Dataset: Counts of meroplankton collected with McLane Pump, Sentry/SyPRID, or larval traps from vent field at the Eastern Lau Spreading Center-Valu Fa Ridge on cruise TN401 in Apr 2022

To estimate larval supply to the seafloor, two replicate larval tube traps were simultaneously deployed for approximately two weeks at the base of a vent chimney at each site (except Mariner or Mata Tolu) in an animal-free patches. These self-opening tube traps (described in Young et al. 2015) consisted of four tubes made of three 50-mL Falcon tubes conjoined with cyanoacrylate adhesive to form a single tube that was 23 cm high with a 3-cm in diameter opening (7.6 aspect ratio) with two internal funnels in the middle preventing resuspension during recovery. The four tubes were fit in a PVC frame with a central weight. Two tubes on each trap were prefilled with RNA preservative for DNA preservation and the other two were filled with hypersaline 10% formalin buffered for morphological preservation. Tubes were deployed covered with plastic wrap held by rubber bands attached with A2 galvanic time releases that dissolve in 4 °C seawater within 24 hours. After recovery, the samples in RNA preservative were rinsed and stored in fresh RNA preservative, and formalin-fixed samples were rinsed then stored in 70% ethanol at -20 °C until processing. The sorting of larval trap samples was later conducted at Shannon Point Marine Center where samples were imaged and sorted into morphological groups using a dissecting microscope. All RNAlater-preserved gastropod samples in the traps were set aside for mtCO1 genotyping. 

A Large Volume Water Transfer System WTS-LV50 (McLane Research Laboratories, Inc.) was used to collect and quantify larval abundances in the water column among vent chimneys. A mooring suspended the pump ~ 2 meters above the bottom (mab) for 7-18 hour deployments at each site. The pump gently drew water onto a 63-µm Nitex mesh filter, running for 7.3 -18.7 hours and filtering 11.9-30.5 m³ into an insulated compartment upstream from the filter. Upon recovery, live specimens on the pump filter were immediately rinsed with 0.3-µm filtered seawater onto a 63-µm sieve, examined under dissecting microscopes, sorted into morphological groups, and imaged with an Olympus EP50 Camera mounted on an Olympus CX43 compound microscope at 40-100X magnification. Larval samples were then stored in 95% EtOH at -20 °C for CO1 genotyping.

AUV Sentry (National Deep Submergence Facility, Woods Hole Oceanographic Institution) equipped with SyPRID (Sentry Precision Robotic Impeller Driven Sampler) was used to collect larvae in the water column around the periphery of the vent fields and above the vent fields. This device uses an impeller pump to gently suction plankton from the water onto a 150-µm Nitex mesh filter in the cod end (Billings et al. 2016). At each vent field, AUV Sentry collected two SyPRID samples (~11-hour duration each): one sample around the periphery and one above the vent structures, filtering up to 3,619 m³ of seawater per sample. The periphery sample was collected from 8-15 mab in a repeating back-and-forth pattern around the periphery of the target vent field. At Tahi Moana, periphery samples were collected at 30 mab rather than 8-15 mab due to tall vent features and strong currents. At ABE, due to the proximity of a ~20 m tall wall feature to the west, half of the periphery sample was acquired from the base of the wall and the other half was acquired from the top of the wall.  Above vent field samples were taken in a series of parallel tracks back and forth over a standard area over each vent field at approximately 26-45 m above the tallest known hydrothermal chimney structures. The sampling pattern was planned such that spaces between tracks reduced over successive passes and were offset to avoid repeating tracks, encouraging wide sample coverage over the select area. Upon recovery, all SyPRID samples were immediately rinsed with 0.3-µm filtered seawater onto a 63-µm sieve, sorted into morphotypes using dissecting microscopes, imaged with an Olympus EP50 Camera mounted on an Olympus CX43 compound microscope at 40-100X magnification, and stored in 95% EtOH at -20°C for mtCO1 genotyping.

All larvae were sorted under a dissecting microscope, imaged, and identified to larval type by morphology. Gastropod, bivalve, and zooea larvae were identified to the lowest taxonomic level possible using a combination of morphology and sequencing. Sorting and sequencing was conducted between July 2022 and September 2025. 

For sequencing, DNA from individual gastropod larvae was extracted using the Nucleospin Tissue XS DNA (Machery-Nagel, Inc.) and eluted into 30-µl volumes. PCR amplification and sequencing of the mtCO1 gene was conducted for each larva as described above. Morphological identifications were made using the hydrothermal vent larvae identification guide (Mills et al., 2009) and our own identification guides when possible. 

Sequences and images have been submitted to the Barcode of Life Data System v4 (BOLD4) and NCBI.