|Abstract or Summary
- Interface habitats are considered valuable natural systems, tightly linked to adjacent
habitats through the flow of matter and energy. However, there is limited research on
mechanisms of connectivity such as movement of organisms and particulate matter and
ways in which anthropogenic disturbance to interface habitats may affect immediate and
adjacent ecosystems. Mangrove forests, a common interface habitat in tropical coastal
zones, once lined much of the tropical and subtropical shores worldwide. However,
anthropogenic influences on these systems have led to a ~35% reduction in mangrove
area over the last fifty years. In light of the perceived importance of mangrove forests as
coastal habitat, the rapid decline of this habitat type, and the potential implications of mangrove habitat loss to adjacent ecosystems, it is important to build upon the current state of knowledge for mangrove forests. The chapters in this dissertation report on the following topics.
First I review the published literature to examine the available evidence for
connections between mangrove forests and coral reefs. I synthesize previous research
findings, highlight areas of future research priorities, and propose a conceptual model of
how areas of mangrove disturbance and resulting impacts on coral reefs are related.
Second, I assess the effects of mangrove clearing on the immediate habitat. I examine
how the physical environment changes following mangrove clearing by examining
abiotic factors. I also measure changes in algal biomass and diversity to determine what
effects physical changes have on the primary producer community. My results indicate
that mangrove clearing has dramatic effects on both the physical and biotic environment.
Based on measured changes in abiotic and biotic conditions, K. Frasier and I
investigate how larval and zooplankton communities differ between intact and cleared
mangrove areas. We find that diversity and community composition differ between
intact and cleared mangrove areas, highlighting an additional effect of mangrove
disturbance with potential implications for adjacent systems.
To address the unanswered question of whether and how abiotic and biotic
changes in cleared mangrove areas impact adjacent coral reefs, I repeat and expand upon the study I had conducted on abiotic and biotic changes following mangrove removal. The results in the immediate habitat indicate that the effects of mangrove disturbance are broad. Results from the reefs indicate that mangrove disturbance does have effects on adjacent coral reefs.
To determine the relative importance of mangrove-derived nutrients to adjacent
coral reef ecosystems and to examine how distance from mangroves to reefs and clearing
of mangroves affected energy transfer, I sample sessile reef invertebrates. I employ
carbon, nitrogen and sulfur stable isotope analysis as a tool to evaluate whether sessile invertebrates: corals, sponges, a bivalve and feather duster worm, utilize mangrovederived nutrients. Though the pattern varies by taxon, this research provides evidence that sessile reef invertebrates utilize mangrove-derived nutrients.
Finally, I examine the effect of two consecutive storm events, the 2005 Tropical
Storm (later Category 5 Hurricane) Wilma and the subsequent Tropical Storm Gamma,
on the coastal zone. The retention rate of field equipment following storm events
provides a picture of how coastal protection changes following anthropogenic mangrove
disturbance and the implications of continuing mangrove loss as storm frequency and intensity increase in parallel with climate change.
These studies provide new evidence on the effects of disturbance to mangroves on
coastal and reef systems. Many new research areas are raised by the results presented
here. However, these data provide a useful framework for considering conservation and
management strategies for mangrove forest – coral reef systems.