UC San Diego

The spatial distributions of benthic organisms within a coral reef ecosystem are structured by biological and physical mechanisms such as coral competition, reproduction, and reef structure. By examining the neighborhood patterns between scleractinian coral, soft coral, and algae, we can understand who typically lives near who and vice versa in a coral reef ecosystem. This brings insight into how organisms’ interactions, life histories, and the reef’s physical processes all impact the spatial distributions of colonies within their environment. Past coral spatial pattern studies relied on spatial point pattern (SPP) techniques such as nearest neighbor analysis. SPPs utilize the centroid of a colony, which poorly represents benthic organisms due to their variability in shape and size. In this study, we used an in-situ imaging technique to produce 14 plots of the reef based around Palmyra Atoll, covering 1400 m2 of benthic habitat in total. All colonies within these plots were identified to the lowest taxonomic classification possible. The utilization of GIS programming allowed us to take the shape of organisms into account and calculate the percent occupancy in 10 cm buffer regions around each colony. A bootstrapping approach was used to determine if the observed average neighborhood of each taxon and morphological type was more or less frequent compared to that of a null of equal occupancy. Few significant co-occurrence patterns were found due to the high abundance of a few taxa and competition between colonies. Of those significant neighbor patterns found, most positive patterns were intraspecific and biologically driven (via competition, reproduction, and partial mortality), and negative patterns were interspecific and were habitat driven (via physical processes and structure of the physical environment).