Growth and photosynthesis characteristics of three benthic diatoms from the brackish southern Baltic Sea in relation to varying environmental conditions

Abstract:

Three benthic diatom taxa Navicula perminuta, Melosira moniliformis and Nanofrustulum shiloi were isolated from sublittoral sandy sediments from the brackish southern Baltic Sea and established as unialgal cultures. Growth rates were determined under controlled conditions at different incubation temperatures (7–27°C), irradiances (10–600 μmol photons m⁻² s⁻¹) and salinities (1–50). The diatoms exhibited a wide range of growth tolerance. All of them grew well with growth rates of 0.3–1.5 divisons (μ) d⁻¹ under the given gradients of parameters, indicating a classification as euryhaline and eurythermal species. In accordance with these results, photosynthesis was characterised at optimal with suboptimal growth conditions of temperature and irradiance, using the methodological approach of oxygen production. Maximum oxygen production rates after preincubation under 150 μmol photons m⁻² s⁻¹ reached values of 120 to 360 μmol O₂ mg chlorophyll a h⁻¹. All three benthic diatoms from the Baltic Sea are physiologically well adapted to the fluctuating environmental conditions in shallow-water habitats without production loss under suboptimal conditions.

Key Words::

• Ecological tolerance
• Ecophysiology
• Oxygen optode

ACKNOWLEDGEMENTS

The authors thank Horst Ekat (Fa. Kunststoff-Technik Rostock, Germany) for manufacturing the P/E box and algae incubators. For diatom species isolation from field samples we thank Nadine Dolata. Gerhard Fulda, University of Rostock, we thank for assistance in taking scanning electron microscope-pictures of the cultures. This research was funded by the Federal Ministry of Education and Research of Germany (Bundesministerium für Bildung und Forschung; 03F0608O) in the framework of the Biological Impacts of Ocean Acidification (BIOACID) project (subproject 1.1.5).