MEPS 210:285-290 (2001)  -  doi:10.3354/meps210285

Microclimate of the brown alga Feldmannia caespitula interstitium under zero-flow conditions

Martina Pöhn, Kay Vopel*, Eva Grünberger, Jörg Ott

Department of Marine Biology, Institute of Ecology and Conservation Biology, University of Vienna, Althanstr. 14, 1090 Vienna, Austria
*Corresponding author. Present address: Alfred Wegener Institute for Polar and Marine Research, Columbus Center, 27568 Bremerhaven, Germany. E-mail:

ABSTRACT: The microclimate of the brown alga Feldmannia caespitula (J. Agardh) Knoepffler-Péguy interstitium was studied using microelectrode techniques. Zero water flow and irradiances of 170 and 1500 µmol photons m-2 s-1 cause steep O2 gradients peaking 3 to 4 mm below the outer surface of the tufts at 310 and 506% atmospheric saturation, respectively. The mean fluxes of O2 from the interstitium to the surrounding bulk water were 87 ± 21 and 262 ± 68 nmol cm-2 h-1 at low and high quantum flux density. Except for the outer 2 to 4 mm thick margin, the alga interstitium became anoxic within 52 min after abrupt darkening. The rate of dark oxygen uptake was 52 ± 5 nmol cm-2 h-1. The tufts were populated by 9 metazoan taxa: nematodes, harpacticoid copepods, ostracods, gastropods, bivalves, polychaetes, amphipods, isopods and halacarids. Our results suggest that the interstitium of fine-textured algal thalli is a microhabitat of variable water chemistry with temporary anoxia and hyperoxia in an otherwise relatively stable water column. Although the tufts are attractive for meiofauna by providing food and protection from currents and predators, rapid fluctuations in oxygen concentration probably cue temporal emigration of the algal infauna.

KEY WORDS: Phytal · Feldmannia caespitula · Microenvironment · Meiofauna · Oxygen concentration gradients · Oxygen deficiency

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