Periphyton is increasingly used to assess the biological condition of lakes. The predominance of relatively shallow exposed waterbodies in Ireland implies that epilithic diatoms should have a prominent role as bioindicators for the WFD; but epilithic diatom ecology in these Irish systems is poorly described. We characterised spring and summer diatom populations in diverse periphyton communities in 91 Irish lake waterbodies. Six assemblage clusters of diatom species were identified, and variation in their assemblages was predominately associated with environmental gradients of acidity-alkalinity, total phosphorus, and true colour. Diatom composition differed amongst high status lakes in three a priori defined lake alkalinity groups commonly used as a diatom typology for lake classification. However, when waterbodies were evaluated with a lake trophic diatom index (LTDI) their distribution of ‘expected-values’ was equivalent. The LTDI was highly correlated with total phosphorus but also had similar responses in the three lake alkalinity types. These findings indicated that lake typology had a limited role for diatom classification with the LTDI in Ireland. Matched spring and summer sampling across wide environmental gradients allowed the role of seasonality to be investigated. Relatively few benthic diatoms had a significant seasonal indicator value suggesting that unbiased monitoring of the epilithon is possible during any month of the growing season in comparable temperate waterbodies. However, temporal variability was lower at low values of the LTDI and increased unpredictably on a lake by lake basis thereafter. Given that lake diatom classification has been validated we suggest that the approach could be developed and used for more targeted assessment objectives.

附生生物越来越多地用于评估湖泊的生物状况。爱尔兰相对较浅的暴露水体占优势，这意味着附着硅藻应作为 WFD 的生物指标发挥重要作用；但是这些爱尔兰系统中的附生硅藻生态学描述很差。我们对 91 个爱尔兰湖泊水体中不同附生生物群落中的春季和夏季硅藻种群进行了表征。确定了六个硅藻物种组合簇，它们组合的变化主要与酸碱度、总磷和真实颜色的环境梯度有关。三个先验的高地位湖泊的硅藻组成不同定义的湖泊碱度组通常用作湖泊分类的硅藻类型。然而，当使用湖泊营养硅藻指数 (LTDI) 评估水体时，它们的“预期值”分布是等效的。LTDI 与总磷高度相关，但在三种湖泊碱度类型中也有相似的响应。这些发现表明，湖泊类型学对爱尔兰 LTDI 的硅藻分类作用有限。在广泛的环境梯度中匹配的春季和夏季采样允许调查季节性的作用。相对较少的底栖硅藻具有显着的季节性指标值，这表明在可比较的温带水体中，在生长季节的任何月份都可以对附生岩进行无偏见的监测。然而，LTDI 值较低时，时间变异性较低，此后逐湖增加不可预测。鉴于湖泊硅藻分类已得到验证，我们建议可以开发该方法并将其用于更有针对性的评估目标。