The PROWQM physical–biological model with benthic– pelagic coupling applied to the northern North Sea Jae-Young Lee a, * , Paul Tett a , Ken Jones b , Sarah Jones c , Patrick Luyten d , Claire Smith a , Karen Wild-Allen a,e a School of Life Sciences, Napier University, 10 Colinton Road, Edinburgh EH10 5DT, UK b Dunstaffnage Marine Laboratory, P.O. Box 3, Oban, Argyll PA34 4AD, UK c School of Ocean Sciences, University of Wales, Bangor LL59 5EY, UK d Management Unit of the Mathematical Models of the North Sea, Gulledelle 100 B-1200, Brussels, Belgium e Zoology Department, University of Aberdeen, Tillydrone Avenue, Aberdeen AB24 2TZ, UK Received 26 June 2001; accepted 22 February 2002 Abstract PROWQM, a 1-D depth resolving model which couples physical and microbiological processes in the water column with sedimentation/resuspension and benthic mineralisation processes, has been used to simulate seasonal changes of chlorophyll, nutrients and oxygen at the PROVESS north site (59j20VN1j00VE) in the North Sea. PROWQM is derived from the 3-D model COHERENS, and improves COHEREN’s benthic and pelagic biology. The physical sub-model of PROWQM implicitly solves turbulence closure equations forced by climatological, or realistic high-frequency, meteorological and tidal data. The pelagic biological sub-model 2MPPD includes a ‘diatomy’ microplankton (mp1) and a ‘flagellatey’ (or microbial loop) microplankton (mp2), the cycling of silicon and nitrogen, slow-sinking detritus, and fast-sinking phytodetritus. Phytodetritus is formed by shear-driven aggregation of particulate material, using a simple algorithm for bulk processes that is derived by considering the interactions of single cells. The microplankton compartments include heterotrophic bacteria and protozoa as well as phytoplankton, and most microplankton rates are specified with the aid of a ‘heterotroph fraction’ parameter, which was 0.125 for mp1 and 0.6 for mp2. The microbiological system is closed by mesozooplankton grazing pressures imposed as time varying series determined from observed zooplankton abundance. The benthic boundary sub-model includes a superficial fluff layer and a nutrient element reservoir in the consolidated sediment. Particulate material in the fluff layer can be resuspended (in response to bed stress by near-bed flows), mineralised or carried by bioturbation into the underlying, consolidated, sediment, where it is mineralised and its nutrients returned to the water-column at rates mainly dependent on (implicit) macrobenthic pumping. Benthic denitrification can occur when mineralisation rates exceed oxygen supply. Verification of the PROWQM numerical implementation used test cases and checks for nutrient element conservation. Simulations with realistic forcing, for a range of parameter values, were compared with historic observations in the NOWESP data set and during FLEX76, and with those made during the PROVESS cruises in autumn 1998. PROWQM provided a good simulation of the seasonal succession from a diatom-dominated spring bloom to summer dominance by small flagellates. The simulations included sedimentation of organic matter from the spring bloom, and qualitatively realistic behaviour of the fluff layer, but decay rates were too slow and there was almost no denitrification. The simulated surface mixed layer was too shallow 1385-1101/02/$ - see front matter D 2002 Elsevier Science B.V. All rights reserved. PII:S1385-1101(02)00182-X * Corresponding author. E-mail address: j.lee@napier.ac.uk (J.-Y. Lee). www.elsevier.com/locate/seares Journal of Sea Research 48 (2002) 287 – 331