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Helgoland Marine Research

Open Access

The effect of salinity on growth, photosynthesis and respiration in the estuarine red algaBostrychia radicans mont

  • Ulf Karsten1 and
  • Gunter O. Kirst1
Helgoländer Meeresuntersuchungen43:BF02365550


The estuarine red alga,Bostrychia radicans, was subjected to osmotic stresses ranging from hypo-osmotic (9.9‰) to hyperosmotic conditions (37.4‰). The growth rate decreased with increasing salinities and showed a maximum in a mesohaline medium, while the photosynthetic rate and the chlorophyll a content increased under hyper-osmotic conditions. The rate of respiration remained constant over the salinity range tested.B. radicans revealed typical characteristics of “shade plants” having a low light compensation point at 3–4 μE m−2 s−1 correlated with a low photon flux density of 70–100 μE m−2 s−1 for saturation of photosynthesis. These physiological properties may explain the success ofB. radicans in estuarine habitats.


ChlorophyllRespirationPhotosynthesisPhotosynthetic RateOsmotic Stress