Light or electron microscopic counts of life cycle stages/transitions
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| Life cycle stage abundance (microscopy) |
|---|
| Approach: light or electron microscopy counts of morphologically distinct life stages |
| Context: in situ, lab |
| Spatial scale: point sample |
| Temporal scale: days |
| Units: cells L-1; % of population |
| Community captured: specific species with morphologically recognizable life stages |
| Co-measurements: species-specific duration of recognizable life stages (transition times) |
Method Overview
Fixed water samples (e.g. Lugol's iodine, glutaraldehyde, or formalin) are concentrated by settling or centrifugation and examined by light microscopy (LM) or transmission electron microscopy (TEM). Cells are identified and counted by their morphological characteristics, with individual life stages — resting cysts (hypnozygotes), spores, auxospores, vegetative cells, gametes, or temporary cysts — distinguished by their shape, size, wall structure, and pigmentation. Absolute abundances (cells L-1) and relative proportions (% of total population in each stage) are calculated from the counts. Time-series sampling reveals when life cycle transitions occur in natural populations[1].
Scale of measurement
Point samples; days between sample collection points. Some life cycle stages (e.g., gametes, auxospores) may be short-lived and require high-frequency sampling to capture.
Data generated
Abundances and proportions of distinct life cycle stages (cells L-1 and %). Time-series data reveal the timing, duration, and environmental triggers of life cycle transitions.
Units & currency
Units are cells L-1 or % of cells in each life stage. The currency is measured absolute or relative abundance of each life cycle stage.
Sample size
Typical samples are < 1 L in volume.
Repositories & databases
Limitations
Many life cycle stages are morphologically cryptic or indistinguishable from the vegetative cell by LM alone, requiring specialist knowledge or molecular markers. Short-lived stages (e.g., gametes, temporary cysts) may be underrepresented if sampling intervals are long. Fixation can alter cell morphology and mask diagnostic features. Knowledge of species-specific life stage durations is required to convert counts to transition rates.
Example Applications & Protocols
Classic examples
- Crawford (1995) The role of sex in the sedimentation of a marine diatom bloom [1]
- Rynearson et al. (2013) Major contribution of diatom resting spores to vertical flux in the sub-polar North Atlantic [2]
Recent applications
- Šupraha et al. (2016) Coccolithophore life-cycle dynamics in a coastal Mediterranean ecosystem [3]
Common calculations/conversions
- Life stage transition rate = change in stage abundance / known stage duration (from literature or lab experiments).
References
- ↑ 1.0 1.1 Crawford, R. M. (1995). The role of sex in the sedimentation of a marine diatom bloom. Limnology and Oceanography, 40(1), 200–204. https://doi.org/10.4319/lo.1995.40.1.0200
- ↑ Rynearson, T. A., Richardson, K., Lampitt, R. S., Sieracki, M. E., Poulton, A. J., Lyngsgaard, M. M., & Perry, M. J. (2013). Major contribution of diatom resting spores to vertical flux in the sub-polar North Atlantic. Deep-Sea Research Part I, 82, 60–71. https://doi.org/10.1016/j.dsr.2013.07.013
- ↑ Šupraha, L., Gerecht, A. C., Probert, I., & Henderiks, J. (2016). Coccolithophore life-cycle dynamics in a coastal Mediterranean ecosystem: seasonality and species-specific patterns. Journal of Plankton Research, 38, 1178–1193. https://doi.org/10.1093/plankt/fbw061