Tt. Noji et al., CLEARANCE OF PICOPLANKTON-SIZED PARTICLES AND FORMATION OF RAPIDLY SINKING AGGREGATES BY THE PTEROPOD, LIMACINA-RETROVERSA, Journal of plankton research, 19(7), 1997, pp. 863-875
Findings from experiments showed that the web-feeding euthecosomatous
pteropod, Limacina retroversa, can produce rapidly sinking, mucous agg
regates. It is suggested that, by adhesion, these aggregates scavenged
picoplankton-sized particles, which were thus effectively cleared fro
m the medium. In contrast, Calanus finmarchicus was not able to clear
these particles in our experiments. Sedimentation velocities of 10 agg
regates measured in vivo were up to 1000 m day(-1), with an average of
similar to 300 m day(-1) (not including two aggregates with neutral b
uoyancy). Mean velocities measured for feces of C. finmarchicus, Calan
us hyperboreus and Thysanoessa sp. were considerably lower. We suggest
that the sedimentation of L. retroversa aggregates was the source of
mucous flocs collected in sediment traps (Bathmann et al., Deep-Sea Re
s., 38, 1341-1360, 1991) and at the sea floor at 1200 m depth in the s
outhern Norwegian Sea. This process may be an important mediator of se
dimentation to the deep sea, when these pteropods are present in surfa
ce waters in large abundance.