Protecting the biodiversity of mound springs of the Dampier Peninsula, Kimberley region.

A project undertaken at The University of Western Australia and implemented by Brad Pusey

Project Team

Brad Pusey & Peter Davies, Centre for Excellence in Natural Reource Management, The University of Western Australia

Mark Kennard, Australian Rivers Institute, Griffith University

Much of northern Australia's terrestrial and aqautic biodiversity is sustained by the region's groundwater.  Surface expressions of groundwater (mound springs) typically result in high levels of biodiversity and distinctiveness, conferring high conservation value on these areas.  Mound springs typically assume great cultural significance for Indigenous people also.  The moundsprings and associated wetlands of the Dampier Peninsula in the Kimberley region of northern Australia are of  potentially high significance but also potentially threatened by groundwater abstraction associated with development, increased urban use in Broome and changes in agricultural practices and by feral animals. Very little is known of the biota inhabiting them and there currently does not exist a management plan for their protection.  This project aims at providing the first comprehensive assessment of the biodiversity of aquatic vertebrates in spring systems of the Peninsula and the provision of information sufficient to enable the development of a management plan and monitoring protocols in collaboration the Northern Australian Indigenous Land and Sea Management Alliance and the Indigenous Nyul Nyul Rangers of Beagle Bay.  The project aims to survey the freshwater fishes of the wetlands and springs of the Peninsula over a two year period, first concentrating on those within the Nyul Nyul land claim area.  Fish assemblages will be sampled mainly by boat and back pack electrofishing, a non destructive and highly effective sampling method. 

 
The first field trip was conducted in June 2013 during which the heaviest rainfall for over 50 years was experienced.  None-the-less, we were able to sample a number of springs before all movement was curtailed.  Eight species of native fish were recorded, all but one (the Empire gudgeon Hypseleotris compressa)of which was estuarine dependent at some stage in their life history.  This was a surprising finding as it indicated a great deal of connectivity between the springs and the tidal creek near Beagle Bay.  This was later amply demonstrated by the significant flooding and connection between the wetlands and between the wetlands and spring and the marine environment that occurred after the heavy rains experienced during the field trip. The estuarine dependent species recorded included juvenile barramundi (Lates calcarifer), ox-eye herring or tarpon (Megalops cyprinoides), milkfish (Chanos chanos) and nigilbardiny or Indian short-finned eel (Anguilla bicolor).  The presence of these species, some of economic significance, suggests the wetlands and springs play an important nursery role in the region.  The presence of nigilabardiny, the Nyul Nyul language name for A. bicolor, is significant as it is relatively rare in Australia.  For example, the Museum of the Northern Territory contains only a single specimen.  Nigilbardiny are also of very high cultural significance.  The most significant find of the first trip however was the widespread distribution and high abundance of the the alien species Mosquitofish Gambusia holbrooki.  Its presence in the region, which appears to have been of a considerable duration, is of significance as it is the first recorded large and self sustaining population of alien fish in a non-urban area of northern Australia.  Future sampling will determine if there are any spring habitats in the region not inhabited by this pest.

Subsequent sampling revealed stochasticity in assemblage composition driven by varying degrees of connectivity between the wetlands and the nearby estuary of Bobbis Creek associated with wet season rainfall.  Stable isotope analysis of oxygen and hydrogen revealed that the extent to which groundwater inputs balanced evaporative water loss and hence determined temporal changes in habitat structure was important in determining late dry-season changes in fish assemblage composition.  Subsequent sampling determined that the distribution of Gambusia was limited to wetlands and springs of the Bobbis Creek drainage and did not extend to a number of large isolated lake systems.  These systems were devoid of other fish also but had a very rich macroinvertebrate fauna.  Stable isotope analysis of nitrogen and carbon revealed that the food webs of the wetlands of the region are based upon periphyton production.  Although groundwater inputs directly into the food web were not observed, there were slight but discernible differences in food web structure associated with groundwater inputs.  Groundwater extraction therefore has the potential to impact on the ecological value of the aquatic habitats of the region by altering habitat persistence and food web structure. Feral animals, especially donkeys, are abundant in the study region and are having significant impact on the integrity of springs and wetlands, destroying riparian vegetation and bank structure.  Moreover, such activities have resulted in increased delivery of fine sediments to the water bodies potentially altering food web structure if left unmanaged.  Furthermore, donkey visitation was correlated with high levels of coliform bacteria and this had health implications for community members who use the groundwater for drinking and the wetlands for fishing and recreation.  A management and monitoring plan was developed in collaboration with the Nyul Nyul Ranger Group and in consultation with Beagle Bay elders.

Publications

Dobbs, R.J., Davies, C.L., Walker, M.L., Pettit, N.E., Pusey, B.J., Close, P.G., Akune, Y., Walsham, N., Smith, B., Wiggan, A., Cox, P,.. Ward, D.P. Tingle, F., Kennett, R., Jackson, M.V. and Davies, P.M. (2015). Collaborative research partnerships inform monitoring and management of aquatic ecosystems by Indigenous rangers. Rev Fish Biol Fisheries. DOI 10.1007/s11160-015-9401-2

Pettit, N.E., Warte, D.M., Close, P.G., Pusey, B.J., Dobbs, R., Davies, C., Valdez, D. and Davies, P.M. (2016). Carbon sources for aquatic food webs of riverine and lacustrine tropical waterholes with variable groundwater influence. Marine and Freshwater Research. http://dx.doi.org/10.1071/MF15365

Figure 1.

 

Figure 2.

Figure 3. The study team (Brad Pusey on the left, rangers in the middle).

Figure 4. Looking across Rubbabanin (Lake Louisa), one of the study sites.