The coastal area is certainly one of the most diverse ecosystems on Earth. This unique environment is characterized by the encounter of land and sea, forming a distinct ecotone zone. Randuboto and Manyar Sidomukti, fisherman villages located in Gresik Regency, thrives within this kind of diverse coastal ecosystem. The inhabitants rely heavily on their environment. Protecting this environment ensures the continued prosperity and resilience of the village's way of life. Biomonitoring is a method used for biodiversity accounting to indicate the quality of an environment. This process involves the quantification of various biodiversity metrics, including The Shannon-Wienerdiversity index (H index). Using this method, a study was conducted to assess the ecosystem condition in the Randuboto and Manyar Sidomukti coastal area. The mangrove community in Manyar Sidomukti exhibited a higher diversity index (H’ = 0.42 – 0.68) compared to Randuboto (H’ = 0 – 0.082), though both areas fall into the low diversity category with H’ 1. In terms of bird species, Randuboto had a greater number (40 species) than Manyar Sidomukti (37 species). However, the Shannon-Wiener diversity index for birds was higher in Manyar Sidomukti (H’ = 3.33) than in Randuboto (H’ = 2.80). These findings suggest that mangrove populations require additional support to enhance their resilience, whereas bird populations appear to be relatively resilient to environmental changes. Efforts to bolster this include mangrove reforestation, community service and development, and training in community-based biomonitoring.