Spatial benthic community analysis of shallow coral reefs to support coastal management in Culebra Island, Puerto Rico

Abstract

Caribbean coral reefs provide essential ecosystem services to society, including fisheries, tourism and shoreline protection from coastal erosion. However, these reefs are also exhibiting major declining trends, leading to the evolution of novel ecosystems dominated by non-reef building taxa, with potentially altered ecological functions. In the search for effective management strategies, this study characterized coral reefs in front of a touristic beach which provides economic benefits to the surrounding coastal communities yet faces increasing anthropogenic pressures and conservation challenges. Haphazard photo-transects were used to address spatial variation patterns in the reef’s benthic community structure in eight locations. Statistically significant differences were found with increasing distance from the shoreline, reef rugosity, Diadema antillarum density, among reef locations, and as a function of recreational use. Nearshore reefs reflected higher percent macroalgal cover, likely due to increased exposure from both recreational activities and nearby unsustainable land-use practices. However, nearshore reefs still support a high abundance of the endangered reef-building coral Orbicella annularis, highlighting the need to conserve these natural shoreline protectors. There is an opportunity for local stakeholders and regulatory institutions to collaboratively implement sea-urchin propagation, restoration of endangered Acroporid coral populations, and zoning of recreational densities across reefs. Our results illustrate vulnerable reef hotspots where these management interventions are needed and recommend guidelines to address them.

Assessing Effects of Sediment Delivery to Coral Reefs: A Caribbean Watershed Perspective

“…Anecdotal evidence from the 1980s includes the documentation of noticeable sediment entering coral-bearing waters adjacent to recently developed watersheds (Beets et al, 1986;Rogers and Teytaud, 1988) and the tendency for coral-colonized substrates to be located away from stream outlets and large watersheds (Hubbard, 1986;Hubbard et al, 1987). Anecdotal evidence in Culebra was first documented in the early 1990s (Collazo et al, 1992;Hernández-Delgado, 1992) and formally evaluated through modeling (Ramos-Scharrón et al, 2012a) and, much later, monitoring (Otaño-Cruz et al, 2017Gómez-Andújar and Hernández-Delgado, 2020). Sediment-budget studies combining various forms of empirical data, field-based and remotely-sensed reconnaissance of erosion processes by trained personnel, and watershed modeling led to the identification of the unpaved road network as the main source of sediment on many of the islands' watersheds (Figures 2a-c; Anderson and MacDonald, 1998).…”