BIOACCUMULATION OF 2,2′,5,5′-TETRACHLOROBIPHENYL AND PYRENE BY PICOPLANKTON (SYNECHOCOCCUS LEOPOLIENSIS, CYANOPHYCEAE): INFLUENCE OF VARIABLE HUMIC ACID CONCENTRATIONS AND pH

Abstract

Abstract-Natural dissolved organic matter (DOM) controls the aqueous phase partitioning of hydrophobic organic contaminants (HOCs), where the sum of aqueous HOCs is distributed between the bound and free forms of HOCs, that is [. The hypothesis that the bioavailability of aqueous HOCs can be attributed solely to the concentration of the free form of HOCs was tested. Bioavailability was measured as accumulation of [ 14 C]-PCB (IUPAC 52) and [ 14 C]-pyrene over 48 h by the phytoplanktonic cyanobacterium Synechococcus leopoliensis. The phytoplankton were exposed within dialysis sacs to freely dissolved HOC at concentrations that were similar in all sacs (freely dissolved PCB ϳ 125 ng/L, freely dissolved pyrene ϳ55 ng/L). However, humic acid concentrations were varied among the sacs (Suwannee River humic acid [HA] ϭ 0, 2, 5, or 20 mg/L). The experiment was designed to vary the concentrations of HOC-HA and HA while keeping the concentration of freely dissolved HOCs at the same levels in all the sacs. Sorption mechanisms were probed by manipulating the pH of the exposure medium; the hydrophobicities of the cell surface and the humic acid are pH-sensitive, whereas the freely dissolved concentration of HOCs is pH-invariant. Bioaccumulation was predominantly controlled by the freely dissolved concentration of HOC and was greater at pH 4.3 than at pH 7.3. Although sorption of the PCB-HA and pyrene-HA complexes by S. leopoliensis occurred, this mechanism did not contribute significantly to the total accumulation of PCB or pyrene. These results suggest that the accumulation of HOCs by planktonic microorganisms can be predicted on the basis of the concentration of freely dissolved HOC molecules.

Biodegradation of High-Molecular-Weight Polycyclic Aromatic Hydrocarbons by Bacteria

“…Due to their lipophilic nature, PAHs have a high potential for biomagnification through trophic transfers (21,69,98). PAHs are also known to exert acutely toxic effects and/or possess mutagenic, teratogenic, or carcinogenic properties (18,48,82).…”

Porous underwater chamber (PUC) for in‐situ determination of nutrient and pollutant bioavailability to microorganisms

“…In a third set of experiments, the bioreporter was exposed to filtered (<0.4 μm, FW) lakewater in the PUCs and in test tubes and to whole (WW) lake water (PUCs only) sampled from a depth of 5 m from the pelagic zone of Lake Erie at Stations 23, 84, and 357 (see Twiss et al 2000 for location and description). Sampling was performed in July 2004 onboard the C.C.G.S.…”

“…For example, several laboratory studies have demonstrated the ability of plankton to directly or indirectly (siderophores) use particulate or colloidal iron (Yoshida et al 2002;Yoshida et al 2006). In addition, the biological cycling of trace metals can greatly influence their bioavailability in natural open systems (Twiss and Campbell 1998;Twiss et al 1996). For example, the biological cycling of iron has been reported to provide 40% to 80% of the bioavailable iron in a surface seawater Morel 1998, McKay et al 2005).…”

“…Devices have been used to assess nutrient requirements (Durrieu et al 2003) or pressure due to growth and grazing (Furnas 1982, Furnas 1991. Semi-permeable membranes have frequently been used to separate phytoplankton from the influence of chemical constituents of high molecular mass, including humic substances (>1 kDa), in order to determine their influence on the binding and bioavailability of toxic compounds (Twiss et al 1999). Teflon membranes (Tan 1986), regenerated cellulose dialysis membranes (Furnas 1982, Twiss et al 1999, and polycarbonate membranes (Furnas 1982(Furnas , 1991 have been used in the past.…”

“…Semi-permeable membranes have frequently been used to separate phytoplankton from the influence of chemical constituents of high molecular mass, including humic substances (>1 kDa), in order to determine their influence on the binding and bioavailability of toxic compounds (Twiss et al 1999). Teflon membranes (Tan 1986), regenerated cellulose dialysis membranes (Furnas 1982, Twiss et al 1999, and polycarbonate membranes (Furnas 1982(Furnas , 1991 have been used in the past. Furnas (1982) showed that diffusion of solutes through polycarbonate membranes was more rapid than through regenerated cellulose membranes, resulting in higher growth rates.…”