Bioavailability and nutrient effects on the trophic transfer of Cadmium (Cd) associated with microalgae to the marine amphipod, Leptocheirus plumulosus, were investigated. Cd assimilation efficiencies (AE) were measured by a pulse-chase technique using a radiotracer. Cd AE in L. plumulosus significantly varied among algal species tested, and was highest (38.8 %) for the benthic diatom Nitzschia punctata, lowest (5.9%) for the planktonic diatom Thalassiosira weissflogii, and intermediate (15.6%) for the planktonic dinoflagellate Isochrysis galbana. Instantaneous egestion rates of Cd displayed a typical biphasic pattern over 96 h of depuration. Depuration in seawater-only of L. plumulosus yielded the highest Cd AE of 35.0%, whereas AEs in which depuration occurred in natural sediment and processed sediment were only 5.3% and 4.3%, respectively. Body size, ranging from 0.5 to 2.0 mm, of L. plumulosus feeding on labeled T. weissflogii did not affect Cd AEs.
Nitrate enrichment from 0-180 uM on algae significantly increased Cd AEs by L. plumulosus from 9.4-18.8% for T. weissflogii, from 10.0-27.3% for N. punctata, and from 10.0-16.2% for I. galbana. Physiological turnover (elimination) rate constants of Cd in L. plumulosus ranged from 0.016-0.025 h-1 for the three algal species, and were independent of nitrate addition. Algal fractionation revealed that nitrate enrichment strongly enhanced the fraction of Cd associated with cytoplasm, which probably contributed to the increased Cd AEs by L. plumulosus.
Phosphate addition (0 - 7.5 uM) on algae showed that Cd AEs of L. plumulosus were from 26.4-35.8% for T. weissflogii, and from 15.3-18.5% for N. punctata. Phosphate enrichment did not significantly affect trophic transfer of Cd from algae to L. plumulosus. Cd fractionation in cytoplasm showed no obvious correlation with phosphate addition.
Overall, there was a significant linear relationship between the Cd AE of L. plumulosus and the distribution of Cd within algal cells. My work suggests that eutrophication by nitrate enrichment, but not phosphate, has the potential to enhance the trophic transfer of metals from pelagic and benthic microalgae to grazers in coastal benthic food webs.
| Identifer | oai:union.ndltd.org:LSU/oai:etd.lsu.edu:etd-11032004-114106 |
| Date | 04 November 2004 |
| Creators | Yu, Riqing |
| Contributors | Ralph J. Portier, Kevin R. Carman, John W. Fleeger |
| Publisher | LSU |
| Source Sets | Louisiana State University |
| Language | English |
| Detected Language | English |
| Type | text |
| Format | application/pdf |
| Source | http://etd.lsu.edu/docs/available/etd-11032004-114106/ |
| Rights | unrestricted, I hereby certify that, if appropriate, I have obtained and attached herein a written permission statement from the owner(s) of each third party copyrighted matter to be included in my thesis, dissertation, or project report, allowing distribution as specified below. I certify that the version I submitted is the same as that approved by my advisory committee. I hereby grant to LSU or its agents the non-exclusive license to archive and make accessible, under the conditions specified below and in appropriate University policies, my thesis, dissertation, or project report in whole or in part in all forms of media, now or hereafter known. I retain all other ownership rights to the copyright of the thesis, dissertation or project report. I also retain the right to use in future works (such as articles or books) all or part of this thesis, dissertation, or project report. |
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