MEPS 561:203-215 (2016)  -  DOI: https://doi.org/10.3354/meps11940

ABSTRACT: Habitat edges commonly support discrete communities compared to adjoining habitats in response to unique boundary conditions. Coral reefs are often adjacent to other habitats, e.g. sand or seagrass meadows, but little is known about how reef-associated organisms respond to the presence of edges. Here, we examined fish communities and benthic assemblages at varying distance from a coral reef-sand edge. At 25 sites, 30 m transects were placed at 5 locations: 1 along the edge and at 5 m and 10 m away from the edge into reef and sand habitats. Counts were made of 51 fish species and benthic composition surveyed. The fish community along the edge was substantially different to communities only 5 m into the sand and reef habitats. Overall, 61% of the 51 fish species appeared to respond to the edge, with 43% significantly higher or lower in abundance along the edge compared to other locations. Twelve species showed positive edge responses, including the wrasse Thalassoma lunare, which was 30 times more abundant along the edge compared to 10 m into the reef. Ten species exhibited negative edge responses, including the damselfish Pomacentrus moluccensis, which was 7 times more abundant 10 m into the reef compared to the edge. Feeding ecology appears to influence edge-related distribution patterns, with carnivores and omnivores dominating the edges and planktivores more abundant into the reef. These findings suggest that habitat edges may play an important role in structuring coral reef fish communities. Future research should focus on experimental approaches to identify the underlying mechanisms driving edge responses.

KEY WORDS: Edge effects · Habitat fragmentation · Landscape ecology · Seascape ecology · Coral reef fish · Ontogenetic shifts