Content and Language Integrated Learning (CLIL) is becoming more and more valued as an educational solution to teaching foreign languages. The role ascribed to meaning (content) in communicative processes seems to explain the increasing popularity and spread of integrative approaches to teaching foreign languages across Europe and in the world. The explanation of the effectiveness of CLIL can also be sought in our understanding of how second language acquisition takes place. The theoretical part of the paper outlines the links made between the outcomes of second language acquisition research and CLIL and sheds some light on the role of meaning in communicative processes. The empirical study investigates the role of teachers in CLIL science classrooms in the context of writing scientific reports and the role of English of CLIL science classes in teaching referencing skills. The results of the research indicate to the roles that CLIL science teachers should play in the development of writing skills, including the use of referencing styles. There is also some evidence to suggest that in order for the successful integration of content and language to occur, some form of cooperation between language and CLIL content teachers should exist, especially in the context of teaching referencing skills.