Cell abundance
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| Phytoplankton net growth rate (cell counting) |
|---|
| Approach: FCM or microscopy cell counts in time-course incubations |
| Context: incubation |
| Spatial scale: point sample |
| Temporal scale: hours |
| Units: d-1 (net growth rate) |
| Community captured: varies (FCM-resolvable populations or microscopy-counted taxa) |
| Co-measurements: (none specified) |
Method Overview
Cell abundance is tracked over the course of incubation experiments using flow cytometry (FCM) or epifluorescence microscopy. The rate of change in cell concentration over time gives the net growth rate of the incubated population. When paired with dilution treatments (see Incubation dilution experiments), cell counting separates the contributions of growth and grazing to the net change in abundance. In the absence of dilution, the net growth rate (k = µ − g) is obtained directly; resolving µ and g requires an additional experimental manipulation.
Scale of measurement
Point samples after hours of incubation.
Data generated
Net phytoplankton growth rate (d-1) for each counted population. When combined with a dilution series, specific growth rate (µ) and grazing rate (g) are resolved.
Units & currency
Units are d-1. The currency is cells.
Sample size
Typical samples are < 1 L in volume.
Repositories & databases
Limitations
Cell counting alone gives the net rate (µ − g); resolving growth from grazing requires additional experimental manipulation (dilution, additions). FCM cannot distinguish living from recently dead cells, which can bias estimates.
Example Applications & Protocols
Classic examples
Recent applications
Common calculations/conversions
- Net growth rate k (d-1) = ln(Nfinal/Ninitial) / t.