The effects of food quality and abiotic habitat parameters on metal uptake in the blue mussel, mytilus trossulus

The potential transfer of heavy metals via trophic transfer (bioaccumulation) in global aquatic ecosystems is of growing concern amongst members of today's society. Therefore it is important to examine contaminated ecosystems beginning with the organisms that have the highest potential for exposure. Bivalve species have traditionally been considered excellent biomonitors of metal levels in marine environments. My research examines the combined influences of abiotic (salinity, ecosystem quality) and biotic factors (food quality and selection) on heavy metal uptake and availability in the West coast blue mussel Mytilus trossulus. Flow-through (48) and pulse-feeding (66) experiments were conducted using either single or combinations of marine bacteria, phytoplankton, natural sediments and clay food sources. Flow-through experiments involved feeding M. trossulus a marine bacterium containing non-radioactive Mn, Ccl, or Pb oxides and varying amounts of carbon. Bacteria containing higher amounts of carbon had enhanced metal uptake due to an increased clearance rate of the organic rich particles. Pulse-feeding experiments involved feeding M trossulus combinations of radiolabelled '09cd phytoplankton, clay and natural sediments containing varying amounts of carbon. To obtain natural, biologically-relevant sediments unique intertidal sediment traps were designed and deployed at two estuarine habitats. The sediment quality and salinity of these habitats (Boundary Bay and Deep Bay) differed signilicantly (24% C and 25 ppt vs. 15% C and 15 ppt., respectively). Results indicated that lower salinity environments may result in significantly lower dietary cadmium uptake and assimilation efficiencies in M. trossulus when compared to higher salinity environments. My research demonstrated that the active selection of food particles by M. trossulus significantly affected the extent of metal uptake and assimilation. In addition, the bioaccumulation of metals by M trossulus inhabiting different marine habitats varied depending on the natural abiotic conditions within that habitat, such as salinity. I conclude that using M. trossulus as a biomonitor of marine metal levels is useful so long as the feeding behaviour and abiotic habitat parameters are considered when comparing metal levels in M trossulus between different habitats.