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Published on: September 5, 2018
Biological vs. physical mixing effects on benthic food web dynamics
Ulrike Braeckman1, Pieter Provoost, Tom Moens
1Department of Biology, Marine Biology Section, Ghent University, Ghent, Belgium. Ulrike.Braeckman@UGent.be
Plos One
|April 2, 2011
Summary
Marine ecosystem engineers like burrowing worms facilitate lower trophic levels by creating habitats, not by directly providing food. Bioturbation and bio-irrigation create niches, benefiting meiofauna and bacteria long-term.
Area of Science:
- Marine ecology
- Benthic science
- Ecosystem engineering
Background:
- Biological particle mixing (bioturbation) and solute transfer (bio-irrigation) are key sediment processes.
- Macrobenthos influences sediment biogeochemistry and creates niches for smaller organisms.
- The impact of ecosystem engineers on food web dynamics, particularly for lower trophic levels, remains unclear.
Purpose of the Study:
- To investigate the effects of bioturbation and bio-irrigation on nematode survival and food uptake.
- To compare biological mixing with abiotic physical mixing after a simulated phytoplankton bloom.
- To determine if ecosystem engineers facilitate or hinder fresh organic matter assimilation by metazoan food webs.
Main Methods:
- Used microcosms with bioturbators (Abra alba) and bio-irrigators (Lanice conchilega).
- Included control microcosms and those with abiotic manual surface mixing.
- Introduced 13C-labeled diatoms (Skeletonema costatum) to track food uptake by nematodes.
Main Results:
- Nematode survival and density were highest in the bio-irrigator treatment.
- Nematode uptake of added diatoms was greatest in the physical mixing treatment (no macrobenthos).
- Nematodes primarily consumed bulk sedimentary organic matter, not the added diatoms.
Conclusions:
- Bioturbation and bio-irrigation primarily benefit lower trophic levels through long-term niche establishment.
- Ecosystem engineering effects on nematodes were more significant for niche creation than direct food provision.
- Bacterial respiration plays a major role in carbon cycling within these sediments.
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