Seagrass cover is declining across the globe at an accelerating pace. Eutrophication is one of the most widespread anthropogenic pressures that are contributing to this phenomenon due to the strong shading effect from opportunistic species like epiphytic algae. Observation resources for meadow conditions are still limited and required improvement. Hence there is an urgent need to develop a standardised approach to facilitate monitoring programs. A consumer-grade quadcopter was used to conduct aerial surveys over three seasons (June, September, January) in the same intertidal site in northern Spain. Supervised classification results for three orthomosaic show good overall accuracy (>97% in five classes). With ground truthing data, low root mean squared error (RMSE) values between classified and observed coverage were yielded in June and September, but not in January. Coverage of seagrass and macroalgae show distinct seasonality in abundance, so does the spatial extent of overlapping, where competition may take place between species. Understanding such spatial and temporal patterns in intertidal seagrass meadows can provide insights to interpret the importance of habitat loss, and to the underlying processes that control the presence of substrates, essential components to be considered in planning and monitoring of conservation efforts.
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