Browsing by Author "McMinn, A"

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    Cyst and radionuclide evidence demonstrate historic Gymnodinium catenatum dinoflagellate populations in Manukau and Hokianga Harbours, New Zealand
    (Elsevier, 2003-03) Irwin, A; Hallegraeff, GM; McMinn, A; Harrison, JJ; Heijnis, H
    Between May 2000 and February 2001, a major bloom of the toxic dinoflagellate Gymnodinium catenatum (a causative organism of Paralytic Shellfish Poisoning, PSP) affected over 1500 km of coastline of New Zealand’s North Island. As this was the first record of this species in New Zealand, we aimed to resolve whether this represented a recent introduction/spreading event or perhaps an indigenous cryptic species stimulated by environmental/climatic change. To answer this question, we analysed for G. catenatum resting cysts in 210Pb dated sediment cores (18–34 cm long; sedimentation rates 0.34–0.69 cm per year) collected by SCUBA divers from Manukau Harbour, where the species was first detected, and from Hokianga Harbour, where the highest shellfish toxicity was recorded, while using Wellington Harbour as a well-monitored control site. The results of this study conclusively demonstrate that abundant G. catenatum has been in northern New Zealand at least since the early 1980s, increasing up to 1200 cysts/g around the year 2000, but with low cyst concentrations possibly present since at least 1937. In contrast, Wellington Harbour cores contained only very sparse G. catenatum cysts (8 cysts/g), present only to a depth of 7 cm (surface mixed layer depth), reflecting an apparent recent range expansion of this dinoflagellate in New Zealand, possibly stimulated by unusual climatic conditions associated with the 2000 La Nina event. The significant increases since the early 1980s also of Protoperidinium cysts at Hokianga Harbour and of Gonyaulax, Protoperidinium and Protoceratium cysts at Manukau Harbour suggest a broad scale environmental change has occurred in Northland, New Zealand. © 2003 Elsevier Science B.V
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    Ecosystem impacts of feral rabbits on World Heritage sub-Antarctic Macquarie Island: a palaeoecological perspective
    (Elsevier, 2013-11) Saunders, KM; Harrison, JJ; Hodgson, DA; de Jong, R; Mauchle, F; McMinn, A
    The introduction and establishment of non-indigenous species through human activities often poses a major threat to natural biodiversity. In many parts of the world management efforts are therefore focused on their eradication. The environment of World Heritage sub-Antarctic Macquarie Island has been severely damaged by non-indigenous species including rabbits, rats and mice, introduced from the late AD 1800s. An extensive eradication programme is now underway which aims to remove all rabbits and rodents. To provide a long-term context for assessing the Island's pre-invasion state, invasion impacts, and to provide a baseline for monitoring its recovery, we undertook a palaeoecological study using proxies in a lake sediment core. Sedimentological and diatom analyses revealed an unproductive catchment and lake environment persisted for ca. 7100 years prior to the introduction of the invasive species. After ca. AD 1898, unprecedented and statistically significant environmental changes occurred. Lake sediment accumulation rates increased >100 times due to enhanced catchment inputs and within-lake production. Total carbon and total nitrogen contents of the sediments increased by a factor of four. The diatom flora became dominated by two previously rare species. The results strongly suggest a causal link between the anthropogenic introduction of rabbits and the changes identified in the lake sediments. This study provides an example of how palaeoecology may be used to determine baseline conditions prior to the introduction of non-indigenous species, quantify the timing and extent of changes, and help monitor the recovery of the ecosystem and natural biodiversity following successful non-indigenous species eradication programmes. © 2014 Elsevier Ltd.
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    Nuclear detectives - reconstructing histories of toxic dinoflagellates & blue green algae in coastal lakes and estuaries
    (International Atomic Energy Agency, 2004-10-28) Heijnis, H; McMinn, A; Hallegraeff, GM; Srisuksawad, K
    Using isotopic, geochemical and microfossil analyses of sediment cores, it is possible to reconstruct pre and post-colonial environmental conditions of coastal lakes and estuaries and their catchments. This is an important management tool, not only for determining the baseline 'natural' conditions of these ecosystems but also identifying the nature and extent of changes they have experienced through time, including the influx of pollutants and cha nges in sedimentation regimes. Such information is generally not available from historic records. Practical examples includes the following case-studies: 1) Tasmania & South Australia - Over the past couple of decades “alien species” have been introduced to the coastal waters of Australia and of Tasmania in particular, such as the toxic dinoflagellate Gymnodinium Catenatum. Careful dating and reconstruction of sediment archives have revealed the time and nature of this arrival. 2) NSW Blue Green Algae in the Great Lakes Area: The occurrence of blue- green algal blooms in the Great Lakes area of NSW have now been linked with catchment changes and the dynamics of this coastal system, using reconstructed histories from sediment cores. These detailed histories span the last 60 – 80 years, and cover the post World War II coastal population & development expansion.
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    Palaeoecological tools for improving the management of coastal ecosystems: a case study from Lake King (Gippsland Lakes) Australia
    (Springer, 2008-07) Saunders, KM; Hodgson, DA; Harrison, JJ; McMinn, A
    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 Pb-210. 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 mu g/l. Chlorophyll a concentrations were generally below 24 mu g/l/gTOC in the core, but there has been a clear increase since the 1980s, peaking at 120 mu g/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. © 2008, Springer.
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    Recent environmental change and trace metal pollution in World Heritage Bathurst Harbour, southwest Tasmania, Australia
    (Springer Nature, 2013-08-22) Saunders, KM; Harrison, JJ; Butler, ECV; Hodgson, DA; McMinn, A
    Bathurst Harbour in World Heritage southwest Tasmania, Australia, is one of the world’s most pristine estuarine systems. At present there is a lack of data on pollution impacts or long-term natural variability in the harbor. A ca. 350-year-old 210Pb-dated sediment core was analysed for trace metals to track pollution impacts from local and long-range sources. Lead and antimony increased from AD 1870 onwards, which likely reflects remote (i.e. mainland Australian and global) atmospheric pollution sources. Variability in the concentrations of copper and zinc closely followed the history of mining activities in western Tasmania, which began in the AD 1880s. Tin was generally low throughout the core, except for a large peak in AD 1989 ± 0.5 years, which may be a consequence of input from a local small-scale alluvial tin mine. Changes in diatom assemblages were also investigated. The diatom flora was composed mostly of planktonic freshwater and benthic brackish-marine species, consistent with stratified estuarine conditions. Since mining began, however, an overall decrease in the proportion of planktonic to benthic taxa occurred, with the exception of two distinct peaks in the twentieth century that coincided with periods of high rainfall. Despite the region’s remoteness, trace metal analyses revealed evidence of atmospheric pollution from Tasmanian and possibly longer-range mining activities. This, together with recent low rainfall, appears to have contributed to altering the diatom assemblages in one of the most pristine temperate estuaries in the world. © 2013 Springer Science+Business Media Dordrecht
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    Reconstructing past environments: looking back in time to plan for the future
    (Australian Marine Sciences Association, 2007-07) Saunders, KM; Harrison, JJ; McMinn, A