| Literature DB >> 25412343 |
Jūratė Lesutienė1, Elena Gorokhova2, Daiva Stankevičienė3, Eva Bergman4, Larry Greenberg4.
Abstract
Periphyton communities of a boreal stream were exposed to different light and nutrient levels to estimate energy transfer efficiency from primary to secondary producers using labeling with inorganicEntities:
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Year: 2014 PMID: 25412343 PMCID: PMC4239105 DOI: 10.1371/journal.pone.0113675
Source DB: PubMed Journal: PLoS One ISSN: 1932-6203 Impact factor: 3.240
Figure 1The study site as indicated by the arrow in Örbäcken Creek, western Sweden.
The red line shows the catchment area (5.38 km2).
Main characteristics and stoichiometry of the periphyton used in the field and laboratory experiments; (mean ± SE, AFDW = ash free dry weight, TSM = total sedimentary matter).
| Variables | Field experiment(n = 4) | Laboratoryexperiment (n = 3) | t-test, p value |
| Chlorophyll a, µg cm−2 | 1.6±0.22 | 0.71±0.25 | p<0.05 |
| AFDW, mg cm−2, | 1.02±0.19 | 0.51±0.07 | n.s. |
| TSM, mg cm−2 | 5.43±0.69 | 5.69±1.13 | n.s |
| Relative contribution oforganic matter to TSM, % | 19±2 | 9±1 | p<0.05 |
| Autotrophic Index | 634±75 | 836±165 | n.s. |
| C, µg cm−2 | 357±50 | 245±68 | n.s. |
| N, µg cm−2 | 37.8±5.4 | 12.4±2.7 | p<0.05 |
| P, µg cm−2 | 2.1±0.4 | 1.8±0.3 | n.s. |
| C:N molar | 11±0 | 11±1 | n.s. |
| C:P molar | 463±59 | 178±49 | p<0.05 |
| N:P molar | 41.8±4.6 | 16.3±3.9 | p<0.05 |
| C:Chlorophyll | 227±28 | 179±32 | n.s. |
| δ13C ‰ | –32.1±0.5 | –28.8±0.1 | p<0.05 |
Unpaired t-tests were used to compare specific parameters between the field and laboratory experiments, n.s. = not significant, n = number of replicates.
Nutrient concentrations (µmol L−1) in the stream water during the field and laboratory experiments, and in the region during the summer (Nyberg L. pers. communication).
| Concentrations, µmol L−1 | |||||
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| Laboratory experiment | Region | |||
| Nutrient | Ambient | Enriched | Ambient | Enriched | Min-Max, Mean |
| PO4-P | 0.26 | 0.56 | 0.35 | 0.65 | <0.32 |
| NO3-N | 1.57 | 11.57 | 1.21 | 11.21 | 0–8.4, 1.4 |
| NO2-N | 0.57 | 0.57 | 0.21 | 0.21 | n.d. |
| NH4-N | <0.71 | <0.71 | 0.71 | 0.71 | 0–4.8, 0.2 |
| N:P | 10 | 22 | 6 | 19 | >5 |
N.d. = no data.
Figure 2Schematic drawing of the experimental incubation system in the flow-through aquaria.
Water was cooled by circulating it through the cooler as indicated by the arrows. Ellipses denote stones, and G+ and G− denote the addition or lack of grazers.
Figure 3Mean values (± SE) of the δ13C increment (Δ13C) in periphyton grown under different light and nutrient (P- phosphorus, N- nitrogen) additions in the field experiment.
The GLM of Box-Cox transformed Δ13C values in periphyton from the field experiment.
| Variable | Level of effect | Estimate | Wald | p |
| LnChlorophyll | –0.2 | 12.15 | 0.0005 | |
| C:N | –0.04 | 5.58 | 0.0182 | |
| Light | LL | –0.05 | 12.77 | 0.0003 |
| P | not added | –0.05 | 9.94 | 0.0016 |
Light (high vs. low, LL) and P – phosphorus (added vs. not added) are categorical factors, whereas chlorophyll a (µg cm−2) and C:N (molar) are continuous predictors.
Figure 4Composition of periphytic algae.
% of total biovolume at the start and at the end of the laboratory experiment for grazed and ungrazed periphyton at the two light levels: (L+ = PAR of 40 µmol m−2 s−2 and L– = PAR of 6 µmol m−2 s−2). N+ indicates nutrient enrichment and N– ambient nutrient levels. White bars represent diatoms, grey are green algae and black are cyanobacteria and euglenophytes.
Figure 5Algal biovolume.
Mean (± SE) biovolume of diatoms, green algae and cyanobacteria subjected to grazing/non-grazing and four different light (high = L+; low = L–) and nutrient (addition = N+; ambient = N–) conditions at the end of the laboratory experiment. Note the scale of the y-axis differs among panels.
Effect sizes (η2) for the effects of nutrient additions, light, grazing and time of sampling on periphyton biomass (chlorophyll a and AFDW), inorganic carbon uptake (Δ13C, biomass-specific 13C uptake (Δ13C/Chl a and Δ13C/AFDW), nutrient content (C, N, and P) and nutrient ratios (N:P, C:P, and C:N).
| Parameter | Chl | AFDW | Δ13C | Δ13C/Chl | Δ13C/AFDW | C | N | P | N:P | C:P | C:N |
| Light | 0.17 | 0.004 |
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| 0.04 | 0.00 | 0.00 | 0.09 | 0.16 | 0.12 |
| Nutrients | 0.20 | 0.10 | 0.03 | 0.14 | 0.03 | 0.12 | 0.20 | 0.19 | 0.00 | 0.00 | 0.06 |
| Light×nutrients | 0.06 | 0.06 | 0.02 | 0.01 | 0.002 | 0.01 | 0.00 | 0.01 | 0.02 | 0.01 | 0.05 |
| Time | 0.18 |
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| 0.10 | 0.23 |
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| Time×light | 0.03 | 0.02 | 0.08 | 0.06 | 0.17 | 0.13 | 0.07 | 0.03 | 0.09 | 0.10 | 0.05 |
| Time×nutrients | 0.01 | 0.02 | 0.03 | 0.05 | 0.07 | 0.08 | 0.05 | 0.04 | 0.02 | 0.04 | 0.04 |
| Grazing |
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| 0.00 | 0.21 |
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| Grazing×light | 0.12 | 0.02 | 0.15 | 0.03 | 0.31 | 0.05 | 0.01 | 0.00 | 0.23 | 0.25 | 0.06 |
| Grazing×nutrients | 0.00 | 0.02 | 0.05 | 0.01 | 0.00 | 0.07 | 0.04 | 0.05 | 0.00 | 0.01 | 0.06 |
| Time×grazing |
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| 0.12 | 0.14 |
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| 0.12 |
All data are from the laboratory experiment and analyzed by repeated measures ANOVA. Significant effects are in boldface and denoted by *p<0.05, **p<0.01, ***p<0.001; for marginally significant effects, p values are given. The 3rd order interactions are not presented as none were significant.
Figure 6Mean values of periphyton biomass (chlorophyll a and AFDW), elemental (C, P, and N) concentrations and nutrient ratios (N:P, C:N, and C:P) over the 14 day-long laboratory experiment.
Squares and circles denote grazed and ungrazed conditions, respectively. Filled symbols denote low light and open high light treatments. Asterisks denote significant grazer effects for each sampling day (RM ANOVA, with grazing as within-group factor, *p<0.05, **p<0.01, ***p<0.001).
Figure 7The δ13C increment (Δ13C) (means ± SE) in periphyton subjected to grazing/non-grazing and four different light (high = L+; low = L–) and nutrient (addition = N+; ambient = N–) conditions after 2, 5 and 14 days.
Figure 8Mean biomass-specific 13C uptake for the four light and grazer treatments over time in the laboratory experiment.
Squares and circles denote grazed and ungrazed conditions, respectively. Filled and open symbols denote low and high light treatments, respectively.
Figure 9The δ13C increment (mean± SE) for caddisflies and periphyton, as well as the carbon transfer efficiency (expressed as Δ13Ccaddisflies/Δ13Cperiphyton) for the four different light (high = L+; low = L–) and nutrient (addition = N+; ambient = N–) conditions after 5 days in the laboratory experiment.
The three separate two-way ANOVAs were used to test significance of light, the δ13C increment for caddisflies, periphyton and transfer efficiency (Δ13Ccaddisflies/Δ13Cperiphyton).