Award: OCE-1030453

This project explored the mechanisms by which deep-sea animals move among isolated habitas using microscopic planktonic larvae. Methane seeps are localized areas where methane gas bubbles from the ocean floor. Many of the specialized animals living at these seeps are dependent on methane for their nutrition. Most of them reproduce by means of larval forms that migrate up into the water column to disperse and locate new habitats. We modeled the distances and directions that these larvae disperse to predict how populations throughout the western Atlantic might be connected genetically. The models required information on water currents as well as biological information about the larvae, including spawning time, larval duration, and the depths where larvae swim. Using opening-closing plankton nets (MOCNESS) and a newly developed plankton collector (SyPRID) deployed on the autonomous undersea vehicle Sentry, we collected more than 10,000 larvae from depths as great at 5000m from the southern Caribbean (Barbados), the Gulf of Mexico, and the Atlantic continental margin. Larvae of bivalves and some other deep-sea animals were identified by genetic barcoding. We discovered that some seep molluscs are able to migrate all the way to the upper water column, where they may disperse for vast distances. Biophysical models incorporating ocean currents predicted that these larvae can disperse thousands of kilometers. For example, larvae from the Gulf of Mexico off Louisiana can be carried around Florida and north in the Gulf Stream to colonize seeps off the Atlantic seaboard up to a year later. By contrast, larvae from the same area drifting near the sea floor disperse much shorter distances and in the opposite direction. Several new kinds of larval development were discovered. The spawning of bivalves was studied using thin sections of gonads from animals collected with the Alvin submersible. Mussels of three different species occurring at depths from 500m to 3000m all had similar egg sizes and similar patterns of gamete production. Our study of larval dispersal among isolated habitats has practical implications for other isolated habitats in the deep sea, including hydrothermal vents and seamounts. The former are targeted for large-scale mining operations and the latter are threatened by deep-sea fishing and other human activities. Information from this project was disseminated through scientific publications, and to the public through a museum display at the Charleston Marine Life Center in Oregon. Websites show pictures of larval forms and describe the new SyPRID sampling system. Numerous college students were trained at sea in oceanographic work and larval biology. Last Modified: 02/21/2017 Submitted by: Craig M Young