Epiphyton in Agricultural Streams: Structural Control and Comparison to Epilithon

Abstract

Stream biofilms play an important role in the structure, functioning, and integrity of agricultural streams. In many lowland streams, macrophyte vegetation is abundant and functions as an important substrate for biofilm (epiphyton) in addition to the gravel and stone substrate for epilithon on the stream bed. We expect that reach-scale habitat conditions in streams (e.g., nutrient availability, hydraulic conditions) affect the epiphyton and epilithon biomass and composition, and that this effect will be substrate-specific (macrophytes and stones). The objectives of our study were (i) to describe concurrent changes in epiphyton and epilithon biomass and composition over a year in agricultural streams, and (ii) to determine the substrate specific reach-scale habitat drivers for the epiphyton and epilithon structure. We monitored epiphyton and epilithon biofilm biomass and composition at three-week intervals and reach-scale environmental conditions daily during a year for two agricultural steams. The results showed that epiphyton and epilithon communities differed in biomass, having high substrate specific biomass in epilithon compared to epiphyton. Epiphyton was mainly composed of diatom and green algae, while cyanobacteria were more important in epilithon, and the diatom species composition varied between the two biofilm types. Epiphyton structural properties were less influenced by reach-scale hydrology and nutrient availability compared to epilithon. The overall explanatory power of the measured environmental variables was low, probably due to micro-scale habitat effects and interactive processes within stream biofilms. Knowledge of biofilm control in agricultural streams is important in order to improve management strategies, and future studies should improve the understanding of micro-scale habitat conditions, interactive relationships within biofilms and between the biofilm and the substrates.

Microbial community structural characteristics and associated relationships with environmental factors in different ecological habitats

“…The results of the correlation analysis con rmed that TN and TP may jointly promote the growth of periphytic microorganisms, this was consistent with the conclusions of previous studies (Huang et al, 2018;Stelzer and Lamberti, 2001;Weitere et al, 2021). AFDW indicated positive association with SRP rather than Chl-a, this can be contributed to light availability (Bengtsson et al, 2018) or temperature (Wijewardene et al, 2021). DOC served as a nutrient for the heterotrophic community but high DOC concentration may lead to limited light availability for autotrophs and for their photosynthesis (Levesque et al, 2017).…”

“…There are several possible explanations for some negative correlations in microbial community. Firstly, the respiration of algae may lead to an increase in the pH of the periphytic bio lms that may have been harmful to bacterial dynamics (Wijewardene et al, 2021;. Secondly, heterotrophic prokaryotes competed with eukaryotes for inorganic nutrients, which were more e cient at utilizing nitrogen from organic compounds than eukaryotes .…”

SER: An R package to characterize environmental regimes

“…These data provide scientists a chance to explore research questions at time scales that were not possible earlier. Further, high‐frequency data allow computing environmental regimes that can be potential variables to increase the explained variation of biological communities (e.g., Guo et al, 2020; Wijewardene, Wu, Giménez‐Grau, et al, 2021; Wu et al, 2019). Therefore, this study aims to facilitate the computation of those indices by providing a common and extensible platform.…”

SER: an R package to compute environmental regime over a certain time period

“…These data provide scientists a chance to explore research questions at time scales that were not possible earlier. Further, high-frequency data allow computing environmental regimes that can be potential variables to increase explained variation of biological communities (e.g., Wu et al 2019;Guo et al 2020;Wijewardene et al 2021a).…”