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  • 1
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    Chapter 6 Biology and Ecology of the Globally Significant Kelp Ecklonia radiata (2021)
    Taylor & Francis | Oceanography and Marine Biology | Oceanography and Marine Biology | CRC Press
    Details
    Publication Date: 2024-04-05
    Description: Ecklonia radiata is one of the most widespread kelps globally, dominating temperate reefs throughout much of Australasia and southeastern Africa. Throughout much of its range, it is the only laminarian kelp and hence plays a key role in facilitating biodiversity and driving food webs, and it underpins immense ecological and socioeconomic values. This review synthesises the growing literature on E. radiata from its phylogeny and distribution through to its biology, ecology and recent changes. It provides an assessment of the state of knowledge and identifies gaps in our understanding of this important species. Despite being tolerant of a wide range of abiotic conditions, recent environmental change has caused direct and indirect loss of E. radiata forests, with extensive areas transitioning to turf and urchin barrens. Ongoing climate change may require application of multifaceted and novel strategies to increase its resistance and resilience to future conditions. By integrating variation across space, time and environmental change, this review provides a description of the current status and possible future trajectories of E. radiata forests.
    Keywords: biology ; ecology ; kelp ; thema EDItEUR::P Mathematics and Science::PS Biology, life sciences
    Language: English
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    E-BOOK
  • 2
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    The genus Ptilothamnion (Ceramiaceae, Rhodophyta) in South Africa, with the description of P. goukammae spec. nov (2002)
    In:  Blumea: Biodiversity, Evolution and Biogeography of Plants vol. 47 no. 3, pp. 581-595
    Details
    Publication Date: 2024-01-12
    Description: The genus Ptilothamnion Thur. in Le Jolis is represented in South Africa by three, or possibly four species: P. codicolum, P. polysporum, P. goukammae spec. nov., and reportedly P. subsimplex, all recorded after 1983. An earlier record of P. pluma is probably erroneous.\nThe new species differs from known representatives of the genus by producing strictly one involucral filament from the hypogenous cell and additionally one from the subhypogenous cell. Ptilothamnion is a widespread genus, but rarely with more than two species in any given regional flora. A critical comparison of the c. 12 species shows that very few characters are shared by all of them.
    Keywords: Ceramiaceae ; Ptilothamnion ; Spermothamnieae ; South Africa ; taxonomy
    Repository Name: National Museum of Natural History, Netherlands
    Type: info:eu-repo/semantics/article
    Format: application/pdf
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    PAPER (OA)
  • 3
    Electronic Resource
    Electronic Resource
    Distribution and population dynamics of Porphyra (Bangiales, Rhodophyta) in the southern Western Cape, South Africa (1999)
    Springer
    Journal of applied phycology 11 (1999), S. 429-436 
    Details
    ISSN: 1573-5176
    Keywords: distribution ; harvesting ; Porphyra ; recruitment ; seasonality ; South Africa ; taxonomy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Although Porphyra is commercially farmed in many countries, in South Africa only small harvests of wild populations for sale as nori have been carried out. The discovery that Porphyra improves growth of South African abalone (Haliotis midae) farmed inland-based tanks has led to increased pressure to harvest wild populations. This paper reports on a survey of the distribution and seasonality of Porphyra in the southern Western Cape. Porphyrawas present at all sites surveyed, and showed considerable temporal variation. A significant amount of the Porphyra present is in reserves and therefore protected from harvesting. Close rexamination of one site revealed seasonal populations of Porphyra that occupied different niches dependent on season. Recruitment peaked in spring and autumn, leading to dense summer and winter populations. Summer populations generally grew lower in the eulittoral than winter populations. No pattern in the mortality of larger thalli wasde tected, though sporeling mortality was high following recruitment peaks. Although it seems that most sites in the southern Western Cape are suitable for harvesting, the taxonomy of the genus in the region urgently needs revision if populations are to be appropriately managed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1008173321969
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  • 4
    Electronic Resource
    Electronic Resource
    Book review (1992)
    Springer
    Journal of applied phycology 4 (1992), S. 391-392 
    Details
    ISSN: 1573-5176
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02185798
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    Paper (German National Licenses)
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  • 5
    Electronic Resource
    Electronic Resource
    Organismic determinants and their effect on growth and regeneration in Gracilaria gracilis (1999)
    Springer
    Journal of applied phycology 11 (1999), S. 293-299 
    Details
    ISSN: 1573-5176
    Keywords: organismic determinants ; Gracilaria gracilis ; Rhodophyta ; regeneration ; growth ; mariculture
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract 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. Knowledge of these factors is essential in order to increase production from suspended seaweed rafts seeded with vegetative G. gracilis fragments. Seeding netlons with seaweed material freshly collected from subtidal populations provided up to 30% higher relative growth rates than seaweed maintained on the netlons for successive months. Initial seedstock length greatly affected growth rates and yields 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 the higher contribution to overall biomass by growth of lateral branches. Comparisons of the growth of apical and basal fragments suggest 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 extensive 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. These factors have implications for the successful cultivation of G. gracilis on commercial mariculture systems.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1008102409472
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  • 6
    Electronic Resource
    Electronic Resource
    Filamentous freshwater macroalgae in South Africa — a literature review and perspective on the development and control of weed problems (1996)
    Springer
    Hydrobiologia 340 (1996), S. 295-300 
    Details
    ISSN: 1573-5117
    Keywords: South Africa ; filamentous macroalgae ; copper sulphate
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Studies on freshwater filamentous algae have not been undertaken in South Africa for some thirty years. Early investigations were mainly of a taxonomic nature and ecological information is virtually non-existent. However, in the recent years the spread of urban settlement and increasing demand for both industrial and domestic water have highlighted the problems facing current water supplies. Irrigation systems in particular have suffered increasing interferences from filamentous algal blooms, mainly Cladophora glomerata. As nutrient loads have increased in impoundments and rivers, the presence of this alga has become more obvious, causing decreased water flow in canals and an escalation in costs associated with its control. Copper sulphate and predosing with commercial sulphuric acid to reduce pH are now the commonest control method in most of the irrigation systems. A synopsis of current conditions is presented and proposed avenues of research are discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00012771
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  • 7
    Electronic Resource
    Electronic Resource
    Patterns of species diversity and endemism in comparable temperate brown algal floras (1996)
    Springer
    Hydrobiologia 326-327 (1996), S. 173-178 
    Details
    ISSN: 1573-5117
    Keywords: diversity ; endemism ; global ; Phaeophyta ; seaweed ; upwelling
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Brown algal species diversity is compared in 100 km sections of the coastlines of four warm temperate regions: southern Australia, California, southwestern Africa, north-central Chile. The highest diversity (over 140 species per section) is found in southern Australia. California has a reasonable diversity (around 70 species per section), and both southern Australia and California have high regional endemism. Sections of north-central Chile and southwestern Africa have similar patterns, with low diversity (〈 30 species per 100 km section), low endemism, few or no fucoids, and up to 25% of the brown algal flora are environmentally tolerant species of Scytosiphonales. Species turnover between contiguous sections of coast is generally related to relative change in temperature regime. Thus the high diversity of southern Australia is due to high species diversity within the 100 km sections, with little turnover, except for a rapid reduction in eastern Victoria likely to be related to lack of rocky substatum. It is hypothesized that low diversity and endemism in Chile and southwestern Africa can be explained by the occurrence of major environmental perturbations (upwelling and El Nino effects) in these regions, producing variable inter-annual temperature conditions that select out tolerant species from the local floras.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00047803
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  • 8
    Electronic Resource
    Electronic Resource
    Form variation and productivity of an intertidal foliose Gigartina species (Rhodophyta) in relation to wave exposure (1990)
    Springer
    Hydrobiologia 204-205 (1990), S. 57-64 
    Details
    ISSN: 1573-5117
    Keywords: Gigartina ; polymorphy ; Rhodophyta ; seaweed ; South Africa ; wave exposure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Gametophytes from lower intertidal populations of the South African rhodophyte Gigartina radula, collected from sites subjected to different conditions of wave exposure, were compared with respect to various morphological, physiological and population attributes. A multivariate analysis of 13 variables revealed that variation in most parameters does not correlate directly with the wave exposure gradient. A clear pattern of response is revealed that suggests that environmental stresses occur at both the exposed and the sheltered sites although they are more extreme at the exposed sites. A number of important variables, notably photosynthetic production, showed maximum values in plants from semi-exposed sites.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00040215
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  • 9
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    Global patterns of kelp forest change over the past half-century (2016)
    National Academy of Sciences
    Details
    Publication Date: 2016-11-14
    Description: Kelp forests (Order Laminariales) form key biogenic habitats in coastal regions of temperate and Arctic seas worldwide, providing ecosystem services valued in the range of billions of dollars annually. Although local evidence suggests that kelp forests are increasingly threatened by a variety of stressors, no comprehensive global analysis of change in kelp abundances currently exists. Here, we build and analyze a global database of kelp time series spanning the past half-century to assess regional and global trends in kelp abundances. We detected a high degree of geographic variation in trends, with regional variability in the direction and magnitude of change far exceeding a small global average decline (instantaneous rate of change = −0.018 y−1). Our analysis identified declines in 38% of ecoregions for which there are data (−0.015 to −0.18 y−1), increases in 27% of ecoregions (0.015 to 0.11 y−1), and no detectable change in 35% of ecoregions. These spatially variable trajectories reflected regional differences in the drivers of change, uncertainty in some regions owing to poor spatial and temporal data coverage, and the dynamic nature of kelp populations. We conclude that although global drivers could be affecting kelp forests at multiple scales, local stressors and regional variation in the effects of these drivers dominate kelp dynamics, in contrast to many other marine and terrestrial foundation species.
    Print ISSN: 0027-8424
    Electronic ISSN: 1091-6490
    Topics: Biology , Medicine , Natural Sciences in General
    Published by National Academy of Sciences
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  • 10
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    Patterns of species diversity and endemism in comparable temperate brown algal floras (1996)
    Springer
    Details
    Publication Date: 1996-07-01
    Print ISSN: 0018-8158
    Electronic ISSN: 1573-5117
    Topics: Biology
    Published by Springer
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