Potential sources of variability in mesocosm experiments on the response of phytoplankton to ocean acidification
Mesocosm experiments on phytoplankton dynamics under high CO<sub>2</sub> concentrations mimic the response of marine primary producers to future ocean acidification. However, potential acidification effects can be hindered by the high standard deviation typically found in the replicates...
| Main Authors: | , , |
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| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2017-04-01
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| Series: | Biogeosciences |
| Online Access: | http://www.biogeosciences.net/14/1883/2017/bg-14-1883-2017.pdf |
| Summary: | Mesocosm experiments on phytoplankton dynamics under high CO<sub>2</sub>
concentrations mimic the response of marine primary producers to future ocean
acidification. However, potential acidification effects can be hindered by
the high standard deviation typically found in the replicates of the same
CO<sub>2</sub> treatment level. In experiments with multiple unresolved
factors and a sub-optimal number of replicates, post-processing statistical
inference tools might fail to detect an effect that is present. We propose
that in such cases, data-based model analyses might be suitable tools to
unearth potential responses to the treatment and identify the uncertainties
that could produce the observed variability. As test cases, we used data from
two independent mesocosm experiments. Both experiments showed high standard
deviations and, according to statistical inference tools, biomass appeared
insensitive to changing CO<sub>2</sub> conditions. Conversely, our
simulations showed earlier and more intense phytoplankton blooms in modeled
replicates at high CO<sub>2</sub> concentrations and suggested that
uncertainties in average cell size, phytoplankton biomass losses, and initial
nutrient concentration potentially outweigh acidification effects by
triggering strong variability during the bloom phase. We also estimated the
thresholds below which uncertainties do not escalate to high variability.
This information might help in designing future mesocosm experiments and
interpreting controversial results on the effect of acidification or other
pressures on ecosystem functions. |
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| ISSN: | 1726-4170 1726-4189 |