NEW PROJECT TROFOALBORAN

Abstract of the new project TROFOALBORAN that will replace from the project NITROALBORAN

During the last years, interannual changes in the structure (biodiversity) of the planktonic communities growing at the northwest area of the Alboran Sea (Mediterranean Sea) have been assesed. These changes are probably due to the impact of the human activity (incluiding from changes in the nutrient regime to over-fishing). The analysis of the available time data series about phytoplankton and meso-zooplankton communities in coastal area out off Malaga indicates that the atmospheric forcing explains only partially the seasonal and interannual varibility of these communities. Therefore, the trophic relationships could play a key role in reglating the ecosystem response to the enviromental changes. Thus, meso-zooplankton appears to control the abundance and composition of the phytoplankton communities, probably via phytoplankton-ciliate-zooplankton interactions. In addition, meso-zooplankton communities could be subject to top-down control by planktivorous, which in the study area are mainly small pelagic fishes (quantitatively, the most important specie is Sardina pilchardus). However, substantial changes in the nutritional condition of the sardine larvae have been described in the study area during the seasonal cycle, probably due to the seasonal cycle of the plankton (with a higher contribution of the phytoplankton to the larval diet in spring season). Therefore, the possible regulator role of the small pelagic fishes on the meso-zooplankton could be soften by a bottom-up control exerted by phytoplankton and zooplankton over the larval phases. The main objective of this project is to determinate which are the trophic relationships regulating the structure and function of the pelagic ecosystem at the upwelling area around the Alboran sea. For this goal, (1) the seasonal variability in the taxonomic composition and size structure of the plankton communities will be analysed, (2) the dominant trophic relationships among the different size fractions of the plankton and between the plankton and the small pelagic fishes will be determined and (3) the effects of the changes in the structure of the ecosystem pelagic on the trophic energy flow will be quantified. The C and N stable isotope technique will be applied to the different size fractions of the plankton and to larval, juvenile and adult individuals of small pelagic fishes in order to study the conectivity in the ecosystem. The yield of trophic energy flow from primary producers to the other trophic compartments will be studied from measurements of primary productivity and respiration (as calculated from the electron transport system activity, ETS). The sampling intensity that is needed for reaching these objectives will be split out into different oceanographic surveys performed during different periods of the seasonal cycle and two annual cycles in two coastal upwelling areas, the bays of Málaga and Almería.