Monitoring aquatic plants: An evaluation of hydroacoustic, on-site digitising and airborne remote sensing techniques | Knowledge and Management of Aquatic Ecosystems

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Table 2

Summary table identifying consideration when employing each macrophyte monitoring methodology.

	Method
Consideration	Trimble mapping − On site digitizing	Hydroacoustic 200 khz sonar	Hydroacoustic 800 khz downscan	Hydroacoustic 800 kHz side scan	Duel-frequency identification sonar (DIDSON)	Aireborn remote sensing (satelite imagery)	Optical videography
Turbidity	Turbidity dependent	Turbidity independent	Turbidity independent	Turbidity independent	Turbidity independent	Turbidity dependent	Turbidity dependent
Identifies species	Can identify species	Cannot distinguish between species	Cannot distinguish between species	Cannot distinguish between species	Cannot distinguish between species	Cannot distinguish between species; grond truthing data required	Can identify species
Macrophytes mapped	Submerged, emergent, floating	Submerged	Submerged	Submerged	Submerged	Submerged, emergent, floating	Submerged
Provides spatial distribution maps	Yes	Provides georeferenced transect data	Provides georeferenced transect data	Yes	Provides georeferenced transect data	Yes	Provides georeferenced transect data
Consistency of data collection between field operators	High variation	Minimal variation	Minimal variation	Minimal variation	Minimal variation	N/A	Minimal variation
Consistency of data processing between interpretors	N/A	Minimal variation	Minimal variation	High variation	Minimal variation	Minimal variation	Minimal variation
Data collection time	Highly dependent upon macrophyte abundance	Independent of macrophyte abundance	Independent of macrophyte abundance	Independent of macrophyte abundance	Independent of macrophyte abundance	No field data collection required	Independent of macrophyte abundance
Post-data collection processing	Minimal	Moderate	Moderate	High	High	Moderate	High
Equipment expenses	High	Moderate	Moderate	Modeate	Very high	Nill	Low
Identifies depth of macrophyte growth	No	Yes	Yes	No	No	No	No
Identifies percentage of water column occupied by macrophytes	No	Yes	Yes	No	No	No	No
Other	Visibility of macrophytes during on site digitising is highly dependent upon turbidity and surface conditions at the time of sampling	Sonar may not penetrate through dense macrophytes resulting in lost Can be difficult to run boat transects through dense macrophyte due to fouling of boat propellor False macrophyte detections can result from submerged tree branches and other debris	Sonar may not penetrate through dense macrophytes resulting in lost Can be difficult to run boat transects through dense macrophyte due to fouling of boat propellor	Identiyfing macrophyte beds from sidescan imagery can be difficult without ground truting data Sidescan sonar in some instances may not penetrate through dense surface-to-substrate macrophyte beds, therefore only indicating near edge macrophytes boundaries, not full spatial extents	Can be difficult to run boat transects through dense macrophyte due to fouling of boat propellor	Temporal availability of cloud free satelite imagery may be restrictive	Can be difficult to run boat transects through dense macrophyte due to fouling of boat propellor

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