This study investigates the concentration of [Chl-a] using the data of field observation and MODIS-Aqua imagery. The field observation data were retrieved by using a conventional method and processed using spectrometric analysis. This study covers the coastal and near land areas which have different levels of anthropogenic activity. The results showed that the coastal waters of Semarang with a high level of anthropogenic activity persistently show a concentration of chlorophyll a [Chl-a] twice as large as Jepara coastal waters. This comparison value is obtained based on imagery and field data. Meanwhile, the ratio of [Chl-a] field data in each region shows a value of ±5 times greater than the MODIS data. Field observation data shows a higher value than the MODIS-Aqua imagery data. The use of imagery data can be employed as a method of monitoring the eutrophication process on the coast. On the basis of the chlorophyll a classification and field observations, the coastal water of Semarang are classified as eutropic waters and Jepara is categorized as mesotropic category. The classification results will be different if monitoring is carried out using the image data with a location far from the mainland, the Semarang waters are included in the mesotropic category (> 2 mg m-3) and Jepara is included in the oligotropic water category (<2 mg m-3).