Tiparra Nearshore Marine Biounit
2010 Aquatic Ecosystem Condition Report

The Tiparra biounit ranges from Point Riley just north of Wallaroo, south to Island Point just north of Port Victoria on Yorke Peninsula (see map). The shoreline of the biounit has a westerly orientation generating low to moderate wave energies

There are numerous coastal towns on the shores of the Tiparra biounit, with Moonta Bay being the largest with 4,238 people in 2011. Other significant towns are Wallaroo and Port Hughes. There is considerable coastal development in this biounit with many new dwellings and new large residential developments around these existing towns. The main industries are cereal crops throughout the region and there is a large port facility at Wallaroo to export grain.

There are two community wastewater management systems (CWMS) in this biounit (at  Moonta/Moonta Bay/Port Hughes and Balgowan) although they are considered to be exceeding their capacity. On site sewage treatment systems (i.e. septic tanks) are also commonly used in coastal townships.

The Jussieu biounit was expected to be in Good condition, based on an assessment of threats to the nearshore habitats.

The condition of habitats in waters between 2 – 15 m deep throughout the Tiparra biounit was assessed based on monitoring data collected during autumn and spring 2010. There are large areas within the biounit that are deeper than 15 m which are not included as a part of this evaluation.

The Tiparra biounit was observed to be in Excellent condition. The seagrass habitats monitored were generally dense and continuous and the rocky reef habitat monitored covered in large brown canopy algae including Cystophora sp.

While the habitats were intact, the seagrass habitats were found to be under significant stress due to excessive growth of epiphytes on the seagrass leaves, which if prolonged, can impact on the seagrass condition and if prolonged can result in seagrass loss.

4 sites were monitored during autumn and spring in 2010 to assess the condition of the biounit; 76% of the habitats monitored were covered in seagrass, while 24% were covered in rocky reef.

The results showed that seagrass coverage throughout the sites monitored in the biounit was excellent with all areas supporting dense and continuous seagrass meadows of Posidonia sp. The rocky reef community monitored at Cape Elizabeth was also in good condition with extensive coverage of large brown canopy algae (Cystophora sp.).

While the habitats monitored were in excellent condition there were numerous indicators suggesting an excess of nutrients, including seagrasses coated in a thick covering of epiphytic algae observed during both autumn and spring sampling events. Additionally the levels of nitrogen in the water were greater than that is typical of unimpacted locations, particularly during autumn.

These findings suggest that the nearshore marine habitats are in excellent condition. However the biounit is under significant stress due to the excess of nutrients. On going stress to these marine habitats could result in habitat loss. If habitats are lost there could be:

• Impacts on the productivity of fisheries
• Increased erosion and sand movement on beaches
• Reduced wave attenuation along the coast
• A negative impact on marine biodiversity.

• Download the 2010 habitat and water quality data
• Download the Methods Report for the nearshore marine ecosystems monitoring, evaluation and reporting program.