Research method
Mesocosm Experiment
4 studies
A mesocosm experiment holds a simplified piece of an ecosystem — submerged sediment tanks, potted trees, experimental islands or aquaria — under controlled treatments so a process (litter decay, ¹⁵N uptake, fungal inoculum, pH drop) can be measured. It is stronger on mechanism than a field census and weaker on scaling: an 80-day tank or a potted spruce is not a whole lake, forest or century of ocean acidification.
Biogeochemists and restoration ecologists use mesocosms when they need to isolate a driver they cannot independently vary at landscape scale. The design answers 'under this treatment, do production, tracer recovery, growth or mineral structure change?' Its main limitation is that two lakes, LILA islands or Loch Sween thalli cannot be read as a regional carbon budget, and a rate-of-change effect in a tank may not match gradual field ocean acidification.
Studies
4
Findings
4
4 supporting · 0 challenging · 0 qualifying citations
Open tensions
2
Currently
What we know
- Submerged-sediment mesocosms with graded deciduous/coniferous litter in a clear lake (Swan) and a dark lake (Laurentian) near Sudbury found that a 25% rise in aromaticity cut bacterial production 14.5%. The dark lake paid a respiratory cost, while the clearer lake was more nutrient-limited and more photo-oxidizing. A two-lake comparison cannot isolate nutrients from light, and the tanks do not measure whole-lake carbon burial over years.
- Potted Sitka spruce mesocosms received ¹⁵N on canopies versus soil from February 2013 to March 2014. Canopy N uptake recovered about three times more tracer aboveground and four times more in wood than soil-targeted deposition; needle δ¹⁵N reached about 120‰ versus 38‰. The harvest does not measure whole-forest carbon stocks or prove that canopy uptake changes landscape-scale sequestration.
- Soil fungi were sequenced from 8 constructed and 14 natural Everglades tree islands, then four native tree species were grown with live versus sterile inoculum under constrained versus unconstrained water. Diversity and guild mix became similar without actively restoring fungi, but composition along PCo2 still differed. Under flooded (unconstrained) water, live inoculum made that compositional axis matter for trunk diameter; constrained water washed the effect out. Results are from LILA experimental islands and a pot/mesocosm assay, not a landscape planting census.
- Live and dead Lithothamnion glaciale thalli were held 80 days in control seawater (pH 8.1), a gradual drop to pH 7.7 (0.05 units per day over 10 days), or an abrupt drop (0.25 units per day over two days from day 52). Bicarbonate (a dissolution marker) was absent in live control thalli but appeared under low and especially abrupt pH. Live algae in stable low pH calcified more by day than they dissolved at night — about twice control daytime rates — without changing photosynthesis or respiration. Dead thalli dissolved faster at low pH and could not buffer. Abrupt-pH calcification was not measured.
Largest unresolved question
These mesocosms do not test one carbon-cycle claim. Litter tanks show aromaticity cutting bacterial production 14.5% with lake-colour differences in respiratory cost versus photo-oxidation. Canopy ¹⁵N recovers 3–4× more tracer in wood than soil targeting but does not scale to forest C stocks. Everglades inoculum effects on trunk diameter appear only under unconstrained flooding. Coralline algae are more sensitive to the rate of the pH drop than to low pH as a level, and live thalli at stable pH 7.7 increased daytime calcification. 'Mesocosms show carbon or OA effects' is not a single result.
Common misconceptions
If canopy ¹⁵N recovery is three to four times soil targeting, canopy uptake has been shown to raise landscape carbon sequestration.
The mesocosms recovered more tracer aboveground and in wood (needle δ¹⁵N ~120‰ versus 38‰). That is a allocation/recovery contrast in potted Sitka spruce, not a measured change in whole-forest carbon stocks.
Bicarbonate appearing in live thalli at low pH means the algae are simply dissolving and failing.
Bicarbonate was a dissolution marker that was absent in live controls and stronger under abrupt pH, but live algae in stable low pH still calcified more by day than they dissolved at night (~twice control daytime rates) without changing photosynthesis or respiration. Rate of pH change, live versus dead, and unmeasured abrupt-pH calcification all matter.
If fungal diversity on constructed islands matches natural islands, restoration has rebuilt microbial function.
Guild mix converged without actively restoring fungi, but composition along PCo2 still differed, and live inoculum affected trunk diameter only under unconstrained flooding. Constrained water washed the growth effect out.
Related
Claim ledger
What the evidence shows
Drawn from 4 studies in this library. Mix labels say which citation roles are present; they are not a strength score. Supports means evidence for a finding; Challenges means evidence against a stated position; Qualifies marks scope.
Submerged-sediment mesocosms with graded deciduous/coniferous litter in a clear lake (Swan) and a dark lake (Laurentian) near Sudbury found that a 25% rise in aromaticity cut bacterial production 14.5%. The dark lake paid a respiratory cost, while the clearer lake was more nutrient-limited and more photo-oxidizing. A two-lake comparison cannot isolate nutrients from light, and the tanks do not measure whole-lake carbon burial over years.
Potted Sitka spruce mesocosms received ¹⁵N on canopies versus soil from February 2013 to March 2014. Canopy N uptake recovered about three times more tracer aboveground and four times more in wood than soil-targeted deposition; needle δ¹⁵N reached about 120‰ versus 38‰. The harvest does not measure whole-forest carbon stocks or prove that canopy uptake changes landscape-scale sequestration.
Soil fungi were sequenced from 8 constructed and 14 natural Everglades tree islands, then four native tree species were grown with live versus sterile inoculum under constrained versus unconstrained water. Diversity and guild mix became similar without actively restoring fungi, but composition along PCo2 still differed. Under flooded (unconstrained) water, live inoculum made that compositional axis matter for trunk diameter; constrained water washed the effect out. Results are from LILA experimental islands and a pot/mesocosm assay, not a landscape planting census.
Live and dead Lithothamnion glaciale thalli were held 80 days in control seawater (pH 8.1), a gradual drop to pH 7.7 (0.05 units per day over 10 days), or an abrupt drop (0.25 units per day over two days from day 52). Bicarbonate (a dissolution marker) was absent in live control thalli but appeared under low and especially abrupt pH. Live algae in stable low pH calcified more by day than they dissolved at night — about twice control daytime rates — without changing photosynthesis or respiration. Dead thalli dissolved faster at low pH and could not buffer. Abrupt-pH calcification was not measured.
Debates
Tensions and limits
Some items are genuine disagreements on the same question. Others mark different assays, populations, or outcomes.
These mesocosms do not test one carbon-cycle claim. Litter tanks show aromaticity cutting bacterial production 14.5% with lake-colour differences in respiratory cost versus photo-oxidation. Canopy ¹⁵N recovers 3–4× more tracer in wood than soil targeting but does not scale to forest C stocks. Everglades inoculum effects on trunk diameter appear only under unconstrained flooding. Coralline algae are more sensitive to the rate of the pH drop than to low pH as a level, and live thalli at stable pH 7.7 increased daytime calcification. 'Mesocosms show carbon or OA effects' is not a single result.
These mesocosms do not test one carbon-cycle claim. Litter tanks show aromaticity cutting bacterial production 14.5% with lake-colour differences in respiratory cost versus photo-oxidation. Canopy ¹⁵N recovers 3–4× more tracer in wood than soil targeting but does not scale to forest C stocks. Everglades inoculum effects on trunk diameter appear only under unconstrained flooding. Coralline algae are more sensitive to the rate of the pH drop than to low pH as a level, and live thalli at stable pH 7.7 increased daytime calcification. 'Mesocosms show carbon or OA effects' is not a single result.
- Dark lakes change how microbes eat land carbon
- Canopy nitrogen and tree carbon uptake
- Constructed Everglades islands differ in soil fungi
- Fast pH drops damage coralline algae more than slow OA
Study Role Design N Population Outcome Dark lakes change how microbes eat land carbon Supports Animal / in-vitroSediment mesocosms with graded litter in clear vs dark lakes near Sudbury N=48 · 24 mesocosms per lake × 2 lakes Benthic microbial communities in Swan Lake and Lake Laurentian, Ontario Bacterial production, enzymes, and CO2 response to terrestrial organic-matter aromaticity Canopy nitrogen and tree carbon uptake Supports Animal / in-vitro15N tracer mesocosm comparing canopy vs soil nitrogen targeting in Sitka spruce Potted Sitka spruce mesocosms; mean aboveground biomass 370 g/tree — exact tree N not primary in stored text Potted Sitka spruce trees Aboveground and wood recovery of canopy-applied vs soil-applied 15N Constructed Everglades islands differ in soil fungi Supports OtherSoil fungal survey of Everglades islands plus factorial greenhouse inoculum × hydrology growth trial N=22 · 8 constructed + 14 natural tree islands surveyed; soil DNA N=43 samples Constructed and natural Everglades tree-island soils and four native tree species Fungal composition divergence and effects on tree growth under flood vs constrained water Fast pH drops damage coralline algae more than slow OA Supports Animal / in-vitro80-day pH ramp experiment on live and dead Lithothamnion glaciale thalli Thalli incubated in three pH treatments; exact thallus N not a single primary figure in stored text Lithothamnion glaciale coralline algae from Loch Sween, Scotland Calcification, dissolution markers, and physiology under gradual vs abrupt acidification
PaperFren reads this as a limit on how far one study travels — different assays, populations, or outcomes — not a forced fight between papers.
Live versus dead material reverses the practical inference at low pH. Live Lithothamnion in stable low pH calcified more by day (~twice control) without changing photosynthesis or respiration, whereas dead thalli dissolved faster and could not buffer. Using only dead-skeleton dissolution rates would miss the live buffering the authors measured — and they still did not measure calcification in the abrupt treatment.
Live versus dead material reverses the practical inference at low pH. Live Lithothamnion in stable low pH calcified more by day (~twice control) without changing photosynthesis or respiration, whereas dead thalli dissolved faster and could not buffer. Using only dead-skeleton dissolution rates would miss the live buffering the authors measured — and they still did not measure calcification in the abrupt treatment.
PaperFren reads this as a limit on how far one study travels — different assays, populations, or outcomes — not a forced fight between papers.
Timeline
How understanding moved
Study years are when the paper was published. Evidence edits are dated changes to this page's claims. Explanations are when PaperFren added a Discovery — not a claim that the science happened that day.
2026
Concept page published
Mesocosm Experiment
Change log
What changed
Dated edits to this page's evidence: studies added or removed from a claim, claims added or withdrawn, and new explanations tagged here. Coverage edits are distinct from reviewed research changes and corrections. Dates record PaperFren updates; study publication dates appear in the timeline.
- Coverage updated · Concept page published
Papers
4 studies in this library bear on Mesocosm Experiment, ordered by citations.
- Fast pH drops damage coralline algae more than slow OA
Red coralline algae coped with a gradual drop to pH 7.7 but showed more skeletal dissolution when pH fell abruptly.
- Canopy nitrogen and tree carbon uptake
Canopy-applied 15N is recovered aboveground about three times more than soil-applied N.
- Dark lakes change how microbes eat land carbon
In a dark Ontario lake, more aromatic terrestrial organic matter lowered bacterial production and slightly raised CO2.
- Constructed Everglades islands differ in soil fungi
After ~18 years, constructed tree islands match natural islands in fungal diversity but not composition, and that difference changes tree growth when hydrology is unconstrained.
Compare studies
Select 2–10 studies. Design and N are labels, not a ranking.
Nothing selected yet.
Questions
What is still open
These mesocosms do not test one carbon-cycle claim. Litter tanks show aromaticity cutting bacterial production 14.5% with lake-colour differences in respiratory cost versus photo-oxidation. Canopy ¹⁵N recovers 3–4× more tracer in wood than soil targeting but does not scale to forest C stocks. Everglades inoculum effects on trunk diameter appear only under unconstrained flooding. Coralline algae are more sensitive to the rate of the pH drop than to low pH as a level, and live thalli at stable pH 7.7 increased daytime calcification. 'Mesocosms show carbon or OA effects' is not a single result.
Live versus dead material reverses the practical inference at low pH. Live Lithothamnion in stable low pH calcified more by day (~twice control) without changing photosynthesis or respiration, whereas dead thalli dissolved faster and could not buffer. Using only dead-skeleton dissolution rates would miss the live buffering the authors measured — and they still did not measure calcification in the abrupt treatment.
Ask PaperFren about Mesocosm Experiment
Study this conceptflashcards and short-answer questions
A 25% rise in aromaticity cut bacterial production 14.5%, with different costs in a dark versus a clear lake. Why can you not treat that as the whole-lake carbon-burial response to terrestrial litter?
The comparison is two lakes and cannot isolate nutrients from light. Mesocosms measured bacterial production, enzymes, CO₂ and metagenomes over the experiment, not multi-year whole-lake burial.
Needle δ¹⁵N reached about 120‰ with canopy ¹⁵N versus 38‰ with soil targeting, with ~3× aboveground and ~4× wood tracer recovery. What claim is licensed, and what is not?
Licensed: canopy-applied tracer is recovered more in aboveground tissues and wood in these potted spruce. Not licensed: that canopy N uptake increases landscape-scale carbon sequestration or whole-forest C stocks.
Why did live inoculum's effect on trunk diameter depend on the water treatment in the Everglades assay?
Under flooded unconstrained water, live inoculum made the remaining fungal-composition axis (PCo2) matter for diameter; constrained water washed that effect out. Hydrology gated whether the compositional difference was functionally visible.
Control pH was 8.1; gradual OA was 0.05 units/day over 10 days to 7.7; abrupt was 0.25 units/day over two days. Why is 'pH 7.7 is harmful' an incomplete reading of the 80-day result?
Structure was more sensitive to rate than to the low-pH level. Live algae in stable low pH increased daytime calcification (~twice control) without changing photosynthesis or respiration; bicarbonate and dissolution were stronger under the abrupt drop, whose calcification was not measured. Eighty days cannot capture centennial OA or grazing.