Transfer of carbon and a polychlorinated biphenyl through the pelagic microbial food web in a coastal ecosystem

Abstract

Abstract-In order to estimate fluxes of carbon within the microbial community, seawater was collected in a coastal area off Zanzibar Island, Tanzania, during a rainy season (November 1994) and a dry season (September 1996). Diel experiments were conducted in a 24-L polycarbonate bottle and samples were retrieved every third hour over a period of 30 to 33 h. Abundance and production rates of bacteria, nanoflagellates, and microplankton were determined. To determine possible connections between the fluxes of carbon and the fate of 2,2Ј,4,4Ј,5,5Ј-hexachlorobiphenyl International Union of Pure and Applied Chemistry (IUPAC) no. 153, a time-course experiment was conducted after the diel experiment. The initial PCB partitioning was similar in the two experiments, but the subsequent distribution among the organism groups was different. In the rainy season experiment, the PCB concentration in the largest size fraction was almost three times higher than during the dry season experiment. This was in line with results from the diel experiments where the carbon flux through the microbial food web was approximately three times higher during the rainy season than during the dry season experiment. These results suggest that the transfer rate of 2,2Ј,4,4Ј,5,5Ј-hexachlorobiphenyl through the microbial food web is coupled to the carbon flux.

Microbial responses to anthropogenic dissolved organic carbon in the Arctic and Antarctic coastal seawaters

“…For instance, lipid modification in the Arctic and colanic acid biosynthesis in Antarctica was the most differentially expressed genes in the community, indicating reshaping of membranes and cell walls. ADOC concentrations in cell lipids versus water (C Lipids /C Water ) are proportional to the octanol-water partition coefficients (K OW ), and thus concentrations in membranes are 10 4 -to 10 8fold those in the surrounding seawater (Wallberg and Andersson, 2000;Koelmans, 2014). Our results suggest an overall expression response to ADOC compounds consistent with perturbation of cellular membranes due to the nonspecific accumulation of hydrophobic compounds to the cell surfaces and into the membrane lipids that we explored in detail (see below and Fig.…”

“…Hydrophobic OPs accumulate in planktonic organisms, mainly in the lipids of the membranes, and thereby enter into marine food webs (Wallberg and Andersson, 2000;Galbán-Malagón et al, 2012). They cross cell membranes by passive diffusion and can be absorbed into cytoplasmic structures, become inserted into the membrane phospholipid bilayer (absorption), and/or be adsorbed on the outside of the cell wall (Koelmans, 2014).…”

Effects of photodemethylation on the methylmercury budget of boreal Norwegian lakes

“…Meanwhile, French et al [7] reported a unimodal response of invertebrate MeHg bioaccumulation to DOC concentrations, with increasing MeHg bioaccumulation up to a threshold of approximately 8.5 mg C/L and decreased bioaccumulation above this threshold. Dissolved organic carbon-related ecological changes may also influence MeHg uptake and concentrations at higher trophic levels through changes in primary and bacterial productivity [46], in particular, increased importance of bacterial food sources has been shown to lead to elevated food web concentrations of biomagnifying compounds such as MeHg [47] and polychlorinated biphenyls [48,49].…”

Fate of Environmental Pollutants

“…Perkins and Underwood (2000) reported on nutrient and chlorophyll a gradients in a linear eutrophic reservoir. Phosphorus was determined to be the limiting nutrient through in situ addition of nutrients along the length of the reservoir.…”

“…Phosphorus was determined to be the limiting nutrient through in situ addition of nutrients along the length of the reservoir. Dauer et al (2000) noted that chlorophyll a concentrations in Chesapeake Bay were positively correlated with nitrogen and phosphorus concentrations in the water column, but were not correlated with nutrient loads.…”