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SFOS Journeys

Photo by Amanda Rosenberger.

Photo by Amanda Rosenberger.

FISH AND CRITICAL REFUGIA IN AUSTRALIA'S OUTBACK

Photo by McNeil.

Photo by Dale McNeil.

Amanda Rosenberger SFOS journeys

In April of 2010, I travelled to Adelaide, Australia to participate in ongoing fisheries research taking place in the Lake Eyre Basin. My primary collaborator and host, Dale McNeil, works for the South Australian Research Institute and is investigating recovery of fish populations in the Lake Eyre Basin. This basin is typically a quite dry, desert environment - what you would expect of Australia's outback - but this area has recently experienced a drought that was severe even by Lake Eyre standards. This drought lasted for three years, seriously decreasing the availability of water in the basin and knocking back aquatic animals to extremely restricted distributions. For the past three years, however, Lake Eyre has been experiencing normal amounts of rainfall, restoring many of its waterholes and dry riverbeds. This allows us an unprecedented opportunity to document and study mechanisms for fish recovery in an area with a history of drought and stochastic availability of water - suggesting that multiple evolutionary mechanisms may have evolved for continued persistence in this harsh environment.

Photo by Amanda Rosenberger.

Photo by Amanda Rosenberger.

Photo by Amanda Rosenberger.

Photo by Amanda Rosenberger.

It's a rough road for desert fish! Photo by Amanda Rosenberger.

It's a rough road for desert fish! Photo by Amanda Rosenberger.

After a few days in Adelaide, we set out for the deep outback of Australia to sample fish in isolated waterholes and waterways and conduct field experiments on the tolerance of fish to low oxygen conditions and hypersalinity typical of these drought-prone habitats. Refilled by isolated tributary and reach flows during recent wet seasons, many waterholes have recovered their former size and volume. Because the Lake Eyre system has a long evolutionary history of dynamic changes in water availability, we expected to see resilient species with mechanisms for quick establishment into new habitats and resistant species that may radiate less quickly but have a relatively high tolerance to severe conditions in isolated waterholes. Our fieldwork confirmed these expectations; many species are yet to recover to their former distributions, but can be found in peripheral areas with extremely high salinities, water temperatures, and low oxygen conditions (resistant species), while others that were once restricted to a few isolated waterholes were almost immediately found in any newly available habitats (resilient species).

We conducted challenging pilot field trials to investigate differences between those species. As expected, resilient species were relatively less tolerant to high salinities and low oxygen conditions than resistant species. Our most tolerant species was a native goby that maintains presence in numerous, peripheral salt springs during drought periods. This species is restricted in distribution and has not recolonized newly available habitats. Our work suggests multiple evolutionary solutions to a drought-prone landscape and the disproportionately important role of few refuge waterholes in protecting drainage diversity.

At first glance, the applicability of such research to Alaskan issues seems remote; however, we are seeing widespread drying of our wetland habitats in the Yukon Flats refuge and beyond; an understanding of mechanisms for recovery and resilience can easily transfer to Alaskan habitats affected by ongoing climate change. Further, one can hypothesize that the dominant mechanism for continued persistence could affect things like population structuring and local adaptation. A combined study of the Alaska interior and Australia's outback gives an opportunity to compare, for example, genetic consequences of a resilient vs. resistant strategy in a highly dynamic, harsh environment without widespread human intervention - a characteristic common to both environments.

On a more personal note, the trip was a wonderful exposure to another of the world's great wild places, where the biota are permitted to display their full range of adaptive potential. The desert environment was rich with both life and unanswered questions - a paradise for any landscape ecologist. I have never been so muddy, filthy, or fly-ridden. It was a blast. I am grateful to my collaborators, particularly Dale McNeil and the South Australian Research Institute for supporting my travel and participation.