River biofilm communities are the first ones to be exposed to all toxic discharges received via run off from agricultural fields. Hence, changes in river biofilm community structure and growth pattern are considered as indicator of overall health of lotic ecosystem. Toxicants have effect on biofilm biomass, photosynthetic efficiency and chlorophyll a concentrations. Mathematical models may be applied to estimate the overall vigor of riverine ecosystems considering biofilms as indicators. Herein, previous empirical data of Ricart et al. (2009) on long term effects of environmentally relevant concentrations of diuron on biofilm communities of the River Llobregat, Spain was considered as our model inputs. Our objective is to understand the influence of diuron, chlorophyll a concentrations and photosynthetic efficiency on biovolume using a statistical model. The non-linear relationships between biovolume (dependent variable) and diuron, chlorophyll a concentrations and photosynthetic efficiency (independent variables) were represented by constructing three separate basis functions based on day 8 empirical data. Biovolume, due to nonlinear influence as yielded by the basis functions were used in a multiple linear regression model to estimate the net biovolume. Model validation was done based on day 29 empirical data. The experimentally determined biovolume and our model estimated biovolume showed similar trends. Also, diuron and photosynthetic efficiency had significant (p < 0.05) influence on biovolume. Since, the predominance of diatoms as biofilms within periphytic layers is very common in lotic systems, estimation of changes in diatom biovolume will be significant to assess the effect of herbicides. Diatom biovolume of any day (for example day 22) mentioned in the experimental study may be determined by this model, without the requirement of tedious manual biovolume calculation. Our model will be useful in numerous other studies undertaken on the toxic effect of pollutants on biofilms to quickly and accurately estimate the biofilm biovolume.

河流生物膜群落是第一个接触到所有通过农田径流排放的有毒物质的群落。因此，河流生物膜群落结构和生长模式的变化被认为是河流生态系统整体健康的指标。毒物对生物膜生物量、光合作用效率和叶绿素a浓度有影响。考虑到生物膜作为指标，数学模型可用于估计河流生态系统的整体活力。在此，Ricart 等人以前的经验数据。(2009) 关于环境相关浓度敌草隆对西班牙 Llobregat 河生物膜群落的长期影响被视为我们的模型输入。我们的目标是了解敌草隆、叶绿素a使用统计模型在生物量上的浓度和光合效率。生物量（因变量）与敌草隆、叶绿素a之间的非线性关系浓度和光合效率（自变量）通过基于第 8 天的经验数据构建三个独立的基函数来表示。由于基函数产生的非线性影响，生物量被用在多元线性回归模型中来估计净生物量。基于第 29 天的经验数据进行模型验证。实验确定的生物量和我们的模型估计的生物量显示出类似的趋势。此外，敌草隆和光合效率对生物量有显着影响（p < 0.05）。由于硅藻在附生层中作为生物膜的优势在灌溉系统中非常普遍，因此估计硅藻生物量的变化对于评估除草剂的效果非常重要。实验研究中提到的任何一天（例如第22天）的硅藻生物量都可以通过该模型确定，无需繁琐的手动生物量计算。我们的模型将在许多其他关于污染物对生物膜的毒性作用的研究中有用，以快速准确地估计生物膜生物量。