This research has included multi-site assessments within countries (e.g. Courtney and Andersson 2019) methodologies have been developed to quantify reef carbonate budget states (G, in kg CaCO 3 m −2 yr −1), and resultant datasets are providing us with a rapidly improving understanding of contemporary carbonate production regimes. In this context, reef carbonate budgets have been identified as an important indicator variable for the “health” and resilience of coral reefs and their responses to climate change (Mace et al. In particular, there is a growing body of work assessing those geo-ecological processes that sustain reef frameworks through the addition and cycling of skeletal calcium carbonate (Perry and Alvarez-Filip 2019). Recent increases in the magnitude, frequency and spatial footprint of ecological disturbances affecting coral reefs have led to a growing interest in the implications of these disturbances for reef ecosystem functioning (Hughes et al. Whilst some degree of error must necessarily be accepted with such conversion techniques, the approach presented here offers exciting potential to calculate coral carbonate production: (1) from historical imagery to constrain past coral carbonate production rates (2) from high quality aerial imagery for spatial up-scaling exercises and (3) for use in rapid photograph or video-based assessments along reef systems where detailed surveys are not possible.
We then demonstrate potential applications of the conversion metrics in two examples, the first using time-series (2006 to 2018) photo-quadrat imagery from Moorea, and the second using high-resolution drone imagery across different reef flat habitats from the Maldives. The data show a high level of consistency with an error of ~ 10%. We tested this approach by comparing in-situ carbonate production data collected using the ReefBudget methodology against estimates derived from converted colony length data from video imagery. These conversion values allow planar colony dimensions to be converted to estimates of 3D colony contour length, which can be employed within existing census budget methodologies like ReefBudget to estimate coral carbonate production (G, in kg CaCO 3 m −2 yr −1). coral class rugosity values, hereafter termed R coral). To address this disconnect, we collected data on the relationship between linear planar and 3D contour lengths of 62 common Indo-Pacific hard coral genera-morphotypes to establish appropriate conversion metrics (i.e.
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In contrast, data that can be extracted from archive photograph or video imagery and high-resolution aerial imagery are generally planar. Resolving these issues is challenging because carbonate production estimates require three-dimensional survey data, which are typically collected in-situ over small spatial scales. At the same time, there is growing interest in quantifying carbonate production on larger reef-scales. Recent interest in assessing coral reef functions has raised questions about how carbonate production rates have altered over the past few decades of ecological change.
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