Factors contributing to a fish kill in the Australian wet/dry tropics

Townsend, Simon A.; Boland, K. T.; Wrigley, Tim

doi:10.1016/0043-1354(92)90139-u

Cited by 56 publications

(32 citation statements)

References 8 publications

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“…The poor water quality in some of these events results in severe fish kills, with large numbers and many species affected (Townsend et al 1992, Townsend 1994, Townsend and Edwards 2003. These events do occur naturally in tropical savannah rivers, but water extraction could lead to more frequent, severe, and prolonged hypoxia or poor-waterquality events as the 'buffering' capacity of the main channel and refugial waterholes is reduced as a result of lower volumes to dilute poor-quality inflows.…”

Section: Wet-dry Transition: Lowmediummentioning

confidence: 97%

Implications of water extraction on the low-flow hydrology and ecology of tropical savannah rivers: an appraisal for northern Australia

King

Townsend²,

Douglas

et al. 2015

Freshwater Science

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Balancing the freshwater needs of humans and ecosystems is a fundamental challenge for the management of rivers worldwide. River regulation and water extraction can affect all components of the natural flow regime, yet few studies have investigated the effects on the low-flow end of the hydrograph. Low-flow periods are hydrologically distinctive and ecologically important, varying in nature among climatic zones. Tropical savannah rivers are characterized by highly seasonal and predictable flow regimes, but with high interannual variation in the magnitude, timing, and duration of low flows. Many tropical savannah rivers are relatively intact, especially in northern Australia, but many are now receiving increasing attention for water-resource development through surface-and groundwater extraction. We identified the hydroecological effects of water extraction on 3 phases of the seasonal flow regime: the wet-dry transition, dry season, and dry-wet season transition for perennial and intermittent rivers in tropical savannah climates. We propose a conceptual model and 7 predictions that describe the ecological implications of dry-season water extraction in tropical savannah river systems worldwide. The predictions address: 1) connectivity, 2) availability of in-stream habitat, 3) dry-season persistence of in-channel refugia, 4) water quality during dry-wet and wet-dry transition periods, 5) decoupling of wet-and dry-season flows, and the cumulative effects on 6) groundwater-dependent species and 7) whole-ecosystem shifts. We used northern Australia as a case study to review the current level of evidence in support of these predictions and their potential ecological consequences, and used this review to propose key priorities for future research that are globally applicable.

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Section: Wet-dry Transition: Lowmediummentioning

confidence: 97%

Implications of water extraction on the low-flow hydrology and ecology of tropical savannah rivers: an appraisal for northern Australia

King

Townsend²,

Douglas

et al. 2015

Freshwater Science

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“…Furthermore, high concentrations of DOC can abiotically deplete oxygen (O 2 ) by promoting photo-oxidation (Lindell et al 2000) and can decrease the water mixing depth in shallow lakes (Fee et al 1996), diminishing the supply of O 2 -rich waters to deeper layers during stratified periods. In terms of biodiversity, anoxia typically results in significant declines in the biological richness and diversity of a given ecosystem (Townsend et al 1992). The full effects of DOC on aquatic ecosystems may be complex, and, thus, whole-lake studies of rising DOC concentrations (Sadro and Melack 2012) are important yet rare sources of information regarding the net metabolic responses of lakes to high DOC concentrations and are necessary for the meaningful prediction of trends at broader temporal and spatial scales.…”

mentioning

confidence: 99%

A feedback loop links brownification and anoxia in a temperate, shallow lake

Brothers¹,

Köhler²,

Attermeyer³

et al. 2014

Limnology & Oceanography

124

143

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This study examines a natural, rapid, fivefold increase in dissolved organic carbon (DOC) concentrations in a temperate shallow lake, describing the processes by which increased DOC resulted in anoxic conditions and altered existing carbon cycling pathways. High precipitation for two consecutive years led to rising water levels and the flooding of adjacent degraded peatlands. Leaching from the flooded soils provided an initial increase in DOC concentrations (from a 2010 mean of 12 6 1 mg L 21 to a maximum concentration of 53 mg L 21 by June 2012). Increasing water levels, DOC, and phytoplankton concentrations reduced light reaching the sediment surface, eliminating most benthic primary production and promoting anoxia in the hypolimnion. From January to June 2012 there was a sudden increase in total phosphorus (from 57 mg L 21 to 216 mg L 21 ), DOC (from 24.6 mg L 21 to 53 mg L 21 ), and iron (from 0.12 mg L 21 to 1.07 mg L 21 ) concentrations, without any further large fluxes in water levels. We suggest that anoxic conditions at the sediment surface and flooded soils produced a dramatic release of these chemicals that exacerbated brownification and eutrophication, creating anoxic conditions that persisted roughly 6 months below a water depth of 1 m and extended periodically to the water surface. This brownification-anoxia feedback loop resulted in a near-complete loss of macroinvertebrate and fish populations, and increased surface carbon dioxide (CO 2 ) emissions by an order of magnitude relative to previous years.

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“…The effects of iron on the survival of lampreys have probably increased in the recent past, since there has been a trend toward increasing total iron concentration in the river from the 1960s onward; in the 1960s the total iron concentration was approximately 50% of today's value, i.e., 1 mg liter −1 (Jokela and Saastomoinen, 1988). While the iron concentrations in Perhonjoki River and other rivers in the sulfide-rich areas of western Finland are higher than in Finnish waters in general (Table 1), similar, marked increases of total iron con- centration associated with reductions of pH have been observed in various parts of the world (e.g., Townsend et al, 1992;Hindar and Lydersen, 1994).…”

Section: Discussionmentioning

confidence: 90%