Award: OCE-1155703

Intellectual Merit: Organic-rich habitat islands, such as tree falls in terrestrial forests, support specialized communities throughout natural ecosystems, promoting biodiversity and the evolution of new species. Whale bones and wood falls provide organic-rich habitat islands at the normally food-poor deep-sea floor and support remarkable communities; nonetheless, large-scale patterns of biodiversity and ecosystem function in these food-rich habitat islands remain essentially unexplored. We developed a novel experimental approach, using deep-sea bottom landers (Fig. 1), to emplace large whale bones and wood blocks at controlled locations on the seafloor in two ocean basins. With these experiments, we explored how biodiversity and decomposition vary for whale bones and wood falls as a function of ocean depth, distance along an ocean margin, and between the North Pacific and South Atlantic. We deployed multiple landers at two ocean depths (1500 and 3000 m) separated by 250 – 500 km in the NE Pacific and SW Atlantic basins (in collaboration with Brazilian colleagues) and recovered the landers, together with rich communities of animals and microbes living on the wood and bone, after ~15 months. We used a variety of techniques (including DNA sequencing, morphological studies, and photographic and x-radiographic imaging) to analyze faunal and microbial assemblages on recovered whale bones and wood blocks. A high diversity of animals colonized our experiments, with 188 species found across all bone/wood substrates on the Oregon-Washington margin, including many species new to science. Fourteen species were unique to whalebones, 32 species to wood blocks, and 69 species were shared across all substrates. Wood blocks at 1500 m were heavily colonized and decomposed by wood-boring clams (genus Xylophaga) (Fig. 2), while blocks at 3000 m sustained little colonization and degradation, indicating that wood decomposition varies dramatically with ocean depth. Heavily degraded wood blocks had extremely high abundances of a new species of flatworm and a diversity of other invertebrates (Fig. 2). The abundance and diversity of wood-dwelling fauna were strongly correlated with the both abundance of the wood-boring clam and the weight of wood lost through its borings, indicating that Xylophaga is a key ecosystem engineer, increasing the availability of food and habitat space on sunken wood. Degradation of whale bones by the bone-eating worms Osedax was limited (Fig. 3), with only 19 individual Osedax colonizing all 12 bone substrates after 15 months. These experiments indicate that while the borings of bone-eating worms promote the diversity of other colonizers, degradation of large whale bones on the deep Oregon-Washington margin is very slow, suggesting that whale bones may provide food-rich habitats for many years. Key "take-home" messages from our whale/wood experiments in the deep NE Pacific and NW Atlantic include the following: (1) Rates of bone/wood degradation, animal biomass production, and faunal species richness on bone/wood substrates are controlled by the abundance of specialized bone/wood decomposers (Osedax/Xylophaga). (2) Species and genetic exchange among food-rich habitat islands (whale bones and wood falls) is much greater within an ocean depth zone (e.g., at ~1500 m) than between depth zones (i.e., between 1500 and 3000 m depths); this indicates that species disperse more efficiently (e.g., in water currents) for hundreds of kilometers along a particular depth contour than they do between ocean depths separated by only 1.5 km. (3) The identity and diversity of dominant species colonizing sunken whale bones and wood varies significantly between ocean depths and dramatically between the NE Pacific and SW Atlantic. The NE Pacific and SW Atlantic have their own suite of wood-boring (Xylophaga) and bone-boring (Osedax) species, suggesting distinct adaptive radiations. This first experimental study of interactions between key engineering species and biodiversity on whale-bones and wood falls reveals striking functional similarities to other organic-rich habitat islands (e.g., tree falls in terrestrial forests) and helps us to understand how human activities, such as whaling and deforestation, affect deep-sea ecosystems. Broader Impacts: Our project has had broader impacts in four areas: (1) Two graduate students (one women) conducted their PhD research, and four undergraduates and five additional graduate students (including four women) received research training and oceanographic field experience, within the project. (2) We developed a new summer course for advanced undergraduate/graduate students at Friday Harbor Laboratories in summer 2014. The course, titled Deep-Sea Biodiversity, Connectivity and Ecosystem Function, used our bone-wood lander experiments to help 20 class participants learn about the largest ecosystems on our planet. (3) We developed new bone-wood lander technology now used by other researchers in Brazil, Norway, and Canada. (4) We educated the general public about deep-sea science with project web sites and cruise blogs, and through presentations to >2000 people at University of Hawaii open houses and school visits. (4) We presented our scientific results at four international scientific meetings (8 presentations), and published five papers with support from this project in top-tier, peer-reviewed scientific journals (four additional papers are in preparation). Last Modified: 12/07/2017 Submitted by: Craig R Smith