Indications of pollution-induces community tolerance (PICT) of benthic algal communities in contaminated agricultural streams

Abstract

The aim of this study was to examine pollution-induced community tolerance (PICT) of biofilm communities induced by chemical mixtures, characteristic of agricultural aquatic environments. Additionally, the use of biofilms as a natural passive sampler was investigated. In situ biofilms grown on artificial substrate for 4 to 6 weeks from sites located in agricultural areas were used to conduct a PICT short-term experiment, as well as for the extraction of chemicals from the biofilm matrix, adapting a QuEChERS method after using cell disruption.

Biofilm communities from agricultural streams were more tolerant to pesticides than those from reference streams. Higher effect concentrations (EC50) were detected in 9 out of 10 agricultural sites, using IPAM fluorescence (a measure for photosynthesis capacity) as toxicity endpoint. EC50s up to 20 times higher than in reference sites, located outside of agricultural areas, were found. Biofilms derived from agricultural streams had up to ten times higher loads of pollutants than in reference sites, for both samples from May and in June. Pesticides and fragrances dominated the pollution profiles in agricultural streams, while fragrances dominated at the reference sites. Regarding the pesticides, the agricultural stream biofilms showed up to 30 times higher concentrations than the reference biofilms. Further, biofilm showed a more pronounced chemical pollution profile than grab-water samples, both quantitatively and qualitatively. Biofilm samples showed a five times higher number of chemicals detected compared to water samples (June). Further, for a number of selected chemicals, the concentrations of the chemicals were up to 500 times higher in dry weight biofilms than in grab-water samples.

The demonstrated ability of the PICT-approach to detect induced tolerance, in situ, at sites with regional variation in land use strengthens the applicability of the PICT method to assess the ecological integrity of aquatic systems. Furthermore, the findings indicate that biofilms may be used as a natural passive sampler, opening the field of an integrative sampling strategy at an ecologically relevant level, and a suitable tool to characterize the eco-exposome, in situ.

Popular Abstract

How agricultural pesticides may influence algal communities:

Agricultural pesticides may end up in nearby streams and pose a risk to the ecosystem and its functions. Many ecosystem functions are provided by stream biofilms, a combination of several organism groups such as bacteria & micro-algae attached-living to the streambed. Biofilms are known to be sensitive towards pollution resulting in the development of a variety of pollution detection methods.

In my study, I used biofilms grown on artificial substrate in agricultural streams to conduct a pollution-induced community tolerance (PICT) short-term experiment, as well as an extraction of chemicals from the biofilms. The extraction method combined cell disruption and the QuEChERS method to extract chemicals from the biofilm matrix, and chemicals were measured using LC-HRMS. Further, the biofilms’ ability to act as a natural passive sampler of chemicals was assessed by comparing chemicals found in the biofilms to those in grab-water samples.

By testing how pesticides affected photosynthetic activity of biofilm organisms, tolerance was defined as an increased concentration needed during short-term exposure to reduce photosynthetic activity by 50% (EC50). Induced tolerance in 9 out of the 10 surveyed agricultural stream biofilms was detected, with a tolerance up to 20 times higher compared to unpolluted sites. This increased tolerance towards a selected mixture of pesticides illustrates the influence of chemical pollution on biofilm community structure and function in agricultural landscapes.

Chemical pollution was more severe in agricultural streams than in reference streams, as the pollutant load was up to ten times higher in agricultural stream biofilms than at reference sites. Generally, the agricultural streams were mostly polluted by pesticides, biocides, fragrances, industrial chemicals, and UV-filters. Pesticide contamination was found to be 30 times higher in agricultural stream biofilms than in biofilms from reference sites. Interestingly, the reference sites were polluted by fragrances, which is unexpected as the main entry route for pollution was expected to be surface run-off. These results further strengthen the use of the PICT approach as a combined chemical-biological detection tool with ecological relevance.

Biofilm as a natural passive sampler?
From my results, I conclude that biofilms may act as a natural passive sampler, giving a representative picture of both the number and the concentrations of chemicals in the investigated streams. The biofilms contained chemicals that were not found in the water samples, showing their ability to integrate chemicals over time & space. Therefore, biofilms might be useful for integrative assessment of the status of an aquatic system, as biofilms are a cheap and available matrix collecting chemicals and additionally applicable as a bioindicator in ecological risk assessment.

Master’s Degree Project in Biology 30 credits 2021
Department of Biology, Lund University

Advisor: Olof Berglund, Mechthild Schmitt-Jansen (UFZ)
Aquatic Ecology

• author: Fiolka, Franziska
• supervisor: Olof Berglund
• organization: Degree Projects in Biology
• course: BIOM02 20211
• year: 2021
• type: H2 - Master's Degree (Two Years)
• subject: Biology and Life Sciences
• language: English
• id: 9067491
• date added to LUP: 2021-11-01 12:48:52
• date last changed: 2021-11-01 12:48:52