Abstract : Manzala Lake is one of the largest natural resources in Egypt. The research aims to assess the lake region's ecosystem changes by identifying the dynamic change pattern and interactions between three main factors; urban development, lake ecological system and ecosystem services' value. The objectives were achieved by propose a spatiotemporal assessment tools using the earth observation and the computing clouds technologies advantages of Google Earth Engine for historical data extraction and its power for spatial image processing analysis. The assessment tools showed a declination of the lake and agricultural land areas with 3.8% and 2.5% erosion rates as well as declination in the water quality index, meanwhile the fish farming and urban areas has incrementally increased. The analysis also detects the change pattern of the lake environmental services of fish productivity and fishermen's income. The lake encroachment was statistically significance associated by 74% of fish farms areas and by 17% of agricultural land. These findings prove the advantages of the spatiotemporal assessment tools to monitor and study the dynamic changes and interactions within the lake’s ecosystem identifying the crucial lake region factors and the suitable environmental protection actions to preserve the balance between urban development and the quality of ecosystem.