Elizabeth and Middleton reefs

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 (KEFs) 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 Temperate East 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

The location of this KEF exposes it to a mix of tropical and temperate water masses, giving rise to a unique mixed community of species considered particularly rich biologically and recognised for their high levels of endemism.

National and/or regional importance

Elizabeth and Middleton reefs are defined as a key ecological feature as it is an area with high levels of biodiversity, endemism and aggregations of marine life.

Location

The Elizabeth and Middleton reefs are small isolated oceanic platform-reefs on volcanic seamounts of the Lord Howe seamount chain (Kennedy & Woodroffe 2004).

The spatial boundary of this KEF, as defined on the Conservation Values Atlas, is based on areas identified in the Geoscience Australia geomorphic features data set as reefs, or cays.

Description

The reefs are influenced by currents linked to the East Australian Current and represent an overlap of warm-water hermatypic (reef building) and cool-water ahermatypic (non-reef-building) corals (Veron & Done 1979, in Dambacher et al. 2011), which in turn provide habitat for both tropical and temperate fish and invertebrates (Choat et al. 2006, in Dambacher et al. 2011; Oxley et al. 2003).

Elizabeth and Middleton reefs are home to a diverse assemblage of tropical and temperate fish species (Australian Museum 1992, in Dambacher et al. 2011), with a list of over 300 fish species compiled from literature reviews and surveys (Choat et al. 2006, in Dambacher et al. 2011; Oxley et al. 2003). The lagoons of both reefs are strongholds for populations of the black cod and Galapagos shark (Dambacher et al. 2011). A recent study of the genetic diversity and connectivity of the reefs suggests that their gene pools are periodically supplemented by long-distance migrants, which are likely to have population sizes large enough to avoid inbreeding and maintain genetic diversity (Noreen et al. 2009, in Dambacher et al. 2011). For example, 48 % of the coral species of the southern Great Barrier Reef are also found on Elizabeth and Middleton reefs (Dambacher et al. 2011). Many tropical species of reef-building corals are absent, especially those with massive growth forms, and branching corals are dominant (Choat et al. 2006 & Veron & Done 1979, in Dambacher et al. 2011; Harriott & Banks 2002; Oxley et al. 2003).

Model information

The department and CSIRO conducted collaborative research on KEFs to identify indicators for monitoring marine ecosystem health in the Commonwealth marine area. As part of this process, qualitative models were developed for 27 KEFs, including Elizabeth and Middleton reefs. Further information can be found at https://publications.csiro.au/publications/publication/PIcsiro:EP132926.

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.

Pressures assessed as of concern for Elizabeth and Middleton reefs are changes in sea temperature and ocean acidification as a result of climate change.

Pressures assessed as of potential concern are sea level rise and change in oceanography as a result of climate change; chemical pollution; marine debris; light pollution; and oil pollution. 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 a further 1 °C warmer by 2030 (Lough 2009). Elizabeth and Middleton reefs are valued for their aggregations of marine life and biodiversity. Ocean warming is expected to alter food web dynamics (Hoegh-Guldberg & Bruno 2010), potentially increase the frequency or severity of coral bleaching events and result in southerly distribution shifts of pelagic fish species (Hobday et al. 2006). The reefs are at risk from these expected impacts, however, the overall implications for ecosystem processes and responses are not known, and will be influenced by species tolerance and adaptive capacity.

Ocean acidification (climate change)
Driven by increasing levels of atmospheric CO₂ and subsequent chemical changes in the ocean, ocean acidification is already under way and detectable. Since pre-industrial times, acidification has lowered ocean pH by 0.1 units (Howard et al. 2009). Climate models predict this trend will continue, with a further 0.2–0.3 unit decline by 2100 (Howard et al. 2009). Elizabeth and Middleton reefs are valued for their aggregations of marine life and biodiversity, and expected impacts of acidification include a reduction in coral growth rates and resilience, which may make the reef systems more vulnerable to erosion and disturbance from storms (Anthony & Marshall 2009) and affect the ability of molluscs, echinoderms and some planktonic organisms to form skeletal material (Doney et al. 2009). Corals provide structural habitat complexity for a range of invertebrates and fish (Althaus et al. 2009); therefore, any impact on coral reef habitat is likely to result in changes to the distribution and abundance of species that depend on the reefs for food and shelter.

Sea level rise (climate change)
Global sea levels rose by 20 cm between 1870 and 2004, and predictions estimate a further rise of 5–15 cm by 2030, relative to 1990 levels (Church et al. 2009). Longer term predictions estimate increases of 0.5–1 m by 2100, relative to 2000 levels (Climate Commission 2011). Elizabeth and Middleton reefs are shallow water reefs valued for their aggregations of marine life and biodiversity. Over time, rising sea levels are expected to decrease the amount of light that reaches the corals, thereby reducing coral growth rates (Anthony & Marshall 2009). Any impact on coral reef habitat is likely to change the distribution and abundance of species that depend on the reefs for food and shelter (Chambers et al. 2009).

Changes in oceanography (climate change)
Changes in oceanography include consideration of circulation patterns; current intensities; wind strength and direction; the location and strength of eddy and upwelling events; and climatic oscillations such as the El Niño–Southern Oscillation. In the region, changes in oceanography will be primarily influenced by the East Australian Current, which is one of the key drivers of the region’s biological productivity, species distribution and abundance (Dambacher et al. 2011). The East Australian Current has been strengthening, pushing warmer, saltier water further southward along the east coast (for up to 350 km) (Ridgway & Hill 2009). Changes in the strength and extent of the current are likely to impact on productivity, shifting trophic webs, and changing migration patterns and reef and shelf habitats, all of which have implications for marine species (Chin et al. 2010). Offshore, the current is partly responsible for the unique mix of warm and cold water species associated with Elizabeth and Middleton reefs and the Tasmantid and Lord Howe seamount chains (Dambacher et al. 2011).

Chemical pollution
Chemical pollution is of potential concern for key ecological features with values that make them particularly vulnerable to the impacts of a chemical spill, such as important aggregations of marine life at or near the sea surface. Vulnerable key ecological features include Elizabeth and Middleton reefs. As is the case with oil spills, chemical spills are unpredictable events and their likelihood is low in the context of the international and domestic regulatory mitigation measures that apply in Australia. The effects of a major chemical spill can be similar to those of oil spills (GBRMPA 2009), particularly in areas and at times of biological significance for important or threatened species. The impacts vary depending on the toxicity of chemicals, how the materials are packaged and transported, the quantity spilled, the site and ecological sensitivity.

Marine debris
Marine debris is defined as any persistent, manufactured or processed solid material that has been disposed of, or abandoned, in the marine and coastal environment (UNEP 2005). This includes a range of materials from plastics (e.g. bags, bottles, ropes, fibreglass and insulation) to derelict fishing gear, and ship-sourced, solid, non-biodegradable floating materials (DEWHA 2009). Although region-specific marine debris data is limited, key sources for the introduction and spread of debris (such as shipping, commercial fishing and major current systems) are present across the region. This suggests that all KEFs will experience a high degree of overlap with this pressure (Katsanevakis 2008). Marine debris has been listed as a key threatening process under the EPBC Act, in recognition of its negative impacts on substantial numbers of Australia’s marine wildlife, including protected species of birds, turtles and marine mammals. Therefore, this pressure has implications for KEF values such as biodiversity and aggregations of marine life. The Australian Government has developed a threat abatement plan that provides a coordinated national approach to prevent and mitigate the effects of harmful marine debris on marine life (DEWHA 2009).

Light pollution
Light pollution is of potential concern to Elizabeth and Middleton reefs as they are known to support important aggregations of marine life that are vulnerable to light (e.g. turtles). Light quality is important for turtles (Salmon 2003) and lighting from shipping and fishing vessels offshore can attract hatchlings to vessel hulls, exposing them to predation. Shipping traffic, including fishing vessels anchoring in close proximity to Elizabeth and Middleton reefs, have the potential to negatively impact turtles that forage in these areas.

Oil Pollution
Oil pollution is of potential concern for KEFs with values that make them particularly vulnerable to the impacts of an oil spill, such as important aggregations of marine life at or near the sea surface, including Elizabeth and Middleton reefs.

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. While oil spills are unpredictable events and their likelihood is low based on past experience, their consequences, especially for threatened species at important areas can be severe. The level of impact that actually occurs depends on a number of factors including the concentration of oil; chemical and physical properties of the oil (or oil and dispersant mixture).

Also influencing the impact of an oil spill event are the timing of breeding cycles and seasonal migrations of species, the amount of contact, the susceptibility of particular species; and the health, age and reproductive status of the individuals (AMSA 2011).

Particular ecological values associated with the KEFs that may be impacted by such an event include seabirds and turtles that forage at Elizabeth and Middleton reef and the tropical and temperate demersal and pelagic fish assemblages supported by these reefs.

Both the intensity and distribution of activities that might lead to oil spills (such as transport) are expected to increase in the region.