Settlement of <Emphasis Type="Italic">Macoma balthica</Emphasis> larvae in response to benthic diatom films |
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| Authors: | Carl Van Colen J Lenoir A De Backer B Vanelslander M Vincx S Degraer T Ysebaert |
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| Institution: | (1) Department of Biology, Marine Biology Section, Ghent University, Krijgslaan 281/S8, 9000 Ghent, Belgium;(2) Laboratory of Pharmaceutical Technology, Faculty of Pharmaceutical Sciences, Ghent University, Harelbekestraat 72, 9000 Ghent, Belgium;(3) Department of Biology, Laboratory of Protistology and Aquatic Ecology, Ghent University, Krijgslaan 281/S8, 9000 Ghent, Belgium;(4) Management Unit of the of the North Sea Mathematical Model, Marine Ecosystem Management Section, Royal Belgian Institute of Natural Sciences, Gulledelle 100, 1200 Brussels, Belgium;(5) Netherlands Institute for Ecological Research (NIOO-KNAW), Centre for Estuarine and Marine Ecology, POB 140, 4400 AC Yerseke, The Netherlands;(6) Institute for Marine Resources and Ecosystem Studies, Wageningen University, POB 77, 4400 AB Yerseke, The Netherlands |
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| Abstract: | The role of multi-species benthic diatom films (BDF) in the settlement of late pediveliger larvae of the bivalve Macoma balthica was investigated in still-water bioassays and multiple choice flume experiments. Axenic diatom cultures that were isolated
from a tidal mudflat inhabited by M. balthica were selected to develop BDF sediment treatments characterized by a different community structure, biomass, and amount of
extracellular polymeric substances (EPS). Control sediments had no added diatoms. Although all larvae settled and initiated
burrowing within the first minute after their addition in still water, regardless of treatment, only 48–52% had completely
penetrated the high diatom biomass treatments after 5 min, while on average 80 and 69% of the larvae had settled and burrowed
into the control sediments and BDF with a low diatom biomass (<3.5 μg Chl a g−1 dry sediment), respectively. The percentage of larvae settling and burrowing into the sediment was negatively correlated
with the concentration of Chl a and EPS of the BDF. This suggests higher physical resistance to bivalve penetration by the BDF with higher diatom biomass
and more associated sugar and protein compounds. The larval settlement rate in annular flume experiments at flow velocities
of 5 and 15 cm s−1 was distinctly lower compared to the still-water assays. Only 4.6–5.8% of the larvae were recovered from BDF and control
sediments after 3 h. Nonetheless, a clear settlement preference was observed for BDF in the flume experiments; i.e., larvae
settled significantly more in BDF compared to control sediments irrespective of flow speed. Comparison with the settlement
of polystyrene mimics and freeze-killed larvae led to the conclusion that active selection, active secondary dispersal and,
at low flow velocities (5 cm s−1), passive adhesion to the sediment are important mechanisms determining the settlement of M. balthica larvae in estuarine biofilms. |
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