Palaeolimnological evidence for submerged plant loss in a floodplain lake associated with accelerated catchment soil erosion (Murray River,Australia) |
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| Authors: | M A Reid C D Sayer A P Kershaw H Heijnis |
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| Institution: | (1) School of Geography and Environmental Science, Monash University, Victoria, 3800, Australia;(2) Environmental Change Research Centre, Department of Geography, University College London, Pearson Building Gower Street, London, WC1E 6BT, UK;(3) Environmental Division, Australian Nuclear Science and Technology Organisation, Lucas Heights Research Laboratories, PMB1 Menai, New South Wales, Australia;(4) Present address: School of Resource, Environment and Heritage Science, University of Canberra, Canberra, ACT, 2601, Australia |
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| Abstract: | Shallow lakes have been described as existing in two alternative equilibrium states, dominated by either submerged plants
or phytoplankton. Causes of, often catastrophic, shifts between these states have been widely debated but may often result
from displacement of the dominant community by stochastic influence. In Australian cut-off river meanders (also known as ‘billabongs’),
anecdotal and palaeolimnological evidence suggests widespread loss of aquatic macrophytes since European occupation of the
region c. post-1800. Our detailed and high-resolution stratigraphic study of a sediment core from Hogan’s Billabong (Murray
River, Australia) seeks to identify the causes of the loss of aquatic macrophytes. Little direct evidence of the past extent
and composition of submerged macrophyte communities was recovered. Nevertheless, results derived from other sediment proxies,
including declines in the abundance of epiphytic diatoms and in plant-associated invertebrates, provide further indirect evidence
of macrophyte disappearance. Despite limitations with radiometric dating, the sequence of events in the derived record suggests
that a period of high abiotic turbidity, leading to a critical reduction in water transparency and caused by widespread erosion
during the late 19th century, is the most likely factor contributing to loss of submerged vegetation from this billabong. |
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| Keywords: | Submerged plants Alternative stable states Floodplain lakes Soil erosion Pollen Diatoms Macrofossils Murray River Australia |
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