Glomar Shoals

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 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

While the biodiversity associated with the Glomar Shoals has not been studied, the shoals are known to be an important area for a number of commercial and recreational fish species such as rankin cod, brown striped snapper, red emperor, crimson snapper, bream and yellow-spotted triggerfish (Falkner et al. 2009; Fletcher & Santoro 2009). These species have recorded high catch rates associated with the Glomar Shoals, indicating that the shoals are likely to be an area of high productivity.

National and/or regional importance

The Glomar shoals are defined as a key ecological feature for their high productivity and aggregations of marine life.

Location

The Glomar Shoals are a submerged littoral feature located approximately 150 kilometres north of Dampier on the Rowley shelf at depths of 33–77 metres (Falkner et al. 2009).

The spatial boundary of this KEF, as defined in the Conservation Values Atlas, is defined by the area of terrace as defined in the Geoscience Australia geomorphic features dataset.

Description

The shoals consist of a high percentage of marine-derived sediments with high carbonate content and gravels of weathered coralline algae and shells (McLoughlin & Young 1985). The area’s higher concentrations of coarse material in comparison to surrounding areas are indicative of a high-energy environment subject to strong sea-floor currents (Falkner et al. 2009). Cyclones are also frequent in this area of the north-west and stimulate periodic bursts of productivity as a result of increased vertical mixing.

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 Glomar Shoals.

Pressures assessed as of potential concern are changes in sea temperature and ocean acidification as a result of climate change; extraction of living resources; and invasive species. 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).

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 KEF. 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.

Extraction of living resources (commercial fishing)
The main trawl fishery operating over the Glomar Shoals is the Pilbara Demersal Finfish Fishery, which operates in water depths of 50–200 m (Fletcher & Santoro 2009). Data from this fishery indicates that catch is greatest in the area that includes the Glomar Shoals. The fishery as a whole retained 1044 tonnes of demersal finfish species in 2009 and this level of catch is considered sustainable (Fletcher & Santoro 2010). However, it is not known if the catch of non-retained species is sustainable or what the impact of removing target and non-target species is on the Glomar Shoals. Moran and Stephenson (2000) found that the gear used in the fishery removed large epibenthos (organisms greater than 20 cm) density by 15.5 per cent per trawl pass. The removal of biomass and disturbance to benthic communities has the potential to adversely affect the values of the Glomar Shoals.

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.