Exploring the use of nuclear alterations, motility and ecological guilds in epipelic diatoms as biomonitoring tools for water quality improvement in urban impacted lowland streams

•Diatoms are useful biological indicators to assess water quality in rivers.•Less conventional metrics were tested as indicators of water quality improvement.•Diatom motility endpoints are not sensitive indicators of water quality improvement.•Nuclear membrane integrity and ecological guilds respond to water quality improvement.•These metrics could be considered in biomonitoring protocols in lowland streams.