Table of Contents

• Coverage
• Dataset Description
  • Methods & Sampling
  • Data Processing Description
• Data Files
• Supplemental Files
• Related Publications
• Related Datasets
• Parameters
• Instruments
• Deployments
• Project Information
• Funding

Larval collection:
These larvae were collected near three hydrothermal vent sites (Snail, Archaean, or Urashima) on the Mariana Back-Arc Spreading Center in the southern Mariana Trough in September 2010 on R/V Yokosuka cruise YK10-11. See the Sampling Events Supplemental File for specific locations and dates.

To collect larvae, we deployed large-volume plankton pumps (McLane WTS-LV50, East Falmouth, MA, USA) to sample at 3 or 4 m above the bottom. Each pump sampled for up to 24 hrs at 30 liters per minute over a 63 micron mesh, yielding a filtered volume of up to 41.5 cubic meters. We provide as a supplemental data file a table of sampling events matched to Station Information in the Marine Geoscience Data System (https://www.marine-geo.org/tools/search/Events.php?event_set_uid=1185).

Shipboard sample processing:
Upon recovery, pump filters were rinsed with filtered seawater into trays on ice and examined live to select some individuals for experiments reported by Beaulieu et al. (2015, DOI:10.1111/maec.12207). Within an hour the trays were poured over a 63-um sieve and washed using 95% non-denatured ethanol into a 250 mL jar. Individuals used in the experiments were saved separately, either frozen or preserved in ethanol.

Laboratory sorting and morphological identification:
Samples were poured over nested 300-um and 63-um sieves and washed into dishes for sorting under a dissecting scope at magnifications up to 50X. Individuals were identified to morphotypes at lowest taxonomic level (original categories for morphospecies). All morphospecies were enumerated except for ostracods and copepods which were only accounted as “p” present, “a” absent, or “n” not accounted for. We used the original category plus genetic evidence when available to match our lowest-level identification to the World Register of Marine Species (WoRMS) taxonomic database. Some morphotypes contain morphologically indistinguishable larvae from multiple species (e.g., complex nectochaetes); in this case, our final categories for morphospecies group those individuals with genetic evidence into the higher taxon rank. The table is organized such that the first row listing a final category morphospecies is at the higher taxon rank containing the subsequent rows for that category (in general, the subsequent rows are for specimens sent out for genetic analyses). Note that the polychaetes classified to Infraclass Scolecida correspond to the “Capitellid” larval morphotype in Beaulieu et al. (2015). We thank Dr. Takenori Sasaki for guidance for identification of gastropods.

Additional genetic evidence to assist with larval identification:
A subset of these specimens with 28S rRNA sequences is described in a separate BCO-DMO dataset (Beaulieu et al., 2021, DOI:10.26008/1912/bco-dmo.839476.1, https://www.bco-dmo.org/dataset/839476). We'd like to thank Dr. Hiroka Hidaka, Dr. Shigeaki Kojima, and Dr. Hiromi Watanabe for providing histone 3 sequences for gastropod specimens and Dr. Florence Pradillon for providing cytochrome oxidase subunit 1 (CO1) sequences for polychaete specimens. We thank Bethany Fleming for NCBI BLAST query.

Data Processing:
Counts per morphospecies were entered into an electronic online spreadsheet (Google sheet) that was downloaded to a local .xlsx copy. The scientificName column was used with the WoRMS Taxon Match Tool to obtain a text file with the LSID and taxonomic classification and to confirm taxon status accepted on 2022-02-12. The larval_counts sheet in the .xlsx and the Taxon Match .txt were read into an R programming script to join columns into the larval counts data table https://github.com/sbeaulieu/EPR-traits/blob/master/Mariana_larval_counts_BCODMO.R. Another sheet in the .xlsx was exported to a csv file as the sampling event table. The data tables are partially aligned to Darwin Core so that they ultimately can be provided to the Ocean Biodiversity Information System (OBIS) and Global Biodiversity Information Facility (GBIF). Note that 25 individuals with occurrenceID have already been contributed to OBIS and GBIF.

BCO-DMO Processing:
- replaced "NA" with "nd" (no data);
- renamed fields to comply with BCO-DMO naming conventions;
- removed commas from values in columns Fleming_etal_Table, final_category_morphospecies, and original_category_morphospecies;
- changed long text string in original_category_morphospecies, row 13 as requested by PI.

NSF Award Abstract:
Summary: Since the discovery of deep-sea hydrothermal vents over thirty years ago, scientists have been perplexed by the question: How are these vent sites colonized and, more specifically, How are the faunal populations established and maintained at these very discrete and often ephemeral habitats. For animals that are sessile or have limited mobility as adults, dispersal to these habitats occurs early in the life cycle, as planktonic larvae in the water column. Due to the difficulties in sampling deep-sea larvae, including low abundances (dilute concentrations), we have very few quantitative estimates of larval dispersal between or larval supply to hydrothermal vents. We also have little to no knowledge of the behavior of vent larvae. The PIs will use large-volume plankton pumps to collect larvae near vents in the southern Mariana Trough in a collaborative effort to quantify larval abundance, behavior, and dispersal in this little-studied region. The collaboration combines the PI's strengths in the collection and morphological identification of larvae and quantifying and modeling dispersal between deep-sea vents, and those of Japanese partners in rearing larvae of hydrothermal vent fauna, molecular genetic identification of larvae, and population genetics of vent fauna.

Intellectual merit: The southern Mariana Trough is a very interesting region in which to study dispersal of vent-endemic fauna, due to the proximity of vents in the back-arc spreading center to vents along the Mariana Arc. These two tectonic settings create different habitat conditions and support vent communities with different species composition. Vent sites the PIs will visit, in the axis and just off-axis of the back-arc spreading center are as close as 25 km to vents on the arc, yet 600 km south of the other known vents in the back-arc. In addition to the new information on larval abundance, diversity, behavior, and dispersal that will be gained for this little-studied region of the world's ridge system, this project has direct relevance to the integration and synthesis goals of the U.S. Ridge 2000 Program. The PI's lab group has conducted previous work at the Ridge 2000 East Pacific Rise (EPR) Integrated Studies Site (ISS). They will be making a direct comparison of the larval abundance and diversity at the EPR ISS to this very different setting along the global 'baseball seam' of oceanic spreading centers. No other such comparison has been possible due to the lack of sampling effort for larvae with large-volume pumps. Also, they are proposing the first experiments with live vent larvae (to the best of our knowledge - with the exception of brachyuran megalopae at 1 atm) to estimate swimming and sinking rates that are important for adding behavioral information to models of larval dispersal.

Broader Impacts: The project involves reciprocal training and cultural exchange - the PIs will learn field and laboratory research techniques from the Japanese PIs, and they will learn from the U.S. PIs. The project will also benefit the career development of a junior researcher (Beaulieu). The proposed activity broadens the participation of both U.S. and Japanese women scientists in sea-going, oceanographic research. The PIs will broadcast the cruise activities in a web log posted by the international InterRidge Program Office, and they anticipate at least three scientific publications will emerge. New species will be added to the online photographic identification guide for vent larvae and included in the second edition of the printed guide.

Additional cruise data and information are available from MGDS: http://www.marine-geo.org/tools/search/entry.php?id=YK10-11