Nutrient fluxes to the Bay of Biscay from Cantabrian rivers (Spain)

Abstract

Nutrient fluxes to the Bay of Biscay from the Cantabrian basin have been quantified for the first time. Data between 1981 and 1995 of the main 16 Cantabrian rivers from the COCA monitoring programme have been used. Values of water flow and dissolved inorganic nitrogen (DIN), phosphate and silicate concentrations have been taken. Equations are proposed to quantify the fluvial nutrient contributions to the Cantabrian Sea. The annual average of continental outputs to the Bay of Biscay from the Cantabrian basin is 16.1 x 109m30f freshwater, 1.0 x IO9 mol of N in DIN, 0.062 x lo9 mol of phosphate and 1.2 x lo9 mol of silicate. In comparison with the French rivers, those of the Cantabrian have small fluxes and their outflow is very disperse, not forming large coastal plumes. From April to September, when the primary production is relatively important, the DIN contribution to the Cantabrian coastal reservoir is 10 %. Coastal fertilisation due to continental waters could be considered as negligible and only influences areas very close to river mouths, except for the Naldn River. Its flux represents 33 % of nitrate, 39 % of phosphate and 15 % of silicate of the total continental inputs of nutrients to the Cantabrian Sea. 0 Elsevier, Paris nitrate I phosphate I silicate I river I Cantabrian coast RCsumC-Flux de inutriments du bassin versant Cantabrique au golfe de Gascogne. Les flux de nutriments du bassin Cantabrique au golfe de Gascogne sont quantifies pour la premiere fois. Collectees entre 1981 et 1995 dans le cadre du programme de surveillance COCA, les donnees utilisees sont les debits des seize principaux fleuves et leurs concentrations en azote inorganique dissous (DIN), en phosphate et en silicate. Des equations sont proposees pour quantifier les flux de nutriments. En moyennes annuelles, les apports continentaux sont estimes a 16,l x lo9 m3 d'eau deuce, 1,0 x lo9 mol d'azote inorganique: dissous, 0,062 x lo9 mol de phosphate et 1,2 x lo9 mol de silicate. Comparee B celle des fleuves francais, la contribution des fleuves espagnols est faible et tres dispersee, saris grands panaches &tiers. Entre avril et septembre, par forte prloduction primaire, l'apport d'azote inorganique dissous au reservoir &tier Cantabrique est de 10 % du total. La fertilisation cot&e par les eaux continentales est negligeable en dehors des embouchures de fleuves, sauf pour le Nalon ; celui-ci apporte a la mer Cantabrique 33 % du nitrate, 39 % du phosphate et 15 % du silicate.

Assessment of spatial environmental quality status in Ria de Aveiro (Portugal)

“…At the system level, the estimations for the total river inputs into Ria de Aveiro, 11.3 mol s -1 N in DIN, 0.117 mol s -1 P and 7.20 mol s -1 Si, were lower than the inputs from Cantabrian rivers into the Bay of Biscay reported by Prego and Vergara (1998). However, the specific loads (mmol m -2 of drainage basin d -1 ) of the rivers draining into the Ria de Aveiro were much higher than the specific loads into the drainage basin of the river Oitabén-Verdugo reported by Gago et al (2005), which were considered high compared with other unpolluted rivers.…”

“…The nutrient levels recorded in the Oitabén-Verdugo estuary are one order of magnitude lower than those recorded in the polluted rivers draining into the adjacent Cantabrian sea, with comparable drainage basins and river flows (Gago et al, 2005). However, the nutrient levels in the Ria de Aveiro are of the same order of magnitude as those in the polluted rivers draining into the adjacent Cantabrian sea (Prego and Vergara, 1998).…”

Continental inputs of C, N, P and Si species to the Ría de Vigo (NW Spain)

“…Inorganic N and P in the River Oitabén-Verdugo, comparable with the average values proposed by Meybeck (1982) for unpolluted rivers, contrasted with the one-order-ofmagnitude higher concentrations recorded in the polluted 23 rivers draining into the adjacent Cantabrian sea, with comparable drainage basins (average, 800 km 2 ) and river flow regimes (average, 28 l s -1 km -2 ): nitrate, 120±175 µmol N l -1 ; nitrite, 4.7±6.5, µmol N l -1 ; ammonium, 15±27 µmol N l -1 ; and phosphate, 13±19 µmol P l -1 (Prego and Vergara, 1998).…”

Continental and marine sources of organic matter and nitrogen for rías of northern Galicia (Spain)

“…Extrapolation of nutrient measurements in partially mixed, estuarine waters of these rías to zero salinity (as a proxy for nutrient load in river waters) led to the conclusion of an increase in excess N from Ortigueira to Viveiro in a previous study (Xunta de Galicia 2009). The excess nutrients were attributed to increasing agricultural and urbanization pressures, but actual concentration values were typical of uncontaminated rivers in this region (Prego & Vergara 1998, Gago et al 2005). In the present study, ammonium and nitrite concentrations in rivers were quite low (0.2 µM nitrite and up to 4 µM ammonium) compared to values measured in rivers and estuaries with strong anthropogenic pressure (Paerl et al 2006, Castro et al 2007.…”