Browsing by Author "Amosu, Albert Oluwatobi"

Now showing 1 - 2 of 2
  • Thumbnail Image
    Item
    Environmental response and ph tolerance of induced co2 in ulva rigida c.agardh, 1823(Chlorophyta) under controlled conditions
    (PAS FORUM, 2022) Amosu, Albert Oluwatobi
    The increase in integrated multitrophic aquaculture (IMTA), where seaweed (particularly Ulva rigidaC.Agardh, 1823) is used as a feedstock and a wastewater scrubber in South African IMTA systems, has necessitated research into seaweed growth rates, which hassubsequently increased production technologies.Seaweed growth can be increased by controlling the culture media.One of the means to control growth rate is through CO2gas addition to culture media via aeration.This has the potential added benefit of usingwaste CO2 production from an alternative source to decrease overall carbon dioxide emissions. The consequence of elevated CO2 concentration on the pH of culture medium and the equivalent functional reactions in the seaweed were examined using U. rigida in flow-through systems.Toxicity investigation of Hydrogen ion concentrations werecarried out on U. rigida to examine their anatomy cum functional differences arising due to CO2 exerted stress. Elevated CO2 levels and the accompanying decrease in culture media pH (4.71 – 6.67) leadto a significant decrease in biomass with varied sporulation activities. In addition, U. rigida in flow-through systems showed a gradual degeneration in specific growth rate, from day 7, atvarying rates until the end of the experiment in the following sequence pH 7.20 > 8.20 > 7.50 > 7.80.The treatment set at pH 7.20 yielded the greatest specific biomassandthe greatest produce.The cultured input stocking rate of 5 g.l-1 of seawater proved to be suitable for cultivation. ThepH toxicity reaction was significant in predicting the suitability of seaweed cultured under CO2 induced concentrations.
  • Thumbnail Image
    Item
    Using Ulva (Chlorophyta) for the production of biomethane and mitigation against coastal acidification
    (University of the Western Cape, 2016) Amosu, Albert Oluwatobi; Maneveldt, Gavin W.; Roberson-Andersson, Deborah V.; Bolton, John J.
    In South Africa the green macroalga Ulva armoricana is the main species of macroalgae cultured. The species is currently the largest aquaculture (2884.61 tonnes) product by weight with a corresponding capacity for biogas (CH₄) production. We have shown that biotransformation of U. armoricana to Liquefied Petroleum Gas (LPG) is viable and economically feasible as a clean fuel. pH toxicity tests showed that U. armoricana can be used as a health index, under potentially increased CO₂ concentrations that can occur in IMTA carbon sequestration. We have shown sporulation to be the morphological response to environmental stress, which is indicative of chlorophyll degradation and a reduction in the photosynthetic activity of the alga. With the exception of Cadmium (Cd), the physico-chemical values obtained and the dissolved nutrient/heavy metals uptake by the alga all fell within the FAO/WHO permissible standards. Our Cd values therefore negate the use of these macroalgae for human consumption. We have also shown that U. armoricana can be used in eco-monitoring by playing a significant role in wastewater filtration and bioaccumulation. Nutrient utilization and proximate composition results show that African mud catfish (Clarias gariepinus) grow well on a protein-enriched Ulva diet, suggesting that enriched Ulva has the potential to be a successful fish feed. This thesis suggests among others, that South Africa could take advantage by being the first African country to propose specific standards for edible macroalgae as its successful research innovations and development provides a template for other African countries to further their aquaculture sectors. Additional benefits (bioremediation, ocean de-acidification through the capture of atmospheric and dissolved CO₂ during growth to assist in climate change mitigation) from Ulva farming activities bode well for the aquaculture industry.