UC San Diego
Human impacts on Caribbean coral reef ecosystems
- Author(s): Hardt, Marah Justine
- et al.
Fishing is one of the oldest anthropogenic disturbances in the ocean, differing from other impacts in its direct removal of biomass from the ecosystem. Despite the centuries of fishing activities, there is much we still do not understand regarding the effects of fish removal on the benthic community. I use an interdisciplinary approach to investigate the affect of human disturbance, primarily the alteration of fish communities, on major functional groups of coral reefs, over extended temporal and spatial scales. In Chapter 2, historical analyses reveal that relatively small human populations and simple fishing technologies can negatively impact reef fish communities. Significant declines are evident in Pre Columbian times and by the mid 19th C. Declines were exacerbated by simple innovations of gear, such as chicken wire, and government subsidies, which expanded degradation to offshore and deeper reefs. In Chapter 3, I identify six major ecological guilds of common Caribbean coral species and show that changes in the abundance of these guilds from the Pleistocene to the present day can be understood in terms of recent human disturbance events. Formerly advantageous life history strategies no longer apply. Instead, guilds with the ability to withstand physical disturbance from storms, sedimentation, and pollution remain present on reefs, while strategies for high recruitment and rapid space colonization increase the relative abundance of another guild. Overall, no guild successfully competes with macroalgae for space and all corals have declined. In Chapter 4, I show that benthic and fish communities across the northwestern Caribbean are largely homogenized as a result of human disturbance. The exception is fish communities in large, no-take marine reserves, which resemble relatively healthy communities of low-impacted reefs in the Pacific. A negative correlation between fish and algal biomass indicate that reserves may facilitate coral recovery, although corals have not yet increased. Chapter 5 describes a novel method for calculating the wet and dry animal tissue mass per unit area of corals. Chapter 6 integrates these findings and demonstrates the importance of increased temporal, spatial, and ecosystem scale in effective research and management of degraded Caribbean coral reefs