Phytoplankton biomass and temperature trends in offshore waters of the Basque country

Journal of Plankton Research, 2008

Climate Research, 2011

The Atlantic coast of Iberian Peninsula offers an excellent opportunity for a study of upwelling filaments and their importance in lateral exchanges of nutrient and biota. Simultaneous acquisition SeaWIFS (Sea Viewing Wide Field Sensor) and AVHRR (Advanced Very High Resolution Radiometer) NOAA imagery of the north-west of the Iberian Margin were obtained on August 1998. Satellite-derived chlorophyll-a from SeaWiFS data, which have been provided by the Remote Sensing Group at Plymouth Marine Laboratory and sea surface temperature (SST) from AVHRR data were compared in function to find a correlation between sea surface temperature and chlorophyll-a.

Biogeochemistry, 2011

Eutrophication is a major threat to coastal ecosystems. Within Europe, the Water Framework Directive (WFD) has established the need of developing methods of assessment. Bulk chlorophyll ''a'' is used worldwide as an indicator of eutrophication. However, the size structure of the phytoplankton communities has not been investigated, in detail, in relation to eutrophication pressures. This study investigates the suitability of fractionated chlorophyll ''a'' (\10 and [10 lm), as an indicator of eutrophication. Along the Basque coast (northern Spain) several water bodies, ranging from offshore waters to the heads of the estuaries, were surveyed during 2008. Physico-chemical conditions and chlorophyll ''a'' showed a distinct spatial gradient. Trophic richness increased towards the middle and inner parts of the estuaries, where nutrient inputs, from natural or anthropogenic sources, together with the residence time of the water are usually higher. In summer, phytoplankton biomass and abundance decreased, generally, in offshore and coastal waters; in estuaries, they tended to increase. The chlorophyll distribution within the two size fractions was coherent with the phytoplankton taxonomic composition. In summer, the relative abundance of small-sized cells (diatoms and non-siliceous taxa) increased. The relationships between size-fractionated chlorophyll and physicochemical variables differed, when comparing the offshore and coastal waters, with the estuaries. In the offshore and coastal waters, a strong seasonality was observed; in estuaries, an important spatial component was found. Fractionated chlorophyll provided complementary useful information on anthropogenic pressures. However, more research is necessary to utilise this variable as a tool for ecological status assessment, within the WFD.

Continental Shelf Research, 2001

Differences in phytoplankton assemblages were studied along a transect inshore-offshore in the Ria de A Coru * n na (NW Spain) and the adjacent continental shelf from April 1994 to April 1995. Samples were obtained monthly at three stations, two in the ria (one in the centre and the other in the inner harbour area), and one in the open shelf waters outside the ria. Observations were grouped into five main oceanographic stages, according to hydrography, dissolved nutrients and biological characteristics. Inshore differences between both stations of the ria were only quantitative. Phytoplankton biomass was much higher in the harbour area compared to biomass in the centre of the ria. These differences were due to accumulation processes, since nutrient concentrations, hydrography and phytoplankton composition were similar. Characteristics of oceanographic periods revealed some inshore-offshore differences. Spring bloom was very important inshore, while it was weak in the adjacent shelf. However, upwelling processes were persistent offshore, and seemed to be of less importance inshore. Nevertheless, if we take into account all information available for the shelf (since 1989 up to present), we can conclude that the spring bloom is a general characteristic of the shelf (except for 1994 when the spring bloom was very weak), with values of phytoplankton biomass in the range of that observed in the centre of the ria. However, the development of phytoplankton spring blooms in the shelf is related to the increase in surface irradiance, whilst in the ria it was mainly due to saline stratification. According to our results, the Ria de A Coru * n na can be considered as a bay with a large oceanic influence, except for the enclosed inner harbour zone where water turnover is very low, resulting in a retention of phytoplankton in the area. Finally, the study of microflagellate biomass can be a useful tool to discriminate between the shelf and the ria, being the contribution to phytoplankton of this component which is significantly higher in the former.

Journal of Marine Systems, 2002

The primary productivity of the NW Iberian margin has been determined by a combination of 14 C incorporation experiments on natural phytoplankton assemblages and satellite remote sensing with the ocean colour sensor, SeaWiFS. The approach to the field determination of phytoplankton production was Eulerian, involving measurements on a fixed grid of stations covering the region from 41j30VN to 43j00VN and 09j00VW to 10j30VW. Three different laboratories made primary production measurements over a 3-year period. Each group used variations of the 14 C method-in situ incubations and two modelling approaches based on P -E parameter derivation. An intercalibration experiment showed acceptable agreement between the three estimates. Measurements by the three groups on eight cruises have been merged to provide estimates of regional productivity. However, the temporal coverage of the data was too limited to provide robust seasonal estimates since few experiments were done in the autumn and winter months. A second approach to the estimation of primary production utilised surface pigment concentrations derived from satellite remote sensing. Two models were used. Firstly, an empirical relationship was found between depth-integrated primary production and surface chlorophyll concentration, which explained 78% of the variance in the production estimates. The second approach used a semi-analytical model which incorporates irradiance and temperature as well as chlorophyll-derived parameters. Both models have been applied to SeaWiFS-derived, surface chlorophyll concentrations to estimate primary production during 1998, 1999 and 2000 for three regions-the shelf, the slope and the open ocean of the region of study. Using the semi-analytical model, the mean primary production for the 3 years is estimated to be 319 g C m À 2 year À 1 for the shelf, 280 g C m À 2 year À 1 for the slope and 217 g C m À 2 year À 1 for the adjacent open ocean. Interannual variation in production on the shelf ranged from 334 g C m À 2 year À 1 in 1998 to 301 g C m À 2 year À 1 in 2000. It is estimated that upwelling increased primary production, relative to that in the open ocean, by f 50%. Satellite-derived estimates of the ratio of new production to primary production were 0.37, 0.28 and 0.40 for the shelf region during the upwelling seasons of 1998, 1999 and 2000. D

Observations of a winter upwelling event off Western Iberia shelf/slope in the area of influence of the Western Iberia Buoyant Plume (WIBP) were conducted in February 2000. Spatial patterns and time evolution of the chlorophyll-a (chl-a) biomass are analysed, based on in situ and satellite data. SeaWiFS-derived chl-a concentration L2 products were used to track the chlorophyll front and estimate its westward migration velocity (maximum up to 29 km day À1 ), as well as to characterize the frontal system and its evolution. A method associating the type of spectral signature of a pixel to the fraction of chlorophyll probed by SeaWiFS enabled the estimation of the chl-a biomass within error intervals. High chlorophyll concentrations (for wintertime) were observed over the shelf and slope, up to large distances to the coast. Due to the WIBP, a shallow Ekman layer developed, being nearly coincident with the stratified upper meters. The transport comprised westward advection and stretching of the plume, with little entrainment with the offshore deep mixed layer waters. The relative enlargement of the total area of the Inside-Front Zone (IFZ) during the upwelling event was roughly accompanied by the maintenance of the average biomass per unit of area, considering the water column up to depths of interest. This suggests that there was a net increase of chl-a biomass inside the water column associated with the IFZ, roughly proportional to the increase in the IFZ area. Retention of phytoplankton in the shallow stratified nutrient-rich waters of the WIBP was a key factor for this increase in chl-a biomass. D

2002

The building damage assessment is a very important task after a strong earthquake. For taking decisions about the building habitability and reparability it is necessary evaluate the building damage, but the expert professionals are insufficient, and therefore voluntary non-experts professionals must be including in the task. This personnel type displays the tendency to aggravate or to underestimate the real level of damage. This paper develops an expert system for post-earthquake evaluation of building damage, which supports the building damage evaluation by non-experts. It is based on the model considers the damage in structural and architectural elements as well as site seismic effects.

Astronomy Letters, 2011

This work is devoted to the numerical multidimensional computational modeling of a gaseous disk in an external potential of the spiral stellar density wave. We investigated the possibility of the polygonal structures formation (see works Chernin ([1], [2]), Chernin et al. ([5], [10])) in the spiral galaxies. Many factors were taken into account.Polygonal structures are essentially non-stationary patterns. The characteristic time of formation of straightened segments does not exceed the period of revolution of the periphery of the stellar disk. Polygonal structures arise in models with slow rotation of spiral arms, if corotation radius is at periphery of the disk. We also make a comparisons of polygonal structures in 2D and 3D models which have a good agreement.

Lubricants, 2015

On the basis of the V. K. Stokes micro-continuum theory, the effects of couple stresses on the nonlinear dynamic response of the unbalanced Jeffcott's flexible rotor supported by layered hydrodynamic journal bearings is presented in this paper. A nonlinear transient modified Reynolds' equation is derived and discretized by the finite element method to obtain the fluid-film pressure field as well as the film thickness by means of the implicit Euler method. The nonlinear orbits of the rotor center are determined by solving the nonlinear differential equations of motion with the explicit Euler's scheme taking into account the flexibility of rotor. According to the obtained results, the combined effects of couple stresses due to the presence of polymer additives in lubricant and the pressure dependent viscosity on the nonlinear dynamic response of the rotor-bearing system are significant and cannot be ignored or overlooked. As expected, these effects are more noticeable for polymers characterized by higher length molecular chains.