Supply of gastropod larvae to hydrothermal vents reflects transport from local larval sources

Variation in larval supply to disjunct marine populations can provide insight into larval transport and delivery mechanisms, especially when compared with observations of physical transport. Daily variability in larval supply at two mussel-dominated hydrothermal vents, East Wall and Choo Choo, near 9º50'N, East Pacific Rise, was quantified concurrently with hydrodynamic observations to investigate local dispersal processes. The magnitude and temporal variation in supply differed between the two vent sites despite their close proximity, 1.6 km. Larval supply was relatively high and uninterrupted at East Wall compared to low and episodic at Choo Choo. Observed variation in larval supply was compared to predictions based on advective transport from larval sources at neighboring vents. Variation in larval supply at Choo Choo correlated with along-axis southward currents, consistent with larval transport from a northern larval source. Larval supply to East Wall appeared to be independent of current velocities, suggesting that larvae came from multiple sources north of and south of and possibly including East Wall. Transport of larvae from discrete local sources can explain differences in larval supply to vent communities, even on spatial scales of kilometers.