Palaeoecological tools for improving the management of coastal ecosystems: a case study from Lake King (Gippsland Lakes) Australia |
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Authors: | Krystyna M Saunders Dominic A Hodgson Jennifer Harrison Andrew McMinn |
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Institution: | (1) Institute of Antarctic and Southern Ocean Studies, University of Tasmania, Private Bag 77, Hobart, TAS, 7001, Australia;(2) British Antarctic Survey, Natural Environment Research Council, High Cross, Madingley Road, Cambridge, CB3 0ET, UK;(3) Australian Nuclear Science and Technology Organisation, PMB1, Menai, NSW, 2234, Australia |
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Abstract: | Since European settlement began over 200 years ago, many southeast Australian coastal lakes and lagoons have experienced substantial
human impacts, including nutrient enrichment. Present day management and conservation efforts are often hampered by a lack
of data on pre-impact conditions. We used a palaeoecological approach at Lake King, Gippsland Lakes, southeast Australia in
order to determine its pre-impact condition and to establish the nature and direction of subsequent environmental changes,
including responses to the construction of a permanent entrance to the sea in 1889. A 120 cm sediment core was analysed for
diatoms, chlorophyll a, total carbon, nitrogen and sulphur, and dated using 210Pb. Past phosphate and salinity concentrations were reconstructed using diatom-phosphate and diatom-salinity transfer functions
developed from a calibration set based on 53 sites from 14 southeast Australian coastal lakes and lagoons. Results show changes
in the diatom assemblage that record a shift from a brackish-water to marine diatom flora since construction of the permanent
entrance. Phosphate concentrations increased at the same time and experienced major peaks in the 1940s and 1950s to >100 μg/l.
Chlorophyll a concentrations were generally below 24 μg/l/gTOC in the core, but there has been a clear increase since the 1980s, peaking
at 120 μg/l/gTOC, likely associated with a recorded increase in the frequency of nuisance algal blooms. These results indicate
that the Lake King environment is now very different to that present during early European settlement. We conclude that by
identifying the nature and direction of environmental change, palaeoecological studies can contribute towards developing realistic
and well-informed management, conservation and restoration strategies in Australian coastal ecosystems. |
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Keywords: | Diatoms Human impacts Coast Nutrients Radionuclide dating 210Pb |
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