Analysis of these data will allow us to answer several questions that are crucial to the conservation
and restoration of the world's coral reef environment. By focusing on the data from the undisturbed
reefs of Palmyra and Kingman, we will provide the best-available baseline data regarding the functional
characteristics of healthy coral reef ecosystems, in particular focusing upon the distribution of groups
of organisms on the reef. By repeating our detailed ecosystem surveys across a gradient of anthropogenic
disturbance, we will reveal the ecosystem functions and services that are most vulnerable to human activities.
In particular, we will gain a unique view into the groups of organisms that are lost, the species interactions
that are altered, and the changes in the trophic dynamics as a reef changes from pristine to disturbed, across
an increasing gradient of human involvement. This study will be the first of its kind to control for biogeographic
differences among sites, to include such a broad taxonomic sampling, and to include truly pristine reef sites into
analysis of human impacts on coral reefs.
The four hypotheses posited by Jackson and colleagues (see above) will be addressed through the following analyses of our data:
Loss of megafauna
We will compare the size-frequency distributions of the fish communities across the
transect of disturbance. Our expectation is that on pristine reefs, the majority of the biomass will be
comprised of large-bodied individuals. In contrast, harvest by humans will reduce the average size of
fish within the community, resulting in a ?left-shifted? size-frequency distribution.
Change of food web structure
Pristine food webs are dominated by long-lived, large-bodied, predatory
species. As such, a classic food pyramid will appear inverted, with the higher trophic levels comprising
the majority of the biomass in the ecosystem. Because humans disproportionately deplete larger, predatory
species, we expect the distribution of biomass to shift to lower trophic levels, including small-bodied
vertebrates and invertebrate species, resulting in a more classically shaped biomass pyramid to be
present in more stressed ecosystems.
Decreased energetic efficiency
Ecological theory of marine ecosystems suggests that smaller,
faster-moving organisms are less efficient at using energy (and hence they are less productive) than
are larger organisms. Additionally, the high turnover of microbial species leads to higher rates of
energetic loss from the ecosystem. Through analyses of the size structure of the algal, invertebrate,
and fish community, and through estimations of microbial density, we will test for systematic changes
across the transect of human disturbance.
Loss of habitat complexity
Hermatypic corals are the dominant producers of habitat structure and
complexity on tropical reefs. As such, factors that decrease the abundance and the productivity of corals
also lead to the reduction of structural accretion. We will test for patterns of change in coral abundance
and of coral health across the Line Islands to test for effects of human disturbance on the rate of habitat
generation, and therefore, the maintenance of habitat complexity.