Marine Biology 99, 177-186 (1988)

Filter feeding by Oikopleura vanhoeffeni grazing impact
on suspended particles in cold ocean waters

D. Deibel

Newfoundland Institute for Cold Ocean Science, and Marine Sciences Research Laboratory,
Memorial University of Newfoundland. St. John's. Newfoundland A1C 5S7. Canada



Abstract

Because of the abundance and size of Oikopleura vanhoeffeni its quantitative role as a suspension feeder in cold ocean waters needs to be defined. To minimize the effect of manipulation and containment, and to assess the effect of naturally occurring factors on clearance rate, I used an in situ latex microbead technique in Logy Bay, Newfoundland, from February 1985 to June 1986. Individual clearance rates ranged from 8-944 ml h¬¹, increasing exponentially with increasing trunk length. Partial correlation and principal components analysis indicated that trunk length and the concentration of ingestible chlorophyll a accounted for a majority of the variation in clearance rate. At densities of 4 - 110 m¬³, O. vanhoeffeni populations removed from < 1 to 13% of the standing stock of ingestible food particles each day. Grazing by near-surface populations was lowest during the spring diatom bloom (< 1.4% of daily particle production removed per day), and was highest in June during the post-bloom crash (4 to 10% of daily production removed). Some populations in mid-depth waters had much higher population clearance rates (ca. 50% of daily production removed) because of a greater proportion of large animals. The median percentage daily ration (µg C x µg C¬¹ x d¬¹ x 100%) of 64% accounted for observed house production rates (1 to 2 d¬¹, with each house=23% of body carbon).