THESIS APPROVAL
THESIS APPROVAL
THESIS APPROVAL
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7. Toxic Effects in Aquatic Organisms<br />
PAHs readily have biological effects in aquatic organisms. They may interact<br />
physically with hydrophobic sites in the cell, causing molecular deformation and<br />
perturbation. Alternatively, PAHs metabolites may undergo a variety of spontaneous<br />
or enzyme-mediated chemical reaction leading to cell damage, mutagenesis,<br />
teratogenesis and cancer (Neff, 1985). Furthermore, these chemicals appear to bind<br />
selective to the surface of plasma membranes (Roubal and Collier, 1975). This<br />
binding causes perturbations in surface organization, increasing membrane<br />
permeability (Goldacre, 1968). By disrupting, PAHs might also affect the activity of<br />
the many enzymes bound to plasma membranes and essential for cell function.<br />
The toxicity of PAHs will be proportional to the concentration associated with<br />
the membrane surface. Less soluble aromatics tend to have s greater effect at a given<br />
concentration than more soluble ones (Neff, 1985). Although acute toxicity of PAHs<br />
to aquatic organisms increases as molecular weight increases, the relationship is not<br />
absolute. Only low molecular weight including naphthalene, fluoranthene and pyrene<br />
are acutely toxic to aquatic organisms, while the higher molecular weight PAHs are<br />
not acutely toxic. Variability in response to water-borne PAHs and sedimentassociated<br />
PAHs in several species of aquatic animals were shown in Table 6 and<br />
Table 7, respectively.<br />
It should be recognized that the acute toxicity data do not adequately reflect<br />
the potential impact of chronic low-level PAH contamination produced sublethal<br />
responses in aquatic organisms. These sublethal effects may be detrimental to the<br />
long-term survival. In addition, chronic exposure to certain PAH, such as 4-6 rings<br />
and highly angular configurations, may induce mutation and cancer in sensitive<br />
species (Zedeck, 1980). Several experimental conducted on sublethal effect of PAH<br />
in aquatic biota have reported particularly on naphthalene. The behavioral response<br />
had been studied in blue crabs Callinectes sapidus which detected extremely low<br />
concentrations of naphthalene in solution and responded by increased antennular<br />
flicking rate (Pearson and Olla, 1980). Donahue et al. (1977) found that several<br />
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