Document ID: chunk:federal_register_of_legislation:F2016L00300:body:0:p15
Version: federal_register_of_legislation:F2016L00300
Segment Type: other
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Character Range: 41347–44422

sediment and nutrient loads are associated with urban and industrial development and changes in catchment use (Australian Government Land and Coasts, 2010). A high abundance of these oysters was observed at a site in the Derwent Estuary in the late 1990s. The proliferation of this oyster at this site, 'may have affected the recruitment of spotted handfish by smothering egg masses, hindering development and hatching of emerging fish or smothering sediments and restricting access of juvenile fish to benthic prey' (Green and Bruce 2000).
The native sea urchin (Heliocidaris erythrogramma) has also increased in abundance, possibly due to fishing activities that remove its predators, such as rock lobsters (Jasus edwardsii) (Brereton, pers comm., 2010) and wrasse species (Labridae family) (Flukes, pers comm., 2014; Gowlett-Holmes, pers comm., 2014). H. erythrogramma form into large aggregations, known as barrens, that remove larger macroalgae (potential handfish spawning substrate) from the reef resulting in overgrazed habitat (Edgar, 1997) with low productivity and biodiversity (Valentine and Johnson, 2005).

4.2.2 Pollution and siltation of waterways
Anthropogenic activities such as land clearing, land reclamation, dredging, port construction, damming and industrial and urban waste inputs often have significant impacts on estuarine ecosystems and can lead to increases in run-off and sediment loads and reductions in water quality, habitat quality and availability, and fish abundance (Edgar et al., 2000). The Derwent Estuary is no exception. After the city of Hobart was established on the western bank of the Derwent in the early 1800s extensive land clearing and agriculture development commenced, followed by the damming of the river (Butler, 2006). A rapidly expanding population led to increases in industrialisation and urbanisation around the shores of the Derwent Estuary during the 20th century (Butler, 2006). Discharges into the Derwent River increased considerably throughout the first two centuries of European settlement in the catchment (Butler, 2006).
The Derwent Estuary has been identified as one of the most heavily polluted waterways in the world with high concentrations of heavy metals in the estuary's soft sediments (Whitehead et al., 2013). Historic sources of contamination include a zinc smelter and paper and pulp mill which operated along the estuary in the 1900s, while current sources include sewage, storm water, contaminated ground water from the zinc smelter, and aerial emissions (Whitehead et al., 2013). Toxicity effects to fish from exposure to metals are influenced by a range of biogeochemical, cellular, physiological and anatomical characteristics, and thus vary from species to species (Newman, 2003). Documented impacts to fish from exposure of the gills to dissolved or colloidal metals include disruptions and/or alterations to gas exchange, ammonia excretion, ion regulation and osmotic regulation (Newman, 2003) as well as structural lesions and other functional disturbances (Jezierska & Witeska, 2006).
Due