Cellular uptake and subcellular distribution of copper were measured in the coastal marine diatom Thalassiosira weissflogii grown with free Cu ion concentrations (10-14.79-10-9.79 M) that are typical of coastal waters. Intracellular Cu quotas increased 2-3-fold and 4-5-fold per decade increase in free Cu ion concentration over the pCu (pCu = -log [Cu2+]) ranges of 14.79-11.79 and 11.79-9.79, respectively. The trophically available cytoplasmic pool of Cu increased by 2 orders of magnitude in T. weissflogii cells (0.53 x 1017-75 x 10-17 mol Cu cell-1) grown with 10-14.8-10-9.8 M free Cu. A 2-fold increase in intracellular and cytoplasmic Cu concentrations was observed in response to lowering the free concentration of the potentially antagonistic metal Zn by a factor of 10. However, the percent of intracellular Cu in the cytoplasmic fraction of T. weissflogii (≃ 40%) was relatively constant over the range of cupric ion activities and [Cu2+):[Zn2+] ratios applied. The assimilation efficiency (AE) of copper in marine copepods fed T. weissflogii, determined using the inert-tracer ratio method, was 40.3 ± 6.3% for copepods fed diatoms grown at pCu = 12.79 and 50.3 ± 9.7% for copepods fed diatoms grown at pCu = 10.79. Our results suggest that, above free Cu concentrations of 10-11.8 M, the availability of Cu for trophic transfer in coastal waters increases as a result of rapidly increasing concentrations of Cu in the assimilable, cytoplasmic fraction of diatoms and potentially higher Cu AEs at the base of the pelagic food web.
All Science Journal Classification (ASJC) codes
- Environmental Chemistry