Abstract
With the unprecedented degradation and loss of coral reefs at multiple scales, the underlying changes in abiotic and biotic features relevant to the three-dimensional architecture of coral reefs are critical to conservation and restoration. This study characterized the spatiotemporal variation of habitat metrics at eight fore-reef sites representing three management zones in the Florida Keys, USA using visual habitat surveys (2017–2018) acquired before and after Hurricane Irma. Post-hurricane, five of those sites were surveyed using structure-from-motion photogrammetry to further investigate coral morphology on structural complexity. Multivariate results for visual surveys identified moderate separation among sites, with fished sites characterized by complex physical features such as depth and vertical hard relief while protected sites generally harbored high abundances of live coral cover. Three-dimensional models of mapped sites showed within site variation as another driver in site separation. Additionally, fine-scale orthoimage analyses identified significant differences in dominant coral morphologies at each mapped site. This study suggests protected reef sites generally harbor higher live coral cover despite some fished sites being structurally similar in seabed topography. Our work provides fine-scale spatial data on several managed sites within a marine sanctuary and highlights the contribution of diverse coral assemblages to the coral reef framework.
Highlights
Coral reefs are highly productive, biologically rich, and structurally complex ecosystems supporting 25% of marine life in the world’s oceans [1]
Sites characterized by physical seabed features with low presence in coral cover were grouped together along the first canonical axis such as sample sites SDK, N1M, and Nine Foot Stake (NFS) (Figure 4a), whereas sites with high percentages in biotic cover such as Western Sambo ER (WSB), Looe Key SPA (LKP), and Looe Key SUA (LKU) generally resulted in more distinct separations among sites (Figure 4b)
Spur-andgroove sites NFS and LKP were similar in depth (>7 m); there was a significant difference in percent rubble (p = 0.02) as LKP had the lowest percentage of rubble cover at 16% (Figure 5a)
Summary
Coral reefs are highly productive, biologically rich, and structurally complex ecosystems supporting 25% of marine life in the world’s oceans [1]. They support a broad range of ecosystem services [2,3,4] with recreational and cultural benefits [5,6,7], as well as resources that support the economically important pharmaceutical, fisheries, aquarium trade, and construction industries [8,9,10]. Coral reefs are increasingly threatened by a broad array of chronic and acute stressors. Not as detrimental as large-sale anthropogenic stressors, the residual effects of long-term recreational SCUBA diving on coral reefs can decrease structural complexity from broken and abraded benthos [24]
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