Discrete Organic Phosphorus Signatures are Evident in Pollutant Sources within a Lake Erie Tributary.

Phosphorus loads are strongly associated with the severity of harmful algal blooms in Lake Erie, a Great Lake situated between the United States and Canada. Inorganic and total phosphorus measurements have historically been used to estimate nonpoint and point source contributions, from contributing watersheds with organic phosphorus often neglected. Here, we used ultrahigh resolution mass spectrometry to characterize the dissolved organic matter and specifically dissolved organic phosphorus composition of several nutrient pollutant source materials and aqueous samples in a Lake Erie tributary. We detected between 23 and 313 organic phosphorus formulas across our samples, with manure samples having greater abundance of phosphorus- and nitrogen containing compounds compared to other samples. Manures also were enriched in lipids and protein-like compounds. The greatest similarities were observed between the Sandusky River and wastewater treatment plant effluent (WWTP), or the Sandusky River and agricultural edge of field samples. These sample pairs shared 84% of organic compounds and 59-73% of P-containing organic compounds, respectively. This similarity suggests that agricultural and/or WWTP sources dominate the supply of organic phosphorus compounds to the river. We identify formulas shared between the river and pollutant sources that could serve as possible markers of source contamination in the tributary.

Marine protozoa produce organic matter with a high affinity for PCBs during grazing.

Processes influencing organic carbon distribution and composition can control the speciation of organic contaminants such as polychlorinated biphenyls (PCBs) and ultimately determine their residence time in aquatic environments. Protozoan grazers are active in the remineralization and recycling of organic material both in the water column and at the sediment-water interface. Thus, they influence the quality and quantity of potential PCB binding substrates in the suspended and dissolved phases of aqueous systems. In this study, common headspace systems were used to compare the chlorobiphenyl-binding affinity of dissolved organic carbon (DOC) in protozoan and bacterial culture filtrates (<0.2 microm) relative to DOC in a seawater control. Culture filtrates from three marine protozoan species were compared-Uronema sp., Cafeteria sp., and Paraphysomonas imperforata. Each protozoan species was fed the same bacterial prey, Halomonas halodurans, which was also used as a bacterial control. Affinities of culture DOC for [14C]3,3',4,4'-tetrachlorobiphenyl (IUPAC 77) were normalized to DOC and surfactant concentrations. Values of DOC equilibrium partition coefficients (K(DOC)) ranged from 10(4.6) in seawater (Vineyard Sound, MA) to 10(5.4) and 10(5.5) in protist cultures, indicating that grazer-modified DOC was a better sorbent for PCBs than DOC in bacterial or seawater controls.

Importance of passive diffusion in the uptake of polychlorinated biphenyls by phagotrophic protozoa.

Unicellular protozoan grazers represent a size class of organisms where a transition in the mechanism of chlorobiphenyl (CB) introduction, from diffusion through surface membranes to ingestion of contaminated prey, could occur. This study compares the relative importance of these two processes in the overall uptake of polychlorinated biphenyls by protists. Uptake rates and steady-state concentrations were compared in laboratory cultures of grazing and nongrazing protozoa. These experiments were conducted with a 10-microm marine scuticociliate (Uronema sp.), bacterial prey (Halomonas halodurans), and a suite of 21 CB congeners spanning a range of aqueous solubilities. The dominant pathway of CB uptake by both grazing and nongrazing protozoa was diffusion. Organic-carbon-normalized CB concentrations (in the protozoan cell) were equivalent in grazing and nongrazing protozoa for all congeners studied. Rate constants for uptake into and loss from the protozoan cell were independently determined by using [3,3',4, 4'-(14)C]tetrachlorobiphenyl (IUPAC no. 77), 0.38 +/- 0.03 min(-1) and (1.1 +/- 0.1) x 10(-5) (g of organic carbon)(-1) min(-1), respectively. Magnitudes of the uptake and loss processes were calculated and compared by using a numerical model. The model result was consistent with data from the bioaccumulation experiment and supported the hypothesis that diffusive uptake is faster than ingestive uptake in phagotrophic unicellular protozoa.