Biofilms Provide New Insight into Pesticide Occurrence in Streams and Links to Aquatic Ecological Communities

Abstract

Streambed sediment is commonly analyzed to assess occurrence of hydrophobic pesticides and risks to aquatic communities. However, stream biofilms also have the potential to accumulate pesticides and may be consumed by aquatic organisms. To better characterize risks to aquatic life, the U.S. Geological Survey Regional Stream Quality Assessment measured 93 current-use and 3 legacy pesticides in bed sediment and biofilm from 54 small streams in California across a range of land-use settings. On average, 4 times as many current-use pesticides were detected in biofilm at a site (median of 2) as in sediment (median of 0.5). Of 31 current-use pesticides detected, 20 were detected more frequently in biofilm than in sediment and 10 with equal frequency. Pyrethroids as a class were the most potentially toxic to benthic invertebrates, and of the 9 pyrethroids detected, 7 occurred more frequently in biofilm than sediment. We constructed general additive models to investigate relations between pesticides and 6 metrics of benthic community structure. Pesticides in biofilm improved fit in 4 of the 6 models, and pesticides in sediment improved fit in 2. The results indicate that the sampling of stream biofilms can complement bed-sediment sampling by identification of more current-use pesticides present and better estimation of ecological risks.

Ecological consequences of neonicotinoid mixtures in streams

“…GAMs relate a univariate response variable (i.e., total mayfly abundance) with parametric predictors (i.e., measured of pesticide exposure and covariates) that depend on nonparametric smoother functions. First, we related total mayfly abundance to 10 natural covariates used in California Stream Condition Index to account for naturally occurring variation in aquatic assemblages and to minimize confounding (spurious associations between natural and anthropogenic factors) with anthropogenic stressors, in this case, pesticides ( 81 , 82 ). The covariates represent measures of site location (latitude, longitude, site elevation, and elevation range of watershed), basin size, long-term air temperature, precipitation (long-term and summer average), bulk soil density, and soil erodibility ( 81 ).…”

Streambed pollution: A comprehensive review of its sources, eco-hydro-geo-chemical impacts, assessment, and mitigation strategies

“…The source receptor modeling and mass fraction analysis are widely being used to identify potential PAH sources in streambed sediment samples [194]. Biofilms and aquatic organisms have been employed as bio-indicators to detect and assess the impacts associated with streambed pollution [195,196]. The general impact assessment methodology includes finding the sources and occurrence of the pollutants, verification/quantification of the pollutant concentration in the streambed using analytical methods in the laboratory and comparing with standard values (as given in any guidelines) followed by statistical analysis and development of impact indices [39].…”

The significance of biofilms to human, animal, plant and ecosystem health

“…This ‘ecological memory’ made biofilms reliable indicators to assess and monitor the health of aquatic ecosystems, with the development of many structurally based or functionally based methods (Burns & Ryder, 2001; Sabater et al., 2007; Wu, 2017h). In a recent survey monitoring pesticide occurrence in 54 Californian small streams, biofilms were shown to contain, in average, four times as many current‐use pesticides like pyrethroids as in streambed sediments (Mahler et al., 2020). As biofilms adsorb toxicants and form the basis of aquatic food webs, they make toxicants bioavailable to consumers, thus posing a risk to their health (see part 4.3).…”

“…As biofilms adsorb toxicants and form the basis of aquatic food webs, they make toxicants bioavailable to consumers, thus posing a risk to their health (see part 4.3). In conclusion, not only are biofilms the sentinels of aquatic ecosystems, they are also a critical control point to monitor and understand the fate of toxicants in food webs (Bonnineau et al., 2020; Mahler et al., 2020).…”