SCIENTIFIC METHODS

Combining a team of some of the world's foremost coral reef biologists, we are engaged in a five-week expedition to the Line Islands in August-September 2005 to describe and catalogue the reef ecosystems on each of the five islands. We will quantify all major groups of organisms on the reefs at the lowest taxonomic level possible. Our goal is to provide an accurate estimate of the biodiversity, abundance, biomass, and structure of the coral reef community of each island. We anticipate completing a thorough sampling of 4-6 sites around each island, with the field protocols determined by the taxon in focus. The research team thus will be divided into the following three major groups based on taxonomic focus:

Fish community

The fish community of the Line Islands' coral reefs includes species ranging from small, cryptic species (weighing on the order of 1g) to large, apex predators (weighing on the order of 100kg). Accurate sampling of the entire community therefore will involve multiple protocols. Our four-person fish team will include individuals highly experienced in reef fish sampling techniques and the local fish diversity. At each site, two teams of two observers will count the site-attached fish along four 50m transects, inspecting all crevices in the reef substrate for smaller cryptic species. More mobile fish species will be sampled through repeated scan samples along each section of the transect, thereby controlling for over-counting due to rapid fish movement. Finally, the largest fish species, including reef sharks and larger snappers, tend to be attracted to the disturbance caused by divers. Therefore, we will use remote videography to estimate the density of these species. Three video cameras will be left in unvisited parts of the reef each day and set to record 2s every 30s throughout the day, recording fish community activity in the absence of divers. Each 2s section of tape will serve as a scan sample of the fish community, and averages throughout the day will offer an estimation of the true density of larger fish in each section of the reef (Sandin and Pacala in press). By combining fine-scale sampling of smaller species with undisturbed views of the larger fish visitation rates and densities, we will generate an accurate view of the diversity, abundance, and size structure of the fish community. By referring to published length-biomass relationships, we will be able to estimate the mass of each fish sampled, thus enabling more detailed views into the fish community and trophodynamics. Additionally, we will refer to the literature to determine the likely dietary range and trophic level of each species, in order to lump fish into functional guilds, thus providing a snapshot of the trophic distribution of the fish community on the reefs of each island.

Benthic habitat

The benthic habitat of a coral reef is shaped by the coral community that accretes the limestone structure characterizing the habitat. In addition to the reef-building corals on the shallow sea bottom, there are hundreds of other species of plants and animals. The benthic habitat team will quantify the diversity, coverage, and abundance of all plant and animal species inhabiting the bottom along the same transects sampled by the fish team. The four-member team will be composed of two experts on coral taxonomy for the region (Maragos and Obura), one tropical algal specialist (Smith), and one expert on non-coral invertebrate taxonomy (Paulay). The coral diversity of the region, including both hard and soft coral species, has been described through previous work of Maragos and colleagues. This survey will add information on the size-frequency distributions of each species and their distribution across the mid-depth (10-15m) regions of the Line Islands. Similarly, the efforts of the National Oceanic and Atmospheric Administration (NOAA) have revealed much of the other invertebrate and algal diversity of Palmyra and Kingman. This sampling will extend existing invertebrate and algal diversity sampling to the lower Line Islands and will quantify the abundance and biomass of each species. Such sampling will be particularly important for the algal community, as recent commercial efforts in the Republic of Kiribati have begun introductions of non-native algal species for aquaculture. Our survey will be the most comprehensive in the region describing the ecological impacts of this algal aquaculture to regions outside of the actively harvested areas.

Microbial community

A major goal of the expedition is to catalog the microbial diversity and dynamics of the untouched reefs and to compare them with human impacted reefs. The microbial community (i.e., the large diversity of bacteria living in the reef environment; Knowlton and Rohwer 2003, Azam and Worden 2004) will be described with a mixture of in situ procedures and collections with subsequent laboratory analyses. These data are vital because one of the major uses of reef decline is coral disease associated with humans. As such, it is essential to know if the microbes causing coral disease are absent from untouched reefs and are instead being introduced by human. Alternatively, sease-causing microbes might already be present on coral reefs and humans are simply disrupting the normal symbioses between corals and microbes. To test among these alternative hypotheses, data of the microbial community will be collected from the water column and from the reef substrate in a five-step procedure. (1) For water column studies, we will collect 10-liter water samples from 10 sites per island. (2) Measuring reef-associated microbes consists of taking small 1cm x 1cm samples of corals for DNA extractions and microscopy work. Five samples of each of 20 coral species per site (100 samples total) on each island are needed to assure sufficient statistical power. Note that previous work indicates that these samples cause little to no long-term damage to the coral colonies that are sampled. (3) To separate the microbial activity of corals from that of other benthic substrata, we will gather a similar number of algal and sediment samples, which are potential reservoirs of coral pathogens. (4) To study microbial growth rates on corals, we will remove mucus from 10 samples of each of 20 coral species. This procedure involves suctioning small volumes of coral mucus, resulting in no short term or long term effect on the corals. (5) Finally, if diseased corals are found, opportunistic sampling of fragments of these corals are needed to strengthen empirical relationships between pathogens and microbes on 'pristine' coral reefs. Because of the low incidence of coral disease on Palmyra and Kingman, <20 such samples are predicted to be needed, though we cannot predict the exact number of samples. Subsequent laboratory analyses of these samples will provide descriptions of the microbial community found in various sections and substrata across the reef. These descriptions from Palmyra and Kingman will offer the first view of the undisturbed composition of the microbial community across coral reefs. Comparison of these data with those from the other Line Islands will reveal the direct effects of human impacts on coral reefs, in particular revealing whether humans (and their activities) tend to introduce new microbial strains or simply to change competitive interactions within the existing microbial community.