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Marine Ecology Progress Series

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MEPS 293:1-16 (2005)  -  doi:10.3354/meps293001

Vertical, lateral and temporal structure in larval distributions at hydrothermal vents

L. S. Mullineaux1,*, S. W. Mills1, A. K. Sweetman2, A. H. Beaudreau3, A. Metaxas4, H. L. Hunt5

1Woods Hole Oceanographic Institution, MS 34, Woods Hole, Massachusetts 02543, USA
2Max-Planck-Institut für marine Mikrobiologie, Celsiusstraße 1, 28359 Bremen, Germany
3University of Washington, Box 355020, Seattle, Washington 98195, USA
4Dalhousie University, Halifax, Nova Scotia B3H 4J1, Canada
5University of New Brunswick, PO Box 5050, Saint John, New Brunswick E2L 4L5, Canada

ABSTRACT: We examined larval abundance patterns near deep-sea hydrothermal vents along the East Pacific Rise to investigate how physical transport processes and larval behavior may interact to influence larval dispersal from, and supply to, vent populations. We characterized vertical and lateral distributions and temporal variation of larvae of vent species using high-volume pumps that recovered larvae in good condition (some still alive) and in high numbers (up to 450 individuals sample–1). Moorings supported pumps at heights of 1, 20, and 175 m above the seafloor, and were positioned directly above and at 10s to 100s of meters away from vent communities. Sampling was conducted on 4 cruises between November 1998 and May 2000. Larvae of 22 benthic species, including gastropods, a bivalve, polychaetes, and a crab, were identified unequivocally as vent species, and 15 additional species, or species-groups, comprised larvae of probable vent origin. For most taxa, abundances decreased significantly with increasing height above bottom. When vent sites within the confines of the axial valley were considered, larval abundances were significantly higher on-vent than off, suggesting that larvae may be retained within the valley. Abundances of all vent species varied significantly among sample dates; the variation was not synchronized among taxa, except for consistently low abundances during November 1998. Lateral distributions did not vary among major larval groups (gastropods, polychaetes and bivalves), although polychaetes showed anomalously high abundances off-vent at 1 m above bottom. Lateral patterns also did not vary among species of gastropods, indicating that hydrodynamic processes may be transporting diverse species in similar ways. However, the species-level differences in temporal patterns indicate that there is substantial discontinuity in the abundance of individual species at vent communities, possibly due to timing of spawning and/or behavioral interactions with flow.

KEY WORDS: Hydrothermal vent · East Pacific Rise · Larva · Dispersal · Connectivity · Bathymodiolus thermophilus · Lepetodrilus

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