CASE STUDY – SELECTED SPECIES AND COMMUNITIES – WESTERN AUSTRALIA
Stygofaunal communities of north-west Western Australia
Description
Stygofauna are animals that permanently or opportunistically inhabit groundwater
aquifers. The Pilbara and Cape Range regions (herein referred to as the north-west)
have been shown to have some of the richest stygal communities in the world
(Eberhard et al 2005, Scanlon 2006). These are dominated by crustaceans but include
other invertebrates and even a fish and an eel (at Cape Range). The north-west
stygofauna is distinctive, with numerous (higher level) taxa not found elsewhere
within the State or continent. Within the region, stygofaunal community composition
varies greatly between aquifers and subregions. About 400 species have been recorded
so far, with ostracods and copepods especially speciose by world standards
(Karanovic 2006, Karanovic 2007).
A few widespread stygofaunal species occur in both groundwater and surface waters.
Most, however, are restricted to groundwater and many are restricted to particular
aquifers and have only rarely been recorded. Elements of the Pilbara stygofauna have
phylogenetic affinities to other taxa from inland surface waters, marine waters, other
groundwaters and some elements have Tethyan, Pangean or Gondwanan affinities
(Humphreys 1993a and b, Knott & Halse 1999). Many species are geographically
isolated relicts derived from surface dwelling ancestors which colonized subsurface
waters in response to increasing aridity. Hence, short range endemism is a
characteristic feature.
Obligate stygofaunal species (stygobites) display specialisations to subterranean life,
including reduction or loss of eyes and pigment, elongation of appendages and
enhancement of non-optic sensory structures. Little is known about their ecology but
groundwater food webs are generally dependant on dissolved and particulate organic
matter and nutrients derived from the surface. Most invertebrate species would feed on
particulate organic matter and microflora. Dispersal between aquifers, where it occurs,
is slow and limited, with springs and the hyporheic zones of rivers (Halse et al 2002)
providing a likely dispersal route between aquifers.
Significance
Within the stygofaunal communities of north-west Western Australia, several
crustacean species are listed as threatened species under the Western Australian (WA)
Wildlife Conservation Act 1950. One species, Lasionectes exleyi (Crustacea:
Remipedia), from Cape Range is listed as vulnerable under the Commonwealth’s
Environment Protection and Biodiversity Conservation Act 1999 (EPBC Act). These
species are listed due to their highly restricted distributions. Short range endemism is
also a characteristic feature hence, species are vulnerable to extinction from a range of
threatening processes that may affect the physical environment where they occur, or
the hydric characteristics of the sites.
Under WA’s category of threat criteria, the Cape Range Remipede Community is
listed as a Critically Endangered Threatened Ecological Community (TEC) and the
Ethel Gorge Aquifer Stygobiont Community is listed as an Endangered TEC. The
stygofaunal communities are also linked to surface water and groundwater ecotone
communities.
Data and information
Numerous Environmental Impact Statement surveys have been undertaken by
consultants. There have also been studies by the Western Australian Museum and the
University of Western Australia (see references in Eberhard et al 2005). The largest
study (1100 samples from 500 bores and wells) was undertaken by the Department of
Environment and Conservation in 2002-2007 and is still being analysed.
The overall nature and diversity of regional stygofauna is reasonably well known,
though further surveys in particular subregions will continue to reveal new taxa, new
records and range extensions of already recorded species. There are still gaps in
information relating to disturbance response data, taxonomic resolution of some
groups, knowledge of biology, ecology and tolerances to better predict responses to
disturbance, and recovery potential (especially aquifer dewatering).
Management requirements and issues
Public and private sector water abstraction and dewatering of aquifers for mining
below water tables are major threats to stygofauna. Contamination of aquifers from
above ground activities and re-injection of water from dewatering activities, as well as
disruption of anchialine groundwater systems also act as threats. Climate change could
also raise sea-levels to inundate low-lying coastal/anchialine areas and affect
associated aquifers.
Ongoing conservation management needs to be undertaken for stygofauna.
Appropriate environmental impact assessment, management and amelioration and
environmental water provisions all need to be addressed to manage stygofaunal
communities correctly.
Management actions and responses
The management of the north-west Western Australian stygofaunal communities is
ongoing. An Interim Recovery Plan (IRP) for the Cape Range Remipede Community
(Black et al 2001) has been implemented and approximately $100 000 has been
invested for the period of this IRP. The North West Cape Karst Management Advisory
2
ASSESSMENT OF AUSTRALIA’S TERRESTRIAL BIODIVERSITY 2008
Committee was appointed as the recovery team for this community. There are
currently no specific natural resource management or species management plans.
Current reservation includes the Bundera Remipede Community, as it is located on
Commonwealth Department of Defence land. The conservation needs (including
progress towards a CAR reserve system) of the Pilbara region are also currently being
reviewed, including consideration of stygofauna.
Protection of stygofauna is assisted by Western Australia’s Environmental Protection
Authority Guidance Statements 54 and 54a, as they provide protocols for
environmental impact assessment of stygofauna communities. The Water Corporation
and the Department of Water are undertaking extensive stygofauna monitoring as part
of a groundwater management program on Cape Range.
Outcomes
No trend data are currently available to analyse the current trends and effectiveness of
actions. Analyses of eight years of monitoring data from the Exmouth region will be
available in 2008. Stygofauna communities are qualitatively listed as static, declining,
rapidly declining, or status unknown in McKenzie & May (2002).
Exmouth stygofauna is being monitored by the Water Corporation. Some resource
companies are also monitoring stygofauna in aquifers associated with mining
activities but these have only recently commenced and the data are not currently
available.
Future scenario
Many aquifers are expected to be affected by mining (pit excavation and dewatering)
and water resource development. There is potential for this to result in local
population extinctions, loss of genetic diversity and possibly species extinctions.
There has been a significant increase in resource development in the Pilbara region
which requires dewatering of stygofauna habitat. Water resource development in the
Pilbara and Cape Range are also emerging issues. Stygofauna should be included in
future regional biodiversity surveys where appropriate. Many species and
communities are probably suitable for threatened species and ecological community
nomination once adequate data are available.
It is vital that impact assessment and monitoring by industry continues. Biogeographic
analyses of stygofauna (from the Pilbara Biological Survey) need to be included in
regional conservation planning. Further research into systematics (especially
molecular work on species and population genetics) and ecological requirements of
stygofauna, and potential for recovery from impacts needs to be promoted.
ASSESSMENT OF AUSTRALIA’S TERRESTRIAL BIODIVERSITY 2008
3
Figure 1
Location map. Bores sampled for stygofauna during DEC’s Pilbara
biological survey in the Pilbara and adjacent IBRA regions.
Melitid amphipod (left) and sampling stygofauna from a bore (right)
4
ASSESSMENT OF AUSTRALIA’S TERRESTRIAL BIODIVERSITY 2008
References
Black S, Burbidge A, Brooks D, Green P, Humphreys WF, Kendrick P, Myers D,
Shephard R, Wann J (2001). Cape range remipede community (Bundera Sinkhole) and
Cape Range remipede interim recovery plan 2000-2003. Interim recovery plan no. 75.
Department of Conservation and Land Management, Perth. 25p.
Eberhard S, Halse SA and Humphreys WF (2005). Stygofauna in the Pilbara region,
north-west Western Australia: a review. Journal of the Royal Society of Western
Australia 88: 167-176.
Halse SA, Scanlon MD and Cocking JS (2002). Do springs provide a window to the
groundwater fauna of the Australian arid zone. Balancing the Groundwater Budget:
Proceedings of an International Groundwater Conference, Darwin, 2002.
Humphreys WF (1993a). Stygofauna in semi-arid tropical Australia: A Tethyan
connection. Memoire de Biospeleologie 20: 111-116.
Humphreys WF (1993b). The significance of the subterranean fauna in
biogeographical reconstruction: examples from Cape Range Peninsula, Western
Australia. Records of the Western Australian Museum Supplement 45: 165-192.
Karanovic I (2007). Candoninaen (Ostracoda) from the Pilbara Region in Western
Australia. Crustaceana Monograph, 7: 1-433.
Karanovic T (2006). Subterranean copepods (Crustacea, Copepoda) from the Pilbara
region in Western Australia. Records of the Western Australian Museum, Supplement
70: 1-239.
Knott B and Halse SA (1999). Pilbaraphreatoicus n. gen., n.sp. (Isopoda:
Phreatoicidea: Amphisopodidae) from the Pilbara region of Western Australia.
Records of the Australian Museum 51: 33-42.
McKenzie NL and May JE (2002). A Biodiversity Audit of Western Australia's 53
Biogeographic Subregions in 2002. Department of Conservation and Land
Management. 724p.
Scanlon MD, Cocking JS, McRae JM and Barron HJ (2006). Beasts of the
underworld. Landscope 52: 51-55.
Yager J and Humphreys WF (1996). Lasionectes exleyi, sp. nov., the first remipede
crustacean recorded from Australia and the Indian Ocean, with a key to the world
species. Invertebrate Taxonomy 10: 171-187.
ASSESSMENT OF AUSTRALIA’S TERRESTRIAL BIODIVERSITY 2008
5