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<p>Benthic diatoms are sensitive indicators of freshwater ecosystem health, yet their spatial diversity patterns in tropical rivers remain poorly understood. This study investigated β-diversity of benthic diatom assemblages along the Sangker River, northwestern Cambodia. β-Diversity was quantified using the Sørensen index and partitioned into turnover (βsim) and nestedness (βsne) components, based on 7 sampling campaigns from 2018 to 2022. Local (LCBD) and taxa (SCBD) contributions identified unique sites and influential taxa (genera). Twelve environmental variables, including nine physical and chemical and three spatial factors, were analyzed along the upstream–downstream gradient. A total of 78 genera were recorded, dominated by <i>Gomphonema</i>, <i>Nitzschia</i>, <i>Navicula</i>, and <i>Achnanthidium</i>. Alpha diversity declined downstream, reflecting reduced habitat heterogeneity and increasing nutrient enrichment, while evenness remained stable. Overall β-diversity was high (βsor = 0.748), driven mainly by species turnover (βsim = 0.639), indicating distinct assemblages across river sections. Certain sites located in tributaries exhibited high-LCBD values, whereas total phosphorus and total suspended solids significantly influenced LCBD. These findings highlight the strong roles of environmental filtering and longitudinal (upstream–downstream) gradients in structuring diatom assemblages. Targeting high-LCBD sites and key indicator genera can enhance biomonitoring efficiency and guide freshwater conservation under growing anthropogenic pressures in tropical river systems.</p>

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Beta diversity patterns of diatom assemblages along the largest north-western river of Cambodia (Sangker River): implication for biomonitoring

  • 期刊论文

  • 发表日期：

    2026年2月23日

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  • Ratha Chea,
  • Thierry Oberdorff,
  • Paul Baudron,
  • Socheat Chrea,
  • Loïc Tudesque

摘要

Benthic diatoms are sensitive indicators of freshwater ecosystem health, yet their spatial diversity patterns in tropical rivers remain poorly understood. This study investigated β-diversity of benthic diatom assemblages along the Sangker River, northwestern Cambodia. β-Diversity was quantified using the Sørensen index and partitioned into turnover (βsim) and nestedness (βsne) components, based on 7 sampling campaigns from 2018 to 2022. Local (LCBD) and taxa (SCBD) contributions identified unique sites and influential taxa (genera). Twelve environmental variables, including nine physical and chemical and three spatial factors, were analyzed along the upstream–downstream gradient. A total of 78 genera were recorded, dominated by Gomphonema, Nitzschia, Navicula, and Achnanthidium. Alpha diversity declined downstream, reflecting reduced habitat heterogeneity and increasing nutrient enrichment, while evenness remained stable. Overall β-diversity was high (βsor = 0.748), driven mainly by species turnover (βsim = 0.639), indicating distinct assemblages across river sections. Certain sites located in tributaries exhibited high-LCBD values, whereas total phosphorus and total suspended solids significantly influenced LCBD. These findings highlight the strong roles of environmental filtering and longitudinal (upstream–downstream) gradients in structuring diatom assemblages. Targeting high-LCBD sites and key indicator genera can enhance biomonitoring efficiency and guide freshwater conservation under growing anthropogenic pressures in tropical river systems.