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The purpose of this research was to examine the ability of the cold water, green, marine, macroalga Acrosiphonia coalita to take up and metabolize polycyclic aromatic hydrocarbons (PAH) from seawater. Axenic suspension tissue cultures of the alga were contacted with seawater containing PAH in sealed experimental vessels. Uptake time courses and equilibrium partitioning were examined. To determine if uptake was passive or active, equilibrium partitioning was also examined for uptake by heat-killed A. coalita tissue. Additionally, the seawater and biomass were monitored for the formation of PAH metabolites. The two model PAH compounds used in this study were naphthalene and phenanthrene.
The results of this study indicate that A. coalita did remove PAH from seawater, but that uptake was passive and the PAH was not metabolized. Both phenanthrene and naphthalene were taken up very quickly by the alga. Equilibrium partitioning between the seawater and biomass was achieved within 24 hours. Additionally, both compounds were found to partition linearly between A. coalita tissues and seawater. A. coalita removed significantly more phenanthrene than naphthalene from the seawater. The equilibrium partition coefficients for phenanthrene and naphthalene partitioning into living A. coalita tissue were 0.171 ± 0.0083 L/g FW and 0.0500 ± 0.0025 L/g FW, respectively. Naphthalene partitioning into heat-killed A. coalita tissue was equivalent to naphthalene partitioning into living A. coalita tissue, indicating that uptake was likely passive. No compounds were detected in the seawater or biomass that could be identified as a products of PAH degradation. Additionally, all unidentified compounds that were present in the experiments with PAH and biomass were also present in the control experiments without PAH. The absence of detectable products of degradation indicates that the PAH was not metabolized. |
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