Students of Marine Mass Extinctions Take Note: Biotic Recovery of Hypoxic Benthic Environments

Organism-Sediment Interactions Govern Post-Hypoxia Recovery of Ecosystem Functioning

Authors:

1. Carl Van Colen (a)
2. Francesca Rossi (b,c)
3. Francesc Montserrat (b)
4. Maria G. I. Andersson (b)
5. Britta Gribsholt (b)
6. Peter M. J. Herman (b)
7. Steven Degraer (a,d)
8. Magda Vincx (a)
9. Tom Ysebaert (b,e)
10. Jack J. Middelburg (b,f)

Affiliations:

a. Department of Biology, Marine Biology Section, Ghent University, Ghent, Belgium

b. Netherlands Institute for Sea Research (NIOZ-Yerseke), Yerseke, The Netherlands

c. Ecologie des systèmes marins côtiers (Ecosysm) UMR 5119 CNRS-Université Montpellier 2-IRD-Ifremer Place Eugène Bataillon, Université Montpellier II, Case 093, F-34095 Montpellier, France

d. Management Unit of the of the North Sea Mathematical Model, Marine Ecosystem Management Section, Royal Belgian Institute of Natural Sciences, Brussels, Belgium

e. Wageningen University, Institute for Marine Resources & Ecosystem Studies, Yerseke, The Netherlands

f. Faculty of Geosciences, Utrecht University, Utrecht, The Netherlands

Abstract:

Hypoxia represents one of the major causes of biodiversity and ecosystem functioning loss for coastal waters. Since eutrophication-induced hypoxic events are becoming increasingly frequent and intense, understanding the response of ecosystems to hypoxia is of primary importance to understand and predict the stability of ecosystem functioning. Such ecological stability may greatly depend on the recovery patterns of communities and the return time of the system properties associated to these patterns. Here, we have examined how the reassembly of a benthic community contributed to the recovery of ecosystem functioning following experimentally-induced hypoxia in a tidal flat. We demonstrate that organism-sediment interactions that depend on organism size and relate to mobility traits and sediment reworking capacities are generally more important than recovering species richness to set the return time of the measured sediment processes and properties. Specifically, increasing macrofauna bioturbation potential during community reassembly significantly contributed to the recovery of sediment processes and properties such as denitrification, bedload sediment transport, primary production and deep pore water ammonium concentration. Such bioturbation potential was due to the replacement of the small-sized organisms that recolonised at early stages by large-sized bioturbating organisms, which had a disproportionately stronger influence on sediment. This study suggests that the complete recovery of organism-sediment interactions is a necessary condition for ecosystem functioning recovery, and that such process requires long periods after disturbance due to the slow growth of juveniles into adult stages involved in these interactions. Consequently, repeated episodes of disturbance at intervals smaller than the time needed for the system to fully recover organism-sediment interactions may greatly impair the resilience of ecosystem functioning.