We investigated spatial and temporal the distribution of trace metals and sedimentary particles in order to identify the relationship between benthic foraminifera and trace metals pollution within Gunnamatta Bay, Port Hacking Estuary, NSW, Australia. Risk assessments of surface sediments were conducted using hierarchical cluster analysis (HCA).A total of 59 surface sediment samples and seven subsurface sediment samples were collected in order to determine the spatial and temporal distribution of trace metals in the bay. Further, six surface sediment samples were examined for existing foraminiferal assemblages. These included muddy samples which had high and low concentrations of trace metals and sandy samples. The trace metals distribution showed that chromium, nickel, copper, zinc, arsenic, lead, rubidium and bromine had similar distributions in surface sediments. The results of trace metal concentrations were also compared with the deleterious biological effect values in marine sediments. The means of most concentrations of trace metals for the Bay were below the Effect Range Median (ERM) or the Effect Range Low(ERL), except for copper. The highest concentrations of these metals were found to be in the north east of the bay, close to discharge points and a boat yard at GU55, with concentrations of 107, 14, 398, 413, 8, 203, 27 and 182ppm respectively. Also, this trace metal pollution was found to be concentrated in the inner part of the bay, which is deep and has organic matter and clay minerals. The benthic foraminiferal assemblages had lower species diversity in the muddy samples than in the fine sandy particle samples.Furthermore, the muddy particles that had high levels of trace metals were dominated by pollution-tolerant species such as Ammonia beccarii, Brizalina spathulata and Elphidium excavatum, which have had more opportunity to flourish. In addition, the levels of trace metals dramatically declined with increasing depth. This indicates that the potential source of trace metal pollution has been from human activity, such as boating and emission of gasoline fumes, since early European settlement in this area.

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