Project Details

Overview

This project addresses a biogeographic conundrum by investigating where and how the larvae of methane seep animals disperse. Similar deep-sea methane seeps are found in the Gulf of Mexico and on the Atlantic Continental margin of the U.S., yet many of the chemosynthetic species living in the GOM are absent from apparently suitable Atlantic seeps. It is hypothesized that species differences in dispersal depth may explain this major biogeographic pattern. Larvae will be sampled using the SyPRID plankton sampler deployed on AUV Sentry, and by trapping larvae in year-long deployments of larval collectors on the sea floor. The work will focus on seep sites at three depths on each side of the Florida peninsula. Oxygen isotopes and elemental composition of larval and juvenile mollusk shells will be used to obtain independent information about the depths where larvae drift and the variability in dispersal trajectories. Knowledge of connectivity among deep-sea metapopulations is central to predicting population and community dynamics, as well as guiding conservation and understanding biogeographic patterns. Biophysical models of dispersal and connectivity require data on biological parameters such as spawning times and locations, planktonic larval duration, vertical distribution in the water column, and swimming behavior. Vertical movements and other dispersal strategies may have profound effects on metapopulation connectivity and biogeography, yet the extent and timing of vertical migrations remain unknown for all deep-sea larvae. This project will produce the first deep-sea biophysical models that are informed by multiple biological parameters measured empirically.

Intellectual Merit

Reliable estimates of connectivity among metapopulations are increasingly important in marine conservation biology, ecology and phylogeography yet biological parameters for biophysical models in the deep sea remain largely unavailable. This project will advance the entire field by using state-of-the-art observations on larval migration, physiology and behavior to inform bio-physical transport models. It will be the first study to attempt quantification of demersal drift, which has been proposed repeatedly as a dispersal mechanism in the deep sea. The methods, which include both direct and indirect approaches, will find application not only with chemosynthetic organisms, but also in many other deep-sea environments, including ones that are currently endangered by human activities such as trawling, oil extraction and mining. Cold seep organisms such as mussels live at incredibly high densities, and have virtually unlimited energy for reproduction. It has been hypothesized that such organisms export significant quantities of carbon and energy in the form of gametes. This work on dispersal depths will inform future studies on the role of gametes and larvae in benthic and pelagic food webs. This study will also yield important insights into the reasons why many methane seep animals are found on both sides of the vast Atlantic Ocean.

Broader Impacts

In addition to advancing applied fields such as conservation biology and the siting of marine reserves, the results will have important value for education. The findings will be disseminated through interactive exhibits on deep-sea biology, larval biology, and the conservation implications of connectivity. These materials will be developed jointly by the PIs with help from formal classes in scientific communication, and shared among three museums and aquaria in Oregon, Washington and North Carolina. It is expected that the displays will be seen by tens of thousands of visitors, including school children, annually. The project will contribute to the development of human resources in oceanography by providing postdocs, graduate students, and many undergraduates the practical skills associated with reproductive and larval work at sea, as well as interdisciplinary training in biological, physical, and geochemical oceanography and ocean modeling. Students, including underrepresented minorities, will go to sea and participate in onboard courses and hands-on research, where they will learn the seldom-taught yet essential skills of sorting plankton, culturing deep-sea larvae, and recognizing larval forms using morphological criteria.