Algal regulation of extracellular enzyme activity in stream microbial communities associated with inert substrata and detritus

Rier, Steven T.; Kuehn, Kevin A.; Francoeur, Steven N.

doi:10.1899/06-080.1

Cited by 87 publications

(79 citation statements)

References 31 publications

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“…This could be due directly to algal enzyme production, especially in the case of phosphatase. Two alternative mechanisms involving heterotrophs are more likely, however, at least for the carbon-acquiring enzymes: heterotrophs may excrete enzymes using carbon compounds of algal origin as the main substrate, or the organic carbon supplied by algae serves as priming agent facilitating the enzymatic cleavage of recalcitrant carbon compounds from other sources (Rier et al, 2007;Guenet et al, 2010). Such priming might indeed be an important mechanism in the Chicken Creek catchment, because dissolved organic carbon is abundant (B14 mg l -1 ) but highly recalcitrant (Gerull et al, 2011).…”

Section: Temporal Variability Of Potential Enzyme Activitiesmentioning

confidence: 99%

Disconnect of microbial structure and function: enzyme activities and bacterial communities in nascent stream corridors

et al. 2011

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A fundamental issue in microbial and general ecology is the question to what extent environmental conditions dictate the structure of communities and the linkages with functional properties of ecosystems (that is, ecosystem function). We approached this question by taking advantage of environmental gradients established in soil and sediments of small stream corridors in a recently created, early successional catchment. Specifically, we determined spatial and temporal patterns of bacterial community structure and their linkages with potential microbial enzyme activities along the hydrological flow paths of the catchment. Soil and sediments were sampled in a total of 15 sites on four occasions spread throughout a year. Denaturing gradient gel electrophoresis (DGGE) was used to characterize bacterial communities, and substrate analogs linked to fluorescent molecules served to track 10 different enzymes as specific measures of ecosystem function. Potential enzyme activities varied little among sites, despite contrasting environmental conditions, especially in terms of water availability. Temporal changes, in contrast, were pronounced and remarkably variable among the enzymes tested. This suggests much greater importance of temporal dynamics than spatial heterogeneity in affecting specific ecosystem functions. Most strikingly, bacterial community structure revealed neither temporal nor spatial patterns. The resulting disconnect between bacterial community structure and potential enzyme activities indicates high functional redundancy within microbial communities even in the physically and biologically simplified stream corridors of early successional landscapes.

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Section: Temporal Variability Of Potential Enzyme Activitiesmentioning

confidence: 99%

Disconnect of microbial structure and function: enzyme activities and bacterial communities in nascent stream corridors

et al. 2011

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“…Low ratios indicate greater importance of allochthonous C sources requiring hydrolysis of hemicellulose by XYLO, whereas high ratios indicate greater importance of glucose obtained by hydrolysis of cellobiose, which originates mostly from algae (Romani and Sabater 2000). In addition to being a source of C, algal photosynthesis may increase the activities of extracellular enzymes by enhancing redox and pH conditions that could stimulate heterotrophic activity (Espeland et al 2001, Rier et al 2007. As a result, reduced algal biomass could indirectly exacerbate AMD effects on bacterial function by providing less C needed for cellular functions.…”

Section: And Nutrient Dynamicsmentioning

confidence: 99%

Acid mine drainage affects the development and function of epilithic biofilms in streams

Smucker

Vis

2011

Journal of the North American Benthological Society

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“…The latter typically experience larger temporal variation in water movements and transportation of organic and inorganic particulate matter, have higher contribution of leaf litter and therefore higher relative abundance of fungi and have less contribution from anaerobic microbial processes. In shallow lotic systems, microbial biofilms on rocks, wood or macrophytes containing both photosynthetic microalgae and non-photosynthetic microorganisms (Rier et al, 2007) can constitute a large but highly dynamic component of the microbial community (Hudson et al, 1992;Findlay et al, 1993).…”

Section: Microorganismsmentioning

confidence: 99%

Scientific Opinion on the effect assessment for pesticides on sediment organisms in edge‐of‐field surface water

2015

EFS2

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The EFSA Panel on Plant Protection Products and their Residues (PPR Panel) was tasked to revise the Guidance Document (GD) on Aquatic Ecotoxicology under Council Directive 91/414/EEC (SANCO/3268/2001 rev. 4 (final), 17 October 2002. This scientific opinion of the PPR Panel is the second of three requested deliverables within this mandate. The scientific background for the risk assessment on sediment organisms in edge-of-field surface waters is provided, with reference to benthic ecology and ecotoxicology, available test protocols and current knowledge on exposure and effects of sediment-bound plant protection products (PPPs). The scientific opinion provides approaches on how to derive regulatory acceptable concentrations (RACs) for sediment organisms and exposure to active substances of PPPs and transformation products of these substances, and how to link them in a tiered approach to predicted environmental concentrations (PECs) for the sediment compartment. A list of uncertainties in relation to such approaches is given. SUMMARYSediment Environmental Risk Assessment (ERA) is a combination of exposure and effect assessment. Proposals for these assessments are provided. The opinion describes specific protection goals (SPGs) for sediment-inhabiting organisms based on two options (1) the ecological threshold option (ETO), accepting negligible population effects only, and (2) if applicable, the ecological recovery option (ERO), accepting some population-level effects if ecological recovery takes place within an acceptable time period.Triggers for sediment ecotoxicity testing are proposed together with a decision scheme for when additional testing may be required. The ecotoxicologically relevant concentrations (ERCs) for sediment organisms are proposed, as this will be influenced by the choice of sediment layer, exposure metric and test duration.The current Forum for the co-ordination of pesticide fate models and their use (FOCUS) methodology for surface water does not consider the effect of multi-year applications, which could possibly lead to accumulation of pesticides in sediment. To account for this deficit, a proposed methodology for introducing an accumulation factor that can be used until an updated FOCUS methodology becomes available is presented in this opinion. The accumulation factor can be considered a conservative approach, since it does not include any possible transport processes, such as leaching or volatilisation, which may reduce the accumulation in sediment in the real field situation.A tiered effect assessment approach is proposed for different sediment organisms and how to link regulatory acceptable concentrations (RACs) to predicted environmental concentration (PECs). The assessment of bioaccumulation, biomagnification and secondary poisoning is discussed, as well as the prospect of improving ERA for sediment microorganisms.Transformation products from active substances also may need to be assessed, as well as mixture toxicity of formulations of plant protection products (PPPs). The op...

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Algal regulation of extracellular enzyme activity in stream microbial communities associated with inert substrata and detritus

Cited by 87 publications

References 31 publications

Disconnect of microbial structure and function: enzyme activities and bacterial communities in nascent stream corridors

Disconnect of microbial structure and function: enzyme activities and bacterial communities in nascent stream corridors

Acid mine drainage affects the development and function of epilithic biofilms in streams

Scientific Opinion on the effect assessment for pesticides on sediment organisms in edge‐of‐field surface water

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