Ajustement de modèles mathématiques de la croissance d'algues phytoplanctoniques en culture

Introduction: This document is the End of Second Year internship report for Rennes University 1's Senior Math and Computer Science Modelisation Professional diploma. This two month internship was completed at the Brest IFREMER center at the Coastal Ecology department.
IFREMER participates, in the course of its institutional missions, in observation and coastal sea surveillance, in order to improve on the knowledge, protection methods and restoration of the marine environment. Marine phytoplankton proliferation is an important study subject because of its potential cause for nuisance, for men, consumers of sea products as well as for the ecosystem. During Spring and Summer, shellfish become invariably unsuitable for consumption due to toxins produced by phytoplanktonic algae.
We now know that domestic, industrial and agricultural discharges can promote the growth of phytoplanktonic algae. Rightly so, most pollutants discharged in the environment will eventually reach the marine environment, either indirectly through rivers, run offs, the atmosphere or directly into the sea. That is why studies were led in 1993 and 1994 in the Seine bay at the mouth of one of the most polluted rivers in Europe, in order to study the influence of polluting discharges on the growth of marine phytoplankton. Cultured phytoplankton populations were subject to different nutritive conditions.
Along that line, studies were conducted between 1998 and 1999 in order to determine the effects of herbicides on the development of toxic marine microalgae in the Morlaix bay waters.
The purpose of this work is to test the contribution of diverse optimisation methods for the improvement of simple mathematical models formulation regarding cultured phytoplanktonic growth. The first part of this document presents the host organization where this internship took place. The second part introduces the mathematical model planned for the evolution of phytoplankton among pollutants and the optimization techniques, which have been applied, are described. The third part deals with exploitation measures concerning the effect of herbicides on microalgae.