Stable isotopes and community surveys reveal differential use of artificial and natural reefs by South Florida fishes

Artificial reefs may enhance the biological production of reef-associated flora and fauna, but their trophic structure relative to that of natural reefs remains understudied. We assessed trophic relationships by 1) comparing reef fish communities and 2) comparing delta C-13 and delta N-15 in 43 fish species from both artificial reef sites and adjacent natural reef tracts in Broward County, Florida. We tested the effect of sampling location (artificial, first, and second reef), general feeding strategy (herbivore, omnivore, invertivore, and carnivore), phylogeny, and standard length on delta C-13 and d15N. The reef fish communities of the artificial and natural reef tracts were significantly different; the artificial sites also exhibited more variability. For all samples, delta C-13 and delta N-15 ranged from -19.5 to -13.1% and 6.7-13.3%, respectively. Significant effects were detected for both general feeding strategy and phylogeny. Significant differences were also seen in delta C-13 and delta N-15 profiles between artificial and natural reefs; however, these changes were primarily driven by differences in fish community structure, rather than by changes in the feeding strategy or trophic relationships of individual fish taxa. The trophic guild invertivore was the only group of fish to demonstrate significant isotopic differences between both reef tracts (inner and outer) and reef types (artificial and natural). The artificial reef may act more as a foraging corridor between the natural first and second reef tracts for omnivores and carnivores. If the function of artificial reefs is to provide additional foraging habitat for fishes, then perhaps more time is needed for the trophically important, infaunal invertebrate community to develop similarly to the natural reef environment.

Automated summary

This study found significant differences in fish communities between artificial reefs and natural reefs, with artificial reefs exhibiting greater variability. The trophic relationships were significantly influenced by general feeding strategy and phylogeny, and the differences in carbon and nitrogen isotopes between artificial and natural reefs were primarily driven by differences in fish community structure.