Short-term variability of primary production and inorganic nitrogen uptake related to the environmental conditions in a shallow coastal area (Gulf of Trieste, N Adriatic Sea)

Primary production (PP) and, nitrate (QNO(3)) and ammonium (QNH(4)) uptakes were measured together with other environmental parameters from October 1999 to February 2001 in the Gulf of Trieste (N Adriatic Sea). Their trends showed a high variability because of the combined effects of meteorological conditions, water circulation and river discharges. PP ranged from 0.2 to 1.5.9 mumol C dm(-3) d(-1), whereas QNO(3) varied from 0.8 to 442 nmol N dm(-3) d(-1), showing a trend similar to that of carbon basically ascribable to the autotrophic activity. QNH(4) ranged from 20 to 1308 nmol N dm-3 d-' and it reached the highest values during the declining phases of phytoplankton blooms, indicating that bacterial community can also be involved in its uptake. Regenerated PP generally prevailed over the new production (depth-integrated f-ratios from 0.05 to 0.50). C/N uptake ratios by planktonic community (annual average of 16 +/- 11) showed the repetitive carbon overconsumption (23-33) during periods of high production, and lower values (2-13) during: the post-bloom phases and in the months of scarce autotrophic activity. Residence time of freshwater in the area (1 d in November and January, up to 23 d in July) indicated the fast export of low salinity waters in winter and their longer permanence in summer. These values were closer to the ammonium turnover times (1-34 d) than to the nitrate ones (2-831 d). Riverine nitrate load (3-67 t N d-') generally exceed the biological demand of this nutrient (uptakes from 0.2 to 8 t N d-'), whereas the ammonium load (0.1-33 t N d(-1)) was almost always insufficient (uptakes, from 2.6 to 33 t N d(-1)). These results evidenced the major role of physical transport and recycling processes to regulate, respectively, nitrate and ammonium availability in this shallow ecosystem.La production primaire et l’assimilation de nitrates et d’ammonium ont été mesurées en même temps que les facteurs du milieu entre octobre 1999 et février 2001 dans le golfe de Trieste. La variabilité est élevée en raison de l’action combinée des conditions météorologiques, de la circulation et des apports des rivières. La production primaire varie entre 0,2 et 15,9 μmol C dm–3 j–1 alors que l’assimilation de nitrates va de 0,8 à 442 nmol N dm–3 j–1, montrant une tendance identique au carbone lié à la production autotrophe. L’assimilation d’ammonium varie entre 20 et 1308 nmol N dm–3 j–1 et elle atteint ses valeurs maximales durant le déclin de la floraison planctonique, indiquant que la communauté bactérienne est impliquée dans cette assimilation. La production primaire régénérée surpasse la production nouvelle (le facteur f intégré en fonction de la profondeur varie entre 0,05 et 0,5). Les taux C/N d’assimilation de la communauté planctonique (moyenne annuelle de 16 ± 11) soulignent la surconsommation répétitive de carbone (23–33) durant les phases de production actives ; les valeurs minimales (2–13) caractérisent les phases postérieures à la floraison et les mois de faible activité autotrophe. Le temps de résidence d’eau douce dans la zone (d’un jour en novembre et janvier à 23 jours en juillet) indiquent l’exportation rapide d’eau de basse salinité en hiver et leur permanence en été. Ces valeurs sont plus proches des temps de renouvellement de l’ammonium (1 à 34 jours) que des nitrates (2 à 831 jours). L’apport de nitrates par les fleuves (3–67 t N j–1) surpasse les besoins (0,2 à 8 t N j–) alors que l’apport d’ammonium (0,1–3,3 t N j–1) est presque toujours insuffisant (assimilation de 2,6 à 33 t N j–). Ces résultats mettent en lumière le rôle majeur du transport et du recyclage dans la régulation de la disponibilité en nitrate et ammonium dans des écosystèmes de faible profondeur

Minimizing Warehouse Space with a Dedicated Storage Policy

Given the increasingly significant impact of an efficient product-location strategy on warehouses' performance from a service level and operational costs perspective, this paper presents a possible operations research-oriented solution to provide a tangible reduction of the overall required warehousing space, thereby translating the storage location assignment problem (SLAP) into a vertex colouring problem (VCP). Developing the topic of their previous work on the development of an effective multi-product slot-code optimization heuristic, the authors focused on finding a cost-effective way to solve the SLAP through a mathematical-optimization approach. The formulation validation on a real industrial case showed its high optimization potential, and benchmarking simulations displayed performances significantly close to the best theoretical case. Indeed, the optimized value results were definitively close to the SLAP lower bound calculated assuming a randomized storage policy which, distinct from the developed solution, must inevitably be supported by warehouse management system software. On the contrary, the proposed methodology relies upon a dedicated storage policy, which is easily implementable by companies of all sizes without the need for investing in expensive IT tools