Abstract
The dispersal of organisms in an isolated environment of a hydrothermal vent remains unclear. Here, we provide direct evidence that meroplanktonic larvae may migrate thousands of meters above the ocean floor. The morphological quantitative measurements of mesozooplankton were conducted in the Onnuri Vent Field (OVF), the Solitaire Fields (SF), and the reference site (ref-site). Only one species of bivalve larva that appeared at the OVF and the ref-site (0–200 m) was similar to Bathymodiolus spp. Sixteen species of gastropod larvae were distinguished, among which, species 1–4, 6, and 13 had holoplanktonic features (Atlanta, Oxygrus, and Limacina), whereas species 5, 7–12, and 14–16 had meroplanktonic features. Species 5, 11, and 12 appeared only at the OVF, 9 and 10 appeared only in the SF, 14–16 appeared only at the ref-site, and species 7 and 8 appeared in all surveyed stations. The species 5, 8, 12, 14, and 15 have morphological features similar to Vetulonia spp., and species 7 was similar to Lepetodrilidae; species 9–11 and 16 were similar to Phymorphynchus protoconchs. The morphologically distinguished mollusk larvae in the upper layers of the water column (0–200 m) indicate that larvae associated with deep-sea hydrothermal vents may disperse approximately 2000 m above the vents.
Highlights
Benthic animals produce planktotrophic larvae, which spend weeks to months in the pelagic environment, feeding and developing through their free-swimming stage [1,2,3,4]
The temperature observation showed that the depth of the surface mixed layer (SML) increased with an increase in latitude (◦ S) (Figure 2)
Similar results were reported in the waters of the Onnuri Vent Field (OVF), Similar results were reported in the waters of the Guaymas Basin hyhydrothermal vents,where wherethe thebenthopelagic benthopelagiczooplankton zooplankton biomass biomass was about drothermal vents, about 0.02–0.08%
Summary
Benthic animals produce planktotrophic larvae, which spend weeks to months in the pelagic environment, feeding and developing through their free-swimming stage [1,2,3,4]. Planktonic larval duration (PLD) is the amount of time larvae take to develop to the settlement stage [5]. PLD and dispersal strategies may differ depending on the species, climate zone, and habitat types [7]. Shanks (2009) reported that shallow-water and coastal species are more concentrated in complex hydrodynamic and fast-speed currents than in the deep-sea. The intertidal and shallow subtidal species are transported from inshore waters into large-scale coastal currents and eventually return to the inshore waters of another location [9]. Deep-sea species have complicated PLD, where larval transport distance depends on the development, behavior, and physiology of the larvae [5]. Veliger larvae such as limpets (e.g., Leptodrilus spp.) tend to remain near the bottom and in slower currents [10]; tubeworms (e.g., Riftia pachyptila) are buoyant and more likely to be transported above the bottom (e.g., ridge-controlled currents) [11]; and swimming larvae such as mussels (e.g., Bathymodiolus childressi) migrate up into the oceanic currents near the surface [12]
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