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RESEARCH ARTICLE
Contents Vol 58(4)

Potential for algal blooms in tropical rivers of the Northern Territory, Australia

George G. Ganf A C and Naomi Rea B
+ Author Affiliations
- Author Affiliations

A School of Earth and Environmental Sciences, The University of Adelaide, Adelaide, SA 5005, Australia.

B School of Australian Indigenous Knowledge Systems, Charles Darwin University, Darwin, NT 0909, Australia.

C Corresponding author. Email: george.ganf@adelaide.edu.au

Marine and Freshwater Research 58(4) 315-326 https://doi.org/10.1071/MF06161
Submitted: 6 September 2006  Accepted: 15 January 2007   Published: 16 April 2007

Abstract

Rivers in the Northern Territory (NT) of Australia are under pressure from increasing vegetation clearance, land use and nutrient run-off. The literature on algal blooms clearly identifies the predisposing factors but in the NT, these factors are not well researched. We report on the potential for tropical rivers to experience problems related to algal growth. NT rivers were found to have a low nutrient status and a viable inoculum of blue-green, brown and green algal communities. The growth response of these algal groups to nutrient enrichment via bioassays and pulse-amplitude-modulation (PAM) fluorometry measurements varied among rivers and the addition of N, P or N&P. However, the overwhelming findings were that all rivers had the potential to experience algal blooms with enrichment. Back-calculations based on the chlorophyll concentrations recorded in bioassay experiments and stoichiometric ratios of chlorophyll:nutrients suggest there are pools of biologically available organic forms of N and P in addition to inorganic forms. The role of river length in the development of algal blooms was investigated: the longer the river reach, the slower the flow, and the greater the availability of nutrients, the higher potential for algal blooms. Given the strong indications that increased nutrient run-off to tropical rivers will result in algal blooms, prudent land-use and development with nutrient management strategies is essential.

Additional keywords: biologically available nutrients, cyanobacteria, discharge, river length, stoichiometry.


Acknowledgements

Financial support from Land and Water Australia is gratefully acknowledged. The Environmental Research Institute of the Supervising Scientist provided generous laboratory accommodation. G.G.G. was supported by the University of Adelaide Special Studies Program. Dr. Justin Brookes provided helpful comments on the manuscript.


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