Water velocity and groundwater upwelling influence benthic algal biomass in a sandy tropical river: implications for water-resource development

Benthic algae are a major source of carbon supporting aquatic food webs in northern Australia, but little is known about the factors that regulate algal production. We surveyed benthic algal biomass in mainstem habitats of an unregulated sandy tropical river (the Fitzroy River) during a base-flow pe...

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Bibliographic Details
Published in:Hydrobiologia 2020-03, Vol.847 (5), p.1207-1219
Main Authors: Burrows, Ryan M., Beesley, Leah, Douglas, Michael M., Pusey, Bradley J., Kennard, Mark J.
Format: Article
Language:English
Subjects:
Algae
Algal growth
Ammonium
Ammonium compounds
Benthos
Biofilms
Biomass
Biomedical and Life Sciences
Catchment area
Ecology
Food chains
Food webs
Freshwater & Marine Ecology
Groundwater
Groundwater levels
Life Sciences
Ocean circulation
Organic chemistry
Phytobenthos
Ponds
Prediction models
Primary Research Paper
Radon
Resource development
River catchments
Rivers
Storm seepage
Substrates
Surveys
Tropical climate
Upwelling
Velocity
Water resources development
Water table
Water velocity
Water, Underground
Zoology
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Summary:Benthic algae are a major source of carbon supporting aquatic food webs in northern Australia, but little is known about the factors that regulate algal production. We surveyed benthic algal biomass in mainstem habitats of an unregulated sandy tropical river (the Fitzroy River) during a base-flow period. We used predictive models to reveal the physical and chemical parameters controlling algal biomass in mainstem habitats. We found that water velocity was an important driver—algal biomass was lower at higher water velocities. Subsurface flow was also influential—algal biomass increased in locations where groundwater upwelling occurred, as evident by a positive relationship between algal biomass and elevated radon and ammonium concentrations. In this sand-bed river, it is likely that high water velocity destabilises the sandy substrate reducing the establishment of algal biofilms. However, where water velocity is low enough for algal establishment, groundwater upwelling likely promotes algal growth by delivering limiting resources and/or creating stable conditions that promote algal production. The importance of surface and subsurface-flow conditions to benthic algal biomass means that any modification to the Fitzroy River catchment that alters dry-season longitudinal flows (via river regulation) or groundwater levels (via groundwater extraction) may directly influence river algal production.
ISSN:0018-8158
1573-5117
DOI:10.1007/s10750-020-04176-3