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Net ecosystem metabolism of a coastal embayment fertilised by upwelling and continental runoff |
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| Authors: | D Villegas-Ríos XA Álvarez-Salgado G Rosón |
| Institution: | a CSIC, Instituto de Investigacións Mariñas, Eduardo Cabello 6, 36208 Vigo, Spain b Universidade de Vigo, Facultade de Ciencias do Mar, Campus Lagoas-Marcosende, 36200 Vigo, Spain c Bodega Marine Laboratory, University of California, Davis, Bodega, CA, USA |
| Abstract: | O2, N, P and Si net ecosystem metabolism of the Ría de Ares-Betanzos (NW Iberian upwelling system) was estimated during two 3-wk periods of contrasting summer downwelling and autumn upwelling conditions by means of a transient 2-D kinematic box model. The subtidal circulation was positive in both situations, although it was depressed during downwelling and enhanced during upwelling. Concurrently, the ría was fertilised mainly by shelf bottom waters, which introduced from 69% (under downwelling) to almost 100% (under upwelling) of the limiting N nutrients. The ría was an efficient nutrient trap: about 70% of the N nutrients that entered the embayment were retained under downwelling conditions (average flushing time, 9 days) and about 50% under upwelling conditions (average flushing time 3 days). Although the trapping efficiency was lower, the net ecosystem production (NEP) was much higher under upwelling (from 1.0±0.3 to 1.5±0.4 g C m−2 d−1), than under downwelling favourable winds (from 0.2±0.1 to 0.3±0.1 g C m−2). The stoichiometry of NEP suggests that P and N compounds recycled faster than C compounds, specially in the inner segment of the ría. The net degree of silification was twice in the inner than in the outer segment of the ría. |
| Keywords: | Nutrient salts Net ecosystem production Upwelling Downwelling Continental runoff Rí a |
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