Ecological　water　replenishment　is　a　crucial　and　effective　measure　to　improve　the　water　quality　and　ecological　function　of　lakes.　However,　the　effects　of　ecological　water　replenishment　on　the　pollution　characteristics　and　ecological　risks　of　trace　elements　and　bacterial　communities　in　lake　surface　water　are　still　kept　unclear.　We　investigated　the　pollution　levels　and　potential　ecological　risks　for　trace　elements,　as　well　as　variation　of　the　bacterial　community　in　surface　water　in　the　BYD　lake　before　and　after　ecological　water　replenishment.　Our　results　revealed　that　higher　levels　and　pollution　indexes　(Igeo)　of　trace　metals　(e.g.,　As,　Cd,　Co,　Cu　and　Ni;　p　＜　0.05)　after　ecological　water　replenishment　were　observed　than　before　ecological　water　replenishment　and　their　total　potential　ecological　risk　(∑RI)　were　increased.　In　contrast,　the　network　complexity　of　these　trace　elements,　including　nodes,　edges,　average　diameter,　modularity,　clustering　coefficient　and　average　pathlength　showed　a　decrease　after　ecological　water　replenishment　than　before.　The　diversity　(community　richness,　community　diversity　and　phylogenetic　diversity　decreased)　and　community　structure　of　the　bacterial　community　in　the　surface　water　(p　＜　0.05)　were　greatly　changed　after　ecological　water　replenishment　than　before,　with　the　increase　in　heavy　metal-resistant　phylum　(e.g.,　Acidobacteriota).　Moreover,　the　concentration　of　trace　elements　and　∑RI　were　significantly　correlated　with　the　alpha　diversity　of　bacterial　community,　as　well　as　dissolved　organic　carbon　(DOC)　and　ORP,　after　ecological　water　replenishment.　The　findings　indicate　that　it　is　very　necessary　to　continuously　monitor　trace　metal　pollution　levels　and　heavy　metal-resistant　phylum　and　identify　their　potential　pollution　sources　for　water　environment　control　and　lake　ecosystem　health.　©　2024　Elsevier　B.V.