Abstract
Larvaceans, a group of pelagic planktonic tunicates, are gaining attention within marine science. Recent studies have shown the importance of larvacean, or appendicularian, houses as a source of carbon within deep-sea ecosystems. Even though the biomass of these organisms may be less than that of copepods, studies showing their faster growth rate suggest they may be just as important secondary producers. Larvaceans are unique in that they are mesoplankton able to feed on and utilize picoplankton and nanoplankton. Larvaceans themselves are also important prey for larval fishes. Despite the growing realization of their importance in the marine food web, little is known about their distribution. A multiple net system (MOCNESS was used to sample plankton across the Straits of Florida. Nets with differing opening and mesh sizes allowed larvaceans to be sampled alongside their predators in an effort to relate their distribution and abundance to that of larval tunas. Bimonthly cruises throughout 2003 sampled eight stations across the Gulf Stream, at four depth intervals, down to 100 meters. Vertically, larvaceans tend to live high in the water column, in the upper 50 meters. They are also denser closer to Miami, Florida than Bimini, Bahamas. Seasonality was observed east of the core of the Florida Current, with densities being lower in summer months. Along the western Straits of Florida where the current is greatest and primary production is highest, they show little variation between seasons. Future work may show how larvacean distributions relate to larval tuna growth, and even spawning.