Assimilation of trace elements and carbon by the mussel Mytilus edulis: Effects of food composition

Abstract

Assimilation efficiency (AE) is an important physiological parameter in determining trace element influx from food sources into aquatic animals. We used radiotracer techniques to examine the influence of diet [seven species of algae (two diatoms, two chlorophytes, a prasinophyte, and two dinoflagellates) and glass beads] on the assimilation of seven trace elements (Ag, Am, Cd, Co, Cr, Se, Zn) and C in the mussel Mytilus edulis. Trace element assimilation was related to C assimilation and cytoplasmic distribution in the algae and to gut passage time in the mussels. Mussels displayed different C AEs for the different algal diets; the chlorophytes, which had highly refractory cell walls, were the least digestible food. Assimilation of Cd, Se, and Zn was directly correlated with C assimilation; for Am, Ag, and Cr, no relationship with C assimilation was apparent. For each species except the chlorophytes, AEs of all elements significantly correlated with their cytoplasmic distribution within each algal cell. Among all species, AEs of Am, Co, and Se also increased with elemental penetration into the cytoplasm; however, this relationship was not statistically significant for Ag, Cd, or Zn. With the exception of Cr, AEs of elements increased with gut passage time, implying more efficient digestion-absorption when the element was retained longer in the digestive tract. In waters containing large mussel populations, unassimilated particle-reactive elements should be removed from suspension and enriched in biodeposits in sediments, whereas assimilated metals should be enriched in mussel tissues.For bivalve molluscs, both dissolved and particulate sources can contribute to metal accumulation in tissues. Uptake of metals from the dissolved phase occurs primarily across the gills, after which metals are transported into various organs. Accumulation of metals from particulate sources occurs by ingesting and assimilating metals from particulate sources. Metal influx from particles is a direct function of the assimilation efficiency (AE) of metals, the metal concentration in the ingested particles, and the ingestion activity of the animal (Thomann 198 1;Luoma et al. 1992). Assimilation represents a first-order physiological process that can be compared among different metals, food types, and environmental conditions, and AE can be used to measure metal bioavailability from specific foods.l Corresponding author.

Influence of a selective feeding behaviour by the blue mussel Mytilus trossulus on the assimilation of 109Cd from environmentally relevant seston matrices

“…Maximum 'OqCd-AES occurred at a DQ of 60%) for just algae and at a DQ of 33% for 25 mg 1-' SPM, where maximum C-AEs for this species have been previously noted. This relationship supported the previous findings of Wang & Fisher (1996b), who noted a positive relationship between carbon assimilation and ""Cd-AE for the filter-feeding blue mussel.…”

Heavy metal and Pb isotopic compositions of aquatic organisms in the Pearl River Estuary, South China

“…The present study indicated that fish might be bioassimilating Pb from anthropogenic sources such as atmospheric deposits suspended in water columns. Previous studies have also reported that the highest trace metal concentrations in fish were found in their gills (Eisler, 1979;Wang and Fisher, 1996;Barata et al, 2002). This issue can be further investigated in the future by examining the differences in the Pb isotopic composition in the gills, livers, stomachs and fleshes of fish.…”

Effects of sediment composition on cadmium bioaccumulation in the clam Meretrix meretrix Linnaeus

“…Trace metal assimilation efficiency varies with food items. It has been reported that assimilation efficiency differed by up to fivefold for Se, ninefold for Ag, and 10-fold for Cr(VI) in mussels feeding on different food particles [43]. The assimilation efficiencies of Cr (III) bound with bacteria and phytoplankton could also be 20-fold different for clams M. balthica [2].…”