The Effect of Urbanisation on Aquatic Weeds in Australia
Abstract:As Australian cities expand, adjacent peri-urban, semi-rural waterways can experience changes in disturbance frequency and intensity, increased input of nutrient pollutants and reduction in riparian (river bank) forest cover. These changes, combined with the introduction of weed species, mean these waterways are at risk. Weeds in waterways (aquatic weeds) can impact on habitat for native fauna and may cause catchment-scale processes to become unbalanced. Because stream systems are interconnected, it is important that weed invasions are identified and managed before they can spread downstream. CSIRO researchers have studied the impacts of peri-urban development on aquatic weeds in Australia to look at: the size of the current aquatic weed problem (species, location, and abundance); whether invasions are the result of changes to the environment such as nutrient inflow, water flows and riparian canopy structure; and the development of management practices that reduce aquatic weed spread and impact. A ranked list of the top 24 species invading peri-urban waterways around nine cities representing all Australian states and territories has been developed. The list concentrated on non-graminoid herbs of running water. To gain a better understanding of the direct effects of environmental factors on aquatic weeds, the group conducted two controlled experiments on one of the highly-ranked weeds, Cabomba caroliniana. Firstly, they looked at the effect of nitrogen enrichment on cabomba growth. The nitrogen levels they used were higher than those generally found in Australian rivers, but were not unusual in dams and eutrophic (rich in mineral and organic nutrients) lakes. The cabomba showed an immediate response to these nitrogen-enriched environments by increasing its stem height.
Document Type: Research Article
Publication date: December 1, 2008
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