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AME 38:71-79 (2005)
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Abstract
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Structuring of epilithic biofilms by the caddisfly Tinodes rostocki: photosynthetic activity and photopigment distribution in and beside larval retreats
Peter Stief1, Georg Becker2,*
1Max Planck Institute for Marine Microbiology, Celsiusstr. 1, 28359 Bremen, Germany
2Limnological River Station of the Max Planck Institute for Limnology, Damenweg 1, 36110 Schlitz, Germany
*Corresponding author. Email: gbecker@mpil-schlitz.mpg.de
ABSTRACT: Tinodes rostocki larvae (Trichoptera: Psychomyiidae) cover large proportions of stream hard substrata with retreats constructed of mineral particles and larval silk. We consider these retreats as 3-dimensional extensions of the epilithic
biofilm that may possess a distinct microenvironment, community metabolism and composition. Therefore, we compared the photosynthetic/respiratory activities (O2 and pH microsensors) and the photopigment composition (HPLC) of larval retreats and
the surrounding epilithic biofilms. In retreats, pigment contents and photosynthetic/respiratory activities were highest in sections with a visible microphytobenthic biofilm that were mostly the older parts of the retreats. In contrast, newly constructed
sections of the retreats and the surrounding epilithic biofilm had approximately 5-fold lower values. The fucoxanthin-to-chlorophyll ratio of the retreat biofilm was high (fuco/chl a = 1.27) and indicated diatom dominance, which was not evident in
the surrounding epilithic biofilm (fuco/chl a = 0.15). Experimental transplantation of larval retreats to microscope slides allowed microsensor measurements through the 500 to 700 µm-thick wall and inside the lumen. In the light,
O2 concentration and pH values increased significantly across the wall and remained high in the lumen of the retreat, whereas in darkness O2 and pH depressions in both wall and lumen were moderate or even absent. Our data suggest
that T. rostocki larvae construct and maintain retreats with a particular physico-chemical microenvironment that favours a distinct microbial community. Thereby, abundant T. rostocki larvae might significantly influence benthic primary
production and heterotrophic metabolism in small streams.
KEY WORDS: Stream · Epilithic biofilm · Microalgae · Photosynthesis · Trichoptera · Grazing · Microsensors · Photopigments
Full text in pdf format
Published in AME Vol.
38, No. 1
(2005) on January 21
Print ISSN: 0948-3055; Online ISSN: 1616-1564.
Copyright © Inter-Research, Oldendorf/Luhe, 2005
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