| dc.description.abstract |
<p>Across the globe, management and conservation agencies undertake numerous local
actions to mitigate losses to coral reef ecosystems and aid in their recovery. While
many of these strategies are designed to exploit natural ecological interactions between
corals and other reef-associated organisms, only a few interactions are the focus
of these approaches despite a suite of relationships that affect corals and likely
impact the outcomes of coral reef conservation actions. Additionally, in the wake
of major worldwide coral bleaching events in 2014-2016, several studies and news articles
have argued that local management actions have little effect on protecting coral reefs
from climate change events. In this dissertation, I evaluate how ecological interactions
between corals and other reef inhabitants affect the success of current management
strategies to better inform the use of local efforts that promote coral reef recovery.
To do this, I use a combination of scientific literature review, large-scale observational
surveys, and manipulative field experiments to apply ecological theory in this applied
context. Reviews of past studies reveal there are numerous interactions that facilitate
corals and could be used in the designs of current coral restoration and transplantation
efforts, including mutualisms, long-distance facilitation, density-dependence, legacy
and biodiversity effects, and trophic interactions (e.g., trophic cascades) (Chapter
1). Because coral predators (‘corallivores’) are considered major threats to reefs
worldwide and coral restoration efforts in the Caribbean, I examined the role of corallivores
in limiting coral restoration success alone and when combined with physical stress
(Chapter 2), the effects of their removals during major climate change events (Chapter
3), and factors controlling corallivore population densities within no-take marine
protected areas (Chapter 4). In these studies, I find that chronic, but partial, predation
by corallivorous snails increases coral stress that may ultimately hinder coral reef
recovery. For instance, partial predation by snails lead to full colony mortality
in a third of experimental corals, substantially reduced growth rates by up to 80%,
and facilitated algal colonization on small colonies of the endangered staghorn coral
(Acropora cervicornis) often used in restoration programs. Although overall tissue
loss due to predation was low, removal of corallivorous snails from coral colonies
during a warm temperature event significantly reduced the severity of coral bleaching
as well as tissue mortality after bleaching, suggesting that tissue loss may considerably
underestimate the negative effects of chronic predation and that removal of predation
stress increased resistance and recovery (i.e., resilience) to climate change. While
manual removals of corallivores is likely to be most feasible for managers at small
scales, I found corallivorous snail densities were nearly 50% lower inside no-take
marine protected areas within the Florida Keys National Marine Sanctuary, and that
snail densities were negatively correlated with two potential predators, black margate
(Anisotremus surinamensis) and Caribbean spiny lobster (Panulirus argus), which were
both significantly more abundant in protected areas. The research findings presented
in this dissertation demonstrate that local strategies can play an important role
in coral reef resilience and recovery, and that understanding the ecological interactions
between corals and reef-associated organisms is paramount to achieving success in
these efforts.</p>
|
|
