Albany canyon group and adjacent shelf break

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 South-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

In contrast to other canyon systems in the region, the Albany canyon group is immediately adjacent to, and interacts with, a large section of continental shelf break. The area is thought to be associated with small, periodic subsurface upwelling events (Pattiaratchi 2007) that may drive localised regions of high productivity, contributing to the ecological functioning and integrity of this area. The canyons are known to be a feeding area for the sperm whale (Bannister et al. 1996) and sites of orange roughy aggregations (Caton & McLoughlin 2004). Anecdotal evidence also indicates that this area supports fish aggregations that attract large predatory fish, sharks, and toothed, deep-diving whales such as sperm whale.

National and/or regional importance

The Albany Canyon group and adjacent shelf break is defined as a key ecological feature for its high productivity, aggregations of marine life, and as a unique seafloor feature with ecological properties of regional significance (Pattiaratchi 2007). Both benthic and demersal habitats within the feature are of conservation value.

Location

The Albany canyon group extends 700 km from Cape Leeuwin to east of Esperance, Western Australia (from 115–124° E). The group consists of 32 canyons that cut deeply into the steep continental slope. The canyon system extends from Broke Canyon in the west, to the Albany, Vancouver, Wilyunup, Bremer and Malcolm canyons to the east. These submarine canyons start on the uppermost continental slope and extend up to 90 km offshore, reaching the lowermost slope and extending onto the abyssal plain (Exon et al. 2005). Sonar surveys have shown individual canyons up to 90 km long and to depths of 2000 m.

The spatial boundary of this KEF, as defined on the Conservation Values Atlas, encompasses all canyons in the Geoscience Australia geomorphic features dataset along a 700 km stretch of continental slope from approximately 115° E to 124° E, including Broke Canyon in the west and Malcolm Canyon in the east.

Description

Canyons in the Albany canyon group are numerous and closely spaced. They connect a wide range of depth-related habitat types and increase the habitat heterogeneity of the south-western Australian continental margin. High habitat heterogeneity is thought to be linked to increased biodiversity, although the study of this relationship is still in its infancy (Levin et al. 2010). The majority of canyons in the group cut into the shelf or occur just off the shelf edge; these cutting canyons experience high sediment load from offshore transport and receive organic material from productive shelf waters (Richardson et al. 2005). Areas with numerous, closely spaced canyons, such as the Albany canyon group, may allow high amounts of organic matter to reach the abyssal plain. Therefore, biodiversity may be higher on the abyssal plain in regions of closely spaced canyons (Richardson et al. 2005).

The biological productivity of the South-west Marine Region is low by global standards and in comparison with other Australian marine regions. This is due to the low-nutrient tropical waters carried south by the Leeuwin Current and its effect in suppressing upwelling of nutrients from deeper cold waters and the absence of significant rivers contributing nutrients into the marine environment through run-off. Small seasonal upwellings occur regularly at known locations and, because of the overall nutrient-poor nature of the region’s waters, these hotspots of productivity have a disproportionate influence on the region’s ecosystems, which is the reason that they are identified as a key ecological feature. The Albany canyon group is one of several areas of relatively higher seasonal productivity in the South-west Marine Region along with the Perth Canyon, Kangaroo Island canyons and pool, Cape Mentelle and eddy fields that spin off the Leeuwin Current along the west and south coasts of Western Australia.

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 the Albany Canyon group and adjacent shelf break.

Pressures assessed as of potential concern are changes in sea temperature, change in oceanography and ocean acidification as a result of climate change, noise pollution and bycatch. These pressures are described in more detail below.

Changes in sea temperature (climate change)
Sea temperatures have warmed by 0.7 °C between 1910–1929 and 1989–2008, and current projections estimate ocean temperatures will be 1 °C warmer by 2030 (Lough 2009). The implications of changes to the region’s sea temperatures and oceanography for deeper ocean environments are uncertain, although sea-water warming at depth is expected to have significant implications for benthic and demersal fish.

Change in oceanography (climate change)
The strength of the Leeuwin Current has decreased slightly since the 1970s. This weakening is expected to continue, although this prediction currently has low confidence (Feng et al. 2009). The Leeuwin Current is the basis of much of the region’s biological productivity, and its strength and seasonal/climatic variability are a primary driver for the intensity, timing and locations of productivity events in the region, from the waters off Geraldton to the Great Australian Bight (Pattiaratchi 2007). Numerous water bodies and currents converge at the Naturaliste Plateau, including the subtropical convergence front. These complex water dynamics are likely to experience considerable changes if there are significant changes to ocean circulation in the region, with flow-on effects for the entire ecosystem.

Ocean acidification (climate change)
Driven by increasing levels of atmospheric CO_² 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). Projected changes in Australian waters by 2070 include a decline in pH of 0.2 units (Lawrence et al. 2007). There is a high level of uncertainty about the effects of ocean acidification on marine life. While some organisms might be able to adapt (Orr et al. 2009), anticipated changes to phytoplankton and zooplankton have the potential to detrimentally affect ecosystem processes and the structure of ecological communities. Research on the impact of ocean acidification on Antarctic krill has found that increased levels of CO₂ kill their embryos (Kawaguchi et al. 2011). Krill are an important part of the food chain because they feed on phytoplankton and zooplankton, and are a key food source for many species that occur in Australian waters. Consequently, acidification impacts have the potential to affect species further up the food chain. The potential effects of increased acidity on the region’s biodiversity also include changes to growth and population dynamics of some shell-forming organisms, impacts on the reproductive and metabolic functions of a number of fish and invertebrate species, and sensitivity of some early-life stages to acidification (Orr et al. 2009).

Noise pollution
All sources of man-made noise in the region—shipping, marine infrastructure construction and operation involving underwater blasting and pile driving, defence naval exercises and seismic surveys—are predicted to increase (Clifton et al. 2007). Many marine organisms use sound for a number of biological functions, including navigation, social communication and location of prey. The effects of seismic activities on large whales have received the most attention in the region; however, there have also been experimental studies into the effects of seismic surveys on fish (Popper et al. 2002; McCauley et al. 2003). Although extrapolation from experimental studies to wild populations is problematic, the evidence available to date justifies a precautionary approach. The Royal Australian Navy’s Western Australia exercise area is located off Perth, and its operation involves noise-generating activities, including firing of live ammunition, shipping exercises and use of active sonar. Guidelines under the EPBC Act are in place to mitigate the effect of noise generated by seismic surveys on whales; similarly, the Royal Australian Navy implements operational procedures to minimise environmental impacts.

Bycatch
There is a general lack of evidence to demonstrate the performance of bycatch mitigation measures (Bensley et al. 2010). In relation to bycatch of non-protected species, Phillips et al. (2010) indicate that current levels of independent observers preclude a cumulative assessment of the catch of non-target species, but recommend that such assessment is important to understand more broadly the environmental effects of fishing and to underpin an ecosystem approach to fisheries management (Phillips et al. 2010). In the absence of an integrated assessment of the cumulative ecosystem effects of current catch rates for a number of non-target species, this pressure is of potential concern.