Abstract
Oysters support an economically important fishery in many locations in the United States and provide benefits to the surrounding environment by filtering water, providing habitat for fish, and stabilizing shorelines. Changes in oyster reef health reflect variations in factors such as recreational and commercial harvests, predation, disease, storms, and broader anthropogenic influences, such as climate change. Consistent measurements of reef area and morphology can help effectively monitor oyster habitat across locations. However, traditional approaches to acquiring these data are time-consuming and can be costly. Unoccupied aircraft systems (UAS) present a rapid and reliable method for assessing oyster habitat that may overcome these limitations, although little information on the accuracy of platforms and processing techniques is available. In the present study, oyster reefs ranging in size from 30 m2 to 300 m2 were surveyed using both fixed-wing and multirotor UAS and compared with ground-based surveys of each reef conducted with a real-time kinematic global positioning system (RTK-GPS). Survey images from UAS were processed using structure from motion (SfM) stereo photogrammetry techniques, with and without the use of ground control point (GCP) correction, to create reef-scale measures of area and morphology for comparison to ground-based measures. UAS-based estimates of both reef area and morphology were consistently lower than ground-based estimates, and the results of matched pairs analyses revealed that differences in reef area did not vary significantly by aircraft or the use of GCPs. However, the use of GCPs increased the accuracy of UAS-based reef morphology measurements, particularly in areas with the presence of water and/or homogeneous spectral characteristics. Our results indicate that both fixed-wing and multirotor UAS can be used to accurately monitor intertidal oyster reefs over time and that proper ground control techniques will improve measurements of reef morphology. These non-destructive methods help modernize oyster habitat monitoring by providing useful and accurate knowledge about the structure and health of oyster reefs ecosystems.
Highlights
Eastern oyster (Crassostrea virginica) reefs are important components of coastal and estuarine systems along the Atlantic coast of the United States
Accurate oyster reef dimensions are important for estimations of the total reef area, health and persistence, population abundance, and overall quantity of ecosystem services provided by the oyster reef system to the surrounding environment [2,8,17,18]
Visual examination of the resulting orthomosaics indicated that the global positioning system (GPS) points lined up well on both ground control point (GCP) corrected and uncorrected imagery from Town Marsh and on the corrected imagery at Middle Marsh, but the uncorrected imagery from Middle Marsh resulted in misalignment from the true position (Figure 3)
Summary
Eastern oyster (Crassostrea virginica) reefs are important components of coastal and estuarine systems along the Atlantic coast of the United States. Accurate oyster reef dimensions are important for estimations of the total reef area, health and persistence, population abundance, and overall quantity of ecosystem services provided by the oyster reef system to the surrounding environment [2,8,17,18]. Monitoring metrics, such as oyster reef area and morphology, have been noted as key indicators for oyster reef health and growth [19,20,21,22,23,24]. Reef morphology refers to the structural complexities of an intertidal oyster reef, including elevation and rugosity
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
