https://commons.ufh.ac.za/vital/access/manager/Index ${session.getAttribute("locale")} 5 https://commons.ufh.ac.za/vital/access/manager/Repository/vital:42197 Wed 23 Jun 2021 09:36:39 SAST ]]> https://commons.ufh.ac.za/vital/access/manager/Repository/vital:41619 80 μg∙L-1, ≥ 2781 H. akashiwo cells∙mL-1). Dissolved oxygen differed significantly by bloom state, with the highest dissolved oxygen concentrations. Larval fish density, diversity and community structure variability were lower during hypereutrophic blooms compared to standard blooms and bloom absence, albeit statistically insignificant. Estuarine resident larval density was negatively correlated with dissolved oxygen concentration (P < 0.001). Dominant prey copepod of G. aestuaria larvae, P. hessei, was less abundant and variable during hypereutrophic blooms (mean: 664, range: 4-4301 individuals per m3) compared to standard blooms (mean: 950, range: 2-5237 individuals per m3) and bloom absence (mean: 1182, range: 23-7259 individuals per m3). Although HABs did not appear to drive a mismatch between prey and G. aestuaria larvae, early juvenile larvae made only a small contribution to the assemblage (0.2-1.8%). In terms of predator effects, yolk sac larvae were negatively related to R. terranatalis (P < 0.05). A significant positive relationship was found between prey, P. hessei and G. aestuaria preflexion (P < 0.001), flexion (P < 0.001) and postflexion (P < 0.05) larvae. In a world first, the effects of HABs were investigated on a larval fish species, Gilchristella aestuaria, using biochemical body condition analyses. During severe bloom conditions, G. aestuaria larvae were smaller and the assemblage consisted of mainly early developmental stages (stats). Body condition (RNA per dry weight) was poorest in the presence of hypereutrophic blooms (P < 0.001). A bell-curved relationship between RNA/DW and dissolved oxygen concentration was also produced in a 3-day time-lagged GAM (P < 0.001). In conclusion, hypereutrophic bloom conditions appeared to trigger adult G. aestuaria spawning in the upper mesohaline zone of the estuary in response to heightened primary productivity which occurs during the early bloom stage. However, reductions in copepod abundance (P. hessei) and unfavourable oxygen concentrations interfered with grow-out of G. aestuaria larvae. This research showed that HABs can alter nursery properties to the detriment of G. aestuaria larvae can have serious knock-on effects up the food chain. The loss in abundance of adult, juvenile and larval G. aestuaria, a key forage fish in South African estuaries, has major implications for estuarine food webs, especially in reduced prey availability to juvenile fishes and birds. There is still much to learn about the effects of HABs on the physiological and behavioural aspects on plankton communities worldwide.]]> Wed 13 Mar 2024 14:10:51 SAST ]]> https://commons.ufh.ac.za/vital/access/manager/Repository/vital:41606 Wed 13 Mar 2024 09:37:38 SAST ]]> https://commons.ufh.ac.za/vital/access/manager/Repository/vital:39482 Wed 12 May 2021 22:33:26 SAST ]]> https://commons.ufh.ac.za/vital/access/manager/Repository/vital:39810 Wed 12 May 2021 22:29:37 SAST ]]> https://commons.ufh.ac.za/vital/access/manager/Repository/vital:39408 Wed 12 May 2021 20:27:28 SAST ]]> https://commons.ufh.ac.za/vital/access/manager/Repository/vital:39509 Wed 12 May 2021 17:20:28 SAST ]]> https://commons.ufh.ac.za/vital/access/manager/Repository/vital:39515 Wed 12 May 2021 16:43:30 SAST ]]> https://commons.ufh.ac.za/vital/access/manager/Repository/vital:41618 Wed 12 May 2021 15:10:54 SAST ]]> https://commons.ufh.ac.za/vital/access/manager/Repository/vital:41620 Wed 12 May 2021 15:05:32 SAST ]]> https://commons.ufh.ac.za/vital/access/manager/Repository/vital:42111 Wed 12 May 2021 15:04:32 SAST ]]> https://commons.ufh.ac.za/vital/access/manager/Repository/vital:41595 Wed 12 May 2021 14:42:47 SAST ]]> https://commons.ufh.ac.za/vital/access/manager/Repository/vital:41605 Wed 12 May 2021 14:32:55 SAST ]]> https://commons.ufh.ac.za/vital/access/manager/Repository/vital:42873 Wed 12 May 2021 14:32:43 SAST ]]> https://commons.ufh.ac.za/vital/access/manager/Repository/vital:42329 Wed 12 May 2021 14:19:44 SAST ]]> https://commons.ufh.ac.za/vital/access/manager/Repository/vital:42167 Wed 12 May 2021 14:18:55 SAST ]]> https://commons.ufh.ac.za/vital/access/manager/Repository/vital:41615 Wed 12 May 2021 14:17:26 SAST ]]> https://commons.ufh.ac.za/vital/access/manager/Repository/vital:41596 Wed 12 May 2021 14:14:01 SAST ]]> https://commons.ufh.ac.za/vital/access/manager/Repository/vital:41621 Wed 12 May 2021 14:13:24 SAST ]]> https://commons.ufh.ac.za/vital/access/manager/Repository/vital:41598 150 K) a divalent acceptor is extracted with an activation energy varying between samples based on compensation in a range of 90 meV to 70 meV. Photoluminescence measurements show four peaks with recombination mechanisms linked to the native acceptor identified in literature as either the gallium antisite and/or vacant gallium site. A fifth peak observed is attributed to the longitudinal phonon of the native acceptor. InAs and InAsSb epilayer are all grown at a temperature of 600 °C and cell pressure of 600 Torr. InAs is grown at a V/III ratio of 9.5 on GaAs substrate. Photoluminescence of the InAs layer shows two distinct peaks, one of which is an extrinsic band to band recombination. The other is attributed to free electron to acceptor or a donor-acceptor pair transition. An additional weak peak is also observed which is assigned to the longitudinal phonon of the band to band. InAsSb growth was conducted under a range of V/III ratios of 4.8 to 5, with a vapour phase composition of 0.4 to 0.435. Structural analysis via X-ray diffraction showed a 6 % to 12 % solid antimony content. Photoluminescence exhibited a single broad peak for all samples, with extended band tails. Temperature and power dependant analysis of luminescence indicated a convolution of extrinsic band to tail and band to band recombinations. Hall measurements indicated the InAsSb was n-type material with an apparent measured maximum mobility at 120 K of 9.5 × 103 cm2/V.s. and a room temperature apparent mobility of 7.5 × 103 cm2/V.s. Analysis of hall results using a two-layer model calculated a true bulk mobility of the epilayer at room temperature with an increased value of 15.4 × 103 cm2/V.s. The two-layer model details the effects of the surface conduction. From photoconductivity measurements and further analysis a resultant effective lifetime, at room temperature, was found to be on same order of magnitude as that of InAs materials. Application of a single Einstein oscillator extrapolated 0 K energy gaps for two samples of solid Sb contents of 6 % and 12 %, of 354 meV and 332 meV, respectively. Finally consideration was given to the growth of aluminium containing compounds, particularly AlGaSb. Multiple phases were observed under scanning electron microscope showing growth of GaSb regions surrounded by amorphous solid aluminium and/or aluminium oxide phases. The failure of the aluminium to incorporate into the desired crystal structure is speculated to be due to impure precursor introducing oxygen into the films. Additionally, the effectiveness of the gallium precursor compared to the aluminium precursor in helping the removal of the methyl groups at the growth surface, could also promote a preference for GaSb growth.]]> Wed 12 May 2021 13:53:32 SAST ]]> https://commons.ufh.ac.za/vital/access/manager/Repository/vital:41614 Wed 12 May 2021 13:48:44 SAST ]]> https://commons.ufh.ac.za/vital/access/manager/Repository/vital:39669 Tue 24 May 2022 13:55:38 SAST ]]> https://commons.ufh.ac.za/vital/access/manager/Repository/vital:39403 Thu 13 May 2021 08:54:11 SAST ]]> https://commons.ufh.ac.za/vital/access/manager/Repository/vital:39514 Thu 13 May 2021 06:28:25 SAST ]]> https://commons.ufh.ac.za/vital/access/manager/Repository/vital:39811 Thu 13 May 2021 01:49:35 SAST ]]>