Mesozooplankton dynamics along the Northwest and north Iberian Shelf.

Abstract

Within the framework of the RADIALES time series monitoring program carried out by the Instituto Español de Oceanografía (IEO), 10 stations were monthly sampled for zooplankton biomass, abundance and taxonomic composition. Additionally, hydrographic features and nutrient concentrations were also measured. From the beginning of the program, a total of 2179 zooplankton samples have been collected. The sampling stations are located along four coastal-ocean sections in the Northwest and North Iberian shelf, off Vigo, A Coruña, Gijón and Santander beginning in 1994, 1991, 2001, 1992, respectively. There is classically a contrasted situation between the Galician and the Cantabrian coast. Since the Galician coast represents the northern limit of the Canary upwelling system, coastal upwelling has a major influence on their hydrodynamic behavior and nutrient distributions. In the Cantabrian coast, upwelling is restricted to occasional events during summer and nutrient fertilization depends mostly on the deep convection occurring during winter. In this communication we aim to describe the long-term dynamics of zooplankton biomass for oceanic and shelf waters of the northwest and north Iberian Peninsula focusing in the common period sampled in all the stations (2001-2013, representing 1405 sampling events). We used a method able to cope with the non-stationary nature of the data, namely wavelet analysis. It allows describing the periodic components of the signal as classically obtained with the Fourier analysis. But in addition, the wavelet analysis approach provides information of the variability of the periodic components along the time series. Indeed the principal periodic components (1, 1,5 and 3 years) appear to be transient in both hydrologic and zooplankton biomass series. A pair-wise comparison between the power spectrum matrices of each zooplankton biomass time series allowed us to detect common dynamics between the coastal Cantabrian stations, the oceanic Cantabrian stations and the Galician ones.