Seasonal variation of vertical flux of phytoplankton and biogenic matter at Nordvestbanken, north Norwegian shelf in 1994
Andreassen, I.; Wassmann, P.; Ratkova, T.N. (1999). Seasonal variation of vertical flux of phytoplankton and biogenic matter at Nordvestbanken, north Norwegian shelf in 1994. Sarsia 84: 227-238
In: Sarsia. University of Bergen. Universitetsforlaget: Bergen. ISSN 0036-4827; e-ISSN 1503-1128, more
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| Authors | | Top |
- Andreassen, I.
- Wassmann, P.
- Ratkova, T.N.
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| Abstract |
The seasonal magnitude and biochemical composition of vertical flux of biogenic matter and phytoplankton at the north Norwegian shelf break was investigated at 14 depths between 20 and 200 m depth. Data of vertical flux were collected for 24 hours at monthly intervals using free-drifting sediment traps. Samples were analysed for particulate organic carbon and nitrogen (POC and PON), chlorophyll a (Chl a ), phaeopigments (Phaeo)and phytoplankton composition. Two main periods of POC and PON vertical flux were observed in May and July with sedimentation rates ~300 mg POC m - 2 d - 1 at 200 m depth. During the other periods vertical flux was ~100 mg POC m - 2 d -1 at 200 m depth. Vertical flux of Phaeo and POC had maxima in concert and Phaeo was always larger than Chl a vertical flux. Chl a vertical flux was low. The largest vertical flux was recorded in the upper water column in May and June (0.4-0.7 mg Chl a m -2 d - 1 at 20 m)and decreased rapidly with depth. The highest Chl a flux at depth was recorded during June and August (0.2-0.5 mg Chl a m -2 d -1 ). Flagellates dominated the vertical plankton flux throughout the investigation and contributed significantly to the vertical POC flux (5-30 %). Net plankton (>20 µm) and ciliates never contributed significantly to vertical POC flux. Biological processes were most important in regulating the vertical flux of biogenic matter which was regulated and controlled by the abundance of some key species of mesozooplankton. |
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