ISSN:
1573-5117
Schlagwort(e):
bacterivory
;
bioaccumulation
;
microbial food web
;
PCBs
;
polychlorinated biphenyls
;
protozoa
Quelle:
Springer Online Journal Archives 1860-2000
Thema:
Biologie
Notizen:
Abstract Experiments were conducted to study the distribution of three selectedpolychlorinated biphenyl (PCB) congeners within the microbial food web attwo different nutrient levels; control and nutrient enriched. The objectivewas to quantify the uptake of PCBs through grazing by protozoa. The14C-PCBs tested were 4-chlorobiphenyl (IUPAC # 3),2,2′,5,5′-tetrachlorobiphenyl (IUPAC # 52), and2,2′,4,4′,5,5′-hexachlorobiphenyl (IUPAC # 153). EachPCB was incubated in triplicate seawater samples at 20 idref;Cover one week. Daily, samples were separated into four fractions; 〈0.2µm (dissolved), 0.2-2 µm (bacteria), 2-10 µm(flagellate), and 〉 10 µm (microplankton; phytoplankton andprotozoa) by selective filtration. Of the PCB fraction that initiallyadsorbed to particles, 60–100% was associated to the bacterialfraction and 0–5% to the microplankton fraction. The totaluptake was highest in the nutrient enriched samples, but when normalized tothe carbon biomass the concentration was lower or equal to the control inall particle fractions. The recovery of the PCBs in the particulatefractions depended on the degree of chlorination, as the highest values wereobserved for the 2,2′,4,4′,5,5′-hexachlorobiphenyl and thelowest for the 4-chlorobiphenyl. The concentrations in the bacterial andflagellate fractions decreased over the first 48–96 hours whilst theconcentration increased in the highest trophic level (〉10 µmfraction). Approximately 75% of the increase in concentration of the2,2′,4,4′,5,5′-hexachlorobiphenyl in the 〉 10 µmfraction was estimated to be the result of bacterivory. Our results indicatethe microbial food web can contribute to a rapid uptake of higherchlorinated PCBs, particularly in oligotrophic ecosystems where thebacterial biomass dominates.
Materialart:
Digitale Medien
URL:
http://dx.doi.org/10.1023/A:1003122500557
Permalink
