Ria Of Pontevedra Research Articles

The black-pygmy mussel Limnoperna securis in Galician Rias (north-eastern Atlantic): new records and first evidence of larval stages predation by copepods

The presence of the non-indigenous species, the black-pygmy mussel Limnoperna securis , was surveyed for the first time in the Rias of Pontevedra and Arousa, areas adjacent to the first location (Ria of Vigo) of this potential invader in Atlantic waters. Molecular identification of the mussels was conducted by polymerase chain reaction amplification and sequencing of nuclear and mitochondrial genes. This paper describes for the first time the species in the Ria of Pontevedra, confirming that this invader was absent in an intense shellfish farming area of the Ria of Arousa (Galicia, north-western Spain). Field sampling revealed that relatively high concentrations of this mytilid bivalve have colonized some localities of the inner part of the Ria of Pontevedra located in brackish waters. A comparison between population densities, size and substrate preference of L. securis in the Rias of Pontevedra and Vigo was conducted. Dispersion capacity of L. securis is discussed based on molecular detection of larval stages in the stomach contents of the copepod Centropages typicus coupled with physical oceanography of the southern Galician Rias. The invasive role of L. securis is also discussed in the context of the bissus secretion and attachment strength, ecological tolerance of the species, and the recent finding of settlements of this species on numerous colonies of the economically important blue mussel Mytilus galloprovincialis .

Characterization of fall–winter upwelling recurrence along the Galician western coast (NW Spain) from 2000 to 2005: Dependence on atmospheric forcing

Upwelling events driving ENACW (Eastern North Atlantic Coastal Water) into the Galician western coast rias had been considered typical spring–summer processes, according to the research developed in this area. However, they can also be observed in fall or winter under northerly winds blowing at shelf. Six different upwelling events were analyzed in the Ria of Pontevedra during the wet season (NDJF) from 2000 to 2005. These events were characterized by means of the zonal Ekman transport ( Q x ) at four control points in front of the western rias (locally known as Rias Baixas) and thermohaline variables measured at a fixed station in the main mouth of the Ria of Pontevedra. The duration of the upwelling events ranged from 27 days (during February and March 2002) to 69 days (during November–December 2004 and January 2005). Upwelling events studied in the Ria of Pontevedra from 2000 to 2005 showed the similarity in upwelling features during both seasons (similar wind forcing and upwelled water). Finally, Q x was correlated with the most representative atmospheric patterns in the Northern Hemisphere (EA, NAO, EA/WR, POL and SCA) from 1966 to 2005. The winter EA pattern has the most influence on Q x showing an annual evolution with a prevalence of the positive phase from 1976 on. This positive phase is directly correlated with a prevalence of positive values of Q x which are upwelling unfavorable in the Rias Baixas.

Miño River dams discharge on neighbor Galician Rias Baixas (NW Iberian Peninsula): Hydrological, chemical and biological changes in water column

An unusual intrusion of low-salinity water coming from the Miño River (40 km south of the Ria of Pontevedra) was observed in the Ria of Pontevedra (NW Spain) on 12–13 May, 1998. The abnormally high discharge was due to the sudden release of water from the dams that control the Miño River run-off. This release results in a strong cross-axis salinity gradient: salinity decreases seawards, giving rise to a two-layered circulation pattern, with water near the riverbed moving seawards and water near the surface moving landwards. In addition, a clear gradient of chemical and biological variables was observed in the ria, with decreasing values being evident towards the middle zone. The nutrient salts, the oxygen, the chlorophyll and the phytoplankton patterns suggest the existence of a bloom that penetrates the ria, embedded in a water mass that is fresher than the estuarine one. The high concentration of the phytoplankton Skeletonema costatum was observed as late as May, which also supports the idea that this bloom exhibits the features of a typical early spring bloom in the Rias Baixas and that this is linked to haline stratification that is caused by an important supply of continental water.

Negative estuarine circulation in the Ria of Pontevedra (NW Spain)

An along estuary negative circulation was measured in the Ria of Pontevedra (NW Spain) on May 13, 1998. This two-layered circulation pattern, with near bed water moving seaward and near surface water landward, was generated by the existence of two different water masses at intermediate depths. Water in the inner part of the estuary was a mixture of estuarine water and Eastern North Atlantic Central Water (ENACW), which had entered the estuary some days before due to an intense upwelling event. Water in the middle part of the estuary was a mixture of estuarine water and fresh water coming from the river discharge, which had been higher during the days previous to May 13. This water mass distribution gave rise to the existence of denser water in the inner part of the estuary than in the middle one, generating the observed negative circulation pattern.

Dependence of the water residence time in Ria of Pontevedra (NW Spain) on the seawater inflow and the river discharge

The dependence of the residence time on the seawater inflow and the river discharge was analyzed by means of a stationary box model in the Ria of Pontevedra. The Ria, which is a partially stratified estuary, is divided into three boxes containing 11 CTD measuring points. The mean residence time calculated during the period October 1997 to October 1998 varies from around 3 days at the inner box to around 8 days at the external one. The residence time is shown to depend simultaneously on the river discharge and on the seawater inflow, which is characterized in terms of the upwelling index. This dependence on the upwelling index is observed to decrease upstream.

Assessment of coastal marine pollution in Galicia (NW Iberian Peninsula); metal concentrations in seawater, sediments and mussels (Mytilus galloprovincialis) versus embryo-larval bioassays using Paracentrotus lividus and Ciona intestinalis.

Sediments from three Galician Rias were tested for toxicity using sea-urchin and ascidian sediment elutriate embryo-larval bioassays. Trace metal contents in seawater, sediments and mussels were also determined and subjected to multidimensional scaling methods which grouped stations according to chemical contamination. High metal contents were found in seawater, sediments and mussels from the Ria of Pontevedra, and moderate levels were detected in the Ria of Vigo and Ria of Arousa. The results revealed that samples assessed as toxic, according to the sea-urchin and ascidian embryo-larval bioassays, were among the most polluted by trace metals. A good agreement was reported between ordination plots resulting from applying multidimensional scaling to the chemical data, and the results of the biological endpoints tested.

Integrative assessment of marine pollution in Galician estuaries using sediment chemistry, mussel bioaccumulation, and embryo-larval toxicity bioassays

An integrative assessment of environmental quality was carried out in selected sites along the Galician coast (NW Iberian Peninsula) combining analytical chemistry of seawater and sediments, bioaccumulation in the marine mussel, and embryo-larval sediment toxicity bioassays, in order to link biological and chemical criteria for the assessment of coastal pollution. Maximum values of Hg and Cu in seawater, sediment and mussels, were found in the inner part of Ria of Pontevedra, while maximum levels of organics (polychlorinated biphenyls, hexachlorobenzene and aldrin) were found in mussels from A Coruña. Outstanding values of Cu, Pb and Zn have been found in seawater and sediment from a single site, P3, which also was the most toxic in the embryo-larval bioassays performed with four different phyla of marine organisms: mollusks, echinoderms, arthropods and chordates. Sediment quality effects range-median values provided a valuable reference to predict biological effects from sediment chemistry data, while effects range-low values were too conservative. Sediment toxicity could also be predicted by using a toxic-unit model based on published EC 50 values for trace metals and mobilization factors independently obtained from measurements of metal contents in sediments and their elutriates. When chemical and toxicological data are independently used to arrange sampling sites by using non-metric multidimensional scaling, a remarkable degree of concordance between both types of configurations could be observed.

Hydrographic characterization of a winter-upwelling event in the Ria of Pontevedra (NW Spain)

An unusual winter-upwelling event was observed in the Ria of Pontevedra during a cruise carried out on 27 January 1998. Upwelled water masses inside the estuary are observed to depend on the season due to the annual variation of water circulation at the adjacent shelf. The winter upwelled water corresponds to the water mass transported by the poleward current, which is saltier and warmer, but less dense than the Eastern North Atlantic Central Water observed in spring and summer.

Wind and Tidal Influence on Water Circulation in a Galician Ria (NW Spain)

The wind effect on water circulation was described by means of hydrodynamical and thermohaline measurements carried out in the ria of Pontevedra (NW Spain) from February to July 1998. The samples were measured both at an anchored station situated in the inner part of the ria and at other stations located in the main channel. In this way, temporal and spatial events were related. Thermohaline variables (salinity and temperature) were used to clarify the current patterns measured at the anchored station. It has been observed that there is a clear predominance of wind in the main estuary axis direction. The wind direction is strongly dependent on topography. Wind speeds higher than 4ms−1are able to dominate the current at surface layers, even against tidal effect. Easterly winds force water to leave the estuary at surface layers while westerly winds force water to enter it. Diurnal breezes associated with westerly winds were rarely recorded. Bottom layers were controlled by tide, except during an upwelling event.

Green mass aggregations of Gyrodinium cf. aureolum Hulburt in the Ria of Pontevedra (north-west Spain)

Green mass aggregations of <i>Gyrodinium</i> cf. <i>aureolum</i> Hulburt in the Ria of Pontevedra (north-west Spain)

Relationship between carbon, nitrogen and chlorophyll a in the Ria of Pontevedra, NW Spain : Figueiras, F.G. and F.X. Niell, 1987. Investigación pesq., Barcelona, 51(1):3–21. (In Spanish, English abstract.) Inst. de Investigaciones Mar., Muelle de Bouzas, s/n 36208 Vigo, Pontevedra, Spain

Relationship between carbon, nitrogen and chlorophyll a in the Ria of Pontevedra, NW Spain : Figueiras, F.G. and F.X. Niell, 1987. Investigación pesq., Barcelona, 51(1):3–21. (In Spanish, English abstract.) Inst. de Investigaciones Mar., Muelle de Bouzas, s/n 36208 Vigo, Pontevedra, Spain