Atlantic Multidecadal Oscillation (AMO) and sea surface temperature in the Bay of Biscay and adjacent regions

Abstract

Little information is available on the maternal -embryonic relationships among sharks. Birdbeak dogfish (Deania calcea) has been described as ovoviviparous, but this term comprises a wide range of forms on how the embryos are nourished including lecithotrophy and matrotrophy. To evaluate the maternal -embryonic relationship in birdbeak dogfish we have analysed chemical features (fatty acid composition and mercury (Hg) levels) and biological characteristics (egg and embryo dry weight variation, uterus characterization). Monounsaturated fatty acids were the dominant fatty acids in eggs while polyunsaturated fatty acids (PUFA) were the dominant fatty acids in both pregnant females and embryos. Significant differences were found among eggs, embryos and pregnant females for all fatty acids groups with the exception of saturated fatty acids for embryos and pregnant females. The principal components analysis revealed that embryos are particularly related to n-6 PUFA and pregnant females with n-3 PUFA. A close relationship exists between the Hg level of pregnant females and the Hg level of their embryos which indicates that there is a transfer of mercury from maternal sources. The comparison of the mean dry weight between eggs and embryos showed a gain of 3.8% obtained in the embryos. Histological sections of the uteri of pregnant females showed a high level of both superficial and inner vascularization in the uterine villi as well as the presence of secretor cells. Until now, the importance of this species maternal contribution and interference for the embryos development has never been documented. However, the biological and chemical results observed in the present work show that there is a matrotrophic strategy for the birdbeak dogfish.

Seasonal and inter-annual variability in nutrient supply in relation to mixing in the Bay of Biscay

“…A very negative North Atlantic Oscillation index will cool sea surface temperatures from the Azores region to the Bay of Biscay (Pingree, 2005;Garcia-Soto & Pingree, 2012) These positive winter NAO years are associated with shallow winter MLDs, lower seasonal amplitudes of nitrate and winter nutrient concentrations with correspondingly reduced spring time productivity as shown in the dataset (see also Jiang et al, 2013).…”

“…Behrenfeld et al (2006) suggested a general trend has occurred of decreased convective mixing, increased stratification and consequent decrease in production in the Northeast Atlantic from 1999 onwards and predicts a decrease in productivity in a warming ocean. There has been a progressive warming of surface waters in the Bay of Biscay over the last 30 years (Garcia-Soto et al 2002, Somavilla et al, 2011Holt et al 2012;Taboada & Anadon, 2012, Garcia-Soto & Pingree, 2012. Winter mixing was studied extensively in Pingree & New (1989).…”

Seasonality and interannual variability of the European Slope Current from 20years of altimeter data compared with in situ measurements

“…This may link to the stronger slope current anomaly between 1995 and 1997 on most of the shelves. The winter situation for NW Spain with respect to NAO and associated wind stress pattern is illustrated and explained in detail by Garcia-Soto and Pingree (2011). The local wind stress forcing component for the European SC is driven more effectively with a low or negative sea level pressure anomaly against the ocean margin (not in the central ocean) so we do not expect the slope current changes to have its maximum response with respect to NAO changes.…”

Surface circulation and Lagrangian transport in the SE Bay of Biscay from HF radar data

“…Over the slope, the Iberian Poleward current flows towards the east and north of the Spanish and French coasts with relatively weak mean currents (~ 0.2 m.s -1 ). This current presents a marked seasonality, with stronger currents in winter that are frequently associated to positive SST anomalies over the northern Spanish slope [4,5,6,7,8,9,10]. Moreover, significant mesoscale variability has been observed along the slope, where the interaction of the current and the bathymetry gives rise to mesoscale eddies, commonly known as SWODDIES -Slope Water Eddies [5,7,11,12].…”