In situ ingestion rates of appendicularian tunicates in the Northeast Water Polynya (NE Greenland)

We report in situ ingestion rates of individual oikopleurid appendicularian s from the Northeast Water Polynya (NEW) determined by a modification of th e gut pigment technique. Appendicularians were most abundant at ice edge st ations and were rare at open water stations in the centre of the polynya. G ut passage time (GPT), which was determined in experiments onboard ship, wa s not related to body size (mean +/- SD = 74 +/- 23 min). Gut chlorophyll c ontent (GCC) excluding phaeopigments (i.e. GCC = chlorophyll a + b + c), av eraged 4.06 ng ind.(-1), with quartiles of 1.20 to 4.73 ng ind.(-1) There w as no evidence of a diel feeding rhythm. GCC was higher and more variable a t non-bloom (i.e. at chlorophyll concentrations <0.8 mg m(-3)) than at bloo m stations, and was inversely related to the relative proportion of chlorop hyll in particles >5 mu m in size. This suggests inhibition of ingestion ra tes at ice edge stations with diatom blooms. The ingestion rate (IR, ng chl orophyll ind.(-1) d(-1)) of individual appendicularians in the NEW can be p redicted by IR = 2.5 BL:(BT-0.41TL2.14) (r(2) = 0.43) where BL:BT is the ra tio of chlorophyll a in particles >5 mu m in diameter to the total chloroph yll biomass, and TL (mm) is the trunk length.