Prediction of habitat complexity using a trait-based approach on coral reefs in Guam

Abstract

Scleractinian corals are primary contributors to the structural complexity of coral reef ecosystems. The structure derived from their carbonate skeletons underpins the biodiversity and myriad of ecosystem services provided by coral reefs. This study used a trait-based approach to provide new insights into the relationships between habitat complexity and coral morphology. Three-Dimensional (3D) photogrammetry techniques were used to survey 208 study plots on the island of Guam, from which structural complexity metrics were derived and physical traits of corals were quantified. Three traits at the individual colony level (e.g., morphology, size, and genera) and two site-level environmental characteristics (e.g., wave exposure and substratum-habitat type) were examined. Standard taxonomy-based metrics were also included at the reef-plot level (e.g., coral abundance, richness, and diversity). Different traits disproportionately contributed to 3D metrics of habitat complexity. Larger colonies with a columnar morphology have the highest contribution to surface complexity, slope, and vector ruggedness measure, whereas branching and encrusting columnar colonies have the highest contribution to planform and profile curvature. These results highlight the importance of considering colony morphology and size in addition to conventional taxonomic metrics for the understanding and monitoring reef structural complexity. The approach presented here provides a framework for studies in other locations to predict the trajectory of reefs under changing environmental conditions.

Structural Complexity of Coral Reefs in Guam, Mariana Islands

“…The positive correlation between coral cover and slope at most sites is in contrast with a recent study on Guam conducted by Ferreira et al [93], which reported the opposite relationship. These contrasting findings can, in part, be explained by the difference in spatial coverage between the two studies.…”

“…These contrasting findings can, in part, be explained by the difference in spatial coverage between the two studies. Most of the plots studied by Ferreira et al [93] were placed on reefs that are dominated by Porites rus (communities of low macrobenthic species richness) and situated along steep reef slopes. Incidentally, Finger Reef, one of the two sites at which coral cover was negatively correlated with the slope (as well as VRM and roughness magnitude), possesses a similar community as those found in the plots investigated by Ferreira et al [93].…”

“…Most of the plots studied by Ferreira et al [93] were placed on reefs that are dominated by Porites rus (communities of low macrobenthic species richness) and situated along steep reef slopes. Incidentally, Finger Reef, one of the two sites at which coral cover was negatively correlated with the slope (as well as VRM and roughness magnitude), possesses a similar community as those found in the plots investigated by Ferreira et al [93]. Interestingly, another reef that is shaped and dominated by P. rus colonies (Gab Gab) was positively correlated with all three significant terrain metrics, indicating that the negative relationship between the slope and coral cover is not consistent across sites with comparable biological communities.…”

“…The sites investigated in this study covered a broader range of benthic communities [69,70]. Furthermore, while Ferreira et al [93] examined 4 m 2 plots, we measured the complexity and coral cover over ~50 m 2 transects. This difference in survey scale has an effect on the average measures of structural complexity as mentioned above.…”

Community-Based Monitoring for Rapid Assessment of Nearshore Coral Reefs Amid Disturbances in Teahupo’o, Tahiti

“…SfM techniques enable coral reef monitoring to produce spatially accurate 3D reconstructions at much larger spatial scales than conventional techniques while using simple and affordable single-lens camera systems [7,15,16]. This approach produces 3D reconstructions which can be used to render spatially rectified orthomosaics and digital elevation models, which in turn can be processed in a multitude of ways using various geospatial software tools to analyze the composition and 3D structure of benthic communities [7,[15][16][17][18][19][20].…”