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Vilagarcía de Arousa, Spain

Ospina-Alvarez N.,CSIC - Institute of Marine Research | Prego R.,CSIC - Institute of Marine Research | Alvarez I.,University of Vigo | deCastro M.,University of Vigo | And 7 more authors.
Continental Shelf Research | Year: 2010

Summer upwelling and downwelling processes were characterized in the Northern Galician Rias during July and August 2008 by means of sampling carried out onboard R/V Mytilus (CSIC) and R/V Lura (IEO). Thermohaline variables, dissolved oxygen, nutrients, chlorophyll, phytoplankton, ciliates and zooplankton abundances were measured at sections located in the Rias of Viveiro, Barqueiro and Ortigueira and their adjacent shelves. Ekman transport was calculated from QuikSCAT satellite, upwelling intensity estimated with upwelling index from the average daily geostrophic winds, and SST maps obtained from NASA GHRSST satellite. Ekman transport and SST behaviour showed two different patterns: (i) offshore and upwelling favourable conditions on 13-22nd of July; (ii) onshore and downwelling favourable conditions from 23rd July to 19th August. During upwelling, TS diagram showed an intrusion of Eastern North Atlantic Central Water affecting the continental shelf but not the rias. Nutrient salt concentrations increased with depth, reaching their maximum values near the mouth of Ortigueira Ria. During downwelling, coastal water increased its temperature (18.5-19.8°C) and was retained inside rias; nutrients were nearly depleted, except for the innermost ria (estuarine zone) due to fluvial nutrient inputs. In this inner area, the maximum of chlorophyll-a (Barqueiro Ria) was observed. Low phytoplankton abundances were measured in both cases, even though a short increase in the plankton biomass was observed inside rias during upwelling, while under downwelling a small red tide of Lingulodinium polyedrum was detected. During the upwelling period Northern Rias tend to be mesotrophic systems as revealed by nutrient concentrations, chlorophyll levels and plankton abundances. On the contrary, in similar situations, the Western Rias behaves as eutrophics.In the Northern Galician shelf, the average of upwelling (downwelling) was 1.9±0.8 (2.1±1.0)eventsyr-1 from May to September (1990-2008) considering at least one week with favourable wind conditions and UI averages out of the range of ±500m3s-1km-1. © 2010 Elsevier Ltd.

Ospina-Alvarez N.,CSIC - Institute of Marine Research | Ospina-Alvarez N.,University of Warsaw | Varela M.,Spanish Institute of Oceanography | Doval M.D.,INTECMAR Xunta de Galicia | And 4 more authors.
Estuarine, Coastal and Shelf Science | Year: 2014

The Atlantic Galician rias show the effect of natural eutrophication during ENACW upwelling episodes when large amounts of nutrients are injected. However, the Cantabrian Galician rias do not appear to be disturbed by upwelling events and it can be hypothesized that eutrophy is not inherent to the Galician rias. This question was tackled regarding the biogeochemical and phytoplankton characteristic in the Ria of Barqueiro, located on the western boundary of the Cantabrian Sea, from January 2008 to January 2009. Thermohaline, PAR and fluorescence profiles, dissolved oxygen, nutrient salts, DOC, DON and chlorophyll concentrations, phytoplankton abundances and primary production were monthly determined in a monitoring station (43°45.509'N-07°39.493'W); moreover, the daily upwelling index information and fluvial contributions from Sor River were considered. Throughout the year only four annual oceanographic periods were observed: spring, summer stratification, autumn and winter, unlike the Atlantic rias, where a long upwelling period occurs with usually outstanding upwelling processes. Nutrient concentrations (a maximum of 6.2μM of nitrate, 0.5μM of nitrite, 2.8μM of ammonium, 0.4μM of phosphate and 5.7μM of silicate), organic matter (98μM of DOC, 14μM of DON, 16.4μM of POC and 2.0μM of PON), Chl-a (1.1μgL-1), primary production (280gCm-2yr-1) and phytoplankton abundance were clearly lower (about half) when compared to those reported for the other rias during upwelling. Diatoms dominated the phytoplankton assemblages especially during spring and autumn blooms. In summer, although the wind conditions were favorable, upwelling was not observed in the Ria and a mixing of diatoms and dinoflagellates co-dominated the phytoplankton community with a lower contribution of diatoms in comparison to the Atlantic rias. The paradigm of natural eutrophication reported for the Galician rias was not observed in the Ria of Barqueiro, which may be classified as an oligo-mesotrophic ria-type, according to its environmental patterns. © 2013 Elsevier Ltd.

Alvarez-Vazquez M.A.,CSIC - Institute of Marine Research | Prego R.,CSIC - Institute of Marine Research | Ospina-Alvarez N.,CSIC - Institute of Marine Research | Ospina-Alvarez N.,University of Warsaw | And 6 more authors.
Estuarine, Coastal and Shelf Science | Year: 2015

The modification of chemical inputs into estuaries/rias by wastewater discharges is poorly documented. Concentrations and fluxes of nutrient salts, organic matter and trace metals in rivers and wastewaters to the mesotrophic Rias of Ortigueira (38km2) and Viveiro (27km2), located on the western Cantabrian coast (Bay of Biscay), were evaluated to assess changes in the land-sea fluxes. Water was sampled monthly during a year in the Mera (6.0m3s-1) and Landro (9.4m3s-1) rivers flowing into the Rias of Ortigueira and Viveiro, respectively. The urban effluents of Ortigueira (1800 inhabitants; treated sewage) and the Viveiro (7100 inhabitants; municipal treated sewage and untreated industrial wastewaters) were also monitored. Concentrations of chemical compounds and their fluxes were quite similar and close to pristine conditions in both rivers. Nitrate (98% of DIN), the limiting nutrient of ria primary production, was controlled by river flow while phosphate by wastewater discharge. Sewage discharges should not disturb the Ria of Ortigueira. Wastewaters fluxes of phosphate, POC, PON, dissolved Cu and particulate Cd, Cu and Zn into the Ria of Viveiro exceeded those of the Landro River, mainly during summer. Also, untreated wastewater effluents from fish food processing in such small fishing ports can be a source of contamination. The Rias of Ortigueira and Vivieiro are a reference point to evaluate fluvial pristine conditions and wastewater discharges on small estuary-ria receptor systems. © 2015 Elsevier Ltd.

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