LArval Dispersal along the Deep East pacific Rise (LADDER)
[co-PIs: L.S. Mullineaux, A.M. Thurnherr, J.R. Ledwell, D. McGillicuddy, and J.W. Lavelle]
Project Summary
When hydrothermal vent communities were first discovered 25 years ago,
biologists immediately recognized the key role of dispersal in the
dynamics and persistence of the populations. Despite substantial
progress on this topic over the past 10 years, some very important
questions remain unanswered about the mechanisms of dispersal and their
effects on population dynamics, population genetics and community
structure. Investigators have hypothesized that larval dispersal is
driven largely by physical transport processes. The primary objectives
of the present proposal are to investigate how larval
behaviors interact with topographically-influenced flows on mid-ocean
ridges, and determine how these interactions affect dispersal
trajectories, maximal dispersal distances, and relative probabilities
of supply to natal versus remote vents.
We have identified three specific ecological questions to address:
- What are the influences of advection and eddy diffusion on the
maximal dispersal distance of vent species with given larval life
spans?;
- What are the effects of ontogenetic changes in larval behavior
(i.e., vertical positioning) on species' dispersal distances; and
- How are the probabilities that larvae will be lost from the ridge
system influenced by topography and flow? Might the axial summit trough
inhibit off-axis transport of larvae, and serve as a conduit between
habitable vent sites?
Our proposal also addresses several issues of
interest to the physical oceanography community, including:
- What are the mean and temporally varying flows in the vicinity of a
mid-ocean ridge crest, and what is their spatial structure and
coherence?;
- What is the magnitude of the diapycnal diffusivity near the ridge
crest?;
- How rapid is lateral dispersion, and how effective is lateral
homogenization by eddy diffusion near the ridge crest?
Our dispersal questions cannot be answered without an integrated set of
physical and biological approaches. We have assembled a diverse team of
observationalists and modelers to investigate relevant aspects of
ridge-associated oceanography and biology, and to combine them into a
quantitative model of dispersal. The approach includes a tracer release
in the field, current meter measurements, a hydrodynamic/transport
model, measurements of larval positions and stages in the field, and a
coupled biological/physical model. We have chosen to study the region
near 9:50N on the East Pacific Rise (EPR), a site that has been the
focus of much interdisciplinary research in the past and has been
selected as an Integrated Study Site by the NSF Ridge 2000 program.
Broad impact of this result will be achieved through several different
activities. The approaches and results from the proposed studies will
be incorporated into graduate courses, and into presentations given to
local K-12 classes. Two graduate students will be supported, and
undergraduates will be integrated through the WHOI Summer Student
Fellowship program and the NSF REU program. We will link our research
with web-based outreach efforts including Dive and Discover
(www.divediscover.whoi.edu) and
Women Exploring the Oceans (wexo.whoi.edu).
The long-term benefits of the proposed activity to society will be
achieved by contributing to a general understanding of retention,
dispersal, and connectivity of marine populations, and to a better
understanding of seafloor topographic effects on flows and mixing. Vent
systems are subject to increasing use by researchers, tourists and
industry (e.g., extracting polymetallic minerals, and sampling fauna
for natural products discovery and pharmaceutical applications). Our
results will inform efforts to develop plans for sustainable use of
vent ecosystems.
Further Reading
Disclaimer
The material found on this page is based upon work supported by the
National Science Foundation under Grant No. 0425361. Any opinions,
findings, and conclusions or recommendations expressed in this material
are those of the author and do not necessarily reflect the views of the
National Science Foundation.
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