Mercury Contamination in Components of an Estuarine Ecosystem

Abstract

Tne Forth Estuary, Scotland, has received a discharge containing mercury for several decades. This study describes the ecological effects of that discharge as contamination in many components of the ecosystem and attempts to quantify the standing mass of Hg within those components. The contaminated area is contrasted with a less-contaminated area, 19km downstream, and shown to have significantly greater Hg levels in most components (sediments, plankton, infauna, epi-fauna, macroalgae and fish). The standing mass of Hg in the biota is 1% of that in the non-biotic components (sediments, suspended material and soluble phase); sediments alone contain 97% of that standing mass. The critical pathways in this system are (i) the sediment-infauna-estuarine demersal fish and wading birds, and (ii) suspended material-mussels-oystercatchers. Therefore, the top consumers in each of these are most at risk from increased contamination. However, in assessing the biological effects of increased contamination, there was no change at the contaminated area in fecundity in the viviparous estuarine demersal fish, Zoarces viviparus.