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Experimental studies on the bioaccumulation and bioavailability of colloidally-bound trace metals to penaeid shrimp
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Trace metals in estuarine systems frequently exist as colloid-ion complexes and the chemical characteristics of these complexes may alter their bioavailability. The relative hydrophobicity of the colloid-ion complex could influence bio-uptake across bi-lipid membranes. Penaeid shrimp are useful bioindicators because of their close trophic linkage to trace metal sinks (detritus, benthos, and sediments), and their broad geographical distributions. Radiotracers were used to compare the bioaccumulation, sites of accumulation, and deputation of colloidally-complexed and dissolved phase (free-ionic) forms of Ag, Cd, Ba, Fe, Sn, Zn, Co, Hg, and Mn in juvenile penaeid shrimp. The duration of the uptake experiment was 14 days, and the deputation experiment lasted 7 days. The experiments clearly demonstrated that colloidally-complexed forms of trace metals were bioavailable to shrimp. Differences in rates and extent of uptake and deputation in the colloidal and free-ionic treatments were noted for whole body and individual tissues (abdomen, carapace, and hepatopancreas). For example, colloidally-bound trace metals generally had higher concentration factors compared to free-ionic metals in the hepatopancreas after 14 days of uptake, except for Ag, Ba, and Zn. Conversely, free-ionic trace metals tended to exhibit higher concentration factors compared to colloidal metals in the abdomen and carapace, with the exceptions of Mn in the abdomen, and Co in the carapace. Concentration factors for metals in whole shrimp were generally higher for free-ionic forms compared to colloidal forms. However, statistically significant differences in overall rates and extents of uptake were not observed in these experiments. Results indicate that mass specific accumulation within the hepatopancreas far exceeded loadings within the carapace or abdomen in both treatments for all metals tested. Depuration of metals from whole body and tissues was noted for both treatment regimes, with metals introduced as free-ionic species showing greater retention in shrimp than metals introduced as colloidally-bound species. Accumulation of metals from treatment solution into the internal tissues is linked to the intake of water for respiration at the site of the gills. Metals are then internalized by active transport mechanisms mediated by specific carriers.
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Includes bibliographical references: p. 70-80.
Issued also on microfiche from Lange Micrographics.
Carvalho, Roberta Anne (1996). Experimental studies on the bioaccumulation and bioavailability of colloidally-bound trace metals to penaeid shrimp. Master's thesis, Texas A&M University. Available electronically from
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