Browsing by Subject "Mussels"

Now showing 1 - 2 of 2
  • Thumbnail Image
    Item
    Open Access
    Relation of crystalline style function to food availability and environmental conditions in South African mussels
    (1987) Fielding, Peter John; Hemsted, W R T
    The mussels Choromytilus meridionalis, Mytilus galloprovincialis, Perna perna and Aulacomya ater are important and often dominant organisms on the littoral and sublittoral shores of the South Africa. M. galloprovincialis has only recently been identified as a separate species, but a cons1derable body of information exists on the physiology and energetics of c. meridionalis, P. perna and A. ater. However, it is not clear what factors determine the different intertidal and geographic distributions of these mytilids. Work in the kelp beds has shown that the energy budgets of mussels depends on the utilisation of particulate material from both kelp and phytoplankton production, which have very different structural complexities and biochemical compositions. There is very little information on the digestive enzymes of South African mussels. The activity of these enzymes will be an important factor affecting the ability of the mussels to effectively utilise a food resource, and this may be a mechanism which partially accounts for their differing distributions. This work examines the quantitative and qualitative nature of the suspended particulate food resource at the boundary of the east and west coast mussel ranges, the differences in the digestive enzyme activities of the four mussel species that might utilise the food resource, and 'the animals' abilities to digest this particulate material.
  • Thumbnail Image
    Item
    Open Access
    Spatio-temporal variation in effects of upwelling on the fatty acid composition of benthic filter feeders in the Southern Benguela ecosystem: not all upwelling is equal
    (Public Library of Science, 2016) Puccinelli, Eleonora; McQuaid, Christopher David; Noyon, Margaux
    Variability in mesoscale nearshore oceanographic conditions plays an important role in the distribution of primary production and food availability for intertidal consumers. Advection of nutrient rich waters by upwelling usually allows the proliferation of diatoms, later replaced by dinoflagellates. We examined upwelling effects on the fatty acid (FA) signature of a benthic intertidal filter feeder to identify its response to pulsed variability in food availability. The study took place in two contrasting seasons and at two upwelling and two non-upwelling sites interspersed within the southern Benguela upwelling system of South Africa. We investigated the FA composition of the adductor muscles and gonads of the mussel Mytilus galloprovincialis to assess how FA are apportioned to the different tissues and whether this changes between upwelling and non-upwelling conditions. In situ temperature loggers used to identify upwelling conditions at the four sites indicated that such events occurred only at the upwelling centres and only in summer. Tissues differed strongly, with gonads presenting a higher proportion of essential FAs. This could reflect the faster turnover rate of gonad tissue or preferential retention of specific FA for reproductive purposes. FA composition did not vary as a direct function of upwelling, but there were strong dissimilarities among sites. Upwelling influenced mussel diets at one upwelling site while at the other, the expected signature of upwelling was displaced downstream of the core of upwelling. Condition Index (CI) and Gonad Index (GI) differed among sites and were not influenced by upwelling, with GI being comparable among sites. In addition, FA proportions were consistent among sites, indicating similar food quality and quantity over time and under upwelling and non-upwelling conditions. This suggests that the influence of upwelling on the west coast of South Africa is pervasive and diffuse, rather than discrete; while nearshore retention or advection of upwelled water is critical and site-specific so that the effects of upwelling differ even among sites categorised as upwelling centres.