Can body burden in the barnacle Balanus amphitrite indicate seasonal variation in cadmium concentrations?

Two three-month sampling programs measuring Cd in the environment and a biomonitor (Balanus amphitrite) were undertaken in the austral winter of 2002 and summer of 2004 in Ross Creek, North Queensland, Australia. The objective was to test whether the burden of Cd in the biomonitor responded to any variation in the dissolved and particulate phase Cd concentrations in Ross Creek, caused by rainfall variation. The barnacles from the most Cd contaminated site were exposed to a total Cd concentration twice that in winter (93.6 ng L−1) than in summer (45.6 ng L−1). However, no significant variation was identified for the Cd concentration in the biomonitor between winter (8.4 mg kg−1) and summer (7.4 mg kg−1). A budget analysis based on a bioenergetic kinetic model indicated that Cd flux from food contributes >80% to the Cd concentration in B. amphitrite. A sensitivity analysis showed that physiological characteristics of the biomonitor are the key parameters controlling Cd accumulation in B. amphitrite, rather than the metal concentration in the dissolved or particulate phases. These two model's outcomes suggest that a tight coupling between Cd in the biomonitor and its availability in the environment does not occur.