Award: OCE-1851383

Factors thought to determine the composition of deep-sea animal communities include the ability of microscopic offspring (larvae) to disperse long distances, to locate suitable adult habitat, and to pass through or around geographic barriers. This proposal explored the potential of larvae spawned at methane seeps in the deep Gulf of Mexico to pass through the relatively warm and shallow waters off Florida and to establish themselves in the Atlantic. Using submersibles, autonomous vehicles and closing nets, we characterized seep communities and larval distributions in both regions. Larval traps were deployed at seeps found at three different depths in each ocean basin, and larvae collected in various seasons were used to explore sources, vertical swimming ability, and dispersal paths of larvae. Oxygen isotopes of the microscopic shells of larval and juvenile mussels showed that some larvae disperse in warm surface waters, even when their adults live in cold bottom water more than 3000m deep. Although mussel larvae can drift for more than a year, enabling very long distance dispersal near the surface, some individuals spend their entire larval lives in deep water where they are more likely to locate the patchy seep habitats required for settlement. This is the only known example of a bet-hedging dispersal strategy in the deep sea. Larvae of several giant tubeworm species in the Gulf of Mexico swim for only a few weeks and cannot tolerate warm waters near the surface. Tubeworms are conspicuously absent in the Atlantic, suggesting that the larvae do not tolerate the warmer waters around Florida. Reproduction of mussels was seasonal at all depths, varying between ocean basins and correlating with surface phytoplankton production. Egg production of individual mussels was quantified in large mussel beds in the Atlantic. These studies revealed that methane-based mussel beds on the bottom produce a significant amount of energy that is exported to the upper water column, where it supplements photosynthetic production in a  non-trivial way. A very abundant species of sabellid polychaete worm was found to be a new species whose diet consists of free-living methanotrophic bacteria.  In addition to new insights about the dispersal, reproduction and biogeography of methane seep organisms, numerous biology students from several universities were trained in oceanographic and embryological research, and many were given opportunities to dive in Alvin.  With NSF support from another program, some of these participated in an IMAX film that will be widely distributed to theatres worldwide, with the goal of encouraging young people to consider careers in marine science. 

Last Modified: 05/13/2026
Modified by: Craig M Young