Development of blooms of <Emphasis Type="Italic">Cyclotella meneghiniana</Emphasis> and <Emphasis Type="Italic">Nitzschia</Emphasis> spp. (Bacillariophyceae) in a shallow river and estimation of effective suppression flows |
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Authors: | Simon M Mitrovic Bruce C Chessman Alec Davie Estelle L Avery Natasha Ryan |
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Institution: | (1) NSW Department of Water and Energy, P.O. Box 3720, Parramatta, NSW, 2124, Australia;(2) Department of Environmental Sciences, University of Technology, Sydney, Australia |
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Abstract: | Diatom blooms in the middle reaches of the shallow, freshwater, Hunter River, Australia, are a frequent nuisance to river
users. During a 4-year study, blooms of Cyclotella meneghiniana and Nitzschia spp. coincided with water temperatures above 23°C and flows below 400 Ml d−1 that lasted for more than 12 days. Redundancy analysis showed that water temperature was positively related, and antecedent
flow was negatively related, to the abundance of both taxa. Addition experiments indicated that nutrients are seldom limiting
to growth. It is suggested that a combination of faster growth rates at higher temperatures and longer retention times at
low flows allows bloom populations to develop. Simulation modelling showed that flow regulation and water extraction have
decreased flows in the river during summer, and consequently have probably increased the number of diatom blooms. Environmental
flows have been provided to the river, but are not sufficient to prevent blooms. Discharges required for bloom suppression
are described. |
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Keywords: | Nitzschia Cyclotella Diatoms Flow management Growth suppression |
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