Seamounts: Window on Ocean Biodiversity

eamounts are undersea mountains that rise at least 1,000 meters above the surrounding seafloor, and even though they don’t break the water’s surface, scientists call them islands of biodiversity. Based on initial studies of 300 seamounts, biologists think many of the tens of thousands of seamounts worldwide are havens for unique, locally occurring endemic species. Seamounts may also serve as stepping stones for transoceanic species dispersal. "There is a strong parallel with island biogeography, which has a history dating back to Darwin, and a substantial body of knowledge and methodology that we can draw on," said biological oceanographer Karen Stocks, a postdoctoral fellow with a joint appointment at SDSC and the Scripps Institution of Oceanography (SIO). She and her colleagues are uniting the sparse and far-flung biological and environmental data on seamounts into an interactive website. Through this resource, scientists will be able to gain new insights into marine biodiversity.

Figure 1. Seamount Life The biological diversity of seamounts is evident in these photographs: antipatharian corals (top) at 580 meters on the Fieberling Guyot; deep-sea rattail fish and seastar (middle) also on the Fieberling Guyot; and Gorgonian corals or sea fans (bottom) at 1,100 meters on the Hoke seamount. Photographs courtesy of Lisa Levin, whose research was sponsored by ONR.

"Basically, what we want to know is what species occur where, and when," said Stocks, who is working with SDSC research scientist David Stockwell and SIO Professor Lisa Levin. "But the marine environment is tremendously undersampled–there are so many things we simply don’t know about biodiversity in the oceans." Moreover, the data sets that exist often are spread out, incomplete, and difficult to access. Stocks and her colleagues are taking a habitat-specific approach, studying seamounts as a key step toward building an overall picture of marine biodiversity.

Historically, marine biologists produced museum data sets viewed as having lasting value. "Then, oceanographic research became hypothesis driven, and data were seen as important primarily to answer a specific question–their long-term value was often overlooked," said Stocks. "But now the pendulum is swinging back, and people are realizing that regardless of why data sets were sampled, they can have wider uses."

By combining physical, chemical, biological, and other oceanographic data, scientists can build models of species occurrence. Such models will be vital for managing biodiversity under changing environmental conditions, whether naturally occurring or human-induced. "People are waking up to the urgent need to preserve and federate biological data sets," said Stocks.

UNDERSEA‘ISLANDS’ OF VARIETY

"Seamounts are considered excellent case studies for understanding patterns in marine biodiversity," said Stocks. In addition to their high endemism and possible role in species dispersal, seamounts may also serve as refuges for species with contracting ranges and as "hot spots" of speciation. These factors make it possible to gain deeper insight into patterns of marine biodiversity by conducting targeted research on seamounts. In addition, seamounts are productive areas that may support fisheries and coral mining, and require careful management based on scientific information to prevent habitat damage.

Other characteristics that make seamounts attractive to study include their wide distribution (they are found in all ocean basins), their wide range of physical, geological, and chemical conditions (some are tectonically active with hydrothermal vents and associated communities), and they’re discrete, like islands.

Figure 2. Sampled seamounts Map of some of the 300 seamounts–out of what is believed to be tens of thousands of seamounts worldwide–that have been sampled biologically.

ONLINE DATA AND ANALYSIS

"This is definitely a case where the whole is greater than the sum of the parts," said Stocks. She expects major advances in scientists’ understanding of patterns of ocean life to come through integrating data on the spatial distribution of organisms with environmental oceanographic data, especially across traditional disciplinary lines.

The initial phase of the National Science Foundation-funded research involves creating a multidisciplinary database and linked geographic information system to compile seamounts data sets that are now dispersed. Stocks said that the database will be made available on the Web at SeamountsOnline. This will provide a free resource for searching, downloading, mapping, and analyzing patterns of biogeography in the data. SeamountsOnline is part of the Ocean Biogeographic Information System at Rutgers University, which is part of the 10-year international Census of Marine Life project. The website is designed both to facilitate research on seamount ecology and to act as a resource for managers.

The second phase of the research will involve using the database to produce large-scale maps to reveal patterns of biodiversity and endemism on seamounts. Finally, the third phase involves applying advanced analytical tools to test hypotheses about the environmental conditions that support the species patterns discovered. Based on similar environments, researchers will test hypotheses that seamount biodiversity decreases with latitude and that it has a mid-depth maximum.

"One mystery we would like to probe is that while the biodiversity of seamounts is generally high compared to surrounding seafloor diversity, it’s intriguing that this isn’t always true," said Stocks. "Some seamounts have lower diversity than expected, and we would like to investigate why."

Like so many things about the oceans, few seamounts have been sampled biologically (Figure 2). "There are seamounts off San Diego that Lisa Levin of SIO has worked on," said Stocks. "She’s very interested in our project being able to predict species occurrences that she can then go out and measure."

"Seamounts can serve as undersea laboratories for the study of organism response to hard substrate and strong flows in the deep sea," said Levin. "They are the ‘reefs’ of deep water, supporting a myriad of large, very old, filter-feeding invertebrates, as well as sandy bottom ecosystems."

SeamountsOnline is an example of modern interdisciplinary research that integrates data, tools, and knowledge across disciplines and institutions. "The computing and data management expertise of SDSC combined with the oceanographic expertise and data collections of SIO make this an ideal environment for doing this research," said Stocks.

She is also collaborating with Professor Hubert Staudigel and researcher Anthony Koppers of the Institute of Geophysics and Planetary Physics at SIO. Staudigel and Koppers are building EarthRef.org, which includes an online seamount database containing such physical information as bathymetric or depth data (Figure 3). "We’re working to link their physical data with our biological data," said Stocks.

A key aspect of this research is encouraging people to contribute data sets to SeamountsOnline. There will be a mix of data entered directly into it, and links to data curated at the site of origin. "Many people are willing to participate, but it takes effort to prepare the data," said Stocks. "There’s a need for some organized mechanism to make resources available for this to benefit the whole community."

Figure 3. Depth map of the Ufiata and Pogisa Tokelau Seamounts SeamountsOnline will integrate physical data–deep (blue) to shallow (red/brown)–with environmental and species occur-rence data, enabling analyses and modeling to test hypotheses and predict the effects of natural and human-induced change on ocean biodiversity. Image and data from NSF-supported Earthref.org, courtesy Anthony Koppers, IGPP-SIO, UCSD. Contour interval 125 m; grid size 100 m; sun azimuth 340°.

INFORMATION TECHNOLOGY FOR BIOLOGICAL INSIGHT

Once data sets are linked or collected in the database, modern analytical tools may help discover knowledge never before available. "My background is in marine-community ecology, and it’s very exciting to be able to work with SDSC environmental informatics researcher David Stockwell," said Stocks.

To go from point data on where species are found to estimating broader biodiversity patterns depends sensitively on the number of samples and other factors. Great care must be taken to use data correctly in order to reach statistically reliable conclusions.

Stockwell and his informatics colleagues have developed statistical techniques for analyzing species-distribution data that are capable of dealing with such problems as sparse and biased sampling, scale mismatches between data sets, varying levels of accuracy, and even taxonomic uncertainty.

These tools can help determine which environmental factors do the best job of predicting where species will be found. "If we identify which combinations of environmental factors best predict species occurrence, this makes possible reliable predictions, which can guide future field work," said Stocks. Since ship time is expensive, these tools will make field research more targeted and productive.

"The analysis applications being incorporated into SeamountsOnline are operated as free Web services, and they’re also available to the general biodiversity community," said Stockwell.

The researchers also want to inform the wider community about these technologies. "We’re planning to show how well these powerful new analytical tools complement traditional analysis tools that biologists are already familiar with," said Stocks. Seemingly little things can make a big difference in the usefulness of a resource like SeamountsOnline, so Stocks is doing such things as using units familiar to each discipline.

"We’re developing tools and analytical research experience that can later be applied beyond seamounts," said Stocks. "They can help in the study of other marine ecosystems in more systematic ways than previously possible." –PT