HOLOPLANKTON, MEROPLANKTON, AND MEIOFAUNA ASSOCIATED WITH MARINE SNOW

The associations of holoplankton, meroplankton and meiofauna with mari ne snow, as well as their behavior upon encountering marine snow, were investigated using SCUBA in the field and a vertical flume in the lab oratory. Field samples were collected in the Atlantic Ocean off Charle ston, South Carolina, USA. (3 dates) and in the Pacific Ocean at 2 loc ations in the San Juan Islands, Washington, USA (7 dates). Aggregates were present and abundant on all days (range 1 to 63 aggregates l(-1)) but constituted a small percentage of the water column by volume (avg 0.078 %). Holoplanktonic adult calanoid and cyclopoid copepods, larva ceans, and copepod nauplii were found on aggregates. On average <1% of the calanoid and cyclopoid copepods sampled were on aggregates, indic ating a weak association with marine snow. In contrast, on average 2.6 % of the larvaceans and 4.8 % of the copepod nauplii sampled resided on aggregates, where they were, respectively, 33 to 62 times more conc entrated on marine snow compared to the surrounding water. Percentages of harpacticoid copepods, nematodes, and foraminiferans on aggregates were 12.4, 69.9 and 47.2%, respectively, and all were significantly c oncentrated on aggregates. Cyprids, bryozoan cyphonautes, and larval e chinoderms were either weakly associated with or not found on aggregat es. In contrast, bivalve and gastropod veligers and larval anthozoans were significantly concentrated on marine snow, with 5.8, 9.4, and 13. 5%, respectively, found on aggregates. Observations in a vertical flum e indicated that upon contacting marine snow calanoid and cyclopoid co pepods swam away, copepod nauplii swam inside aggregates for several m inutes before swimming off, and nematodes were observed to remain in a ggregates throughout the observation period adding material from the s urrounding water to the 'home' aggregate. These observations suggest t hat plankters and meiofauna in the water column may spend several hour s d(-1) visiting or residing on aggregates, and may visit from 10s to 100s of aggregates d(-1). The concentration and behavior of organisms on aggregates suggests that marine snow is an important component of t he pelagic environment for a variety of both holoplanktonic and meropl anktonic zooplankton.