Coasts & Estuaries - City of Port Adelaide Enfield - SA.Gov.au

Coast & EstuariesPressure Indicator: Caulerpa taxifolia growth in the upper Port Adelaide RiverIn March and April 2002 distribution surveys of the extent of the Caulerpa taxifolia infestation in thePort Adelaide River were conducted, these observations found a significant population of the alga,particularly northwards of the Railway and Jervois Bridges, with further small patches and singleplants extending as far as the Birkenhead Bridge (refer to Figure 26). Eradication measures wereundertaken to manually eradicate and control the spread. Despite these efforts by the end ofDecember 2003 large areas of healthy C.taxifolia remained in the upper Port Adelaide River and anoutbreak in southern Barker Inlet indicated that the Caulerpa population in the upper Port AdelaideRiver was not fully contained.In follow up to this work, surveys of the upper Port Adelaide River were conducted in January andFebruary 2004 to determine changes in the distribution of C.taxifolia. In 2004 C.taxifolia in the upperPort Adelaide River is spread over two main areas, one mostly south of Jervois Bridge and a secondarea parallel to shore upstream of the Birkenhead Bridge (refer to Figure 27). The combined areacovered is approximately estimated to between 9-12ha (blue and pink shaded areas on Figure 27)although this includes potentially large bare areas.There were some differences in the distribution from the 2002 survey to the 2004 survey. However itshould be noted due to differences in survey methods and environmental constraints, comparison isproblematic. A large shallow zone of patchy weed observed in 2002 to the north of the Railway Bridgewas not present in 2004, otherwise the distribution in 2004 roughly correlates with that observed in2002, indicating that the eradication measures employed in this area have been ineffective.Pollution inputs to the Port Adelaide River included annual doses of 68 tonnes of phosphorus and(previously) 460 tonnes of nitrogen by the Port Adelaide sewage treatment works (now diverted toBolivar), as well as significant heavy metal contamination from various industrial and diffuse sources.This places pressure on native plant growth to compete with and combat the weed infestation (EPA,2002).Photo of Caulerpa taxifolia (Source: PIRSA - Environmental Issues - Caulerpa Taxifolia)146