Abstract
<title>Abstract</title> <p>Marine pollution poses a significant threat to aquatic ecosystem, resulting in decreased biodiversity and potential species extinction. This study investigated sea urchin abundance in Inner Ambon Bay, employing transect sampling at three distinct beaches. Sea urchin specimens were collected during the lowest tide periods, with three sampling stations established per location, stratified by substrate types, along a 5x5 transect. The survey identified six sea urchin species across the three sites, with Poka Beach exhibiting the highest overall abundance. Rumah Tiga Beach, however, recorded the greatest species diversity. Concurrently measured water quality parameters, including temperature salinity, dissolved oxygen and pH, were within established acceptable ranges. The findings suggest that sea urchins hold potential as bioindicators for assessing environmental health in Inner Ambon Bay, evidenced by significant correlation between their abundance and key water quality variables.</p>