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Understanding how larvae from extant hydrothermal vent fields colonize neighbouring regions of the mid-ocean ridge system remains a major challenge in oceanic research. Among the factors considered important in the recruitment of deep-sea larvae are metabolic lifespan, the connectivity of the seafloor topography, and the characteristics of the currents. Here we use current velocity measurements from Endeavour ridge to examine the role of topographically constrained circulation on larval transport along-ridge. We show that the dominant tidal and wind-generated currents in the region are strongly attenuated within the rift valley that splits the ridge crest, and that hydrothermal plumes rising from vent fields in the valley drive a steady near-bottom inflow within the valley. Extrapolation of these findings suggests that the suppression of oscillatory currents within rift valleys of mid-ocean ridges shields larvae from cross-axis dispersal into the inhospitable deep ocean. This effect, augmented by plume-driven circulation within rift valleys having active hydrothermal venting, helps retain larvae near their source. Larvae are then exported preferentially down-ridge during regional flow events that intermittently over-ride the currents within the valley.

Considerable research has compared how students learn science from computer simulations with how they learn from ''traditional'' classes. Little research has compared how students learn science from computer simulations with how they learn from direct experience in the real environment on which the simulations are based. This study compared two college classes studying introductory oceanography. One class learned using an interactive computer simulation based on a dynamic, three-dimensional model of physical oceanography. The other class learned by spending a day on a research ship using scientific tools and instruments to measure physical properties of the ocean directly. In classes preceding and following the simulation or field experience, students performed the same exercises regarding currents and salinity, had the same instructor presentations, and did the same homework. The study found that the field experience helped contextualize learning for students with little prior experience of the ocean while the simulation made it easier for students to connect what they learned from it to other content they learned in class. These and other findings shed light on what computer simulations can and cannot help students learn, and what concepts are best learned in the real environment. ß

[1] We characterize hydrothermal plumes and hydrography within the axial valley of the Endeavour segment (Juan de Fuca ridge, northeast Pacific) using data from an autonomous underwater vehicle, a lowered CTD, and two current meter moorings. Our survey of the Main Endeavour hydrothermal vent field (MEF) shows hydrographic variability on scales as short as $20 m and $10 min. Within the $100 m deep axial valley, the mean flow is 1-5 cm/s to the north, and tidal oscillations have $5 cm/s amplitude. Combining the mean flow with an estimate of the difference in average temperature observed north and south of MEF, we find that the net along-axis horizontal heat flux has a mean magnitude of $8-42 MW. An advection/diffusion model forced by local current records explains the observed temporal hydrographic variability and shows that mean horizontal flux variance is correspondingly high (standard deviation $63 MW). A steady state MEF heat budget, constrained by the observed horizontal flux and measurements of vertical fluxes from other studies, has two implications: the MEF heat flux is partitioned about equally between diffuse and focused vents, and about 85% of the flux from diffuse plumes is entrained by focused plumes.Components: 8328 words, 9 figures.