Browsing by Author "Gibbons, M.J"

Now showing 1 - 4 of 4
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    Records of ctenophores from South Africa
    (PeerJ Inc., 2021) Gibbons, M.J; Haddock, S.H.D; Matsumoto, G.I
    Although ctenophores can be conspicuous components of the plankton in coastal marine ecosystems, only six species have been formally described from around South Africa. Using photographs from local community scientists, we add a further three species (Cestum veneris, Beroe forskalii?, Ocyropsis maculata?) and six morphospecies to the regional fauna. These additions suggest that South Africa has a ctenophore fauna that is amongst the most diverse, globally; an observation in agreement with information from other taxa. Tips on how community scientists can improve their photographic contributions to understanding ctenophore diversity are provided.
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    Role of jellyfish in the plankton ecosystem revealed using a global ocean biogeochemical model
    (Copernicus GmbH, 2021) Wright, R.M; Le Quere, C
    Jellyfish are increasingly recognised as important components of the marine ecosystem, yet their specific role is poorly defined compared to that of other zooplankton groups. This paper presents the first global ocean biogeochemical model that includes an explicit representation of jellyfish and uses the model to gain insight into the influence of jellyfish on the plankton community. The Plankton Type Ocean Model (PlankTOM11) model groups organisms into plankton functional types (PFTs). The jellyfish PFT is parameterised here based on our synthesis of observations on jellyfish growth, grazing, respiration and mortality rates as functions of temperature and jellyfish biomass. The distribution of jellyfish is unique compared to that of other PFTs in the model. The jellyfish global biomass of 0.13 PgC is within the observational range and comparable to the biomass of other zooplankton and phytoplankton PFTs.
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    Studies of foraminifera associated with gelidium pristoides (turner) keutzing (gelidiales: rhodophyta)
    (University of the Western Cape, 2002) Toefy, R; McMillan, K; Gibbons, M.J
    Our understanding of the macrofauna of hard intertidal substrata around South Africa is fairly comprehensive, and we have a good understanding of the environmental factors responsible for structuring macrofaunal communities (McQuaid & Branch, 1985; Bustamante et al., 1996; Emanuel et al., 1992). The same cannot be said for meiofaunal communities of rocky shores, which despite their neglect are known to play an important role in the functioning of many intertidal systems (Gibbons & Griffiths, 1986). While macrofauna may dominate rocky shores in terms of biomass, meiofauna are generally more abundant, and because they have faster turnover rates they make an important contribution to secondary production (Gibbons & Griffiths, 1986).
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    Temporal and spatial variability in copepod abundance, distribution and community structure off Walvis Bay in the northern Benguela Current, 1979-1981
    (University of the Western Cape, 2005) Tsotsobe, Sakhile Vincent; Gibbons, M.J; Verheye, H.M
    The zooplankton samples used for retrospective analysis in this study form part of the historical SWAPELS (South West African Pelagic Egg and Larva Survey) collection from January 1972 to December 1989, which covered the entire Namibian shelf. The SWAPELS Programme was initiated following the collapse of the Namibian sardine fishery during the late 1960s and early 1970s. This study investigates variability in the temporal and spatial distribution of total zooplankton (non-gelatinous) biomass, total copepod abundance, as well as copepod community structure off the coast of Walvis Bay along, primarily, transect 70 (23° S), and secondarily, transects 66 (22°67 S) and 74 (23°33 S), over the period 1979- 1981. Included in the data set are sea surface temperatures (SSTs) and surface salinities, allowing for spatio-temporal trends in the hydrology of this region to be examined. Despite extensive variability in SST (1 1.27- 18.15 °C), the most frequently occurring SSTs were in the 15-16 °C range. In 1979 salinities ranged mostly between 35.1 and 35.2, whereas in 1980 and 1981 modal salinities fell within the 35.0-35.1 and 35.2- 35.3 ranges, respectively. A clear seasonal pattern in the cross-shelf distribution of SST and salinity was observed in 1979-80, when, generally, warm , high-salinity water covered most of transect 70 (23° S) in summer to early autumn. In spring the cool inshore water extended seaward, to recede again into summer. The existence of cool inshore surface water from mid-winter to mid-spring, warming up into summer and extending offshore, was indicative of a typical upwelling cycle off Walvis Bay.