MEPS 154:211-221 (1997)  -  doi:10.3354/meps154211

The association of larval polychaetes with marine snow was investigated (1) with SCUBA to sample marine snow in the field and (2) in laboratory experiments. The field sampling took place in the Atlantic Ocean off Charleston, South Carolina, USA (3 sample dates) and in the Pacific Ocean at 2 locations around the San Juan Islands, Washington, USA (7 sample dates). On all of the sample dates marine snow was present and abundant (range 1 to 63 agg. l^-1). Larval polychaetes were significantly concentrated on aggregates on 7 of the 10 sample dates. Larval polychaetes from 12 families were present in the plankton samples of which 10 families were found associated with aggregates. On average, 16% (SD = 22%) of all larval polychaetes were on aggregates. Precompetent and competent larval polychaetes made up 84 and 16% respectively of the larval polychaetes in the plankton. On average 20% of all precompetent polychaete larvae were on aggregates. In contrast, competent polychaete larvae were strongly associated with aggregates with 80% of the competent larval polychaetes on aggregates. Laboratory experiments using 4 polychaete species and laboratory-made marine snow also found that larval polychaetes were concentrated on aggregates. In a vertical flume, observations were made on the behavior of larval polychaetes following contact with aggregates. Upon contacting marine snow, larval polychaetes crawled into or over the surface of aggregates for several minutes before swimming away. These field and laboratory observations suggest that a precompetent polychaete larva might spend about 5 h d^-1 visiting aggregates and that during a day it may visit about 90 aggregates. Competent larval polychaetes may spend >19 h d^-1 on aggregates. Polychaete larvae visiting or residing on aggregates may be feeding on the aggregate microbial community. Further, the vertical flux and, perhaps, benthic deposition of larvae residing in aggregates is due to the sinking of the marine snow. Clearly, marine snow is an important component of the environment for many types of polychaete larvae and adaptations to life in aggregates may have played a role in the evolution of polychaete larval traits.

Marine snow · Polychaetes · Larvae · Aggregates · Meroplankton · Competent · Precompetent · Settlement