AUTHOR=Spyksma Arie J. P. , Miller Kelsey I. , Shears Nick T. TITLE=Diver-generated photomosaics as a tool for monitoring temperate rocky reef ecosystems JOURNAL=Frontiers in Marine Science VOLUME=9 YEAR=2022 URL=https://www.frontiersin.org/journals/marine-science/articles/10.3389/fmars.2022.953191 DOI=10.3389/fmars.2022.953191 ISSN=2296-7745 ABSTRACT=
Robust monitoring data provides important information on ecosystem responses to anthropogenic stressors; however, traditional monitoring methodologies, which rely heavily on time in the field, are resource intensive. Consequently, trade-offs between data metrics captured and overall spatial and temporal coverage are necessary to fit within realistic monitoring budgets and timeframes. Recent advances in remote sensing technology have reduced the severity of these trade-offs by providing cost-effective, high-quality data at greatly increased temporal and spatial scales. Structure-from-motion (SfM) photogrammetry, a form of remote sensing utilising numerous overlapping images, is well established in terrestrial applications and can be a key tool for monitoring changes in marine benthic ecosystems, which are particularly vulnerable to anthropogenic stressors. Diver-generated photomosaics, an output of SfM photogrammetry, are increasingly being used as a benthic monitoring tool in clear tropical waters, but their utility within temperate rocky reef ecosystems has received less attention. Here we compared benthic monitoring data collected from virtual quadrats placed on photomosaics with traditional diver-based field quadrats to understand the strengths and weaknesses of using photomosaics for monitoring temperate rocky reef ecosystems. In north-eastern New Zealand, we evaluated these methods at three sites where sea urchin barrens were prevalent. We found key metrics (sea urchin densities, macroalgae canopy cover and benthic community cover) were similar between the two methods, but data collected