Davidson Seamount: Ecological Characterization & Habitat Modeling of the Fauna
- Craig McClain
Monterey Bay Aquarium Research Institute
- Jim Barry
Monterey Bay Aquarium Research Institute
- Save the Earth
- NOAA’S Office of Ocean Exploration
- Monterey Bay Aquarium Research Institute
- Monterey Bay National Marine Sanctuary SIMoN
- David and Lucile Packard Foundation
End Date: February 01, 2009
Davidson Seamount is one of the best biologically described seamounts globally. Six expeditions to Davidson Seamount have yielded over 60,000 observations of species at this seamount. Combined with expansive sampling program over the last 20 years on the adjacent continental margin, we are able to confidently construct a faunal list for Davidson Seamount and examine rates of endemicity for an entire assemblage. We add biogeographic range data for the species from both our own databases and through a thorough literature review. We further report preliminary comparison of community structure between seamount and non-seamount communities. This dataset minimizes sampling biases that have hindered previous examinations of seamount endemicity.
Although we find little support for endemicity among megafauna at Davidson, we do find preliminary evidence that communities are structured differently. Overall we find an assemblage of species that also occurs on adjacent continental margins. A large percentage of these species are also cosmopolitan with ranges extending over much of the Pacific Ocean Basin. Overall, the distribution of range sizes also indicates a fauna broadly distributed as been posited for both deep-sea organisms, and marine faunas in general, but rarely tested in the deep sea. Despite the similarity in composition between the seamount and non-seamount communities, we found preliminary evidence that seamount communities may be structured differently and potentially serve as source of larvae for suboptimal, non-seamount habitats.
The developed database has also allowed us to explore how Davidson Seamount communities vary across the flanks and summit. Both the types and densities of species appear to change as depth increases from the summit to the base of the seamount. Communities at the summits, flanks, and base of Davidson are statistically different. This faunal turnover occurring over a relatively small area suggests Davidson, because of changes in biotic variables that covary with depth, may support a concentration of species.
Summary to DateEfforts are currently underway to incorporate Davidson Seamount into the Monterey Bay National Marine Sanctuary (MBNMS). One objective in realizing this goal is to “increase understanding of the seamount through characterization and ecological process studies.” Under this objective, we propose a research line that addresses specific strategies as defined in the MBNMS Draft Management Plan.
Biological Characterization of Davidson Seamount: Seamounts have long been characterized as unique and rugged ocean habitats hosting highly diverse and endemic faunas with high biomass. This notion has become the ‘lore’ of seamount biology, even though it has yet to be examined critically. Several alternative hypotheses have been posited for the role of seamounts in both local and global deep-sea biodiversity. The most prominent is the proposition above that seamounts possess highly endemic faunas reflecting hydrographic and topographic features leading to genetic isolation⎯similar to terrestrial islands. Those who challenge this idea propose instead that seamounts serve are oases, centers of high biomass that in turn increase species diversity. These ideas contrast sharply – in one, seamounts serve as a sink for larval recruits originating in adjacent habitats, while in the other, seamounts are a source of larvae for surrounding areas. Alternatively, seamounts may acquire heightened biodiversity through the presence of coral and sponge fields, which promote local species coexistence by offering increased habitat complexity. High biodiversity of seamounts may also reflect rapid habitat turnover associated with substrate type, currents, temperature, oxygen concentration, and other abiotic/biotic parameters encountered across the flanks and summits of the seamount. Currently, the majority of these hypotheses are not adequately or critically evaluated with field data.
Remotely Operated Vehicle (ROV) dives at Davidson Seamount were conducted in 2000, 2006, and 2007 through a collaboration of MBARI, MBNMS, and NOAA. In addition, during some of these dives, quantitative transects were conducted yielding potential diversity per unit area and faunal densities. For example, in June 2007 100m transects were conducted on the north (1754m) summit of Davidson. The beginning of this transects was tagged with a permanent marker (numbered float anchored to the seafloor). Two additional markers were also placed marking Gorgonian corals and may serve as a start point for planned future transects.
Our goal is quantify the faunal densities found along previous transects to serve as a baseline, and making them publicly available through the SIMoN website. In addition, previous transects at untagged areas may also be relocated and serve as a baseline assessment. The goal of this project is to build on previous efforts to compile data from transects into a single cohesive database. In addition, we plan to add vital ecological information about the species. This provides a unique opportunity to evaluate the above hypotheses and further elucidate the importance of Davidson Seamount to the surrounding deep-sea ecosystem. The total dataset will be able to specifically address the links between the near-shore and deep-water areas currently within the sanctuary (DS-2.4) in the context that Davidson serves as a source or sink of larval recruits in the region.
- Habitat association
- Dissolved oxygen
Study MethodsWe created a faunal inventory for all observed megafauna animals, those organisms readily identifiable in video or caught in trawls. Between 2000-2007, five oceanographic expeditions including remotely operated vehicle (ROV) dives visited Davidson Seamount. All expeditions were conducted with the research vessel Western Flyer and the ROV Tiburon by the Monterey Bay Aquarium Research Institute (MBARI), twice in collaboration with the Monterey Bay National Marine Sanctuary. In total, 28 ROV dives yielded over 60,000 faunal observations on over 200 hours of high-resolution video. Specialists using high-resolution video frame grabs and specimens collected during ROV dives identified megafauna to the lowest possible taxonomic level. All ROV dive video has been reviewed in detail using MBARI’s Video Annotation and Reference System (VARS). This system represents a knowledge database of all biological, geological, technological objects observed on any ROV dive made by MBARI over the last 26 years. The database can be queried with different search terms (e.g., various taxonomic levels) and constrained by a variety of parameters (e.g., location and depth) and thus provides information about the biogeographic ranges within the extent of MBARI’s exploration. Additional information about biogeographic ranges was culled from the literature, Seamounts Online, and FishBase.
We report endemicity (i.e., a species restricted to Davidson Seamount) based on information gathered from the above sources. Species were assigned an endemicity certainty code (ECC) based on the evidence of their occurrence off Davidson. Species assigned an ECC of 1 were considered to have enough supporting data to indicate they are not endemic (i.e., ranges are confirmed by taxonomic specialists). Species of an ECC of 2 have enough support to suggest reasonably that they are not endemic (i.e., ranges are based on morphologically similar species identified in video). Species of an ECC of 0 are known only from Davidson Seamount, and are potential endemics. Estimates of shared species between central California seamounts was taken from Lundsten [in press].
We ranked species abundance overall and among habitat types according to their rarity, determined from the number of observations of a species on Davidson Seamount and in nearby Monterey Canyon. A comparison of rarity among habitats was made by plotting the ranks of species in the two localities. Geographic range was calculated as the maximum linear distance (in km) from Davidson Seamount for the most conservative taxonomic level and identification. Coordinates were transformed into linear distance by assuming the earth is a perfect sphere with a radius of 6,378 km. For species occurring on Davidson Seamount in the Pacific Ocean and also in the Atlantic Ocean, we assume the distance between sampling sites is s straight line (i.e., across North America). We do this as information between sampling localities may be lacking that would indicate a specific route of range expansion. Note that this biases species toward smaller range sizes. Species accumulation curves were calculated in EstimateS with all other analyses conducted in JMP Statistical Software v. 5.
Figures and Images
Figure 1. Bubble gum coral (Paragorgia arborea) on the Davidson Seamount at a depth of 1,313 meters. These corals see no sunlight, are long-lived, and can grow 2 m or taller.
Figure 2. Crinoids (Florometra serratissima), deep-sea corals, sea stars, bryozoans, and anemone on the Davidson Seamount at a depth of 2668 meters.
Figure 3. A yellow sponge (Staurocalyptus sp. nov.) new to science, an orange basket star (Gorgonocephalus sp.) crawling on it, several white ruffle sponges (Farrea occa), and a new species of white-branched sponge (Asbestopluma sp. nov.) on the Davidson Seamount at a depth of 1316 meters.
- Lundsten et al. (2012)Morphological, molecular, and in situ behavioral observations of the rare deep-sea anglerfish Chaunacops coloratus (Garman, 1899), order Lophiiformes, in the eastern North Pacific
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- McClain et al. (2009)Endemicity, Biogeograhy, Composition, and Community Structure On a Northeast. Pacific Seamount. PLoS ONE 4(1): e4141.
1.2 MB PDF