepharis flaccida, Gelidium vittatum and Polysiphonia virgata are conspicuous red algal epiphytes on older kelps and provide habitat and food for numerous animals. Over 4.5 y, we examined the effects of one destructive harvest of E. maxima on these 3 epiphytes. Two 20 × 20m plots of kelp with similar epiphyte loads were demarcated. In one, all E. maxima sporophytes with stipes longer than 50 cm were harvested. The other plot served as a control. After 2.5 y the biomass of E. maxima in the harvested plot had recovered to control levels, but the epiphyte load (g epiphytes. kg kelp−1) was statistically lower in the harvested plot after 2.5 and 3.5 y, and only recovered after 4.5 y. While most commercial harvesters cut through the “heads” (primary blades) of the kelp, effectively killing them, a new, non-lethal method removes secondary blades 20–30 cm from their bases, leaving the meristems and primary blades intact. At 5 sites studied, G. vittatum and P. virgata were found almost entirely on stipes and primary blades, and harvesting only distal parts of secondary blades limited losses to about 50% of C. flaccida biomass. To protect epiphytes, non-lethal harvesting is recommended and permanent non-harvest zones have been established in addition to limiting kelp yields and disallowing harvesting in Marine Protected Areas.

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