Oyster Harbour (Miaritch): Condition of the estuary 2016–19 reports on three years of the Regional Estuaries Initiative (now Healthy Estuaries WA) water quality monitoring program. It summarises the main drivers of estuary health (flow and catchment condition), and the response of the estuary in terms of water quality and seagrass habitat.
Water quality and seagrass cover in Oyster Harbour declined in the late 1970s and ’80s due to catchment clearing and excessive nutrient inputs. Seagrass has recovered remarkably in the last 20 years because of significant seagrass transplanting and improved catchment management activities, resulting in better water quality. Today, Oyster Harbour generally has very good water quality. It is free from nuisance microalgal blooms, fish kills and concentrations of low oxygen, and is a success story of improved water quality in an estuarine environment.