Tiparra Nearshore Marine Biounit
2016 Aquatic Ecosystem Condition Report
On the map, zoom in and click on the dots to view underwater video at each site
- Seagrass habitats throughout the biounit were moderate and continuous Posidonia, with some areas of sparse and patchy Heterozostera spp. and Halophila spp.
- Rocky reef communities were in good to fair condition with extensive brown canopy algae
About the biounit
The Tiparra biounit spans from Point Riley just north of Wallaroo, down 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 Wallaroo being the largest with just over four thousand people in 2016, an increase of just under 1,000 people in 5 years. Other significant towns are Moonta Bay and Port Hughes with a combined population of 2,915 people. The region is subject to substantial coastal development with many new dwellings and new large residential developments around these existing towns. This development can lead to stormwater management issues and erosion of the coastal zone. To manage this the District Council of the Copper Coast is reviewing is Stormwater Management Plan to ensure ongoing improvements are in place.
Since the previous monitoring period there have been significant improvements in wastewater management made by the District Council of the Copper Coast. Many areas previously serviced by onsite disposal systems have now been connected to the new community wastewater management network reducing the risk of pollution to the coast. Two new wastewater treatment plants have been developed, one at the upgraded Wallaroo facility and one in Port Hughes.
The main industries are cereal crops throughout the region and there is a large port facility at Wallaroo to export grain. The area is also home to a large prawn fishing fleet, which reside in a marina associated with an extensive residential development.
An evaluation of potential threats to water quality for the biounit predicted that the biounit was likely to be in good condition.
An additional 2 sites Cape Elizabeth inside (m0145) and North Beach (m0149) were monitored to increase the spatial coverage of the biounit resulting in six sites monitored in 2016. Overall 35% of habitats monitored were seagrass, while 29% were rocky reef, while the remaining 36% was bare sand.
In general the biounit was in good condition in 2016, which is consistent with the predicted condition.
The 2016 AECR score has declined from 2010, where it was classified as Excellent. A comparison of site data collected in 2010 indicated seagrass cover was largely unchanged. The change is due to the addition of the new sites bringing the average condition down.
This AECR assessed the condition of habitats in waters between 2–15 m deep throughout the Tiparra biounit sampled in autumn 2016. There are large areas within the biounit that are deeper than 15 m which are not included as a part of this evaluation.
Seagrass throughout the biounit was largely in good condition, but variable with Wallaroo (m0135) had dense Posidonia spp. at an average of 68% cover, Moonta (m0134) and Moonta inner (m0132) both also supported moderate to dense seagrass and a substantial decrease in epiphyte cover, which is a positive sign. North Beach (m0149) was found to have patchy and sparse Heterozostera spp. and Halophila spp seagrass.
Compared to 2010, seagrass cover has largely remained consistent. The addition of 2 new sites Cape Elizabeth inside (m0145) and North Beach (m0149), where there was little to no seagrass, has resulted in an overall reduction in average seagrass cover for the biounit.
Rocky reefs in Tiparra were also largely in good condition with Cape Elizabeth (m0133) and Cape Elizabeth Inside (m0145) having extensive large brown canopy algae (Cystophora spp.) averaging 83% and 56% respectively. However, Cape Elizabeth Inside (m0145) had 3 times the amount of turfing algae compared to Cape Elizabeth (m0133). Turfing algae is more tolerant to declining water quality and sedimentation, and can be used as an indication of a reef system being under stress. This site is located in an area that could be more prone to sand movement compared to the headland at Cape Elizabeth, which may favour turfing algae.
Water nutrient concentrations throughout the biounit were consistent across all sites. Turbidity was more variable at Cape Elizabeth (m0133) and Cape Elizabeth inside (m0145), which is unsurprising given that reef habitats generally provide less wave attenuation to settle suspended particles compared to the dominant seagrass habitats seen elsewhere in this biounit.
These findings demonstrate that nearshore marine habitats are in good condition with largely intact habitats with only slight changes to structure and function compared to an unimpacted state. It is likely that any changes to habitats are likely to localised and likely to recover over relatively short timeframes.
Pressures and management responses
Stormwater runoff from the coastal towns discharges nutrient and sediment loads to the nearshore waters
The District Council of the Copper Coast is systematically improving the stormwater discharge points within their jurisdiction. The significant upgrade to the Rossiters Rd and Otago Drive discharge points are major achievements. Recent grants obtained from the NRM will see further improvements to two discharge points utilising vegetation to improve the quality of the discharged water. The main Wallaroo discharge point (Office Beach) has been improved with a significant upgrade planned in conjunction with the development of the old Pivot site.
Coastal development is likely to increase the number and density of septic tanks which will contribute nutrients into shallow ground waters which will flow to the sea
Moonta and Wallaroo now have modern sewerage systems with sufficient connections making this scenario highly unlikely. Council will be encouraging infill development that is connected to these schemes. The only area of concern is the North Beach catchment as it currently relies on septic systems. The Council continues to progress connections to the CWMS throughout its jurisdiction.
The Tiparra biounit was in good condition and although the score is different to 2010, this change reflects the addition of two new sites that had very little seagrass bringing the biounit average down.