THESIS APPROVAL

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