Commonwealth waters adjacent to Ningaloo Reef

Legal description

The Commonwealth marine area is a matter of national environmental significance under the Environment Protection and Biodiversity Conservation Act 1999 (EPBC Act). As such, actions that have, will have, or are likely to have, a significant impact on it require approval.

In February 2014, the National Offshore Petroleum Safety and Environmental Management Authority (NOPSEMA) became the sole designated assessor of petroleum and greenhouse gas activities in Commonwealth waters in accordance with the Minister for the Environment’s endorsement of NOPSEMA’s environmental authorisation process under Part 10, section 146 of the EPBC Act. Under the streamlined arrangements, impacts on the Commonwealth marine area by petroleum and greenhouse gas activities will be assessed solely through NOPSEMA.

Key ecological features are not matters of national environmental significance and have no legal status in their own right. However, they may be considered as components of the Commonwealth marine area.

This KEF was identified in the North-west Marine Bioregional Plan. Under section 176 of the EPBC Act, once a bioregional plan has been made the minister responsible for the environment must have regard to it when making any decision under the Act to which the plan is relevant.

Values

Ningaloo reef is globally significant as the only extensive coral reef in the world that fringes the west coast of a continent. It is also globally significant as a seasonal aggregation site for whale sharks. The Commonwealth waters adjacent to Ningaloo Reef and associated canyons and plateau are interconnected and support the high productivity and species richness of Ningaloo Reef. The Leeuwin and Ningaloo currents interact on the seaward side of the reef, leading to areas of enhanced productivity which support aggregations and migration pathways of whale sharks, manta rays, humpback whales, sea snakes, sharks, large predatory fish and seabirds (Donovan et al. 2008; Gunn et al. 1999; Waples & Hollander 2008). Detrital input from phytoplankton production in surface waters and from higher-trophic consumers cycles back to the deeper waters of the shelf and slope (Brewer et al. 2007). Deepwater biodiversity includes fish, molluscs, sponges, soft corals and gorgonians. Some of these sponge and filter-feeding communities appear to be significantly different to those of the Dampier Archipelago and Abrolhos Islands, indicating that the Commonwealth waters of Ningaloo Marine Park have some particular areas of potentially high and unique sponge biodiversity (Rees et al. 2004).

National and/or regional importance

The Commonwealth waters adjacent to Ningaloo Reef are defined as a key ecological feature for their high productivity and aggregations of marine life, which apply to both the benthic and pelagic habitats within the feature.

Location

Ningaloo Reef extends more than 260 km along Cape Range Peninsula with a landward lagoon 200 m to 6 km wide. The outer reef is marked by a well-developed spur and groove system of fingers of coral formations penetrating into the ocean with coral sand channels in between. The spurs support coral growth, while the grooves experience strong scouring surges and tidal run-off and have little coral growth. Seaward of the reef crest, the reef drops gently to depths of 8–10 m. The waters reach 100 m depth, 5–6 km beyond the reef edge. Commonwealth waters over the narrow shelf (10 km at its narrowest) and shelf break are contiguous with Ningaloo Reef and connected via oceanographic and trophic cycling (Brewer et al. 2007; DEWHA 2008b).

The spatial boundary of this KEF, as defined in the Conservation Values Atlas, is defined as the waters contained in the existing Ningaloo Commonwealth Marine Reserve.

Description

The Commonwealth waters adjacent to Ningaloo reef include Ningaloo Commonwealth Marine Reserve (Commonwealth waters) and encompass an area of 2435 km². This feature lies adjacent to the Ningaloo Marine Park (state waters) margin at the 3 nm limit.

Upwellings associated with canyons on the adjacent slope and interactions between the Ningaloo and Leeuwin currents are thought to support the rich aggregations of large marine species present at Ningaloo Reef. The narrow shelf means that the nutrients channelled to the surface via canyons are immediately available to reef species. Low terrestrial nutrient input means that this deepwater source is a major source of nutrients for Ningaloo Reef and therefore very important in maintaining this system (DEWHA 2008b).

Pressure

During the development of marine bioregional plans, a regional pressure analysis was conducted to assess present and emerging pressures affecting conservation values in the Marine Regions and the effectiveness of mitigation and management arrangements that are currently in place to address these pressures. The analysis enabled pressures to be categorised in terms of their relative importance or concern and has informed the identification of regional conservation priorities. For the purpose of the plans, pressures are defined broadly as human-driven processes and events that do or can detrimentally affect the region's conservation values.

No pressures were assessed as of concern for Commonwealth waters adjacent to Ningaloo Reef.

Pressures assessed as of potential concern are changes in sea temperature and ocean acidification as a result of climate change; oil pollution and invasive species. These pressures are described in more detail below.

Changes in sea temperature (climate change)
Sea temperatures have warmed by 0.7 ºC between 1910–1929 and 1989–2008, and current projections estimate ocean temperatures will be 1 ºC warmer by 2030 (Lough 2009). Key ecological features supporting coral reef communities are vulnerable to bleaching and mortality from elevated sea temperatures. Projected temperature changes in Australian seas exceed the threshold for inducing bleaching events on an annual basis (Hobday et al. 2006). A decrease in coral abundance would lead to changes in ecosystem structure, processes, and connectivity between reefs and adjacent waters. Nutrients and organic matter sourced from dynamic reef complexes may be disrupted.

In 1998, high sea temperature led to widespread bleaching of corals at Ashmore and Cartier reefs, the Rowley Shoals, and Scott and Seringapatam reefs (Gilmour et al. 2007; Pittock 2003). At Scott and Seringapatam reefs, corals bleached at depths up to 30 m and hard coral cover decreased from 41 % before the event to 15 % (Pittock 2003). Ningaloo Reef bleached for the first time in February 2011 (Ridgeway 2011) due to prolonged high sea surface temperatures. In 2005, elevated sea surface temperatures resulted in a minor bleaching event at the Rowley Shoals, which impacted a large proportion of benthic organisms, including corals, clams and anemones (Gilmour et al. 2007).

While the effects of increased sea temperatures are likely to vary greatly across communities and ecosystems, there is a high level of agreement from different datasets that warming is affecting distributional ranges and larval phase of tropical marine fishes (Munday et al. 2009). Changes in sea temperature may also result in changes to phytoplankton and zooplankton communities, with implications for trophic dynamics (Richardson et al. 2009) and fish larval supply and survival (Lo-Yat et al. 2011).

Increases in ocean water temperature may also affect deeper water fish species, such as those within the demersal slope fish key ecological feature. Climate change modelling predicts that by 2070 ocean water temperatures at a depth of 500 m will warm by 0.5–1 °C, which could adversely impact larval fish development and survival (Hobday et al. 2006). Benthic and demersal fish species may shift south and some populations may decline where ranges are bounded to the south (Hobday et al. 2006). Structurally complex epifauna (i.e. sponges, algae and coralline algae) may also suffer mortality from elevated water temperatures (Lawrence et al. 2007).

Ocean acidification (climate change)
Driven by increasing levels of atmospheric CO₂ and subsequent chemical changes in the ocean, acidification is already underway and detectible. Since pre-industrial times, acidification has lowered ocean pH by 0.1 units (Howard et al. 2009). Furthermore, climate models predict this trend will continue with a further 0.2–0.3 unit decline by 2100 (Howard et al. 2009).

Ocean acidification will compromise carbon accretion and, together with increasing ocean temperatures, may result in loss of ecosystems based on geologic features formed from coral or coralline algae (Hoegh-Guldberg 2011; Hoegh-Guldberg et al. 2007; Kleypas & Yates 2009; Kuffner et al. 2008). Increasing acidity impairs the ability of species with calcareous shells, such as echinoderms, crustaceans and molluscs, to maintain shell integrity resulting in reductions of the overall abundance and biodiversity of these species (see review by Kleypas & Yates 2009). A decrease in the abundance of fauna with carbonate-based skeletons and coral and coralline algal abundance, and the complex structural habitats they create, could lead to changes in ecosystem structures, processes, and connectivity between the reef complex and the adjacent deeper waters.

Oil pollution (oil rigs)
Oil pollution is of potential concern for key ecological features with values vulnerable to the impacts of an oil spill, such as highly diverse coral communities that support an abundant array of marine species. The North-west Marine region is an area subject to significant petroleum exploration, development and production and this is likely to increase in the future (DEWHA 2008b). Shipping is likely to continue to expand in the region as a result of the growth of the resources sector. Australia has a strong system for regulating industry activity that is the potential source of oil spills and this system has been strengthened further in response to the Montara oil spill. The intensity and distribution of activities implicated in oil spills, such as oil production and transport, are likely to increase in the region.

While oil spills are unpredictable events and their likelihood is low based on past experience, their consequences, especially for threatened species at important areas, could be severe. The level of impact that actually occurs depends on a number of factors including concentration of oil; chemical and physical properties of the oil (or oil and dispersant mixture); the timing of breeding cycles and seasonal migrations of species; the time of contact; susceptibility of particular species; and the health, age and reproductive status of the individuals (AMSA 2011a).

Coral reef communities are highly sensitive to both oil and oil/dispersant mixtures (Shafir et al. 2007). Oil spills are particularly significant for corals when spawning because broadcast coral gametes collect at the surface and may be exposed to petroleum products. Coral eggs and larvae are buoyant for the first few days after spawning and may suffer significant mortality if any oil or oil/dispersant mixture is encountered in significant concentrations. There is also evidence that metamorphosis (around 1–3 weeks following spawning) is particularly susceptible to oil (Negri & Heyward 2000). Scott and Seringapatam reefs and the Rowley Shoals are likely to be self-seeding over ecological timescales (Underwood 2009; Underwood et al. 2007, 2009). Therefore, recovery from damage by oil is likely to be far slower in such isolated reefs than in coastal settings and interconnected groups of reefs.

To manage oil spills, chemical dispersants (powerful detergents) may be applied to oil slicks on the surface to accelerate weathering processes and to disperse the oil into the water column to minimise the surface transport of oil to sensitive habitats, such as foreshores. These dispersants contain toxic elements that can be harmful to coral (Shafir et al. 2007). Certain dispersants combined with crude oil increase the toxicity of oil to some fish and invertebrates (Gulec & Holdway 2000, in Fandry et al. 2006). However, dispersants are only used when all environmental effects have been considered and are generally not used in close proximity to coral reefs (AMSA 2011b).

Invasive species
Invasive species have the potential to impact directly on benthic communities, coral and fish via competition for habitat and food resources. The two primary mechanisms for the inadvertent introduction and spread of invasive marine species are ballast water discharge and vessel biofouling. Key ecological features in areas of high international and domestic shipping traffic are at greater risk of an invasive species incursion. Offshore petroleum development also has the potential to introduce invasive species through the installation of rigs and subsea infrastructure.