Microorganisms are essential for the intensive production of marine shrimps, since they are responsible for maintaining the water with an optimum quality for them. Also, these microorganisms minimize or eliminate water renewal. Among all the microorganisms present in intensive culture systems, without water renewal, microalgae and bacteria play the most important role and are the most abundant ones. In this thesis we analyze the microalgae dynamics using HPLC/CHEMTAX methodology in two intensive culture systems of marine shrimp, a shrimp nursery and a biofloc system. We also test the role of the bacteria Bacillus amyloliquefaciens as a probiotic and its capacity to improve the maturation process of the biofloc system. The results showed that the HPLC/CHEMTAX methodology is a fast and efficient way to analyze phytoplankton and periphyton in intensive culture systems of shrimp, provided that autotrophic processes are predominant. This technique allowed to detect prasinophytes and prymnesiophytes for the first time in the periphyton that grows on the polyvinyl chloride (PVC) tanks. Also, it has allowed to study the influence of trophic state and light exposition on microalgae dynamic in the biofloc systems. The application of Bacillus amyloliquefaciens in biofloc systems strengthens the immune system of shrimp and adds its probiotic effects to that produced by bioflocs. These benefits happen even with doses of 103 cfu/mL, lower than recommended doses for other probiotic bacteria. Other researches indicated that Bacillus amyloliquefaciens might have other effects such as participating in the biofloc system formation, improving water quality and shrimp growth; however, the application of spores in the culture water did not show any statistically significant effect on the system dynamic, water quality or zootechnic parameters. Llario Sempere, F. (2018). IMPORTANCIA DE LOS MICROORGANISMOS EN LA PRODUCCIÓN DE LANGOSTINOS MARINOS EN SISTEMAS DE BIOFLÓCULOS Y SIN RENOVACIÓN DE AGUA [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/111825 TESIS