| In Chapter 1, I present a comprehensive analysis of the relative impacts of a broad suite of anthropogenic stressors on vulnerable marine species. Most marine species face multiple threats: chief among them, overexploitation, habitat degradation, pollution and invasive species. Bycatch, in particular, is a major risk to nearly half the species examined. Networks of marine protected areas (MPAs) are one conservation tool which can address, or mitigate for, many of these key threats. Comprehensive information about the distribution of species and assemblages is required for systematic design of MPA networks, but is often unavailable. Remotely sensed benthic habitats can be used as proxies for the distribution of species or assemblages in MPA site selection. A key assumption of this approach is that habitat classes are a suitable biodiversity surrogate. From detailed surveys of fishes and corals collected in 19 habitat types over >700 km, I test this assumption in Chapter 2, demonstrating that benthic habitats can be suitable surrogates for assemblages of both common and rare fish and coral species in the Bahamas archipelago. In Chapter 3, I ask whether patterns of community similarity in forereef coral and fish communities decline with geographic distance and over what scales. This analysis demonstrates that the scale of regional planning should be that of individual islands or island systems within the archipelago, i.e. ∼125 km or less. At this scale, habitats can be expected to represent reasonably homogeneous assemblages. In addition, reserves or reserve networks should be replicated in multiple regions in order to represent important, island scale variation in habitats and communities. Finally, in Chapter 4, I investigate the role of environmental variation in shaping patterns in coral community structure at the seascape scale, using redundancy analysis (RDA) to assess the importance of a suite of physical and biological factors. Location has an overriding effect on coral communities at this scale, suggesting that historical effects and ongoing disturbance are important. Physical factors such as depth, vertical relief, and exposure help structure these communities. Finally physical factors act in combination with grazing by herbivorous fishes to mediate coral-coral and coral-algal competition. |
