The use of biological indicators for assessing stream health and relationships with catchment activities in the Richmond River NSW, Australia

Susan Gaye Oeding

doi:10.25918/thesis.57

Freshwater streams provide important ecosystem processes supporting essential services for both humans and the natural environment. However, these ecosystems are increasingly susceptible to anthropogenic influence and subsequently both biodiversity and water quality are declining. The declining health of surface waters worldwide has prompted policy makers and managers to improve assessment and monitoring programs in an attempt to quantify and limit the impacts of anthropogenic activities. Understanding the influence of anthropogenic activities on aquatic ecosystem functioning is crucial to develop better assessment and monitoring programs. Over the last few decades, policies and management strategies have evolved to include biological indicators to assess and monitor surface waters worldwide as concerns for diminishing ecological values have emerged. Effective management of rivers depends on the scientific community being able to provide managers with the knowledge and tools necessary to establish realistic management objectives, enabling both environmentally and economically effective remedial actions. The first component of this research focused on the development of a sub-tropical diatom index, the Richmond River Diatom Index (RRDI) as an assessment tool to assess river integrity at a catchment scale. Results indicated that the RRDI provided more accurate inferences on river health than borrowed temperate zone indices and demonstrated the importance of developing indices that are regionally specific. The next phase of the research focused on the application of the RRDI and two macroinvertebrate indices at a micro-catchment scale to assess the influence of land use on river health. This research determined that patterns in diatom and macroinvertebrate diversity and community composition can be attributed to a single land use. The research revealed how, through land use change, the loss of riparian vegetation and instream habitat contributed to the poor health status of these micro-catchment streams. This was particularly evident in the grazing, sugar cane and urban sites with minimal or no riparian vegetation and limited instream habitat available for both macroinvertebrates and diatoms. Stable isotope analysis was applied to determine the influence of land use on allochthonous versus autochthonous carbon sources for the freshwater Atyid shrimp, Paratya australiensisem. The findings indicated that changes in land use that increasingly remove or degrade riparian and instream habitat are reflected in the shrimp diet. The evidence from this research can be used to inform landholders, industry organisations and policy makers enabling rehabilitation efforts to be targeted at the source of the impacts. The research undertaken in this thesis will assist land and water managers in improving the functions, values and outcomes of these ecosystems, contributing to a greater understanding of river systems, according them a greater value to society and the economy.

The use of biological indicators for assessing stream health and relationships with catchment activities in the Richmond River NSW, Australia

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The use of biological indicators for assessing stream health and relationships with catchment activities in the Richmond River NSW, Australia

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