The zooplankton of Msikaba estuary

Stratification is well developed in Msikaba estuary and has a major influence on the distribution of the zooplankton. The oligohaline zooplankton component does not become well established, while marine zooplankton organisms penetrate relatively far up the estuary in the high salinity bottom waters. The euryhaline component becomes relatively well established near the mouth and it would appear that these organisms maintain their position within the estuary by vertical migration between inflowing bottom and outflowing surface waters. Seasonal means of zooplankton biomass were similar and ranged between 16 mg/m8 of water during winter and 15 mg/m8 during summer

The zooplankton of Mgazana, a mangrove estuary in Transkei, Southern Africa

Mgazana, a mangrove estuary inTranskei, was investigated from May 1972 to March 1973 at six-week intervals. Salinities were consistently above 25 parts per thousand in the middle and lower estuary. In the upper estuary the salinity varied between 4 and 29 parts per thousand. Water temperatures varied between I5.5°C and 28°C. One hundred and fifteen taxa of zooplankton organisms were recorded in the samples. The copepods Acartia naialensis and Oithona brevicornis reached high population densities and numbers exceeding 100 000/m3 of water were recorded. Mysids were major contributors to zooplankton biomass. A maximum biomass of I 200 mg/m3 was recorded in February in the middle estuary and was attributed to the mysid Mesopodopsis africana. Species of mysids showed clear seasonal and spatial patterns of distribution in the estuary

Euryhaline zooplankton of the Sundays estuary and notes on trophic relationships

No Abstract

Reproduction and larval distribution of the penaeid prawn Macropetasma africanus (Balss) in Algoa Bay

Breeding adults and larvae of Macropetasma africanus were sampled over a two-year period in Algoa Bay, South Africa. Gonadal macro- and microscopic examination enabled classification of breeding females into four stages of development. Breeding females were present throughout the study with a summer peak of late maturing and mature females. Larvae were present in the plankton throughout the study with peak abundance in summer. Protozoea, mysis and post-larval stages were recorded with the mysis stage most abundant. Significantly higher numbers of the mysis and post-larval stages were taken at shallow stations (5 m) off sandy beaches than at the deeper stations (18 m). The presence of breeding females in the mature stage of ovarian development and the increase in larval abundance in summer indicates spawning throughout the year with peak intensity in summer.S. Afr. l. Zool.1987, 22(3

Meteorological application of Apollo photography Final report

Development of meteorological information and parameters based on cloud photographs taken during Apollo 9 fligh

PHYSICAL FACTORS REGULATING MACROBENTHIC COMMUNITY STRUCTURE ON A SOUTH AFRICAN ESTUARINE FLOOD-TIDAL DELTA

Multivariate techniques were used to identify environmental parameters affecting macrobenthic communities on the flood-tidal delta of the Nahoon Estuary and adjacent beach near East London on the south-east coast of South Africa. Water content of sediments, temperature and exposure were identified as important parameters regulating differences in community structure between high-shore and subtidal sites, and between beach sites of varying elevation. High organic content was important for similarity of communities at sites farthest from the mouth and for distinctness of these communities from the others. Sediment particle size, compactness and current velocity contributed to similar communities of channel sites and their variation from those of other sites, and to distinctness of the lowest beach site from higher beach sites. Sites in the mouth and in the middle of the flood-tidal delta, with similarities in community structure, had varying values for all the measured environmental variables and none of these parameters could explain why these sites had similar communities. In summary, no over-riding parameter was shown to dominate the abiotic driving forces at all sampling sites, and different variables were important for structuring communities at different sites.Afr. J. mar. Sci. 25: 263–27

Towards service-oriented ontology-based coordination

Coordination is a central problem in distributed computing. The aim is towards flexible coordination, managed at run-time, in open, dynamic environments. This approach would benefit from an explicit common vocabulary for coordination and hence, in a previous paper, we modelled coordination in an ontology, describing the activities carried out and the interdependencies among these activities. The purpose of this paper is to show how such an ontology can be used alongside a set of rules to perform coordination by managing the interdependencies among activities. The ontology and rules can then be used to provide a general purpose coordination tool in the form of a Web servic

Climate change promotes parasitism in a coral symbiosis.

Coastal oceans are increasingly eutrophic, warm and acidic through the addition of anthropogenic nitrogen and carbon, respectively. Among the most sensitive taxa to these changes are scleractinian corals, which engineer the most biodiverse ecosystems on Earth. Corals' sensitivity is a consequence of their evolutionary investment in symbiosis with the dinoflagellate alga, Symbiodinium. Together, the coral holobiont has dominated oligotrophic tropical marine habitats. However, warming destabilizes this association and reduces coral fitness. It has been theorized that, when reefs become warm and eutrophic, mutualistic Symbiodinium sequester more resources for their own growth, thus parasitizing their hosts of nutrition. Here, we tested the hypothesis that sub-bleaching temperature and excess nitrogen promotes symbiont parasitism by measuring respiration (costs) and the assimilation and translocation of both carbon (energy) and nitrogen (growth; both benefits) within Orbicella faveolata hosting one of two Symbiodinium phylotypes using a dual stable isotope tracer incubation at ambient (26 °C) and sub-bleaching (31 °C) temperatures under elevated nitrate. Warming to 31 °C reduced holobiont net primary productivity (NPP) by 60% due to increased respiration which decreased host %carbon by 15% with no apparent cost to the symbiont. Concurrently, Symbiodinium carbon and nitrogen assimilation increased by 14 and 32%, respectively while increasing their mitotic index by 15%, whereas hosts did not gain a proportional increase in translocated photosynthates. We conclude that the disparity in benefits and costs to both partners is evidence of symbiont parasitism in the coral symbiosis and has major implications for the resilience of coral reefs under threat of global change

Housing prices and multiple employment nodes: is the relationship nonmonotonic?

Standard urban economic theory predicts that house prices will decline with distance from the central business district. Empirical results have been equivocal, however. Disjoints between theory and empirics may be due to a nonmonotonic relationship between house prices and access to employment arising from the negative externalities associated with proximity to multiple centres of employment. Based on data from Glasgow (Scotland), we use gravity-based measures of accessibility estimated using a flexible functional form that allows for nonmonotonicity. The results are thoroughly tested using recent advances in spatial econometrics. We find compelling evidence of a nonmonotonic effect in the accessibility measure and discuss the implications for planning and housing policy