Carbon conversion and metabolic rate in two marine sponges.
The carbon metabolism of two marine sponges,Haliclona oculataandDysidea avara, has been studied using a13C isotope pulse-chase approach. The sponges were fed13C-labeled diatoms (Skeletonema costatum) for 8 h and they took up between 75 and 85%. At different times, sponges were sampled for total13C enrichment, and fatty acid (FA) composition and13C enrichment. Algal biomarkers present in the sponges were highly labeled after feeding but their labeling levels decreased until none was left 10 days after enrichment. The sponge-specific FAs incorporated13C label already during the first day and the amount of13C label inside these FAs kept increasing until 3 weeks after labeling. The algal-derived carbon captured by the sponges during the 8-h feeding period was thus partly respired and partly metabolized during the weeks following. Apparently, sponges are able to capture enough food during short periods to sustain longer-term metabolism. The change of carbon metabolic rate of fatty acid synthesis due to mechanical damage of sponge tissue was studied by feeding sponges with13C isotope-labeled diatom (Pheaodactylum tricornutum) either after or before damaging and tracing back the13C content in the damaged and healthy tissue. The filtration and respiration in both sponges responded quickly to damage. The rate of respiration inH. oculatareduced immediately after damage, but returned to its initial level after 6 h. The13C data revealed thatH. oculatahas a higher metabolic rate in the tips where growth occurs compared to the rest of the tissue and that the metabolic rate is increased after damage of the tissue. ForD. avara, no differences were found between damaged and non-damaged tissue. However, the filtration rate decreased directly after damage.
Department of Agrotechnology and Food Sciences, Bioprocess Engineering group, Wageningen University, P.O. 8129, 6700 EV Wageningen, The Netherlands.
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Koopmans
Netherlands Institute of Ecology (NIOO-KNAW), P.O. Box 140, 4400 AC Yerseke, The Netherlands.
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van Rijswijk
Department of Agrotechnology and Food Sciences, Bioprocess Engineering group, Wageningen University, P.O. 8129, 6700 EV Wageningen, The Netherlands.
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Martens
Protein Labelling Innovation (PLI), BioScience Park, Archimedesweg 27, 2333 CM Leiden, The Netherlands.
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Egorova-Zachernyuk
Netherlands Institute of Ecology (NIOO-KNAW), P.O. Box 140, 4400 AC Yerseke, The Netherlands ; Faculty of Geosciences, Utrecht University, P.O. Box 80.021, 3508 TA Utrecht, The Netherlands.
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Middelburg
Department of Agrotechnology and Food Sciences, Bioprocess Engineering group, Wageningen University, P.O. 8129, 6700 EV Wageningen, The Netherlands.
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Wijffels