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Northwest Iberian coast Associated Investigators: Related Web Sites: Related Time Series: The A Coruña section is part of the time-series programme RADIALES (Instituto Español de Oceanografiía). Station 2 of the A Coruña section, which was used for this summary, is located off the northwest Iberian coast at 43 25.3'N 8 26.2'W. Zooplankton samples were collected from 65 m to the surface (oblique hauls) on a monthly basis with a Juday-Bogorov net (0.5 m diameter, 200 µm mesh). Samples were preserved in 4% formalin in sodium borate-buffered seawater and then examined in the laboratory for identification and counting of mesozooplankton by the rarefaction method (Omori and Ikeda, 1984). Biomass was calculated as dry weight (Lovegrove, 1962) of samples filtered upon arrival at the laboratory. In the coastal region off Galicia (northwest Spain), the classical pattern of seasonal stratification of the water column in temperate regions is masked by upwelling events from May to September. These upwelling events provide zooplankton populations with favourable conditions for development in summer, which is the opposite of what occurs in other temperate seas in this season of the year. Nevertheless, upwelling is highly variable in intensity and frequency, demonstrating substantial year-to-year variability. The seasonal cycle of zooplankton biomass is characterized by increased values from April to September, with a slight reduction in biomass from June to August resulting in a relatively bimodal seasonal cycle. Both biomass and abundance demonstrate an overall increasing trend, although a decrease in biomass was observed in 2000-2002. Surprisingly, this decrease was not paralleled by a decrease in abundance, suggesting an increased prevalence of small organisms during this period. The abundance and relative fractions of the top ten taxa at A Coruña are shown in Table 14. A comparison of the average composition for 2006 with that of previous years (1994-2005) shows that the relative species compositions both increased (e.g. Paracalanus parvus, Calanus helgolandicus, Oithona similis) and decreased (e.g. Oncaea media, Pseudocalanus elongatus). in situ temperature and Reynolds SST reveal an increasing trend of up to 1 C during the 20 years of the time-series. To further investigate both temperature and zooplankton trends at the site, data were compared with long-term data from CPR and Reynolds SST. Although the increasing trend in SST is also evident in the longer record, with SST increasing almost 1 C during the last half-century, the increase in zooplankton abundance recorded at A Coruña during the last 20 years corresponds to a period of low copepod abundance in CPR standard area F4 . Although the abundance recorded by the CPR during the last 10 years in this area features negative anomalies, there is an increasing trend in the CPR data (i.e. moving from negative to positive), suggesting that the increasing trend observed off A Coruña may be a recovery from a period of low abundance. |