Assessing Spatial Variation in Algal Productivity in a Tropical River Floodplain Using Satellite Remote Sensing

Bianca Molinari,Tim J Malthus,Ben Stewart-Koster,Stuart E Bunn

doi:10.3390/rs13091710

Bianca Molinari, Tim J Malthus + Show 2 more

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https://doi.org/10.3390/rs13091710

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Journal: Remote sensing	Publication Date: Apr 28, 2021
Citations: 10	License type: CC BY 4.0

Affiliation: Griffith University, CSIRO Oceans and Atmosphere

Abstract

Studies of tropical floodplains have shown that algae are the primary source material for higher consumers in freshwater aquatic habitats. Thus, methods that can predict the spatial variation of algal productivity provide an important input to better inform management and conservation of floodplains. In this study, a prediction of the spatial variability in algal productivity was made for the Mitchell River floodplain in northern Australia. The spatial variation of aquatic habitat types and turbidity were estimated using satellite remote sensing and then combined with statistical modelling to map the spatial variation in algal primary productivity. Open water and submerged plants habitats, covering 79% of the freshwater flooded floodplain extent, had higher rates of algal production compared to the 21% cover of emergent and floating aquatic plant habitats. Across the floodplain, the predicted average algal productivity was 150.9 ± 95.47 SD mg C m−2 d−1 and the total daily algal production was estimated to be 85.02 ± 0.07 SD ton C. This study provides a spatially explicit representation of habitat types, turbidity, and algal productivity on a tropical floodplain and presents an approach to map ‘hotspots’ of algal production and provide key insights into the functioning of complex floodplain–river ecosystems. As this approach uses satellite remotely sensed data, it can be applied in different floodplains worldwide to identify areas of high ecological value that may be sensitive to development and be used by decision makers and river managers to protect these important ecological assets.

Highlights

Aquatic food webs on river floodplains depend on primary producers such as phytoplankton and epiphyton as the major basal food sources that support higher order consumers [1,2,3,4]
In 2018, the wet season was delayed and most of the rainfall and discharge at Dunbar gauging station happened between February and April (Figure A1).The Mitchell River floodplain supports a large number of off-stream wetlands [28], which in turn support aquatic macrophytes and algal production [9,25] thereby playing an important role in sustaining aquatic biodiversity
We have applied this methodology to map the spatial variation in algal productivity across the Mitchell River floodplain and identified that most of the production occurs on the floodplain wetlands

Summary

Introduction

Aquatic food webs on river floodplains depend on primary producers such as phytoplankton and epiphyton as the major basal food sources that support higher order consumers [1,2,3,4] Because algae are such an important food resource for higher trophic levels in river systems [5], numerous studies across different ecosystems have developed methods to measure rates of production [6,7,8,9,10,11]. Direct measurement of rates of algal production across inundated floodplains is important as it reflects the amount of carbon being produced per unit of time, which in turn supports the secondary production of aquatic consumers [14] Such field-based measurements provide crucial information at local scales that can be integrated into statistical models and combined with remote sensing data to predict algal productivity in new locations [9].

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