South Australian subtidal reefs are typically rocky outcrops covered in macroalgae which is structured in a number of layers. These layers of algae can range from large brown kelp, forming a dense canopy, an understorey layer of brown, red and green algae down to small turfing and encrusting layers on the hard rocky substrates.
Subtidal rocky reefs provide food and shelter for a wide range of fish and invertebrates, and the macroalgae throughout southern Australia has the greatest diversity of any comparable coastline in the world.
Rocky reefs are a valuable part of South Australia’s marine ecosystem providing biodiversity, nutrient cycling and other ecosystem services which add significant financial value to the state’s economy.
Reefs are constantly changing due to natural variation, but also from human activity. One of the main human factors damaging reefs is believed to be an increase of sediments settling on the reef which fill all the small cracks and crevices in the rock. This can result in the loss of large canopy forming algae, with the structure of the reef changing to be dominated by small turfing algae that can thrive under high sediment loads. The loss of large canopy algae provides little food or shelter for the fish and invertebrates and is likely to reduce the biodiversity.
Nutrients can also damage reefs by changing the types of algae on the reefs or encouraging microscopic algae to become so abundant that they reduce the amount of light getting to the reef.
Monitoring the health of our reefs is important in being able to understand whether water quality is being adequately managed.
Over the last 20 years the amount of research undertaken on reefs has significantly increased with the EPA commissioning studies by the Adelaide and Flinders Universities to undertake the first real broad scale assessment of the health of reefs along Adelaide’s metropolitan coast between 1996 and 2003.
This monitoring raised many new questions and the South Australian Research and Development Institute (SARDI) led a collaborative project, which included the EPA, to investigate nearly 40 reefs, including the ones studied in 1996 and 1999, in more detail to see if there have been changes in health, and to examine the health of many reefs for the first time.
This monitoring showed that the health of reefs was variable over space and time and that the monitoring of these rocky systems is very complex. The results indicated reefs close to the Adelaide metropolitan centre were in worse condition than reefs located further away, this, and further research since these surveys has shown that the reefs along the metropolitan coast are substantially degraded.
The EPA’s Aquatic Ecosystem Condition Reports show the condition of the nearshore environment throughout South Australia and these reports can be used to see whether reefs within the biounits are at risk of impacts from water quality. The AECR for each biounit also include the pressures that may be affecting water quality and the management responses that are currently underway to try to control and manage the pressures, including the Adelaide Coastal Water Quality Improvement Program
- Examining the health of subtidal reef environments in South Australia
Turner DJ, Kildea T and Murray-Jones S 2006, Part 1: Background review and rationale for the development of the monitoring program.
Turner DJ, Kildea T and Westphalen, G 2007, Part 2: Status of selected South Australian reefs based on the results of the 2005 survey.
Turner DJ, Brook J and Murray-Jones S 2006, Part 3: An evaluation of the potential for the community to undertake environmental monitoring of temperate reef habitats: A review of the South Australian Reef watch program.
Collings G, Bryars S, Turner D, Brook J and Theil M 2008, Part 4: Assessment of community reef monitoring and status of selected South Australian reefs based on the results of the 2007 surveys