What is the Role of Sediment Resuspension in the Bioaccumulation of Heavy Metals in Oysters?

The Sydney estuary (Port Jackson) is a highly modified waterway in which surficial sediments are extensively contaminated by a suite of chemicals including trace metals. These surficial sediments undergo resuspension into the water column on a daily basis due to both natural and anthropogenic processes which includes tides, currents, bioturbation, shipping, and dredging. As a result, sediment resuspension significantly increases the risk of trace metal contaminant exposure to marine biota. The status of trace metal contamination in surficial sediments, suspended particulate matter, and aquatic organisms has been studied in detail, and in all three media high concentrations have been detected, particularly for Cu, Pb, and Zn. However, a significant relationship linking these processes together has yet to be made and the effect that sediment-bound trace metals inflict on local fauna has not been documented previously. The current study aims to identify the processes controlling bioaccumulation of trace metal contaminants in Sydney estuary using laboratory-based mesocosm experiments. The native Sydney rock oyster (Saccostrea glomerata) was used as a bioindicator species and was exposed to contaminated suspended sediment at a range of controlled concentrations and loads to mimic previously observed field conditions. The oysters were analysed for total bioaccumulated tissue metal concentrations, as well as changes in protein expression to identify probable early-onset bioindicators. The results from the laboratory experiments will be used to parameterise a biogeochemical model to help explain the different mechanisms of trace metal bioaccumulation in Sydney estuary.