ABSTRACT: The associations of holoplankton, meroplankton and meiofauna with marine snow, as well as their behavior upon encountering marine snow, were investigated using SCUBA in the field and a vertical flume in the laboratory. Field samples were collected in the Atlantic Ocean off Charleston, South Carolina, USA. (3 dates) and in the Pacific Ocean at 2 locations 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, larvaceans, and copepod nauplii were found on aggregates. On average <1% of the calanoid and cyclopoid copepods sampled were on aggregates, indicating 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 concentrated 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 concentrated on aggregates. Cyprids, bryozoan cyphonautes, and larval echinoderms were either weakly associated with or not found on aggregates. 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 flume indicated that upon contacting marine snow calanoid and cyclopoid copepods swam away, copepod nauplii swam inside aggregates for several minutes before swimming off, and nematodes were observed to remain in aggregates throughout the observation period adding material from the surrounding water to the 'home' aggregate. These observations suggest that plankters and meiofauna in the water column may spend several hours 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 the pelagic environment for a variety of both holoplanktonic and meroplanktonic zooplankton.

KEY WORDS: Marine snow · Aggregates · Nauplii · Meroplankton · Veligers · Holoplankton · Copepod · Nematode · Meiofauna

Published in MEPS Vol. 156 (1997) on September 25
ISSN: 0171-8630. Copyright © Inter-Research, Oldendorf/Luhe, 1997