Photosynthesis in relation to D1, PsaA and Rubisco in marine and brackish water ecotypes of Fucus vesiculosus and Fucus radicans (Phaeophyceae)

A Maria Gylle,Carina I Svan,Nils G A Ekelund,Charlotta A Nygård,Tessa Pocock

doi:10.1007/s10750-012-1231-9

Abstract

The aim of this study was to investigate photosynthetic differences between the marine, Norwegian Sea ecotype and the brackish, Bothnian Sea ecotype of F. vesiculosus and F. radicans and to see whether photosynthetic differences could be connected with the relative amounts of D1 protein (PSII), PsaA (PSI) protein and/or Rubisco. For this purpose, we tested if a higher photosynthetic maximum (P max) in the Atlantic Ocean ecotype of F. vesiculosus relative to the Baltic Sea ecotype, and an increase of the P max in Baltic Sea ecotype of F. vesiculosus at higher salinity, could be due to an increase in the relative amounts of Rubisco. The proteins have been evaluated on a relative basis. Immunoblot signals showed that the amount of Rubisco was higher in both ecotypes of F. vesiculosus than in F. radicans, but no differences could be detected between the two ecotypes of F. vesiculosus. The results suggest an uneven photosystem protein stoichiometry in Fucus, with more of the PSI protein PsaA relative to the PSII protein D1. The difference in P max between the two ecotypes of F. vesiculosus might be related to the difficulties for the algae to adapt to the environment in Bothnian Sea.

Highlights

The brown alga Fucus vesiculosus L. is mainly a marine, North Atlantic, intertidal species (Powell, 1963), but the alga grows in the sublittoral of the brackish Baltic Sea, along a salinity gradient down to the range of 2–4 psu (Wærn, 1952)
The results confirm that photosynthetic maximum (Pmax) was significantly higher (57%) in the marine ecotype of F. vesiculosus compared to the brackish ecotype of F. vesiculosus (P \ 0.01; Fig. 1; Table 1)
The results indicated a higher Pmax in the marine ecotype of F. vesiculosus than in the brackish ecotype of F. vesiculosus and F. radicans (Fig. 1; Table 1)

Summary

Introduction

The brown alga Fucus vesiculosus L. is mainly a marine, North Atlantic, intertidal species (Powell, 1963), but the alga grows in the sublittoral of the brackish Baltic Sea, along a salinity gradient down to the range of 2–4 psu (Wærn, 1952). Kautsky (Bergstrom et al, 2005), F. vesiculosus was thought to be the only large belt-forming algal species in the Bothnian Sea, a northerly part of the Baltic Sea (Wallentinus, 1979). F. radicans is most certainly endemic to the Baltic Sea, grows side-by-side with F. vesiculosus and was earlier thought to be the same species. The environmental factors differ greatly between the Norwegian Sea (part of the Atlantic Ocean) and the Bothnian Sea (part of the Baltic Sea). The brackish ecotype of F. vesiculosus is smaller with a thinner thallus (Kalvas & Kautsky, 1993), has greater respiration rates, lower maximum photosynthetic capacities (Pmax), lower mannitol concentration, lower tolerance of emersion stress and contains fewer water soluble organic compounds than the marine ecotype of F. vesiculosus (Back et al, 1992; Ruuskanen & Back, 1999; Pearson et al, 2000; Nygard & Ekelund, 2006; Gylle et al, 2009a, b)

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Conclusion