<?xml version='1.0' encoding='utf-8'?>
<oai_dc:dc xmlns:dc="http://purl.org/dc/elements/1.1/" xmlns:oai_dc="http://www.openarchives.org/OAI/2.0/oai_dc/" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://www.openarchives.org/OAI/2.0/oai_dc/ http://www.openarchives.org/OAI/2.0/oai_dc.xsd">
  <dc:contributor>Samuel N. Luoma</dc:contributor>
  <dc:creator>W.G. Wallace</dc:creator>
  <dc:date>2003</dc:date>
  <dc:description>&lt;p class="abstract_block"&gt;This paper examines how the subcellular partitioning of Cd and Zn in the bivalves&lt;i&gt;&lt;span&gt;&amp;nbsp;&lt;/span&gt;Macoma balthica&lt;span&gt;&amp;nbsp;&lt;/span&gt;&lt;/i&gt;and&lt;i&gt;&lt;span&gt;&amp;nbsp;&lt;/span&gt;Potamocorbula amurensis&lt;/i&gt;&lt;span&gt;&amp;nbsp;&lt;/span&gt;may affect the trophic transfer of metal to predators. Results show that the partitioning of metals to organelles, Œenzymes¹ and metallothioneins (MT) comprise a subcellular compartment containing trophically available metal (TAM; i.e. metal trophically available to predators), and that because this partitioning varies with species, animal size and metal, TAM is similarly influenced. Clams from San Francisco Bay, California, were exposed for 14 d to 3.5 µg l&lt;sup&gt;-1&lt;/sup&gt;&lt;span&gt;&amp;nbsp;&lt;/span&gt;Cd and 20.5 µg l&lt;sup&gt;-1&lt;/sup&gt;&lt;span&gt;&amp;nbsp;&lt;/span&gt;Zn, including&lt;span&gt;&amp;nbsp;&lt;/span&gt;&lt;sup&gt;109&lt;/sup&gt;Cd and&lt;span&gt;&amp;nbsp;&lt;/span&gt;&lt;sup&gt;65&lt;/sup&gt;Zn as radiotracers, and were used in feeding experiments with grass shrimp&lt;span&gt;&amp;nbsp;&lt;/span&gt;&lt;i&gt;Palaemon macrodatylus&lt;/i&gt;, or used to investigate the subcellular partitioning of metal. Grass shrimp fed Cd-contaminated&lt;span&gt;&amp;nbsp;&lt;/span&gt;&lt;i&gt;P. amurensis&lt;/i&gt;&lt;span&gt;&amp;nbsp;&lt;/span&gt;absorbed ~60% of ingested Cd, which was in accordance with the partitioning of Cd to the bivalve¹s TAM compartment (i.e. Cd associated with organelles, Œenzymes¹ and MT); a similar relationship was found in previous studies with grass shrimp fed Cd-contaminated oligochaetes. Thus, TAM may be used as a tool to predict the trophic transfer of at least Cd. Subcellular fractionation revealed that ~34% of both the Cd and Zn accumulated by&lt;span&gt;&amp;nbsp;&lt;/span&gt;&lt;i&gt;M. balthica&lt;/i&gt;&lt;span&gt;&amp;nbsp;&lt;/span&gt;was associated with TAM, while partitioning to TAM in&lt;span&gt;&amp;nbsp;&lt;/span&gt;&lt;i&gt;P. amurensis&lt;/i&gt;&lt;span&gt;&amp;nbsp;&lt;/span&gt;was metal-dependent (~60% for TAM-Cd%, ~73% for TAM-Zn%). The greater TAM-Cd% of&lt;span&gt;&amp;nbsp;&lt;/span&gt;&lt;i&gt;P. amurensis&lt;/i&gt;&lt;span&gt;&amp;nbsp;&lt;/span&gt;than&lt;span&gt;&amp;nbsp;&lt;/span&gt;&lt;i&gt;M. balthica&lt;/i&gt;&lt;span&gt;&amp;nbsp;&lt;/span&gt;is due to preferential binding of Cd to MT and Œenzymes¹, while enhanced TAM-Zn% of&lt;span&gt;&amp;nbsp;&lt;/span&gt;&lt;i&gt;P. amurensis&lt;/i&gt;&lt;span&gt;&amp;nbsp;&lt;/span&gt;results from a greater binding of Zn to organelles. TAM for most species-metal combinations was size-dependent, decreasing with increased clam size. Based on field data, it is estimated that of the 2 bivalves,&lt;span&gt;&amp;nbsp;&lt;/span&gt;&lt;i&gt;P. amurensis&lt;/i&gt;&lt;span&gt;&amp;nbsp;&lt;/span&gt;poses the greater threat of Cd exposure to predators because of higher tissue concentrations and greater partitioning as TAM; exposure of Zn to predators would be similar between these species.&lt;/p&gt;</dc:description>
  <dc:format>application/pdf</dc:format>
  <dc:identifier>10.3354/meps257125</dc:identifier>
  <dc:language>en</dc:language>
  <dc:publisher>Inter-Research</dc:publisher>
  <dc:title>Subcellular compartmentalization of Cd and Zn in two bivalves. II. Significance of trophically available metal (TAM)</dc:title>
  <dc:type>article</dc:type>
</oai_dc:dc>