Stagiaire : Lucie Arribard (2010)
Lieu : Institute for Coastal research, GKSS, Geesthacht, Allemagne
Durée : 2 mois (mai-juillet 2009)
Résumé : Ce rapport présente une analyse statistique de la relation entre la chlorophylle-a (CHL-a) et les matières en suspension (MES) dans la partie allemande de la Mer du Nord pendant les blooms printaniers de 2003 à 2005. Le travail effectué consiste principalement en l’observation de diagrammes de dispersion et régression linéaire. Une méthode combinant ces deux outils statistiques a également été développée, aboutissant à la création d’une carte de régression entre ces deux variables.
Problématique :
In the current environmental context, worries about climate change and anthropogenic impact on ecosystems are growing. To assess our footprint on nature, we need to better understand the different processes and interactions governing our ecosystem, processes which are extremely complex.
Carbon is the most important element in biogeochemical cycles in the ocean and shelf seas, and most models of terrestrial and marine ecosystems are formulated in terms of carbon flux. Phytoplankton, as the driver of biogeochemical cycling, is most effectively expressed in units of organic carbon. The presence of organic carbon in the sea has an important impact on the ecosystem, especially on the fish and marine organisms’ population. This is of great interest for the fishing industry, which, in some regions, is the basis of the local economy.
Nutrient and light availability determine phytoplankton production, and therefore fixation of inorganic carbon into organic carbon. Although the ratio between carbon and chlorophyll is not constant, scientists are more likely to measure phytoplankton biomass. Chlorophyll fluorescence is then an indicator of the quantity of biomass involved in primary production.
In coastal zones, production of phytoplankton is limited by light availability, which is determined by the total suspended matter concentration in the water. For that reason, it is important to have a good understanding of chlorophyll and total suspended matter dynamics in the ocean and their relation to each other.
A good view of the spatial heterogeneity of these two variables is given by satellite scenes. Therefore, the analysis of the distribution of chlorophyll-a and total suspended matter requires to work with remote sensing data.
Mots-clefs : océan