| Summary: | Human activities such as the continued burning of fossil fuels and changing land use are releasing gigatonnes of CO 2 into the atmosphere. As a result of the increase in atmospheric CO 2 concentration, a greenhouse effect is created. The direct consequences of an increased concentration of atmospheric CO 2 include rising global temperature, warming of the ocean waters and acidification of the oceans (lowering of seawater pH). Indirect consequences may include disturbances to the physiological and biological processes in marine organisms. Warming of the ocean waters and lowering of the seawater pH are environmental stresses that could impact the well-being of marine-dwelling organisms. This dissertation aims to examine the short-term effect of increasing seawater temperatures and decreasing seawater pH on the Neutral Red retention time of lysosomes of the green mussels (Perna viridis). Green mussels were subjected to temperature stress at 25 o C (control), 28 o C, 30 o C and 32 o C. With increasing seawater temperatures, the Neutral Red retention time of the lysosomes in the green mussels were significantly reduced. Computed probit graphs of the EC50 dose-response relationship for temperature stress was 31.3 o C and 30.8 o C at 48 hour and 120 hour exposure period, respectively. This indicated that mussel lysosomal membranes were susceptible to damage at high temperatures. In a separate experiment, the green mussels were kept in acidified seawater at pH 8.2 (control), pH 7.5, pH 6.5 and pH 5.6. The Neutral Red retention time of the lysosomes in the green mussels also showed decreased dye retention time during the experimental period. Computed probit graphs of the EC50 dose-response relationship for increased seawater acidification was pH 6.1 and pH 6.4 at 48 hour and 120 hour exposure period, respectively. This showed that chronic exposure of green mussels to low seawater pH (pH 6.5 and below) impairs the integrity of the mussel lysosomal membranes. The temperature and pH regimes selected for this dissertation ...
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