OMEX II-II 1997-2000 : Project Description

Work Package I

Temporal Evolution of Surface Production and Fate of Organic Matter

Work Package I (WP I) aims primarily to quantify the temporal evolution of surface production and fate of organic matter in the most prominent upwelling area on the European shelf, i.e., the margin off the north-west coast of Portugal and Spain.

The short-term (3-5 days) evolution and coupling of physical, biological and biogeochemical processes that control the surface production and fate of organic matter are investigated in the shallow shelf waters (< 200m) and in the upper water column at the shelf edge, mainly during two selected seasons which are representative of the seasonal dynamics of production, retention and sedimentation: the upwelling season (spring/summer) and the downwelling season (autumn/winter). Logistically, this is achieved through repeated tracking of biological and biogeochemical rates for the plankton within physically well-characterised frameworks and vertical regimes (e.g., moving filament, advecting slope current), using a ship-drifting strategy during which the flows of carbon and nitrogen are evaluated through all components of the food web. This approach yields a full set of synchronous rate parameters describing primary production, zooplankton grazing and defecation, bacterial growth and respiration and vertical fallout of biogenic carbon and nitrogen in the upper water column.

Close co-operation with WP II and WP III will ensure that the knowledge gathered by WP I leads to a maximisation of our general understanding of the entire Iberian Margin ecosystem. The understanding and quantification of biogenic matter pools and fluxes on the shelf and between the shelf-edge and the slope at tidal, seasonal and annual time-scales, to be achieved via modelling, are the ultimate goals of WP I.


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