Table of Contents

• Dataset Description
  • Methods & Sampling
  • Data Processing Description
• Data Files
• Parameters
• Instruments
• Deployments
• Project Information
• Funding

This dataset contains counts of the following benthic taxonomic groups: Desmoscolecid nematodes, non-Desmoscolecidae, nauplii, copepods, kinorhynchs, and ostracods.  Station data includes location, depth, distance between stations(km), depth difference between stations (m), distance between lowerings (km), oxygen, temperature, and salinity.
 

Benthic cores were taken along a transect of the Pacific US continental rise from southern Oregon to San Diego. We sampled with an Ocean Instruments (San Diego, CA) MC 800 multiple corer.  The multiple corer had eight 10-cm (inner diameter) core tubes.  The team processed each core from a lowering in a predetermined, random order.  The team imaged the sediment through the side of the transparent core tube, noted any unusual features, collected the water overlying the sediment, imaged the sediment surface, and collected the top 1 cm of sediment.  The water and sediment samples were combined, preserved with cold, 95% ethyl alcohol, and stored at -20ºC.

Salinity, temperature, and oxygen data were collected at about 50 meters above the bottom at each station.

In the laboratory, we randomly selected a station, a lowering within that station, and an apparently undisturbed core from that lowering.  We repeated this procedure three times, yielding 24 samples, which were processed in this order.  For each sample, we measured its volume and separated the 300-µm fraction from the 30-µm fraction.  After staining with rose bengal, one person sorted both fractions from each sample under a stereomicroscope at 25×.  The sorter removed and counted nematodes, nauplii, benthic copepods, kinorhynchs, and ostracods and noted which nematodes belonged to the family Desmoscolecidae.  A second person sorted each sample a second time to ensure accuracy.  We included the specimens of these groups retained by the 300-µm sieve in our counts. 
 

From proposal abstract:

The sediment-covered deep-sea floor is arguably the largest habitat on Earth. Despite the extreme conditions, the number of species present at a given location for some taxa can rival that of the most species-rich groups in the most species-rich habitats on Earth (e.g., insects in rain forests). The nature of this richness is controversial. Some studies have reported that a few species had ranges of 100's to 1,000's of kilometers, but many species were found at only a single location. In other work, many more species were reported to have large ranges. Worse, the existing data may not be completely informative because the decisions about the assignment of individuals to species were made on the basis of morphology, which can fail to distinguish species that are biologically separate, and commonly known as cryptic species. The question of how big is a species range in deep-sea sediments needs to be resolved because it matters profoundly to conceptual models of the ecology of deep-sea sediments. If most species have small ranges, students of the deep sea will want to understand, for example, how species' ranges are bounded in an environment that appears to have few physical barriers. Alternatively, if most species have large ranges, investigators will want to study issues related to the genetic connectivity of species over 100's to 1,000's of kilometers.

The primary objective of this project is to evaluate the possibility that some sediment-dwelling deep-sea species have large ranges. To do that these investigators will collect sediment samples from one station at 2,700 m and one at 3,700 m depth at each of four latitudes (47.6° N, 42.6° N, 36.5° N, and 32.6° N) on the continental slope off the west coast of the United States. The very common harpacticoid copepods will be the target group for this study. Each adult harpacticoid from each sample will be assigned to a species on the basis of traditional morphological characters. Each of these adult harpacticoid copepods will then be cut in two; the posterior portion will be used for DNA-sequence analysis, and the anterior will be retained as a voucher sample. The DNA-sequence analysis will be used to determine whether the individuals deemed to be the same species on the basis of morphology form a well-supported species group based on molecular data. The distribution of these species groups among stations will allow the investigators to know that its range is at least as large as the distance between the stations where they were found.

The proposed research could benefit society by helping policy makers evaluate the environmental cost of human disturbance of the deep-sea floor (e.g., ocean dumpingl) by beginning to clarify the relationship between species ranges and human disturbances. The investigators will also share their results with colleagues through presentations at scientific meetings and in publications and to a wider audience by means of public lectures and a web site. The project will also foster the participation of underrepresented groups in oceanography.