In many nearshore marine systems, microalgae can be chronically exposed to anthropogenic and biogenic phenolic and halophenolic compounds that accumulate in surficial sediments. Although biodegradation of some phenolic compounds has been demonstrated in freshwater algae, this capability has not been tested in marine species. We examined a ubiquitous marine diatom, Thalassiosira sp. HP9101, for its capacity to tolerate, and/or utilize phenol and benzoic acid. We also examined the aromatic ring cleavage reactions of this diatom and its capacity to dechlorinate chlorophenolic compounds. Axenic Thalassiosira sp. cultures were grown at 60 µE m -2 s -1 (12:12 h light:dark cycle) in the presence or absence of phenol, benzoate, catechol or protocatechuate and their growth kinetics and physiological responses determined. Thalassiosira sp. was inhibited by catechol and protocatechuate. Growth in the presence of 1 mM phenol was observed only after an extended lag and was quite slow. Growth in the presence of 0.25 mM phenol occurred after a much shorter lag and phenol was taken up by these cultures at an estimated rate of 0.08 fmol phenol cell . No inhibition of Thalassiosira sp. by 1 mM benzoate was observed. Growth stimulation by added phenolic substrates was not demonstrated, although phenol-supplemented Thalassiosira sp. produced substantial levels of protocatechuate 3, 4-dioxygenase and protocatechuate 4, 5-dioxygenase, the ortho-and meta-pathway aromatic ring cleavage enzymes, respectively. Only protocatechuate 4, 5-dioxygenase activity was detected in Thalassiosira sp. grown with 1 mM benzoate. Phenol supplemented Thalassiosira sp. was also capable of dechlorinating monochlorophenols, 3, 5-dichlorophenol, and 2, 4, 6-trichlorophenol. These reactions were NADH-dependent and were not observed in control cultures grown without phenol.
KEY WORDS: Benthic microalgae · Marine diatom · Phenol · Aromatic ring cleavage · Haloaromatics · Dehalogenation
Resale or republication not permitted without written consent of the publisherMar Ecol Prog Ser 229: [11][12][13][14][15][16][17][18] 2002 tural and residential runoff (Ahlborg & Thunberg 1980), and sewage and wastewater discharges (Chapman et al. 1996). In addition, bromophenolic compounds are natural products of a variety of marine organisms including many species of marine macroalgae (reviews by Butler & Walker 1993, Gribble 1999 and infaunal polychaetes and hemichordates (Woodin et al. 1987, Chen et al. 1991, Woodin 1991, Steward et al. 1992, 1995, Fielman et al. 1999, Gribble 1999. These anthropogenic and biogenic phenolic and halophenolic compounds can accumulate to significant levels in surficial sediments (Karickhoff et al. 1979, Schellenberg et al. 1984, King 1986, Xie et al. 1986, Lincoln et al. 2002, and at least some of these compounds, at concentrations found in sediments, are demonstrably toxic to some of the sediment biota (Woodin 1991, Woodin et al. 1993. Steward et al. (1992) demonstrated that elevated bromophenol concentrations produced by the infa...