Retention efficiency of 0.2 to 6 µm particlesby the appendicularians Oikopleura dioica and Fritillaria borealis

[摘要] ABSTRACT: We used suspensions of 0.2, 0.5, 0.75, 1, 2, 3 and 6 µm fluorescent beads in combination with analytical flow cytometry to determine the efficiency of retention by small (165 µm trunk length), medium (347 µm) and large (689 and 734 µm)Oikopleura dioica, and by large (585 µm) Fritillaria borealis. Large O. dioica and F. borealis were the most efficient at retaining the 2 µm beads, and small and medium O. dioica were most efficient for 1 µm beads. LargeO. dioica and F. borealis showed efficiencies of ca. 15% for 0.2 µm, 33% for 0.5 µm, 58% for 0.75 µm beads, 66% for 1 µm beads and 88% for 2 µm beads. However, small O. dioica showed higher efficiencies, measuringca. 10% for 0.2µm, 43% for 0.5 µm, 72% for 0.75 µm beads, 87% for 1 µm beads and 93% for 2 µm beads. The combination of our measured appendicularian particle-retention efficiency spectra with typical particle size-distribution spectra in the ocean indicates that largeand small appendicularians obtain 80% of their diet from particles smaller than 15 and 7 µm respectively, and that the smallest particles represent a significant part of their diet only when they strongly dominate the biomass size spectra. Comparison withdata from the literature indicates that although the appendicularian:prey length ratio is extremely high, the appendicularian:prey body-carbon ratio (14538:1) is within the reported range for mesozooplankton (1:1 to ca. 3 ×10⁶:1), andstatistically undistinguishable from that of copepods (1603:1).

[学科分类] 海洋学与技术

[关键词] Aerial strip-transect survey;Community occupancy model;Imperfect detection;Seabird habitat relationships;Species distribution models