Biomineralization　has　been　used　for　the　treatment　of　calcareous　sand　to　improve　its　properties.　Although　many　studies　have　been　performed　on　the　biomineralized　calcareous　sand　under　freshwater　conditions,　few　studies　were　focused　on　the　behaviors　of　calcareous　sand　in　seawater.　As　the　freshwater　is　scarce　in　island　areas,　the　freshwater-based　biomineralization　technology　may　be　unsuitable　for　the　treatment.　In　this　study,　seawater-based　bacterial　enzyme induced　carbonate　precipitation　(BEICP)　was　proposed　to　treat　calcareous　sand.　A　series　of　tests　were　conducted　to　verify　the　feasibility　and　efficiency　of　this　treatment　method　through　investigating　the　effects　of　seawater　on　the　biomineralization　and　the　properties　of　biomineralized　calcareous　sand　in　comparison　with　microbially　induced　carbonate　precipitation　(MICP).　Test　results　reveal　that　seawater　leads　to　the　decrease　of　urease　activity　of　bacterial　cells　and　urease.　NaCl,　MgCl2,　Na2SO4,　and　CaCl2　are　the　main　inhibitory　components　in　seawater,　of　which　MgCl2　and　CaCl2　have　a　strong　influence　on　the　urease　activity　of　bacterial　cells　and　urease,　respectively.　Compared　to　MICP　treatment,　BEICP-treated　calcareous　sand　exhibits　higher　unconfined　compressive　strength　and　better　biomineralization　effects.　The　findings　of　this　study　can　contribute　to　the　application　of　biomineralization　technology　in　island　areas.　©　The　Author(s),　under　exclusive　licence　to　Springer-Verlag　GmbH　Germany,　part　of　Springer　Nature　2025.