Habitat degradation can affect trophic ecology by differentially affecting specialist and generalist species, and the number and type of interspecific relationships. However, the effects of habitat degradation on the trophic ecology of coral reefs have received limited attention. We compared the trophic structure and food chain length between two shallow Caribbean coral reefs similar in size and close to each other: one dominated by live coral and the other by macroalgae (i.e., degraded). We subjected samples of basal carbon sources (particulate organic matter and algae) and the same 48 species of consumers (invertebrates and fishes) from both reefs to stable isotope analyses, and determined the trophic position of consumers and relative importance of various carbon sources for herbivores, omnivores, and carnivores. We found that both reefs had similar food chain length and trophic structure, but different trophic pathways. On the coral-dominated reef, turf algae and epiphytes were the most important carbon source for all consumer categories, whereas on the degraded reef, particulate organic matter was a major carbon source for carnivores. Our results suggest that the trophic structure of the communities associated with these reefs is robust enough to adjust to conditions of degradation.

Fixed-site video cameras can be a powerful tool for studying marine animals in the sea without disturbing their behavior. Artificial light is required to use these cameras at night or in dark places such as inside animal dens. Red light is theoretically the best choice because the eyes of many marine animals are relatively insensitive to light above 600 nm wavelength, red light penetrates water much further than infrared, and many video cameras are highly sensitive to red light. This study found that video and red light can be used at night in the sea to study the behavior of spiny lobster, Panulirus argus, without significant effects. The shelter occupancy rate of tethered lobsters was similar in continuous red light as in the dark and red light did not attract or repel free-living lobsters. Red light did attract a small additional number of fish which were already nearby the lobster shelters and did not appear to disturb the lobsters. Loss of P. argus from octopus predation was similar in red light as in the dark. Six species of predators (two triggerfishes, an octopus, two snappers, and a moray eel) were recorded on videotape killing lobsters at shelters in the sea. Predation usually occurred outside the shelters. Other species scavenged on the lobster remains after they were killed. A variety of animals frequently cohabited with lobsters inside shelters for a few minutes to several days. The interactions of these animals with the lobsters rarely involved any strong aggression or defensive behavior.