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Abstract

Water quality around the globe has been in serious decline for many decades. To reverse the
degradation of waterways there must be a significant improvement in the way the coastal zone is
managed. The effective management of the coastal zone requires the ability to effectively monitor
and assess changes in water quality, and the ability to identify past, current and potential impacts
on water quality. In recent years, water quality monitoring and assessment programs have been
significantly improved by the inclusion of biological indicators. Diatoms have been used
extensively as biological indicators in water quality monitoring and assessment studies, and in
palaeo-environmental reconstruction of water quality, in many areas of the world. This study
documents the use of diatoms as biological indicators of water quality, and for environmental
reconstruction, in south-east Tasmania, Australia.
The biomass (chlorophyll a) of marine benthic algal mats was determined along a depth gradient
at two sites within the near-shore marine environment approximately fortnightly for 3 months, to
determine whether depth significantly influenced biomass. Average chl a levels ranged from
approximately 9 to 60 mg/m2 , and varied inconsistently with depth. Physical disturbance of the
substrata may account for the greatest variations in biomass observed. Diatoms were found to
contribute significantly to the productivity of the near-shore, subtidal marine environment of
south-east Tasmania, comprising approximately 95% of the benthic algal community.
Canonical correspondence analysis (CCA) was used to identify causative relationships between
the species composition of diatom communities and the corresponding physical and chemical
variables from 51 sites within the near-shore, sub-tidal marine zone of south-east Tasmania. The
composition of micro-algal communities within these habitats was found to be most strongly
influenced by nutrient concentrations. Transfer functions were generated to infer nitrite/nitrate,
silicate and sediment size at other sites within the geographic region of the study area. The
determination of environmental optima and tolerance ranges for south-east Tasmanian diatom
species, and the generation of transfer functions, provides a valuable water quality monitoring and
assessment resource for this region.
The environmental history of Pittwater Lagoon, an impacted Ramsar wetland site, was
reconstructed from the late 18th century using sediment-core fossil diatoms, 2I0Pb dating, transfer
functions and historical environmental data. A significant change in the diatom flora of the lagoon
was found to have occurred during the past 100 years. The future health of south-east Tasmanian
coastal ecosystems will depend on the ability of responsible stakeholders and caretakers to
incorporate effective biological monitoring and assessment into their management strategies.

Item Type:	Thesis - PhD
Authors/Creators:	Lane, CM
Keywords:	Water quality biological assessment, Water quality, Eutrophication, Diatoms, Diatoms, Fossil, Plant indicators
Copyright Holders:	The Author
Copyright Information:	Copyright the Author - The University is continuing to endeavour to trace the copyright owner(s) and in the meantime this item has been reproduced here in good faith. We would be pleased to hear from the copyright owner(s).
Additional Information:	Thesis (Ph.D.)--University of Tasmania, 2005. Includes bibliographical references
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