Biodegradation of aromatic compounds by high latitude phytoplankton

Van Baalen, C. (Chase), 1925-1986; Gibson, David T.

Biodegradation of aromatic compounds by high latitude phytoplankton

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Date

1982

Authors

Van Baalen, C. (Chase), 1925-1986

Gibson, David T.

Department

Marine Science

Description

"It was the purpose of the work undertaken to bring into pure culture representative diatoms from the Cook Inlet and the ice-edge in the Bering Sea and to examine their capacity for the oxidation of aromatic compounds using naphthalene as a model substrate. Three diatoms from the Cook Inlet (Kasitsna Bay) were shown to metabolize naphthalene at 6 or 12°C to 1-naphthol and other unidentified ethyl acetate and water-soluble products. Likewise, three diatoms isolated from samples collected at the ice-edge in the Bering Sea also formed small amounts of 1-naphthol from naphthalene when incubated in the light at 0 or 10°C. We have not been able to rigorously prove that any algal cell, be it a blue-green alga, a green alga, or a diatom can metabolize (1-¹⁴C) naphthalene far enough to produce ¹⁴CO₂. However, if we assume a stoichiometery of one 1-naphthol in the algae equivalent to one CO₂ in bacteria, then for mesophilic algae, the rate of 1-naphthol production is roughly estimated as 10% of the in situ marine potential, and perhaps higher if only the photic zone is considered. We have as yet, no corresponding values for rate of 1-naphthol formation from naphthalene by cold-adapted or psychrophilic diatom cultures, however, it seems reasonable to suggest that algal aromatic transformations may also be a significant fraction of bacterial activity in cold environments. In addition to studies on the oxidation of naphthalene we have also examined the sensitivity of the Bering Sea psychrophilic diatoms to crude oil samples from Cook Inlet and Prudhoe Bay. The results with pure cultures indicate that the toxicity of crude oil was enhanced in psychrophilic diatoms growing at O°C or 10°C as compared to previous studies with mesophilic forms. There are several important consequences of the results for Alaskan OCS oil and gas development. It is now clear that pure cultures of diatoms isolated from either the lower Cook Inlet or from the ice-edge in the Bering Sea can oxidize aromatic compounds such as naphthalene. Whether the metabolites persist through the food chain and will be more or less toxic than naphthalene itself is not known. The results with naphthalene also imply that the photic zone can be an important sink for aromatic hydrocarbon transformations. There are certainly differences among microalgae in the capacity to oxidize naphthalene. It seems prudent, therefore, to insure, via monitoring, that accidental introduction of aromatic compounds in Alaskan waters does not cause a selective or enrichment effect on existing phytoplankton populations. A second area of environmental concern is the suggestion of an enhanced crude oil toxicity in slower growing psychrophilic diatoms as compared to their mesophilic cousins. Crude oil spills near or under the sea ice may severely impact primary productivity, and thereby higher tropic level.
Final report RD/MPF24-Effects-675
April 30, 1982