Aquatic Sciences Meeting, Albuquerque 2001

SS12 To Sink or Not to Sink: The Role of Zooplankton for Export and Retention of Fecal Pellets and Aggregates (Environmental Connections)

Date: Friday, February 16, 2001, Time: 9:15:00 AM

Location: Aztec

Svensen, C, , Norwegian College of Fishery Science, Tromsø, Norway, camillas@nfh.uit.no

Nejstgaard, J, C, University of Bergen, Bergen, Norway, jens.nejstgaard@ifm.uib.no

SEDIMENTATION OF COPEPOD FAECAL PELLETS DETERMINED BY CALANOID-CYCLOPOID INTERACTIONS? EVIDENCE FROM ENCLOSED ECOSYSTEMS

Vertical flux of faecal pellets was compared in 31 vertically stratified 27 cubic meter in situ seawater enclosures on the Norwegian west coast. Sediment traps were mounted in the non-mixed lower layer. All mesocoms contained pellet producing calanoid copepods, while 8 mesocosms were dominated by small pellet reworking cyclopoid copepods, Oithona spp. In the 23 mesocosms dominated by calanoids sedimentation of pellets was at least as high as was expected from maximum ingestion rates based on available food concentrations. However, in the 8 mesocosms where calanoids were strongly out-numbered by Oithona total vertical pellets flux was insignificant, and only fractions of what was expected from minimum carbon requirements needed to sustain respiration rates of calanoids. Further, the contribution of faecal pellet carbon to particulate organic carbon was 15 percent at most in experiments where calanoids dominated, while the contribution was generally less than 0.5 percent where Oithona prevailed. In accordance with previous investigations we conclude that Oithona has a strong regulating effect on the export of carbon from the euphotic zone in the sea.

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Aquatic Sciences Meeting, Albuquerque 2001

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