O selo dun poeta. Beleza para sempre

Conferencias pronunciadas no Salón Nobre de Fonseca da Universidade de Santiago de Compostela o xoves 15 de maio de 2014 co gallo do Día das Letras Galega

Hydrography of shellfish harvesting areas in the western Cantabrian coast (Rías Altas, NW Iberian Peninsula)

11 pages, 5 figures, 1 tableIntertidal shellfish banks in estuarine areas are influenced by a wide variety of environmental conditions, including the physical and chemical characteristic of the water that floods the grounds. In this study we carry out a cross-comparison of the hydrographic characteristics and nutrient fertilization patterns of the waters that laps the shellfish grounds of a group of five drowned valleys collectively known as “Rías Altas”, located in the western Cantabrian coast (NW Iberian Peninsula). This region is affected by coastal upwelling from June to August resulting in a water exchange between the embayments and the shelf varying between 31.5 and 220.5 ms. The fresh water discharge followed a seasonal cycle too, with maxima in winter and minima in summer, and long-term average flow rates ranging from 5.9 ms to 22.2 m3 s. Significant differences were observed among the five embayments with regard to temperature and salinity and also with inorganic nutrients, chlorophyll a and particulate organic matter concentrations in the continental watersThis work is part of the project “Integral study of the embayments of Ribadeo, Foz, Viveiro, Barqueiro and Ortigueira: hydrography, dynamics, biogeochemistry, sedimentology, ecotoxicology, microbiology, pathology and biology of shellfish areas of interest”. It was funded by the Consellería do Mar through the Operational Program of the European Fisheries Fund (Order of 10 August 2007, Diario Oficial de Galicia No 169 of August 31, 2007, pp. 14583–14595)Peer reviewe

Comparison of biomass and size-spectra derived from OPC data and net samples. Application to the assessment of mesoplankton distribution in the NW and N Iberian shelf

Data from vertical net hauls and from a submersible optical plankton counter (OPC) were compared in terms of biomass and slope of the normalized biomassesize spectra (NBeSS), a proxy for the size structure of the community. The relationship between the estimates of biomass in the overlapping range sampled by both methods (0.2e2 mm equivalent spherical diameter (ESD)) was linear and not significantly different to 1 (BOPC : BNET ¼ 1:1G0:1, r2 ¼ 0:84). However, the relationship varied depending on the size fraction considered; the ratio BOPC:BNET was 0:10G0:04 (r2 ¼ 0:30), 0:8G0:2 (r2 ¼ 0:66), and 2:4G0:5 (r2 ¼ 0:64) for the size fractions 0.2e0.5, 0.5e1, and 1e2 mm ESD, respectively. The discrepancies between methods were presumably due to the combined effect of the limitations of the instrument in the lower detection limit and the errors in the volume of water sampled by the net for the smallest size fraction, and to net avoidance enhanced by clogging for the largest size fraction. The agreement between methods improved when the NBeSS of the different data sets were compared. The slope (b ¼ 1:1) and the intercept (a ¼ 14:6) of the NBeSS integrated across stations were not significantly different (Student’s t-test) for the linear model fitted to net samples, OPC data, or pooled data from both methods. Station by station, the slopes of the NBeSS from the net (bNET) and the OPC (bOPC) were not significantly different in 61% of the stations. This percentage increased to 78% when the comparison was limited to the mesoplankton size range. As an example of the applicability of the OPC, we showed the distribution of mesoplankton biomass and size structure along the NW and N Iberian Shelf during the winterespring transition of 2002 and its relationship with the hydrographic scenario.PELASSES (contract no. 90/10) SARDYN (QLRT-2001-00818