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Chroococcus turgidus (Kützing) Nägeli 1849

Phylum
Cyanobacteriophyta
Class
Cyanophyceae
Order
Chroococcales
Habitat
planktonic
Distinctive features
single strongly pigmented cells or more often two cells, or occasionally small colonies of few cells in distinct, thick colorless envelope(s).
Organization
single cells or colonies of 2 (most common) to 8 cells
Color
blue-green
Cell shape
sphere
Colony shape
spherical
Cell diameter (D)
4 – 13 μm, median: 6.2 μm (N=502). Cell diameter varies significantly over an annual cycle, making it necessary to measure it routinely.
Cell biovolume
40 – 200 μm3. Larger cell size in winter, smaller in summer (see Fig. 2).
Biovolume equation
Sphere V, μm3 = 4/3 π (D/2)3.

Morphological features

Individual spherical cells are surrounded by lamellate sheaths. After division the original sheath remains around each new cell but an additional sheath envelopes both cells, now hemispherical in their shape, that remain attached (Plates 1). The cells are strongly colored, the envelopes are colorless but distinct (Plate 2). Chroococcus turgidus and Chroococcus minutus are difficult to tell apart. The only easy to notice difference is that the envelopes of C. turgidus are laminated (layered), whereas that of C. minutus typically show no layering. On average, C. minutus cells are smaller, but both species show large size variation and the sizes overlap.
Chroococcus turgidus (Kützing) Nägeli 1849 — plate 1 (from source)
Plate 1. Chroococcus turgidus. Two hemispherical cells that remain attached after division. Each cell is surrounded by its own sheath, and another sheath that envelopes both cells. Photo by Alla Alster, 2006.
Chroococcus turgidus (Kützing) Nägeli 1849 — plate 2 (from source)
Plate 2. Large cells of Chroococcus turgidus from the littoral zone. Couples of hemispherical cells that remain attached after division are surrounded by their own sheath, and another sheath that envelopes four cells. Photo by Alla Alster, 2019.

Ecology

An alanlyst effect is apparent in the long-term record of C. minutus and C. turgidus shown in Fig. 1. In particular, it is evident that Analyst 5 (1996-2012) counted more C. minutus whereas Analyst 6 (2013-2020) counted more C. turgidus, probably due to different taxon names given to the same organisms. Chroococcus minutus / turgidus has always been common in lake Kinneret, with long periods of thousands of (mostly 2-celled) colonies mL-1 (Fig. 1). Prior to the decline of Peridinium gatunense and appearance of nostocalean cyanobacteria in the mid 1990s Chroococcus was the most abundant Kinneret cyanobacterial taxon. Like several other Kinneret species, cells are smaller in summer, larger in winter (Fig. 2).

Environmental conditions

Chroococcus turgidus is more abundant at temperature > 22 C. It occurs at all chloride concentrations.

Additional figures

Figure 1. Time series of Chroococcus turgidus and Chroococcus minutus mean epilimnion colony abundance (colonies mL-1) Lake Kinneret, 1987–2020, showing a distinct Analyst Effect.
Figure 2. The annual pattern of water column cell abundance (left) and volume per cell (middle) and number of cells per colony (right) of Chroococcus turgidus, based on data for 2013-2020 (Analyst 6 only). Statistics shown are: median – middle line; 25th to 75th percentiles – box content; 90th and 10th percentiles - top and bottom bars, respectively.

Cite this record as: Dr. Tamar Zohary, Dr. Alla Alster. 21 July 2026. Electronic publication. Israel Oceanographic & Limnological Research. https://kinneret-algae-atlas.org/ Searched on —.

Further reading

  1. Zohary T, Fishbein T, Shlichter M, Naselli-Flores L (2017) Larger cell or colony size in winter, smaller in summer – a pattern shared by many species of Lake Kinneret phytoplankton. Inland Waters 7:200-209.

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