Accelerated eutrophication of marine ecosystems as a result of nutrient enrichment is a widespread problem within European marine margins. Eutrophication has several adverse effects on the marine ecosystem such as the formation of harmful algae blooms reduced water clarity and reduced oxygen levels. The reliable quantification of the causative nutrients is challenging due to the matrix within which they are held. Here we propose methods for the identification and optimisation of appropriate detection chemistries for phosphate, ammonia, nitrate and nitrite in marine matrices. The work presented is carried out as part of the COMMON SENSE FP7 European project. COMMON SENSE aims to provide a reliable sensing platform for in-situ measurements on key parameters relating to eutrophication. The nutrient sensor is based on a combination of microfluidic analytical systems, colorimetric reagent chemistry, low-cost LED-based optical detection, and wireless communications.