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Onset and persistence of cyanobacterial blooms in a large impounded tropical river, Australia

journal contribution
posted on 06.12.2017, 00:00 by M Bormans, Larelle Fabbro, P Ford, G Hancock
The dynamic interplay between physical, chemical and biological factors in the development and persistence of cyanobacterial blooms in impounded rivers is an important topic. Over a 3-year study period, variable climatic conditions were recorded in the Fitzroy River, Queensland, Australia, which is a typical impounded lowland tropical river. Post-flood turbidity reduced the available light in the well-mixed water column to levels insufficient for cyanobacterial growth. Only when the water column stratified and the slowly sinking particles dropped from the surface layer did the ratio of surface mixed layer depth to euphotic depth approach 1, allowing cyanobacterial growth. By the time the light climate became favorable, most of the dissolved nutrients had been scavenged from the water column by settling particles or sequestered by fringing macrophytes and other biogeochemical processes. Cyanobacterial blooms dominated by Cylindospermopsis raciborskii persisted for several months until the next flood flushed the system. The cyanobacterial species dominating that environment were very small and had a high specific phosphorus uptake rates. Their nutrient requirement was met by transfer across the oxycline driven by regular high wind mixing events, entraining nutrient-rich bottom waters. Nutrient fluxes from the sediments into the anoxic bottom layer were sufficient to replace the bottom nutrients lost to the surface layer.

Funding

Category 1 - Australian Competitive Grants (this includes ARC, NHMRC)

History

Volume

55

Issue

1

Start Page

1

End Page

15

Number of Pages

15

ISSN

1323-1650

Location

Collingwood

Publisher

CSIRO Publishing

Language

en-aus

Peer Reviewed

Yes

Open Access

No

External Author Affiliations

CSIRO (Australia); Centre for Environmental Management;

Era Eligible

Yes

Journal

Marine and freshwater research.

Exports

CQUniversity

Exports