Recycle of buried macroalgal detritus in sediments

Authors: Francesca Rossi

Publish Date: 2006/08/24

Volume: 150, Issue: 6, Pages: 1073-1081

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Abstract

In intertidal sediments burial and decomposition of macroalgal detritus can fuel the sediment of carbon C and nitrogen N which can be either promptly mineralised or assimilated to enter the food web This study investigates the transfer of algalderived C and N to the sediment and to the infauna feeding primarily on benthic diatoms Thalli of Ulva spp were 13C and 15Nlabelled in the mesocosm and frozen to create detritus Thawed macroalgae were then buried in the sediment of an intertidal sandflat forming a mosaic of small patches 50 × 50 cm2 enriched with the macroalgae interspersed with bare sediment The area was dominated by Corophium volutator and Hydrobia ulvae The uptake of 13C and 15N was measured in the residual macroalgae in the sediment and in those animals Decomposition of detritus was rapid and after 4 weeks the residual biomass was 3 the amount added Algalderived 13C and 15N were moved to the sediment The total amount of 13C and 15N retained in the sediment after completing the decomposition was 34 ± 05 13C and 27 ± 06 15N the amount decomposed During the first 2 weeks more N than C was assimilated 17 13C and 135 15N During the remaining two weeks N was released from the sediment while there was little accumulation of C +64 ± 20 13C and −77 ± 38 15N At the end of the decomposition animals were 15N and 13Clabelled Considering the total accumulation of label in the sediment they accounted for 35 ± 18 13C and 258 ± 129 15N Similarly considering the mass of the heavy isotopes gained 13C or lost 15N during the remaining 2 weeks the animals accounted for 47 ± 21 of the 13C in excess and for 186 ± 91 of the 15N loss The transfer of C and N to the sediment and to the surface depositfeeders can be a relevant mechanism to remove the excess of detritus from the sedimentI am very grateful to P M J Herman and J J Middelburg for their invaluable suggestions on the field experiment and on the early drafts of this manuscript I also wish to thank G Castaldelli who gave advises how to grow Ulva B Koutstaal J van Soelen and S Como for helping in the field and P van Breugel and C Kleppe for doing the chemical analyses P Kamermans RIKZ and T Ysebaert were of great help in the first phase of this study The comments of B Gribsholt and of Prof L A Levin contributed to improve an early version of this manuscript This study is supported by a MarieCurie grant to F R MC Individual fellowship Contract number EVKCT−200250010 −30 This is the publication 3862 of Netherlands Institute of Ecology NIOOKNAW

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